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PGCE 2005
- Conference date: 06 Dec 2005 - 07 Dec 2005
- Location: Kuala Lumpur, Malaysia
- Published: 06 December 2005
41 results
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Advancement In Geophysical Technology
By Deva GhoshDuring the last fifty years numerous advances have taken place in Geophysics as applied to the Oil and Gas Exploration and Development. This spans a development that started from single fold analogue data in the early 1950 through the digital revolution in the ’60 s and continues to the present date and hopefully well in to the future. The improvements have been in all phases of seismic method including data acquisition, processing, analysis and
3D visualisation volume interpretation. In data acquisition we can highlight the following changes : (1) from analogue recording to digital, (2) from single fold to multifold CDP, (3) from recording with a single component to all components of the wave field, (4) from surface seismic to acquisition on the sea floor, and (5) to imaging in a borehole or across boreholes. The concept of 3D earth mapping has enabled us to move away from 2D into 3D and to
mapping structure direct in depth rather than in time. Wider azimuths are not only possible in land but also in marine. Lately, the emphasis is on preserving geological and rock properties of the earth. With our growing knowledge of rock physics and its influence on the seismic wave propagation we are able to predict through the technology of DHI bright/flat spot and AVO/Inversion the possibility of detecting the presence of not only hydrocarbon and lithology but, under favorable conditions distinguishing oil from gas. Increasingly, geophysics is being applied for reservoir development, characterisation and even in Production to monitor fluid movement, depletion and aid in infill drilling covering the whole suit of Life of field. The other significant development is the proper use of 3D data volume in interpretation. With the aid of modern tools like 3D visualisation we are able to use the benefits of the 3D cube and its various attributes to interpret geological features in their true spatial location. This has helped us to identify complex stratigraphic features, improve our understanding of facies and fault patterns, their stress regimes and seal behavior , and to extend this to oil generation and migration history through synergy with basin modeling. The connectivity issue of reservoirs are now better understood by visualising the geo-bodies. In an Immersive Visualisation environment the geoscientists, reservoir and petroleum engineers, drillers, economists and managers can work together to make a collective techno-commercial decisions faster and better. This results is significant subsurface risk reduction and an improved chance of exploration success. The last 10 years have seen geophysical technology and capability explode and the coming years should be no exception. Geophysics will continue to give us more quantitative assessment of our prospects and reservoirs,including predict properties like : porosity ,gas saturation, absorption and possibly fluid flow and permeability. All these could aid us to drill more successful wells and be better hydrocarbon producers with last minute surprises. Geophysics is bringing geoscientist and the petroleum engineers closer together,and allowing the concept of a single “Shared Earth Model” to become a reality.
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New source and seal types for Malaysia –<br>the key to unlocking the oil<br>potential of deepwater NW Borneo
Authors Sam Algar and Doug WaplesThe discovery of the deepwater Kikeh oil field overturned the widely held belief that the NW Borneo deepwater play was “gas-prone”. This paper will present the data and geological principles that explain why this area has such significant oil potential and hence why it has become one of the most successful oil plays in the recent history of Malaysian oil exploration. A new source rock has been discovered and with the aid of extensive conventional coring, fluid sampling and geochemical evaluation, that Murphy and our partners Carigali have done, a link to the oils and gases reservoired in the deepwater discoveries can be clearly demonstrated. These data point to an entirely new charge system for Malaysia which can be demonstrated from 2D basin modeling to be the likely primary charge mechanism for the deepwater oil discoveries made so far. Further laboratory analyses of core material combined with extensive pressure tests from Kikeh and other Murphy-Carigali discoveries have put the final piece of the puzzle together by proving that the seal type is a crucial element of the oil
story.
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Scenario-based Velocity Modeling for<br>Depth Conversion Uncertainty
Authors Dylan Mair Sdn Bhd and Lee Hong ShienDepth realizations of reservoir surfaces was required for geocellular modeling of two fields in the MTJDA. In addition, a measure of uncertainty in depth was required. The method of this paper depth applied vertical stretch depth conversion and a primary velocity model that integrated well picks, seismic velocities and time-depth functions with surfaces. The velocity modeling process guided iterative improvement of the input interpretation data. Alternative velocity models were then created using different assumptions to capture variations in velocity interpolation. The largest uncertainties were identified in three plausible alternate models: with less smoothing of the seismic velocities; without seismic velocities; and with shallow gas effects modeled from seismic amplitudes.
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Intgerated Sequence Stratigraphy of the Tertiary<br>Deepwater Deposits of Northwest Sabah, Malaysia,<br>Using Well, Seismic, and Outcrop Data
More LessIn onshore East Sabah, Malaysia, deepwater outcrops can be tied to offshore subsurface deepwater deposits just few tens of miles to the north. This will provide a unique opportunity to obtain a better picture of depositional processes that controlled the distribution of hydrocarbon reservoir sands, as well as seal and source rock distribution, and possible migration fairways in the subsurface. Some previous investigations on the basin-floor fan complex of the Crocker Formation provided insight into the depositional nature and sedimentary characteristics of these deposits. However, the present study is intended to provide an integrated approach of studying the deepwater deposits of Northwest Sabah and tie it to subsurface data in order to get a clearer picture of the depositional systems within a sequence stratigraphic framework and to unravel the paleogeographic and chronostratigraphic history of these deposits. The large areal and vertical extents of these deposits is expected to give the chance to better understand the depositional history and, in turn, help create a relatively accurate lead and prospect inventory in the subsurface by providing an analog from surface data. This would be possible by analyzing and interpreting available well logs, cores, and seismic data and integrating them with detailed outcrop sedimentological and biostratigraphic interpretations using a sequence stratigraphic approach.
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A Practical Sequence Stratigraphic Framework for the<br>East Balingian Sub-Province, Offshore Sarawak
Exploration activity in the East Balingian Sub-province (Figure 1) commenced in the 1960’s and resulted in a few discoveries which were predominately gas. Currently there are only two producing fields in this area, the Temana and West Patricia oil fields. In view of the relatively mature stage of exploration in the basin a new sequence stratigraphic scheme was needed in order to provide a detailed framework from which new play concepts could be identified by analysis of the key components of reservoir, seal and source. The present study has established a new practical sequence stratigraphic scheme for the East Balingian Subprovince that follows Vailian sequence stratigraphic principles. The Shell ‘Cycle’ stratigraphy (Ho, 1978 and van Borren et al., 1996) which has been commonly used in Sarawak was innovative for its time. It can be viewed as a forerunner to Galloway-style sequence tratigraphy, as it was largely based on biostratigraphically defined, shale prone marine flooding events. However, review of the Shell Cycles in the East Balingian wells indicates that they are not consistent with seismic correlations defined on modern 2D and 3D seismic. Shell has moved on from the Cycle nomenclature to a sequence stratigraphic approach and recently published the results of its internal study (Morrison & Lee, 2003).
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An integrated workflow to reservoir characterisation<br>providing direct input to the reservoir model of the Muda-Tapi and Jengka Fields
Authors Phil Beal, Frazer Barclay, Ricky Majit and Mohammad El SadanyAn integrated workflow was designed by CPOC and Odegaard to produce high quality 3D inputs to be used in the reservoir modelling of the Muda-Tapi and Jengka fields located within MTJDA. The detailed workflow is shown in Figure 1 but can be summarised into the following key stages:
-Petrophysical and rock physics analysis.
-Simultaneous AVO inversion.
-Lithology/fluid probability classification.
-Reservoir modelling.
It is essential to have reliable and quality controlled well log suites when embarking on an AVO inversion and lithology prediction study. Hence, the project was initialised by evaluating the petrophysical data available with a focus on the elastic properties of the reservoir intervals. The petrophysical analysis involved log editing, volume of clay interpretation, porosity and water saturation calculations on a total of sixteen different wells. Accurate volume of clay interpretations are the corner stone to the overall well log interpretation as they influence the porosities and saturations. A dual VCL indicator was utilized by using the gamma ray log and neutron versus density crossplots and this produced a set of VCL estimates which were consistent among wells. These resulting curves are then used to define the different lithologies and the fluids they contain in the reservoir interval.
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Facies, Depositional Framework and Sequence Stratigraphy of the Miri Formation<br>(Middle Miocene), Miri, Sarawak
Authors Hatem S. Abieda, Abdul Hadi Abd. Rahman and Zuhar Zahir T. HarithThe Middle Miocene Miri Formation records part of the infill of an estuarine valley system that was incised during an early Middle Miocene drop in sea level and subsequently infiled during a transgressive episode later in the Middle Miocene time. Around the Miri town in Sarawak, part of this incised valley succession is exposed and exhibit a wide range of siliciclastic lithofacies which reflect a variety of depositional settings. Three main depositional environments are recognised: tide dominated estuary, distal lower shoreface to offshore transition and s.horeface. The estuarine lithofacies association (FA:1) is characterized by distinct and diagnostic tidal signatures - tidal dune cross-bedding with mud draped cosets and forests including mud couplets, bidirectional (herringbone) cross-bedding, rhythmic stratifications, flaser bedding, wave bedding and lenticular bedding. Distal lower shoreface to offshore transition environment (FA:2A) is represented by interbedded laminated and bioturbated siltstone/sandstone, bioturbated siltstone and laminated mudstone/hummocky sandstone interbedding. Shoreface, storm-and-wave facies association (FA:2B) are represented by swaley cross-stratified sandstones, hummocky cross-stratified sandstones, bioturbated sandstones and associated mudstones. The tidal estuarine deposits form mix aggradational to retrogradational parasequence set, which represent the transgressive valley fills resulting from the establishment of an estuarine system (Early Transgrassive System Tract: E TST) (Figure). This stage (Stage I) represents the early phase of a significant relative sea-level rise, and possibly reflects a southward migration of the paleo Miri shoreline. This stage also characterized by great wave actions coinciding with abrupt sea level rising, which resulted in the deposition of several tempestites at estuary mouth. Stage II records the complete drowning event of the estuarine system, with the development of shallow marine settings (Late Transgressive System Tract: L TST), representing the final phase of transgrassive system tract. Parasequence sets of the transgressive system tract generally display clear, landward shift in facies trend. Shallow marine deposits in the studied rock succession overwhelms the estuarine deposits, displaying a retrograditional set of parasequence. The transgressive trend that started with the establishment of an estuarine system culminated with the deposition of offshore transition facies, which represents the maximum flooding surface (MFS). At the outcrops, this MFS marks the turnaround from retrograditional stacking pattern of TST to aggradational parasequences of HST. Stage III (Highstand System Tract) is represented by a well developed shoreface succession. This stage represents the upper portion of the exposed Miri Formation, which was possibly deposited during stable high and slowly falling sea-level. HST parasequence sets show an aggradational trend, formed during stable high sea-level, to progradational trend, formed during slowly falling sea-level. HST is predominantly composed of upper to middle shoreface deposits (swaley and thick hummocky cross stratified facies) that overlie MFS.
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Comments on the Structural Evolution of the Bukit Lambir Area, Sarawak, Malaysia
More LessThe Neogene sands and shales of Bukit Lambir have witnessed a surprising variety of tectonic events, including inversion, folding and thrusting. Fault measurements carried out in the field in early 2005 were combined with geologic profiles, seismic data, satellite data, and older unpublished data (such as from S.O.L, in the early part of the 20th century), and fed into one single ArcGis project. All data suggest the tectonic evolution of the Bukit Lambir area occurred in four stages: Extensional stress created grabens with faults hading around 125 degrees (Middle-to Late Miocene). The grabens quickly filled with some 12000' of interbedded sands and shales. With the onset of regional compression in the Latest Miocene, inversion of the depo-centre took place leading to moderately dipping sequences and semi-regional uplift. Further compression oblique to the Bukit Lambir trend led to shallow overthrusting, associated folding and further uplift and a steepening of strata dip. Both regional thrusts and folds hade circa 60 degrees. The compressive push originated from the South-East, as also seen in overthrusted synclines further to the south between Bakong and Lapok.
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QC and Processing Requirements for 4D Seismic Projects
By Andrew LongWhilst the parameterization of the acquisition phase of 4D (time lapse) seismic surveys has rapidly become well established, the complexities of the parameterization for the data processing stage are far less established. We discuss robust strategies for the planning, execution and quality control (QC) of 4D surveys. Several case examples demonstrate that
4D QC is the critical element of all stages of 4D projects. To be successful, 4D QC must be pursued as a seamless integration of all the project elements, ideally within a visualization system capable of interactive and "real time" dialogue with those project elements. If the QC
of the 4D acquisition is managed in real time it will be possible to isolate and address each acquisition contribution to the 4D reservoir signal during processing. If the QC of the 4D processing is managed in the same visualization system it will also be possible to isolate and address each processing contribution to the 4D reservoir signal, and it will be possible for project members from all disciplines to work effectively together. All elements of the final data product can then be completely understood, enabling the construction of quantitatively accurate and robust reservoir models for use in reservoir simulation and management projects.
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Vietnam Basement Fracture density determination using seismic acoustic impedance inversion
Authors Vincent W.T. Kong and Nguyen Huy NgocThe basement plays in Vietnam and the recent domestic Peninsular Malaysia discovery of Anding-Utara’s basement potential provide the push to obtain basement fracture patterns from a more areally complete coverage such as the 3D seismic data coverage. Conventionally coherency type technologies have been applied in identifying faults and lineament in 3D seismic data. We have found that the acoustic impedance data from Far angle substack 3D seismic help to better focus faults and fracture imaging. The quality
control/check maps in the seismic inversion process seemed to provide clues toward the
presence of larger clusters of fractures within the basement zone. The observed localized areas of perceived higher fracture density is consistent
with the interpretation of expected denser fracture area from the conjugation of the
larger faults. The well located within the area of interest have tested fairly tight basement rock and this corresponded reasonably well with the perceived lower
fracture density areas of the quality check maps. Where available results of spectral decomposition of the same zone of interest are compared to enable us to arrive at a
consistent deduction of the occurrence of fracture intensity and their related trends.
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Detection and Delineation of hydrocarbon reservoirs using Controlled Source EM Imaging
More LessThe adoption of 3D seismic at the end of the last century dramatically improved drilling success. The annual spend by the hydrocarbon industry on seismic acquisition now exceeds $5 billion, and the resulting data are an integral part of risk management and drilling strategies. However, despite this the majority of exploration wells drilled globally are commercially unsuccessful. To make a significant improvement in exploration performance more prospects must be tested to avoid relinquishing productive acreage, including those prospects considered high risk (for example stratigraphic plays, which often have little or no seismic expression). There is therefore a pressing need for a non-invasive technology able to minimise the risk of drilling unsuccessful exploration wells by confirming (or otherwise) the presence of hydrocarbons prior to drilling. Controlled source electromagnetic imaging (CSEMI) does just that, by bridging the gap between traditional seismic exploration methods and drilling. Whilst seismic data identify the geological structures that may contain hydrocarbons, under many circumstances they do not reveal the presence of hydrocarbons themselves. The presence of hydrocarbons in a reservoir typically increases its electrical resistivity compared to the surrounding water saturated sediments by an order of magnitude or more. This property of hydrocarbon saturated reservoirs is commonly exploited well logging applications. However these methods require a borehole to be drilled. CSEMI provides a method of determining the resistivity within an identified prospect before drilling. CSEMI detects and delineates resistive sub-seafloor layers, which can be associated with hydrocarbons, and gives an indication of their spatial extent. If correctly applied, this means that the possibility of drilling dry exploration wells is significantly reduced, as is the need for extensive appraisal drilling.
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Seismic stratigraphy and thermal considerations in overpressure analysis
More LessThe depth at which the pressure gradient exceed hydrostatic gradient is defined as the on-set of overpressure. The overpressure zone started within fine sediments and is associated with high rate of sedimentation. The principal components in the development of overpressure are lithology and principal stress. The properties of the soft and fine sediments, of low
permeability over extensive areas with thick intervals allows for seismic facies interpretation of the top of overpressure. However, presence of pressure compartments due to faults,
differential compaction and localised rock facies vary the depth to top of on-set overpressure.
The on-set of overpressure may occur near stratigraphic maximum flooding surface (Figures 1
and 2). It has been established that the top of overpressure and the transition zones are readily predicted by seismic data. The problem arise when the drilling progress into the hard overpressure zones where the formation pressure registered during drilling are likely to be higher that the anticipated pressure from seismic. Limitation of well control data and poor seismic reflection data pose constraints in the estimation of overpressure. Incorporating thermal analysis and pressure trend curves in estimation of overpressure in deeper intervals will complement the seismic data for prediction of the pressure. The under prediction of overpressure occurs within the shallow reservoir is uncommon, but it occurrence may surprised drillers. This occurrence of abrupt pressure increase at shallow depth within the overpressure zones is because, of inflationary pressure or the centroid effect. The pressure in the sand bodies is in disequilibrium and of higher pressure than the surrounding shale at shallow depth. This is observed when the sand aquifer is dipping at certain angles. In this situation a pressure-temperature assessment shall provide an estimate
of the pressure. The observed pressure-temperature gradient, superimposed on the velocity profile can produce a better estimation of the pressure within the overpressure zones.
This technique forms a comprehensive method in estimation top of overpressure and hard overpressure and also the prediction of overpressure within the deep reservoirs. By
applying the techniques of seismic velocity inversion and Interval Pressure-Thermal Gradient modeling, provide a robust solution into quantification of the pressure in the deep reservoir. The seismic and thermal data could be integrated to estimate the pressure and predict the pressure at deeper reservoirs. The estimated trend from thermal analysis would complement seismic data in the prediction of overpressures (Figure 3). In fact, in thermal models, the estimated top of over pressure and hard overpressure are shallower than those of seismic prediction and in addition the value of pressure is higher in the estimated trends than those of seismic predicted, for deep reservoirs.
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CSMP's Success and Challenges in North Malay Basin: PM 301/PM 302
CS Mutiara Petroleum is a PCSB-SEPM joint operating company. It is currently operating the PM301 and PM302 PSC. The theme of this paper is to share CSMP’s experience on how it conducted its exploration campaign (to date) to create value in a mature and highly creamed basin. Through a portfolio management approach with consistent volume, risk & value assessment, the following technical challenges were addressed: • Gas sand prediction (coal versus gas sand). • Low saturation versus low resistivity pay. • Shallow velocity layer impact on depth conversion. These challenges have significant impact on the acreage prospectivity & volumetric assessment. CSMP manage to apply “fit for purpose technology” such as application of simultaneous inversion, spectral decomposition techniques and use of open-hole mini DST to understand and to solve for these key challenges: • Based on the portfolio management approach and applying fit for purpose technology, a drilling sequence of the highest ranking prospects was carefully mapped out which resulted in drilling five successive commercial discoveries.
• An appraisal campaign is underway in anticipation of a fast track development with first gas targeted in 2009.
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Identifying the Porosity and Fluid Distribution within a Carbonate Field, Offshore Sarawak
More LessThe Jintan gas field is situated some 250 km North of Bintulu in 130 m of water and has been put on stream mid last year. The field is a structurally simple platform-type carbonate build-up some 5 km South of the M1 Carbonate build-up. The carbonates are of
Late Miocene age and top reservoir occurs at about 1600 m sub-sea. The field is covered by a
good-quality 3D seismic survey, acquired in 1993 as well as by some regional 2D seismic
lines of 1989 and 1990 vintage. The 3D seismic data has been recently reprocessed and one full stack and two sub stacks have been generated. The variability in porosity and permeability within the build-up needs to be addressed and understood for optimal field development. And, this study has been carried out to support the development plan, where two infill wells were planned and are currently being drilled.
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Pore Pressure Prediction for Exploration Drilling in DW Sabah
More LessThe North West Borneo deepwater fold and thrust belt still holds significant potential
for successful hydrocarbon exploration. Top seal analysis is a critical success factor, and seismic velocity based pore pressure prediction is a key ingredient of an integrated workflow
to study trap integrity and retention risk. Moreover, drilling high-pressure, high-temperature (HPHT), low drilling margin wells in a deepwater setting poses substantial HSE risks and significant financial exposure. Accurate pre-drill pore pressure and fracture gradient
evaluation combined with in-depth shallow hazards analysis leads to appropriate and costeffective well-design. Inflationary overpressures at crestal locations on ridges with little overburden, but potentially long connectivity into the basins pose a special challenge. A well
established procedure using results of regional rock property studies converts acoustic
velocities to vertical effective stress. Seismic interval velocities corrected for shale-related anisotropy effects and calibrated to check-shot velocities from the entire deepwater area yield
an initial idea about overpressure. Pressure sampling from past drilling activity shows that reservoirs on high-relief structures are often inflated relative to seismic-derived pressures, which is corrected for using the centroid approximation. During drilling, real-time monitoring and pressure prediction ahead of the bit contributes to timely adjustment of casing schemes and mud weights, whereas continued updates of pressure-vs-depth plots facilitates early
understanding of hydrocarbon column heights and volumetric scenario modeling. Case studies from recently drilled prospects in deepwater Sabah will be used to illustrate the concepts and workflows.
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2D-Macro-Velocity/Depth Model Building Through Multi-Offset Reflection Time Inversion
More LessFor pre-stack depth migration, a macro-velocity/depth model is required which reflects the general subsurface structure and contains the velocity distribution which correctly predicts wave propagation times. Such a macro- model can be determined by non-linear inversion of multi-offset reflection times belonging to seismic horizons picked on CDP gathers along a seismic line. In the inversion scheme, in a 2D earth model, the depths of reflecting interfaces and the laterally and vertically varying velocities within the layer above the interface are solved simultaneously.
Provided accurate multi-offset reflection times, two dimensional velocity anomalies in
single-layers in the shallow section (i.e. in the range 0-2000 m depending on the maximum offset available in seismic data) can be resolved. In the optimization of depth models containing macro-layers with two dimensional velocity distribution, taking the layer boundaries and vertical velocity trends from available sonic log will help in the inversion process in achieving a globally optimum solution. If a sonic log is not available, it is necessary to divide the macro-layers into thinner macro-layers with lateral velocity changes only in order to solve the velocity variation with depth.
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Identifying Overpressuring Mechanisms in<br>Sedimentary Basins<br>from Wireline Logs
More LessAccuracy in pore pressure prediction requires prior understanding of the formation of overpressure in the basin. This may be a challenging task as the generation of overpressure can be attributed to several geological processes, either increase in loading stress (compaction disequilibrium) or volume expansion, or combination of both. The most common cause is due to compaction disequilibrium, whereby the causal mechanism can be eadily verified if the porosity in the overpressured shales remains high (undercompacted). In many instances, the origins of overpressure are combination of several of these causes. In the Malay Basin variable pore pressure profiles are observed. Pore pressure profile is variable due to: (1) choice of methods (empirical or soil mechanics), (2) difficulties in selection of normal compaction trend, (3) multiple origins of overpressure, and (4) chemical ompaction effects. The variability of pressure profiles and log cross-plot trends found in the Malay Basin can also be observed in basins elsewhere in the world. Based on the pressure and wireline log analysis conducted for the Malay Basin, a flowchart has been developed to enable determination on overpressure origin in the basin. Overpressure resulting from disequilibrium compaction, fluid expansion, clay diagenesis, lateral transfer and chemical compaction can be recognized by a combination of prediction methods and well log signatures. Examples presented are taken from several overpressured basins around the world. The wider compaction trends observed in these basins are associated with variable sand and clay content, plus pure unloading signatures associated with fluid expansion mechanisms.
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Overpressure Characterization in Baram Delta: Rock Properties to Seismic Velocities Evaluation
Subsurface geopressure analyses studies in Baram delta were done by many researchers (Schaar, 1976; Mantaring et al., 1994; Wee, 2000, Hoesni, 2004). They tried to predict overpressured areas and evaluated the hydrocarbon expulsion, migration pathway and hydrocarbon entrapment in the Baram Delta region. The information required by drilling engineers for well design were onset of overpressure, maximum pressure with depth and thickness of zone of overpressure In this regional study, we analyzed rock/fluid properties e.g. Poisson Ratio, Vp/Vs and impedances (P-Impedance (IP) and S-Impedance (IS)), Pressure-Temperature (P-T) gradient and seismic wave propagation behaviour under normal and overpressured conditions. This was to determine the origin and mechanism of overpressure as well as to predict and quantify the amount of pore pressure. The objective was to use these information in determining the origin and the mechanism of overpressure as well as to improve prediction and quantification of pore pressure.
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Identifying Hydrocarbon Accumulation with Sea Bed Logging
Authors Matthew Choo, Alexander Bray and John VoonShell’s deepwater portfolio in North West Borneo (NWB) is dominated by Miocene toe thrust anticlines. Although the prospects are broadly supported by direct hydrocarbon indicators (DHI) Quantitative Analysis does not discriminate low from full saturation hydrocarbon. In addition, seismic imaging is poor over some crestal areas, largely due to shallow gas and complex crestal faulting. Electromagnetic Seabed Logging (SBL) is a new technology that utilizes the Controlled Source Electro-Magnetic (CSEM) technique to detect and characterize HC-bearing layers within the subsurface. Modeling suggests that the method is insensitive to low saturated hydrocarbon and has the potential as a tool to de-risk or high-grade prospects in an exploration portfolio. In 2002, a global deployment and implementation plan was exercised for the technology in exploration. In 2004, Shell acquired the region’s first SBL data over 7 prospects in the North-West Borneo Block G and J. Over 350km of EM data was acquired over the prospects within the agreed 30 days of operation. Operational learnings were in abundance, with sliding receivers on the seafloor and potential source-entanglement with submarine cables being included as some of the operational challenges. SBL data was also acquired over the then Malikai-A well. With a processing turn-around time of about a week, the SBL data has positively identified the HC accumulation in the structure, which was proven later with the well and the oil discovery. This result has driven Shell to further utilize this new
exploration technique in the region to accelerate exploration and improve drilling success.
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Carbon Dioxide (CO2) Distribution in the Malay Basin, Malaysia
Authors Mansor Ahmad, Norhafizah Mohamed and Kazuo NakayamaThe carbon dioxide content in both associated and non-associated gases in Malay Basin fields varies up to a maximum of 90%. High CO2 content in natural gas reduces the resource value by lowering the sales gas volume, as well as reducing the BTU content. Also, with CO2 content, special infrastructure is required to develop and process these accumulations. Understanding the reasons for CO2 regional distribution patterns of CO2 will assist the
explorationist in targeting prospects with a lower CO2 content. General current understanding of the CO2 distribution in the basin are CO2 percentage increases with depth and high percentage CO2 accumulation are of inorganic origin and tend to be associated with structures with deep seated faults to facilitate CO2 migration up dip from basement. However, we observe that CO2 percentage varies vertically in a field and does not necessarily
increases with depth and could also decreases with depth. CO2 of same basement origin are present in different reservoirs of a field; and yet one reservoir may have very low CO2 compared to the other reservoirs.
Therefore depth of accumulation and origin of CO2 does not influence the percentage distribution. Geology of traps dictates how much CO2 the container can hold. In closures with good lateral and top seal, high relief structures will accumulate higher percentage CO2 as compared to low relief structures.
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Exploring for High Pressure and High Temperature (HPHT)<br>Hydrocarbon Pools: Technology Challenges Versus Pessimism - Guling Deep-1 Experience
More LessShallow and easy hydrocarbon accumulations are “almost extinct species”. Previously in Malay Basin, not many wells were drilled into and beyond the overpressured formation. The central part of Malay Basin still has untested high pressure and high temperature zones. Deep and overpressured formations will be among the next interesting exploration focus. Current technological developments compliment the drillability of such targets. Persistent general lack of serious commitment hindered the exploratory works. Last year PETRONAS (PMU) tested overpressured reservoirs at Guling Deep-1 location within budgeted time and AFE. The result surpassed pre-drill expectations and proved working petroleum system in the overpressured zones.
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The Prospectivity of Fractured Basement Play of The Malay Basin
More LessSince the 1980s Petronas Carigali Sdn Bhd has actively drilled exploration wells in the Malay Basin with basement rock as one of the secondary objectives. However, most wells were not very successful in testing the hydrocarbon potential in the basement rock. Among some highly debated issues highlighted were the ideal depths of penetration into the basement rock, type of basement play that has been drilled and hydrocarbon charging into the trap. The first discovery of basement play in the basin has undoubtedly proved the hydrocarbon potential in the basin fractured basement play.
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Depth versus Time Imaging of 3D seismic data – Tabu Field
Authors George McKinley and Chris Manuel and Rick WaliaThis paper describes the Kirchhoff Pre-stack Depth Migration processing of marine 3D seismic data acquired over the Tabu prospect, offshore Peninsular Malaysia and compares the results with the Pre-stack Time Migration. The survey covered an area of approximately 230 km2 and was processed through pre-stack time migration and Pre-stack Depth Migration processing flow. There are three target zones that can be identified on a crossline passing through the crest of the anticlinal structure: 1.5 s, 1-1.2 s, and 3.2 s. and the primary objective of the PSDM was to improve the stratigraphic definition of the reservoir obtained from the Kirchhoff pre-stack time migration processing. A new smooth velocity model approach was applied, where the initial model building consisted of a simple Dix conversion of the pre-stack time migration velocities and subsequent smoothing. The resultant velocity model is then perturbed to varying degrees in order to find the percentage of the velocity model which, when applied, will slightly over-correct the CRP gathers. The reason being as slightly overcorrected gathers provide optimum input to the inversion phase. There is a clear trend in the industry to analyze the physical parameters of the subsurface much more densely than previously done. For this kind of dense data, CGG has implemented a new methodology for imaging velocity analysis, based on the RMO inversion method and aimed at: • Improving resolution using the dense automated velocity analysis for model building.
• Reducing overall project turnaround by using automated picking and multi-layer inversion. Compared with the Pre-STM result, the Pre-SDM has resulted in the following: a. sharper fault definition; b. correction for the pushdown due to shallow gas pockets; c. a better understanding of the structure of the deeper events (in some cases a relatively flat structure interpreted at later times on the Pre-STM volume appeared to have a lot more folding associated with it than first thought).
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High resolution Biostratigraphy for enhanced reservoir<br>correlation in the Bergading field
Authors Shamsudin Jirin, Mahani Mohamed, Sanatul Salwa Hassan and Md Wakif SukaharDetailed correlation of reservoir sands is critical to field development and reservoir management. High-resolution biostratigraphy can provide this correlation by supplementing regional biostratigraphic markers with local bioevents, recognised from thin shales within reservoir intervals. This high-resolution data set could reduce risks in the drilling appraisal and development wells. Regional biostratigraphic markers are generally have a resolution of tens of meter or more. Though they permit regional correlation and mapping, they are too broad for correlation at the reservoir scale. Most reservoir objectives occur between these biostratigraphic tops. Therefore, a high resolution technique is necessary. An example of such application is in Tertiary reservoirs of the Bergading Field, Malay Basin where three regional and 59 semi-regional bioevents are used to enhance reservoir correlation. They comprise 43 palynological events i.e. mangrove and palynofacies events, and 16 marine events. These palynological events are believed to be caused primarily by changes in climate and relative sea level, while the marine events are caused by physical and chemical fluctuations in the sea-water mass through time. Palynomorphs, foraminifera and nannofossils imprint these changes onto the accumulating sediments and yield reproducible signals that can be interpreted and correlated across the field. Recognising and documenting these bioevents are the principles behind high resolution biostratigraphy. When integrated with wireline logs and seismic, such signals produce a more refined correlation and subdivision of sediment packages at the reservoir scale.
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Imaging through gas - a case study from the<br>North Sea. Anisotropic depth migration<br>processing of a 4C time-lapse survey
More LessIn late 1994 BP and partners Shell, Total, and Amerada-Hess embarked on what can be described as the industry’s ultimate seismic exercise – the repeated acquisition and processing of 4-component data over the Valhall field, offshore Norway, using a permanent sea-floor receiver installation. The 4D or time-lapse exercise was designed specifically to monitor and manage the Valhall field; a baseline 3D survey and a series of six repeat monitor surveys were acquired and processed at 3-month intervals, in the world’s first “Life of Field” or LoFS seismic program. This case study discusses the processing issues and workflows used to process the baseline and monitor surveys. The primary processing challenge involves imaging the reservoir in depth, in spite of the gas cloud, and required the development of velocity models for both the PP and the converted wave (PS) data. Subsequent 4D processing to compare the baseline survey with the repeated monitor surveys aims to capture true changes in the reservoir.
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3D Facies Modeling of J Reservoirs of Tinggi Field, Offshore Peninsula Malaysia
Authors Mohd Fauzi Abdul Kadir, Stan Rae and Muhd Kamal EmbongThis paper presents workflows and methods were adopted in constructing 3D-stochastic facies model of tide-dominated estuarine and tidal marine reservoirs within Group J of Tinggi field (Fig. 1). The Tinggi field is a mature oil field situated in the southeastern part of the Malay Basin, approximately 280 kms offshore east of Kerteh, Trengganu (Fig. 2). The 3D facies model built was conditioned to well observation, and conceptual facies model (Fig.3). A combination of RMS Facies:Belt and Facies:Composite methods were performed in the modeling (Fig. 4). During the modeling process, great efforts were made to optimise the workflow, and input parameters for each depositional system. This is to ensure that the input data were honoured, and the facies architecture and its characteristics are preserved (Figs. 5 & 6). Geological framework study was conducted in order to generate input for 3D facies modeling. This study, covering seven depositional sequences, was based on well logs, core data and 3D seismic attribute, revealed detailed reservoir facies architecture of tide-dominated estuarine and tidal marine
environments (Fig. 7). Sedimentological reservoir facies include tidal sand bars, tidal sand flats, highand moderate-energy subtidals. Distinctive sedimentological features for each reservoir facies can be observed from well data. Seismic attribute image extracted for the upper reservoirs provide important information about the distribution pattern of the subtidal facies (Fig. 8). Conceptual sedimentological facies model was built by integrating both well and seismic attribute data, as well as modern analogues, and a complete facies interpretation was performed at each well. Depositional model and paleogeographic history were constructed in order to have better understanding on reservoir sand-body geometry and orientation (Fig. 9). Prior to the facies modeling, a 3D structural/stratigraphic model was generated based on depth structure surfaces and fault polygons from two seismic horizons, subsequently was adjusted to well markers during stratigraphic modeling. The 3D model consists of eleven sub grids with 116 layers and about two millions cells (Fig. 10). In conclusion, better-defined facies distribution offered a realistic 3D static model and enhanced the understanding of reservoir properties distribution.
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New Insights on Depositional Styles from the Samarang Field Using Stratal Geometries and 3D Seismic Facies Analysis with a Neural Network Approach
In the Samarang field, log data suggest that the reservoir quality is controlled by an interplay between the tectonics, sediment supply, and available accommodation space. Previous studies referred to a so-called ‘homogeneous’ thick sand package with little variability while the present study unravels significant vertical and lateral heterogeneity. The larger and finer scale progradational units and the amalgamated, massive sands identified from well logs have distinct correlation to seismic stratal geometry and 3D seismic facies as highlighted from this analysis. The stacking pattern of these units is observed at multi-scales and can be related to small- and large-scale cyclicity and variations in the depositional environment.
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Structural lineaments of onshore Sabah and their relationship to the regional geodynamics of Southeast Asia
More LessThe present structural elements of Sabah are the overprint of several phases and episodes of orogenies and geologic events. Several regional tectonic events have converged in this region since early Tertiary producing well developed compressional and extensional structures. The continued regional collision and movement have altered most of the old structures. The pre-existing structures such as regional transcurrent faults provide weakest zones for stress transfer and determined the movement vectors. The study of synthetic aperture radar (SAR) images of onshore Sabah indicated several prominent structural trends. These trends, which have imprinted and reactivated throughout geologic time, are mostly related to the regional geodynamic evolution of SE Asia. The prominent features observed on the onshore Sabah are the structural elements related to the counter-clockwise rotation. The study of the lineaments and their kinematics indicate that most part of the onshore Sabah involved in these rotations. The counter-clockwise rotation of SE Asia occurred since Early Miocene (Hall, 1996) or perhaps
earlier. It is believed to be related to the collision of the northward moving Indo-Australian plate with the Eurasian plate and the Philippine Sea plate. The collision has caused SE Asia region to protrude southeastward and the Philippine Sea plate to rotate in clockwise direction. This rotation caused the area in eastern margin of SE Asia to move in counter-clock wise direction. In general the onshore Sabah can be divided into four structural blocks, Western, Northwest, Central and Eastern blocks (Figure 1). All of these blocks seem to rotate as separate unit in counterclockwise direction. The boundary between these blocks appears as linear features which are mostly
related to the transpression movement. Associated with it is the push-up restraining bends, oblique thrust faults and en echelon drag folds.
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Early generated hydrocarbons: origin and significance for coaly source rocks
More LessPetrographic investigation under normal reflected white light and blue light excitation were performed on a number of coals from the Sarawak basin and from the Batu Arang basin of Peninsula Malaysia. These are oil-prone coals that contain significant amounts of hydrogen-rich liptinitic macerals. The thermal maturity of the samples, based on vitrinite reflectance, ranges from Ro 0.35 to 0.50% and they are therefore thermally immature for significant oil and gas generation. The coal samples from the Sarawak basin, however, show microscopic features of early hydrocarbon generation. These include the presence of exsudatinite, oil droplets, and oil haze all of which occur in close association with the macerals bituminite, suberinite and phlobaphinite. In contrast, no distinctive oil generative features were observed in the Batu Arang coals even though they are of the same maturity as the studied Sarawak basin coals. This is therefore considered to be a consequence of the maceral composition of the Batu Arang coals, specifically the absence or trace occurrence of the macerals bituminite and suberinite.
The early generated hydrocarbons expelled by the oil-prone coals of the Sarawak basin were observed to impregnate the coal fabric and give rise to plastic behaviour in certain macerals1,2. These “oil-like” materials originate mostly from the maceral suberinite. The generated hydrocarbons impregnated the coal fabric as evidenced by the suppressed vitrinite reflectance values. Saturation of pores and surfaces of coal fabric eventually lead to a continuous bitumen network and subsequently fractured the coal fabric as generated materials lead to elevated pore pressure (Figure 1). This is envisaged as an effective means of expulsion of hydrocarbons from coaly source rocks. Coals from wells of offshore Balingian Province show similar oil-generative features as those observed in outcrops of onshore Sarawak. These features, however, are only distinct in early mature to mid mature (0.45-0.75%Ro) coals and are no longer distinct in the latter part of the oil window. It is therefore suggested that early generated materials have a significant role in hydrocarbon generation and expulsion from coaly source rocks.
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The Wave-Influenced Pahang Delta: Geomorphology, Facies and Sedimentation Trends
More LessDeltas are formed primarily by the action of a river (Barrell, 1912; Moore and Asquith, 1971; Bhattacharya and Walker, 1992). Variations in the proportion of wave, tide and river influence are thought to be the primary control on the delta morphology and facies organization (Wright and Coleman, 1973; Galloway, 1975). Recent work of modern deltas have recognized that many deltas exhibit a variety of morphologies and facies formed due the mixing of variable proportion of river-, wave- and tide processes, and longshore drift (Bhattacharya and Walker, 1992; Galloway and Hobday, 1996; Bhattacharya and Giosan, 2003). The mixture of delta types between and within discrete lobes manifests these variations. Deltas may also change from river-, wave- and tide-dominated phases in time, with changes in relative sea level, sedimentation rates and tectonics (Boyd et al., 1989; Bhattacharya and Walker, 1992; Dalrymple 1992). Wave influenced deltas are characterized by facies and morphologic asymmetries between the updrift and the downdrift sides of the delta (Bhattacharya and Giosan, 2003). Plan view of such deltas shows asymmetric distribution of environment and facies; the updrift side comprise of sandy strandplain deposit with the sand being derived from along-strike transport of older lowstand shelf sands, while the downdrift segment is constructed from immature, river derived sediment of both mud and sand. They form barrier islands and back-barrier lagoons and bays (Dominguez et al., 1987; Dominguez, 1996). The Pahang delta on the East coast of Peninsula Malaysia is an excellent example of modern, wave-influenced delta. Abdul Hadi and Mohamad Sakran (2004) describe the morphology and sediment dispersal trends along the Kuala Pahang coast. This paper attempts to analyze and discuss further the morphology, sedimentary processes and facies distribution, and the ongoing sedimentation trends of Pahang delta. This study is based on the analysis of topographic maps and aerial photographs (available for the last 30 years), field investigations and laboratory analysis of sediment samples collected along the Kuala Pahang coast, and analysis of recent satellite images of Kuala Pahang (1988-2000).
The Pahang Delta, the rivermouth of the longest river in Peninsula Malaysia (Pahang River), forms an assymetric deltaic cone at Kuala Pahang, on the east coast of Peninsular Malaysia (Figure 1, 2 & 3). The coastline between Tanjung Gosong-Kuala Pahang-Sungai Miang constitutes the central, most active part of the modern day Pahang delta. The coastline can be geomorphologically separated into : i) a northern, updrift sandy linear beach and strandplain complex, ii) a central river-mouth area at Kuala Pahang, and iii) a southern downdrift, well-vegetated micro-tidal, barrier-lagoon complex. The northern coast forms a broad strand plain consisting of multiple, beach ridges constructed from fine-grained, well-sorted and negatively skewed sand. Analyses of sequential topographic maps and aerial photographs shows that this wave-dominated beach forms an accreting coastline, receiving sand from river-mouths in the north and south, and reworking of shelf sediments. At Kuala Pahang, welldeveloped and extensive mid-channel, river mouth bars are of fine-to-coarse, moderately-sorted sand. The bars are progressively shifted seaward and drifted southward. The river-mouth area forms a transitory depositional basin for sediments from the Pahang River. Downdrift of the rivermouth, mud and sand drifted southward from the rivermouth formed several micro-tidal barrier-spit and lagoons complexes. The tide-influenced coast is an accreting beachfront, with mature barrier beaches and elongated lagoons. The sand here are moderate-to-poorly sorted. Three images of the Pahang coastline were acquired from MACRES; these images are from the year 1988, 1995 and 2000 (Fig. 3). Comparison of these images for the Pahang delta coastline from the year 1988, 1995 and 2000 clearly shows that the accretion and southward transport of sediment, which was also detected from the analysis of sequential topographic maps and aerial photos, is continuing. The most active site of accretion and transport is from the river mouth area at Pulau Syed Hassan, and at Tanjong Agas to Sungai Miang. These sites are clearly marked by the development of southward drifting sand spits. These images indicate that the delta is prograding in the southeastward direction via longshore drift, and in the north by the interaction of wave accretion and longshore transportation of sediments.
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Integration of Seismic Facies Body Extractions in 3D Reservoir Models
More LessThe interpretation and extraction of facies bodies from seismic attributes has become a key tool for optimal targeting of exploration, appraisal and production wells. During the past decade a large number of fields throughout the world have been discovered and successfully appraised using information on facies and reservoir distribution extracted directly from a variety of seismic attributes. As these fields enter into the production phase the seismic bodies also need to be properly integrated with existing well data in 3D reservoir models for in-place volumetric calculations, connectivity analysis and flow simulation studies.
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Nurturing Knowledge Sharing Practices to Close Knowledge Gaps and Building Capabilities in PMU
Authors Che Zan Hj Yassin, M. Rozaidee Harun and Ismail IsaThroughout years of exploration and development in E&P business, lots of successes and failures happen. Experiences staffs’ mobility have created knowledge gaps and therefore time consuming for building right capabilities timely to sustain the performance. These posters highlights on knowledge management initiatives and efforts implemented within PMU to support its business.
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Time-lapse study and acquisition of monitor survey over carbonate gas fields in Sarawak water, East Malaysia
Authors Bor-Seng Lee, Yip-Cheong Kok, Hua Zhu and Chee-Kiong NguTime-lapse feasibility study was carried out over two carbonate fields. The study indicated that 4D signal could be observed after 3 years of production over the fields. The 4D signal could be observed if the 4D non-repeatable RMS (NRMS) noise
level were 0.2 or less. Without previous 4D monitor survey been acquired in the area,
there was an uncertainty on how much repeatability was required to achieve a 4D
NRMS noise level of 0.2. A provisional value of 150m for delta source plus delta receiver (⊗S + ⊗R) error was used for planning purpose. In addition, the 4D monitor
survey could not be acquired at the same month as the base survey. This added
another uncertainty to the amount of repeatability that can be achieved in the 4D
monitor survey. To overcome these uncertainties and achieve as good repeatability as
possible, additional two streamers were deployed and a fair amount of time were
allocated to cater for 4D re-shoot of lines if required. The monitor survey started in
mid August 2005 and was completed in 20 days. The base survey lines (prime and
infill lines) were completed in 15 days while the remaining 5 days were used to
acquire 4D re-shoot lines. Feathering angle was used as immediate QC parameter while more comprehensive QC plots were generated after several lines were
completed before deciding on 4D re-shoot. 4D repeatability measurement of ⊗S + ⊗R at 2500m to 2575m offset indicated a better than 10m error were achieved for some of the line while majority of the lines were less than 75m. The survey achieved its 4D repeatability objective and preliminary processing has shown observable 4D signal.
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Integrated Multiwell Facies Analysis using Core, Borehole Images and Computed Logs - Muda and Jengka Fields
Authors Debnath Basu, Edna Malim, Tanwi Basu, Francis Advent, Ricky Majit, Alwin Djamaoeddin, Suwith Sitha and Nizam A. BakarThis study was commissioned in light of CPOC’s need to meet first gas production in 2008 from two gas fields, Muda and Jengka. The fields are within the Malay Basin and located in the Joint Development Area (JDA), straddling the border between Malaysia and Thailand, some 500km north of Kuala Lumpur.
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Evaluating Textural Changes and Bedding Characteristics Within Clastic Environments Using Electrical Borehole Images
Authors Steven M. Hansen, Edna Malim and Azlina HabibullahElectrical borehole images have been utilized to evaluate clastic environments for over 15 years. During this period an interpreter has classified textural changes only as visual features and all bedding characteristics manually. Now two new semi-automatic products have been developed to capture highresolution textural information from electrical borehole images, and characterize the bedding into bed thickness and bedding trends. These products will add attributes to image analysis that can supplant verbal descriptions of clastic textures. The first method, SandTex, analyzes the total image spectrum in a 1-in. interval around the well bore. An electrical heterogeneity index is calculated from the percentile resistivity distribution of the image spectrum. This resistivity spectrum can be divided into a well-sorted portion and the fractions that are either more resistive or conductive. The resistivities of these three fractions can then all be calculated. The second method, STRATA, is divided into two sections. The first section calculates a levelby-level percentages of sand, silt, shale, tight (cemented), and wet sand based on cutoffs applied to a calibrated image output and then integrates these outputs. The second section is used to calculate bedding density and thickness from three different methods. The bedding characteristics are computed from any or all of the following 1) changes in facies based on the cutoffs listed above, 2) the inflection point on a squared high resolution resistivity curve or 3) from a dip set whether hand picked or computed with an automatic dip computation algorithm. These outputs are calculated and displayed in measured depth (MD), true vertical depth (TVD), true vertical thickness (TVT) and true stratigraphic
thickness (TST).
These outputs, heterogeneity-index, fractional resistivities, variability, along with bedding measurement characteristics and associated open hole log data, can be combined to compute a facies description that captures the textural content of these clastic environments. This high-resolution analysis
can be used to verify the variations seen in nuclear magnetic permeability and relative pore sizes in a more precise geological context. By extracting pertinent information from electrical images, this technique makes image logs more accessible for use in petrophysical as well as geological analyses.
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Fault system analysis with automatic fault displacement estimates: an exploration case study from the Norwegian Sea
Authors A. Carrillat, H.G. Borgos, T. Randen, L. Sonneland, L. Kvamme and K. HanschA procedure for complex fault system analysis is presented where automated fault mapping technology has been coupled with an automated fault displacement estimate algorithm. This new technology is based on classification of seismic extrema identified on either side of the fault plane and allows generating a continuous measurement of the fault displacement along the fault plane and analyzing its variability in space. The driving concept is to enable a system level interpretation, where the interpreter or structural geologist focuses his attention and expertise on analyzing the fault system and quality control of the automatically mapped faults instead of doing manual interpretation work. The key elements characterizing a fault are now provided automatically and include for each individual fault plane: orientation, dip and azimuth, size, position, and statistics on displacement values such as minimum (10th percentile), median (50th percentile) and maximum (90th percentile) displacement. A visual representation of the fault displacement values on the fault plane helps understanding the orientation of paleo-stress and checking if is has a kinematic meaning. This new technology has been applied to a prospective field, characterized by deepwater, Cretaceous turbidite (probably distal) system off Norway and helped the characterization of two apparent polygonal fault networks located at different depth.
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M3 South Discovery in Central Luconia
Authors Donald Sim, Piet Lambregts, Guenter Jaeger and Nicholas TengIn 2003 SSB made a gas-condensate discovery, M3 South, in the prolific Central Luconia Province, 7 km south of the M3 gas field. M3S-1 was drilled in May 2003 on the crest of a steeply dipping carbonate pinnacle build-up. The well encountered 420’ of gas in a GDT situation and the well was abandoned after encountering drilling problems. Initial pressures from the exploration well suggested a much longer hydrocarbon column yet to be proven. An appraisal well was drilled in May 2004 with the successful deployment of pressurised mud cap drilling to handle occurring total losses. The appraisal well, drilled on the steep flank, successfully proved an 1100’ gas column. Pressure measurement suggests that M3 South is situated in a confined pressure setting, with a 400psi aquifer pressure increase from the surrounding fields (M1, Jintan, M3, M4). Gas analysis suggests that M3 South has a unique hydrocarbon source and migration pathway despite being located only several kilometres from producing fields. The steeply dipping flank of the pinnacle made seismic imaging and depth prognosis difficult. Initial PSDM imaging shows significant improvement in the internal imaging of the build-up. The exploration and appraisal campaign were planned using an integrated exploration, well engineering and development team. The benefit of this well coordinated effort was a smooth transition from exploration to production with the Field Development Plan being completed within 6 months after the appraisal campaign.
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Amplitude Extraction and Rock Properties Calibration (AVO Analysis)
More LessSeismic reflections are used in oil business to locate geological structures that have the potential to trap hydrocarbons. Geophysicists discovered that the presence of gas/oil often coincided with the presence of high amplitude reflections known as “bright spots.” The bright spot technique was found to have limitations in that factors other than gas or oil, could cause bright reflections. Wells drilled into “Bright spots” have encountered igneous intrusions, carbonates, hard streaks and wet sands. A more definitive test rather than bright spots detection on a stacked seismic section was sought for the direct detection of gas on seismic records. One such test is the analysis of amplitude variation with offset (AVO). Amplitude versus offset or AVO analysis has played an increasing role over time and is now becoming a routine part of exploration studies. The aim is to minimise the uncertainty associated with the prospect and improve the chance of drilling successful exploration wells. The overall objectives of the AVO analysis are as follows:
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2003 Petronas Tinjar 2d Land Seismic Survey Onshore Sarawak: Field Experiences
Petronas had acquired 520km of 2D Land Seismic Survey over Tinjar Province, onshore Sarawak in 2003 with the objective of identifying potential leads. Land seismic survey over Malaysia is rarely acquired by Petronas or other PSCs. The last survey was conducted over ten to fifteen years ago. The survey area covered different areas which include thick tropical jungle, swampy area and acacia plantations. A total of 520 kilometers of 2D seismic data was acquired within 9 months or equivalent to two hundred fifty five (255) days of operational work. Prospective areas or leads were identified based on Gravity and Magnetic Survey and Synthetic Aperture Radar (SAR) image studies conducted by Petronas. Trap styles in the Tinjar Province are large anticlinal trap with complex wrench-related faults. The structural closures are associated with NWSE dextral faults and NNE-SSW sinistral faults. Principal reservoir plays in the Tinjar province are the Oligocene-Lower Miocene (Cycle I/II) clastics located approximately 1500m deep. In the field, we were assisted by Petronas Representatives to explain regarding the
procedures and workflow sequences of Land seismic operations such as Rintis, Bridging, Recording, etc. In conclusion, we have gathered good field experience and better understanding of land seismic survey operations from the Petronas Tinjar Land Seismic Survey.
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Overview Of Recent Malaysia Oil & Gas Discoveries
More LessFrom the Petronas point of view, the bottom line is good and has been getting better for the last several years. Numerous exploration oil and gas discoveries have been made in Malaysia in Sabah, Sarawak and Malay Basins recently; and examples of many of these discoveries will be presented. The new discovery examples include novel play-types such as fractured basement, and new exploration concepts regarding carbonate pinnacle reef buildups and clastic turbidite fans. These discoveries were made in both shallow and deepwater environments - the larger of which continue to be located in deep water Sabah. The ability of the Malaysian petroleum industry to locate and discover both low CO2 gas structures within CO2 rich corridors, and oil prone discoveries where conventional wisdom expected gas-rich reservoirs will be mentioned. The multitude of new exploration trends available in conjunction with the inventory of undrilled prospects offers a myriad of opportunities for successful exploration, development and production in Malaysia. Some of these new opportunities will be presented.
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Global Exploration & Production Trends - Prospect Shortage….or Shortage of Prospectors
By Jack KerfootOver the last one hundred years, the oil and gas industry has experienced dramatic changes, including periods of expansion, contraction and price fluctuation. The industry can actually be characterized into three distinct periods, Public Sector Growth (1880 to 1935), National Oil Company Growth (1936 to 1985) and Public Sector Consolidation (1986 to Present). The paper address the cause and effects of each of the three periods, the changes that have occurred within public sector major operators, national oil companies and public sector independent operators and the overall impact of these changes on global exploration.
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