- Home
- Conferences
- Conference Proceedings
- Conferences
GEO 2008
- Conference date: 03 Mar 2008 - 05 Mar 2008
- Location: Manama, Bahrain
- Published: 03 January 2008
21 - 40 of 385 results
-
-
Jurassic sequence stratigraphy in the Raudhatain-Sabiriyah area of northern Kuwait
More LessExploration of multiple Jurassic carbonate reservoirs has increased after the discovery of hydrocarbons below the prolific Tertiary-Cretaceous section across Kuwait. The Jurassic of northern Kuwait has been studied in terms of sequence stratigraphy based on 2,686 ft of core and 12 borehole wireline logs. Six sequences have been identified. The key surfaces are sequence boundaries, maximum flooding and flooding surfaces. Each sequence comprises a transgressive systems tract (TST) and a highstand systems tract (HST). Sequence 1 corresponds to the Lower Marrat section, which consists of at least six carbonate/evaporite cycles. Sequences 2 and 3 are referred to the Middle Marrat where carbonates are arranged in shoaling upward parasequences ranging from
a few feet to 10s of feet in thickness. Sequence 4 corresponds to the Upper Marrat section where evaporites occur below an MFS revealing a transgressive depositional environment. The Dhruma and Sargelu formations comprise Sequence 5, whereas Sequence 6 consists of the Najmah shale overlain by Najmah carbonate. The study of cores, combined with petrophysical analysis, has identified seven different lithofacies: lime grainstones to packstones, lime packstones to wackestones, lime wackestones and mudstones, algal boundstone, crystalline dolomite, bituminuous calcareous shale and anhydrite. The results of the study show an improved understanding of the Jurassic carbonate depositional architecture, and its control of hydrocarbon generation and entrapment in northern Kuwait. The results will be used for further exploration and development work in the area.
-
-
-
Tectonic fracture network characterization in the giant Hassi-Messaoud oil field, Algeria
The objective of this presentation is to show the methodology used to characterize the tectonic fracture network in the giant Hassi Messaoud oil field located in Algeria. This field is characterized by a significant number of wells (One Thousand Five Hundred) and data of various origins and forms. The data includes borehole image logs in 100 horizontal wells, cores from 1,000 wells, 2,500 square km of 3-D seismic, as well as dynamic data (production, pressure and water/gas breakthrough) for most of the wells. The fractures are complex objects to analyze. Because their scale is greater than the diameter of the borehole, it is necessary to take into account all the indices (seismic, physical and dynamic) to characterize them. In the Hassi-Messaoud field, tectonic fractures are clustered and associated with faults, and/or organized in fracture swarms. When they are cemented and the matrix is damaged by silica, they behave as barriers. In contrast, when the fractures are open, they provide a preferential path for fluid flow. The fracture network induces anisotropy of permeability, which has a strong impact on the development of the field. A synthetic map, which combined all available information, was constructed to predict and model conductive and barrier trends. The fracture network characterization improved the development of this mature field.
-
-
-
Lateral facies variations of Upper Cretaceous carbonate ramp deposits, Jebel Nefusah, northwest Libya
More LessThe Upper Cretaceous (Cenomanian) platform carbonates of Jebel Nefusah, northwestern Libya, were deposited as part of a regional prograding low-angle ramp system. These deposits are well-exposed in the Jebel Nefusah area but are poorly documented in the literature. Strata in this area are relatively undeformed making this system ideal for the study of lateral facies variation. The Cenomanian Stage is a major cyclic transgressive event over the regional unconformity that overlies the Aptian-Albian fluvio-deltaic sandstones of the Chicla Formation. The system contains an extensive oolitic to rudist-rich member that serves as an alternative analogue for Middle Eastern reservoir-prone facies. Field stops at 17 localities and five detailed sections over an area of 200 km form the base of a stratigraphic correlation panel, including the stacking pattern and depositional context of the recognised members. A geological model is proposed showing three third-order systems tracts during Cenomanian platform evolution. The first unit (less than 40 m thick) consists of inner ramp, tidally-influenced shallowing upward sequences. The second unit is characterised by progradational, inner-ramp oolitic shoal (40 m thick), which pass laterally into the mid- to outer ramp bioclastic, rudist boundstone and rudstone facies. This facies is a regionally developed (more than 200 km wide) member, 4–8 m in thickness. The two units are known as the highly dolomitised Ain Tobi Formation. A third regressive unit, the Yefren Formation, reaching 80 m in
thickness, is formed by restricted inner-ramp marls with inter-bedded evaporitic gypsum layers. The depositional environment corresponds to a supra-tidal to sabkha setting. The architecture and geometry of the Cenomanian passive ramp system was controlled by eustatic sea-level changes rather than localised, abrupt tectonic events.
-
-
-
Seismic array response in the presence of laterally varying thickness of the weathering layer
Authors Jubran Akram and Abdullatif Al-ShuhailWavelet response analysis of seismic arrays is a more convenient and direct method of analysis than using their conventional time-harmonic responses. This is because wavelets, rather than sinusoids, are actually generated by the seismic source. This study involves an investigation of the effect of lateral variations in thickness of the weathering layer over the array length on the array response. Three types of variations were studied; namely, dipping-bottom boundary, channel and irregular bottom boundary of the weathering layer. The investigated parameters were the number of elements (12 and 24 elements), the weighting function (equal and triangular), the incident wavelet (Ricker and Klauder) and the error amount. The degradation in the root-mean square (RMS) amplitude responses generally increased with the error amount. RMS amplitude responses were more degraded in the channel case than the other two cases. Errors affected triangularly weighted arrays more than equally weighted arrays. Klauder wavelet
array responses were more affected by these errors than Ricker wavelet responses. Vertically traveling waves (i.e. signals) were more affected than the horizontally traveling waves (i.e. noise). Since these variations cannot be inferred from the surface topography, they can affect the array responses without being detected, unlike topographic and element’s positional errors. Therefore, it is recommended to test for these effects prior to array layout. Solutions to this problem are to record single-element
data and correct these during processing before summing, or to move the array away from the sources of these effects.
-
-
-
Stratigraphic framework of the Natih Formation in Oman
More LessCarbonates of the Albian to Turonian Natih Formation are important hydrocarbon reservoirs in Oman. A regional sequence stratigraphic study integrating seismic and well data of interior Oman led to a better understanding of the reservoir and seal distribution as well as the stratigraphic trapping potential. Deposition took place on an epeiric shelf with carbonate platform development at the ocean-ward margin, located in northern and eastern Oman, whereas clastics predominated along the exposed Arabian Shield in the southwest. Lateral shifts in clastic and carbonate facies belts, driven by changes in relative sea level and climate, resulted in a hierarchical stacking of depositional cycles of several 10s up to some 150 m thick. Two major flooding events, with widespread deposition of pelagic carbonates, occurred in the Late Albian and Late Cenomanian. Both are associated with the creation of significant depositional topography (up to 100 m) as a result of aggradational carbonate growth along the margin. This was followed
by a strong platform progradation over more than 100 km towards the interior of the epeiric shelf. Variations in the type and amount of sediment input, both in time and space, caused major variations in reservoir geometry and properties within these prograding complexes. A major fall in sea level in the Mid-Cenomanian led to exposure and channel incision of the platforms and a major influx of clastics. Fine-grained clastics also covered most of the Lower Cenomanian platform during the initial stage of the following relative sea-level rise. Quartz sands trapped between the exposed carbonate platforms may provide opportunities for stratigraphic traps.
-
-
-
Multi-disciplinary inversion of Earth models
Authors Olivier Dubrule and Igor Escobar and Danila KuznetsovNow that Earth-modelling packages are used routinely by most petroleum companies, efforts are under way to adapt multi-disciplinary data inversion techniques to better constrain these models by geological, geophysical and dynamic data. There is a convergence between techniques developed in various fields of application, such as Bayesian or geostatistical inversion, regularisationbased optimisation or data assimilation. Geostatistical conditional simulations are usually built using sequential gaussian simulation or by generating non-conditional simulations and conditioning them with a kriged correction. These approaches allow conditioning simulations by any kind of data, as long as these data can be approximated by a linear combination of the inverted
Earth model parameters. Kriging, the average of all realisations, gives the best estimate in a least-squares sense. This is illustrated by examples where we invert multioffset seismic data into higher-resolution realisations of the logarithm of P- and S-impedances. Sensitivities to the various input parameters, such as the variogram, are discussed in detail. In this linear context, a regularized inversion of borehole and seismic data should lead to similar results to those obtained by kriging. In the same
way, both geostatistical stochastic inversion and Kalman Filtering should produce similar a posteriori probability density functions of model parameters. Unfortunately, the forward model cannot always be approximated by a linear operator. This happens when production data must constrain a 3-D dynamic reservoir model. In these situations, algorithms such as Markov Chain Monte Carlo (MCMC) are required. Ensemble Kalman Filtering (EnKF) appears to be less time-consuming than many other MCMC methods, albeit it is not quite as rigorous. An example is given of a recent application of EnKF to an inversion problem on a UK field.
-
-
-
A novel approach to reservoir characterization using seismic inversion, rock physics and Bayesian classification scheme
More LessRock-physics analysis can provide the relationship between the parameters (or seismic attributes) that govern seismic-wave propagation (e.g. Vp, Vs and density in isotropic media) and the reservoir property of interest, such as rock or fluid type, porosity, pressure and saturation. In this process, we need to account for the quality of the seismic data and derive the appropriate uncertainties associated with the seismic data, such as noise, resolution, and inversion artifacts into the reservoir property estimation. In this presentation, we show how to quantitatively propagate seismic data quality issues such as resolution, noise, and inversion accuracy into the lithology estimation in a clastic basin. The method consists of several steps: seismic inversion to obtain elastic
parameters, petrophysical well-log analysis to define a classification scheme based on Bayes’ Theory and probability density functions (PDF); upscaling the PDF’s to seismic scale using Backus’ Theory and finally, applying the final scheme on seismic attributes (Vp, Vs and density) derived from the first step. The use of full-waveform inversion and Bayesian classification techniques provides a mathematical framework that enables us to model and directly relate data quality input into the uncertainty associated with reservoir properties prediction. The final output of this process is a map in 2-D and a cube in 3-D, of rock and fluid types with confidence levels associated with each property at each common mid-point (CMP) and time sample. We illustrate the
procedure with examples from several clastics basins: Gulf of Mexico and India. This methodology can be easily applied to data from carbonates areas as well where inversion techniques are known to yield porosity, pay and fracture properties.
-
-
-
Designing seismic surveys in Greater Burgan field, Kuwait, utilizing forward modeling concepts
The Greater Burgan field consists of the Burgan, Magwa and Ahmadi structures. The Burgan structure is an anticlinal dome with a large number of faults. The three main reservoir units in the Greater Burgan field are the Wara, Mauddud, and the massive Burgan sandstones. The deeper reservoirs, namely the Lower Cretaceous Ratawi and Minagish limestones and the Jurassic Marrat Formation also contain significant oil reserves but are less substantial. Between 1976 and 1987, 2-D seismic data were acquired across the field. From 1996–1998 3-D conventional seismic data was acquired and during 2005, two pilot surveys were acquired utilizing single-sensor technology to assess the applicability of this technology in enhancing both spatial and temporal resolution.
Processing and analysis of legacy and single-sensor data indicated that the signal/noise ratio and bandwidth of the reflection response might be strongly influenced by near-surface transmission effects. We used finitedifference modeling to understand these effects and to test whether various acquisition techniques employing surface and buried sources and/or receivers might improve data quality. Near-surface visco-elastic property estimates, derived from log data, combined with geostatistical simulations of lateral Earth properties were used to generate 1-D and 2-D models. These data were processed to illustrate the effects of the shallow geological section on deeper reflection returns. It is anticipated that based on this study future field trials can be designed so as to provide a step change in the seismic data quality in the Greater Burgan field.
-
-
-
Controlling structural uncertainties in static and dynamic modeling of faulted reservoirs
More LessModeling and reservoir management became an issue in an highly faulted onshore Abu Dhabi field. This presentation reviews the methodologies of controlling structural uncertainties in building the 3-D geological model for the reservoir. The great number of faults and their components such as throw, continuity and segmentation were the major issues in building the structural framework of the model. Integration of well logs and seismic data was implemented to enhance the seismic interpretation, aiming at defining the sub-seismic fault patterns, types and throws. Special attention was focused on the conductive nature of the fault plane and the communication among reservoirs. The driver behind this analysis was the recognition from available dynamic sources that the reservoir zones at the fault planes act as hydraulic communication corridors and have a controlling influence on the reservoir development strategies. Moreover, fault information derived from different seismic interpretation has not effectively clarified the issues. More than 30 wells that intersect faults were reviewed to define the fault throws accurately. The throw of many faults were found to be greater than interpreted from seismic data. Other faults were characterized as fault zones composed of many sub-seismic faults. In addition, the borehole image logs over the fault zone indicated conductive features within the fault plane. This investigation improved the understanding of zonal juxtaposition at the faults and the potential of hydraulic communication pathways between the reservoir zones. As a consequence of this work, both the 3-D static and dynamic models became more robust.
-
-
-
Well placement services used in optimizing production in a large carbonate reservoir
Authors Osama El-Gendi, Rafael Cullen, Waleed Jawad and Sr.and Marian PopescuThe Ratawi reservoir in the Wafra field is a Lower Cretaceous oolitic limestone located in the Partitioned Neutral Zone between Kuwait and Saudi Arabia. The development of the field started with 95 vertical wells, which were drilled between 1956 and 1999. The strong water drive resulted in severe coning in the vertical wells in 1999, a very successful campaign of horizontal drilling commenced (new drilling and horizontal sidetracks). As a result, Ratawi production increased 50% in a 2-year period. The horizontal development plan can be divided into three phases: (1) 1999–2002: 53 horizontal wells were drilled geometrically, using only MWD/gammaray measurements; (2) 2003–2004: 41 wells were drilled using geostopping strategy based on resistivity; and (3) 2005 to present: 26 wells were drilled by geosteering, well placement, using the geological and log-while-drilling resistivity forward model. In this phase geosteering was crucial to remain in a very narrow target of ± 5 feet from the top of the pay zone and away from water coning, water breakthrough and the current oil water contact. Due to the successful implementation of the well placement services, all 20 planned horizontal sidetracks wells for 2007 will be drilled using this method. This case study highlights the benefits of steering in field development in terms of efficiency improvements in geological analysis. It also shows how well-steering decision-making maximized oil production through optimum well placement.
-
-
-
Locating and evaluating bypassed oil in the Minagish Oolite reservoir, Minagish field, West Kuwait
More LessLocating and producing bypassed oil due to water injection is one of the most challenging problems in reservoir management. A successful case from Minagish field in west Kuwait is presented. The Minagish Oolite reservoir is a limestone sequence, about 400 ft thick, whose facies consists of high-permeability ooidal grainstones, interbedded with low-permeability facies that act as baffles and barriers. A tarmat zone is known to occur at the base of the oil column leg. Integration of well-surveillance, geological and 3-D seismic data led to a better understanding of the distribution of bypassed oil above the oil-water contact (OWC) and/or tarmat. Also simulation sensitivity study included core studies, analysis of offset wells, and inverted 3-D seismic data indicated the possibility
of high oil production rates. A 78° deviated well was drilled down the northeast flank of the Minagish structure. The geological uncertainties associated with this well path were: (1) structural top; (2) reservoir quality; and (3) the presence and thickness of tarmat zone(s). To minimize the risk associated with these uncertainties, two advanced measurement technologies were utilized while drilling. A magnetic resonance imaging LWD (logging-while-drilling) tool was employed to characterize fluids in real time to discriminate bypassed zones of light oil from tarmats. Also, laser-induced breakdown spectroscopy was used to measure the elemental geochemistry of cuttings while-drilling, in order to chemostratigraphically confirm borehole position and identify tarmats. Tarmats could be identified with this technology from elevated levels of Ni and V (and sometime S) in the tar mat zones. Use of these technologies resulted in the identification of two zones of mobile oil in the upper reservoir above the tarmat, as well as a highpermeability layer influenced by water coming from nearby injector wells.
-
-
-
Effect of clay content on Tertiary oil recovery
More LessThis work deals with the study of oil displacement by surfactant slug driven by a protective slug of a polymer solution against the driving water. The study is performed on a dimensionally scaled laboratory model. The used porous medium consists mainly of packed sand, but with variable percentages of clay. The results indicated that the recoverable oil is generally affected by both the surfactant slug concentration and clay content. It is directly proportional to the surfactant slug concentration and inversely to the clay content. An optimum value of surfactant slug concentration at each clay content was also determined. The Tertiary oil recovery of a sandstone reservoir, like that of the Rudeis formation pay zone in July oil field can by increased with increasing the surfactant slug concentration according to three considerations: (1) In the case where the clay content is less than 10%, it is more efficient to use a large pore volume of surfactant slug with low concentration 4–5% (2) For clay content greater than 15%, it is recommended to use a small pore volume of surfactant slug, with high concentration (greater than 5%) to compensate for the surfactant loss and consumption. (3) When clay content exceeds 20%, it is not recommended to use the surfactant polymer flood method.
-
-
-
Near-surface attenuation estimation of P and S waves from Middle East data
Authors Nizare El Yadari and Fabian Ernst and Wim A. MulderSeismic waves propagating through the Earth are attenuated by conversion of a fraction of the elastic energy to heat. In seismic studies, attenuation provides more information about rock properties than available from seismic velocities alone. This is particularly important for the characterization and monitoring of hydrocarbon reservoirs because attenuation affects both the amplitude and the phase of the seismic data. In laboratory, as well as field measurements, accurate estimation of attenuation is difficult since seismic amplitudes are not only affected by intrinsic damping, but also by other mechanisms such as geometrical spreading, reflections, refractions, scattering and topography. These effects should be accounted for if we want to measure the true intrinsic
attenuation. Current attenuation-estimation methods lack accuracy and rarely use the complete seismogram for recovering attenuation properties. To improve this situation, we developed a method to recover the nearsurface attenuation properties for realistic geological settings. The method was based on visco-acoustic wavepropagation modelling and included the influence of the source wavelet and the presence of significant surface topography. The technique provided an acceptable result when applied to a data set recorded in the Middle East. Here, we extend the method to the visco-elastic case. Numerical simulations and measurements on field data demonstrate its effectiveness.
-
-
-
What would be the minimum subsurface information before making a decision to develop the field? A case study from El Toor field, Muglad Basin, Sudan
Authors Musab Mohamd Elamhi and Ahmed Abdalla MohammedThe El Toor field was discovered in 1996 and oil production started in early 2000. Cumulative production as of 2004 was 34 million stock tank barrels (MMSTB). El Toor is a fault-bounded anticlinal structure in the Muglad Basin, Sudan. The main reservoir consists of the sandstones of the Lower Cretaceous Bentiu Formation. The Upper Cretaceous Aradeiba E and F sands are secondary oil accumulations. Both sandstone reservoirs are layered and separated by continuous barriers over most of the field. After one year of sustained production, wells started to produce water. Both PCP and ESP are used for artificial lift. A team from the Sudanese Petroleum Corporation (Sudapet) has conducted a field development plan (FDP) to evaluate long-term production, reserve
estimation and techno-economics. The El Toor field FDP will be presented as a case study. The FDP study maximized our geological and reservoir knowledge of the field and specifically the lateral quality of the reservoirs. The subsurface information that was required for the FDP included: (1) seismic data control; (2) structure maps; (3) pay-zone thickness; (4) facies information; (5) petrophysical data; (6) core analysis; (7) fluid contact; (8) fluid properties; (9) water salinity; (10) estimated original-oil-in-place; and (11) well test analysis. The Greater Nile Petroleum Operating Company provided Sudapet with all the available subsurface data. The main problem was the lack of core and VSP data and accordingly data from neighboring fields was used. This resulted in uncertainty for the seismic velocity and difficulty in correlating core porosity to log porosity. The study recommended cutting cores and running vertical seismic profiles (VSP) in the future infill wells.
-
-
-
Potential of Iraqi oil system
By Karim AkrawiEarly exploration surveys in Iraq started at the end of 19th Century. In 1901 the first exploration well in the Middle East, Chai Sorkh-1, was drilled in northern Iraq by a German Company. In 1909, using an old cable tool drilling rig, the first discovery well, Chai Sorkh-9, encountered heavy oil. The first commercial discovery in Iraq was in the Naft Khan-1 well near the Iranian border. In 1925 the Iraq Petroleum Company (IPC) obtained a concession agreement that covered nearly all of the country for 75 years, without relinquishment. In 1927, the first significant oil discovery in Iraq was in well Kirkuk-1, which tested about 100,000 barrels of oil per day. The Iraqi resources are unique when compared to other Middle East countries because Iraq is one of the vastest and least-explored countries in the region. It has an ideal petroleum system with multiple source rocks, reservoirs, cap rocks and trapping systems. The petroleum system extends from the shallow Cenozoic down to deep Paleozoic sequences. Iraq may prove to have one of the greatest petroleum resource bases in the world, with potential oil resources in excess of 215 billions barrels and proven reserves in the region of 114 billions barrels. Moreover, its exploration and development costs are low – amongst the lowest in the Middle East countries. Iraq also is estimated to contain at least 110 trillion cubic ft of natural gas. The country is a focal point for regional and international security issues. Nevertheless, Iraq’s oil is especially attractive to the major international oil companies for several reasons including geographical location, low-risk exploration, low cost per barrel, good oil quality, multiple pipeline access and huge recoverable reserves.
-
-
-
Diagenetic history and its control on reservoir properties in a heterogeneous carbonate field, Kangan/Dalan Formation, Iran
A section of 445 m through the middle-upper Khuff Formation from three wells was selected for the study. A detailed description of the depositional facies and depositional cyclicity was first performed. The diagenetic processes were described by investigating more than 800 thin sections. A paragenetic sequence was established and the most important diagenetic processes with respect to reservoir quality were identified. All thin sections were described and categorized according to diagenetic facies. Important factors in this type of classification are mineralogy, cement type, cement volume and poretypes. The distribution of diagenetic facies will typically not correspond to the lithofacies distribution, since similar lithofacies may be subjected to different diagenetic
processes, even within short distances. However, a higher-order correlation between sedimentary units and diagenetic facies can be demonstrated. The study has shown that this reservoir has been subjected to heavy diagenesis and that these processes, to a large degree, have altered the primary properties of the sediments. A better correlation between reservoir quality and diagenetic facies, rather than to sedimentary facies, can be demonstrated. The diagenetic overprinting therefore has a major control on reservoir quality distribution in the section, which therefore has important implications for the fluid-flow properties of the reservoir. The diagenetic facies have been grouped into associations according to their reservoir properties. These groups were identified with a high level of confidence on wireline logs making it possible to predict diagenesis and reservoir type outside cored sections.
-
-
-
Geophysical reservoir monitoring: Where we are!
In our land environment, areal reservoir monitoring is not just 4-D seismic. It can best be achieved by a combination of various geophysical techniques integrated with well-based surveillance methods. These techniques include active seismic (surface and downhole), passive seismic (microseismic), surface deformation (GPS and satellite), electromagnetic induction, and gravity measurements. Enhanced oil recovery (EOR) projects are the prime candidates for the application of geophysical reservoir monitoring techniques because of the expected large acoustic effect and the large potential value. With EOR techniques becoming ever more important the use of reservoir monitoring techniques will increase significantly. Over the years several blockers for time-lapse
(4D) seismic have been identified including: (1) limited changes of acoustic properties at seismic scale caused by low yearly production rates, (2) poor sweep, (3) stiff carbonate matrix, (4) dense surface infrastructure, (5) small areal scale of an injection pattern, (6) lack of suitable baseline surveys, and (6) difficult reservoirs. The critical success factor for those geophysical reservoir-monitoring projects is the full integration with the well-based monitoring data into the dynamic reservoir model. Involvement at the beginning of a field development program by geophysicists is essential for the success of such projects, as tailor-made solutions require adequate attention for project management, scoping, justification, technical design, tendering and contracting. Based on recent experiences a five-step approach evolved for geophysical reservoir monitoring projects. These include: (1) opportunity screening and selection of relevant technologies, (2) detailed design, (3) implementation, (4) data acquisition and processing, and (5) detailed integrated interpretation.
-
-
-
A fully-integrated approach for rock typing: A new approach to reservoir characterization
More LessThe goal of this study was to develop a methodology for rock-typing in reservoir characterization and modeling. Our proposed method is a multi-disciplinary approach to identify the optimal number (statically and dynamically) of effective rock-types from well logs, core descriptions, routine core analysis and Special Core Analysis (SCAL) data, based on partitioning, correlation and comparability. This approach was used with the aid of multi-variate statistical and neural-network methods. The method consisted of three parts: (1) data partitioning and electrofacies determination using multi-variate statistical methods of Principal Component Analysis (PCA), cluster analysis and neural networks, to classify the data into a desired number of electrofacies; (2) electrofacies-derived correlation with core descriptions using correspondence analysis for the identification of an optimal number of static rock types; (3) dynamic rock-typing (DRT), which is determined by the interpretation of SCAL data (capillary pressure and relative permeability curves) within flow units. We applied our technique to a recently discovered giant carbonate reservoir in southern Iran. We focused on limited data from six exploration wells and sought more accurate results to define rock types for an effective
model and reservoir simulation. In this reservoir, by applying the proposed methodology, seven electrofacies were identified from well log data. By using correspondence analysis on the identified electrofacies and core description facies, five static rock types were recognized. At the final stage, two dynamic rock types in which fluid flow occurs were obtained using SCAL data of available core samples.
-
-
-
Ara stringer carbonate modelling: A case history
More LessThe Ediacaran-Early Cambrian Ara Group intra-salt carbonates located in the South Oman Salt Basin are a unique hydrocarbon system, which currently produce oil and gas from the oldest (producing) reservoirs to be found. The depositional model, facies associations and subsequent diagenetic overprint of these reservoir units provide a challenge to reservoir description and static model construction. A field in southern Oman offers an excellent example of how these reservoirs are modelled. The first step is to capture the uncertainties in facies architecture and property distribution. The second step involves integrating these uncertainties iteratively with dynamic data to produce a robust reservoir model. The field was discovered in 1978 and was brought on stream
in 1982. With ever increasing gas-to-oil ratio (GOR), additional oil production is constrained by the ability to handle the produced additional gas. A robust depositional model exists for the A4C Ara Group carbonate stringer. The reservoir zonation is based on sequence stratigraphic correlations that form the framework for the reservoir architecture and reservoir zones. Reservoir properties are highly variable. There is evidence for a porosity/depth trend, which may or may not be related to porosity reduction below a hydrocarbon-water contact. There is pervasive salt, anhydrite and bitumen plugging throughout the reservoir, however the effects of these plugging agents are localised. The A4C stringer exhibits an excellent relationship between facies and porosity, with porosity modelling biased towards facies, using facies transition simulation. There is no evidence of compartmentalisation, as confirmed by interference and formation pressure data, which exhibit good connectivity and communication between the wells. Flow units have been identified based on the integration of static and production log data. These have improved the history-match for the field and also our ability to predict production and GOR from the producing wells.
-
-
-
Supporting exploration and production with satellite radar data processed by means of the PSInSAR™ technique
More LessPermanent Scatterers SAR Interferometry (PSInSAR™) is today one of the most advanced and successful remote sensing technology used for surface deformation monitoring. In PSInSAR™ long series of satellite radar acquisitions, gathered repeatedly over the same target area, are processed. The analysis resolves, with millimetric precision, surface motions and small-scale features, including displacement rates of individual targets as oil pump, pipeline, plants, buildings, etc. PSInSAR™ data provides a depiction of spatial deformation over the surveyed area with an unprecedented accuracy. Information about surface displacements leads to a better understanding of the terrain and better coordination of production drilling. During production, the possible risks to the local environment can be continuously monitored. The dynamic of ground displacements of an oil-field area in the Middle East, subsidence phenomena and seismic faults in North America and Europe are some of the case studies that will be presented. These
examples will show the potentialities of the PSInSAR™ in assessing the environmental impact of drilling activities and storage areas.
-