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EAGE/FESM Joint Regional Conference Petrophysics Meets Geoscience
- Conference date: February 17-18, 2014
- Location: Kuala Lumpur, Malaysia
- Published: 17 February 2014
1 - 20 of 43 results
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Tackling Diagenesis: Rock Physics Models Applications into Advanced Petrophysics
Authors S. Vorobiev, M. Altunbay and K. B SallehSummaryDiagenetic changes intensely impact petrophysical properties of reservoir rocks. In particulary permeability and tortuosity. Changes in tortuosity influencing cementation exponent and thus saturation evaluation as well. In fractured and vuggy carbonate reservoirs permeability evaluation is impossible without knowledge of porosity components (intergranular, vugs and fractures). Rock-physics templates allows continous evaluation of the diagenetic changes. This paper demonstrates simple and yet elegant solution for the variable cementation exponent evaluation, involving rock-physics workflows. In addition to this new rock-physics model for fractured and vuggy carbonates has been introduced. The model allows either simulate acoustic respond in the fractured and vuggy carbonates. Alternatively porosity components evaluation can be done using measured shear velocity. The evaluation results have been compared to the Image logs. The comparison shows remarkable parity between rock-physics driven porosity components and Image analysis results.
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From Segmentation of Shale Rocks FIB/SEM Images to Properties Simulation and High Resolution Mineralogy
Authors G. Tallec, D. Lichau, D. Lattanzi and N. CombaretSummaryNew segmentation techniques applicable for 3D FIB/SEM shale rock samples can be used to accurately extract the pore structure and minerals.
Combined with BSE and EDS electron microscopy images fusion, the mineralogy can now be obtained in real time at a high resolution.
From these initial steps, material properties such as absolute permeability and molecular diffusivity can be obtained in a reasonable time, taking advantage of modern graphic hardwares.
This will be presented as a complete workflow for core analysis.
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QI Rock Property Models for Reservoir Characterization: Velocity-porosity Example
By S. GelinskySummaryA common goal of quantitative seismic interpretation (QI) workflows is to derive the reservoir properties we seek from the remote sensing data we can record. We describe the crucial role QI rock property models play in establishing this link. To illustrate the connection we focus on sandstones and describe in some detail how compressional and shear velocity information (VP and VS) can be related to porosity and what controls those relationships. We discuss useful velocity-porosity bounds which we utilize to constrain key model parameters and demonstrate our clean sandstone endmember workflow with a real data example.
When building a velocity-porosity model for clean endmember sandstones we find it useful to assemble reservoir-specific models that typically are dominated by local sorting changes related to depositional processes that yield fairly flat velocity-porosity relationships. We typically succeed matching modified HS+ Bounds to our data to constrains both sorting and composition. The resulting reservoir-specific models are only valid for similar compaction and cementation conditions – to extrapolate deeper or shallower, the velocity-porosity change caused by the related difference in diagenesis is provided by the HS+ Bounds.
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Discriminating Depositional Facies from Elastic Logs in the Malay Basin
Authors J. Rindschwentner and S. RaeSummaryThis case study from the Malay Basin demonstrates how the incorporation of elastic logs in the interpretation and correlation of sand bodies can help to discriminate different depositional environments within one reservoir unit. This can have a significant impact on understanding the architecture of a fluvial/ tidal estuarine reservoir of considerable complexity, which is vital for building appropriate static and dynamic reservoir models. Without such understanding, well placement becomes a gamble, which can result in unsuccessful wells and lower recovery.
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Improved Geological Inference from Seismic Data Using Composite, Colour-blended Seismic Attributes
Authors G.S. Paton, N.J. McArdle and J. HendersonSummaryCombining seismic attributes, such as the outputs of frequency decomposition, with 3 channel (RGB/CMY/HSV) colour blending has become a standard tool in seismic interpretation for highlighting depositional geometries. The techniques are powerful because they convey information in a highly intuitive manner and therefore provide a very efficient mechanism for developing an enhanced understanding of the imaged geology. However, the interpretation of information presented in this way is highly subjective and the results are difficult to calibrate. This is linked with the non-uniqueness of the causes of amplitude variations in seismic reflectivity data. Currently, there is a lot of work being done to determine whether examination of the seismic amplitude frequency spectrum can help resolve some of the ambiguities associated with conventional amplitude analysis. In this paper we look at additional methods for increasing the understanding that can be gained from frequency decomposition and colour blending of seismic attributes and examine whether extensions to these methods have the potential to allow objective analysis of the images produced for differentiation of fluid and thickness effects from 3D seismic data.
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The Limitation of 4D in Feasibility Study and Interpretation of Carbonate Field, a Case Study in Central Luconio, Sabah
By A. NurhonoSummary4D seismic reservoir monitoring is a relative new technology consists of repeating 3D seismic survey in order to make time-lapse images of the fluid and pressure fronts as they move in a subsurface reservoir during hydrocarbon production. When successful, 4D seismic can locate areas of bypassed gas and or oil for new drilling opportunities, map out water flooded areas to avoid the costly mistake of drilling new wells into swept zones, and identify the geometry and nature of reservoir flow compartments that are the key to optimizing hydrocarbon recovery.
A successful 4D seismic is depends on repeatable acquisition and processing the monitor with base seismic 3D surveys to achieve detectability responds to production history changes. As the 4D seismic is commonly expensive,feasibility study is required to decide the value of business. we demonstrated a example of integrating Petrophysical and Seismic followed with 4D interpretation. Its limitation of using seismic amplitude differences was analyzed and qualitative “Two End Members” as a possible “Original and Current Hydrocarbon Contact” with its limitation was evaluated.
Finally, recommendation from qualitative to a quantitative 4D elastic inversion is proposed. Despite that its not tested yet, a successful case demonstrated in Norway using this kind of approach.
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Quantitative Investigation of Microstructures within Porous Rocks by Using Very High Resolution X-ray Micro-CT Imaging
Authors G. Zacher, M. Halisch, P. Westenberger, T. Paul and J.W. TehSummaryToday’s high-resolution X-ray CT lends itself naturally to geological and petrological applications. Those include the non-destructive interior examination and textural analysis of rocks and their permeability and porosity, the study of oil occurrences in reservoir lithologies, and the analysis of morphology and density distribution – to name only a few. Especially spatial distribution of pores, mineral phases and fractures are important for the evaluation of reservoir properties. All presented geological CT volume evaluations were performed with GE’s phoenix nanotom, a 180 kV/15W nanofocus CT system for extremely high-resolution.
In our first sample we will show a typical reservoir rock scanned with 1 µm voxel size to characterize the pore space and to extract information about the distribution of mineral components. The segmented in-situ porosity could be easily used for fluid flow modelling purposes, to predict permeability and complex flow processes within these structures.
Next, two very porous pyroclastic rock samples have been examined at a resolution of 1 and 5 µm. One data set has been analysed with the Avizo software tool XLab Hydro. Besides permeability tensor, porosity and pressure drop, the resulting velocity field of the fluid particles can be directly visualized whereas the colour mapping indicates the velocity’s magnitude.
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Borehole Measurement and Significance of Mass-transport Deposits Offshore Borneo: Pores to Mega-structures, the Good, the Bad and the Ugly
Authors A. Bal, N. Hardikar and K.K. KyiSummaryDeep-water deposits (derived from gravity-driven processes) are significant exploration and production targets offshore Borneo. Some of these deposits, such as turbidities provide excellent quality reservoirs, however the interbedded mass-transport deposits comprising slides, slumps and debris flows, within the study area, do not. An increasing amount of borehole data from off-shore Borneo shows that these deposits present challenges to their interpretation if the geology is not considered and integrated into the formation evaluation workflow. Case studies presented here show how identification and interpretation of slumps helps to explain: fluid-type distribution, the ability to acquire formation pressures, and also changes in large-scale paleoslope, potentially diverting sand (reservoir) fairways. These case studies show the value of understanding the geology and the crucial role it plays in formation evaluation and characterising the reservoir from pore-scale to mega-structures. Underestimating, or not appreciating this value, risks ineffective use of resources, by-passed pay, or even abandonment of a potentially productive well. It is recommended that formation evaluation campaigns adequately capture the data required for geological interpretation. In summary it is necessary to integrate geology with petrophysics and reservoir engineering to understand the good, the bad, and the ugly.
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Hierarchical Facies Modeling Driven by Core: A Case Study from Samarang
SummaryA novel approach focused on core driven hierarchical facies association for static modeling has been pioneered in the Samarang field, offshore Sabah. The field is located in a structurally complex area representing paleo shoreface environment. The structure as interpreted from the Seismic represents a crestal collapse area. The area of interest is Late Miocene shallow marine section showing repeated progradation and retrogradation within a major regressive clastic wedge that was building towards the NW. Individual Samarang reservoirs were interpreted to portray wave/storm dominated sand bodies forming in upper to middle to lower shoreface and offshore transitional environments, accumulating in a coastal to inner shelf. The upper to middle shoreface sandstones typically were good reservoir quality - massive to laminated sands, whereas the lower shoreface to offshore transitional environment was characterized by poor-quality, bioturbated to heterolithic sands that were formed as event beds during storms. The shales were typically formed in the offshore inner neritic shelfal environment.The methodology described above, provides a robust integration in facies modeling workflow whereby core-driven facies association in a shoreface environment have been captured, characterized, and represented in static and dynamic models.
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Integrated Core-log and Seismic Analysis for Evaluation of Reservoir Potential in Unconventional Plays
Authors A. Paxton, D. Handwerger, R. Suarez-Rivera and L. SonnelandSummaryEfficient characterization of unconventional plays to define reservoir potential and producibility is of great economic and strategic importance especially during the early phases of exploration.
Unconventional reservoirs are predominantly heterogeneous systems with lateral and vertical variability in rock properties, texture and composition driven by the geologic processes of deposition and diagenesis.
We present a methodology for regional detection of rock heterogeneity based on the relationships between texture, composition and rock properties, and the effect these have on log and seismic data measurements, to identify rock classes with similar responses, and thus similar anticipated rock properties. Core measurements are used to define reservoir quality and completion quality properties for each of the principal rock classes.
The resulting Heterogeneous Earth Model identifies the distribution of regions of highest interest and lowest opportunity in the play, and can assist with optimal well placement and strategic sampling to maximize the time-value of the well log and core data acquisition.
This flexible approach facilitates effective early to mature exploration decisions of reservoir quality and potential productivity. An example of the application in the Haynesville is discussed.
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Developing Saturation Height Models for Brunei Fields; Maximizing the Value of Available Capillary Pressure Data
Authors W. D. Alger and E. van den HeuvelSummarySaturation evaluation from petrophysical logs is problematic in Brunei reservoirs due to the clay rich formations. Laminated and disseminated clays are common throughout reservoir units resulting in a suppression of resistivity log responses. Saturation height models based on capillary pressure data are often not possible as core recovery and the vintage of much of the core results in limited special core analysis measurements.
Through careful quality control of capillary pressure curves a combined database covering all major Brunei reservoirs has been compiled. Saturation trends from capillary pressure curves based on reservoir permeability have been developed and shown to be consistent across the combined field's data. This larger data set enables development of robust saturation modelling trends for fields with a very limited capillary curve database.
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From Core to Well Log: the High Resolution Scratch Profile to Reduce the Effect of Heterogeneity and Resolution Lengths
Authors T.R. Richard, Z. Zulkiflu and C. GermaySummaryThe description of well bores surrounding relies heavily on wireline logs that are intensively used providing extensive but only qualitative data that must be correlated against quantitative petro-physical measurements carried in the laboratory on core samples. The empirical correlations derived between well log data and plug measurements is in part governed by the mismatch between the spatial resolutions of wireline log, typically of the order of one foot and the characteristic scale of plugs, typically of the order of few centimetres. The inherent up-scaling associated with the correlations is affected by (i) the level of heterogeneity commonly smaller than well log resolution and in some instance even smaller than the plug size and (ii) the plugging strategy.
The scratch test yields a log or profile of a direct measure of rock strength with a spatial resolution of the order of the centimetre. This high resolution log of a physical property provides a unique measure of the spatial distribution and length scales of heterogeneities along core samples and eventually can bridge the gap between the length scales associated to core plugs and well logs.
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AML Makes Mudlogging from Underdog to Game Changer, and Workhorse for Unconventionals
More LessSummaryDuring the past ten years, several parties have spent major efforts to advance the capabilities of mudlogging techniques. Thus at present Advanced Mud Logging (AML) can provide a suite of high quality logs, using (1) high frequency, improved accuracy monitoring of all drilling related parameters; (2) enhanced cuttings image acquisition and processing; (3) direct measurements on cuttings, including grain density, porosity, spectral Gamma Ray (GR), Nuclear Magnetic Resonance (NMR), X-ray diffraction (XRD), X-ray Fluorescence (XRF); and (4) sophisticated mud gas analysis capabilities, providing quantitative compositional, including isotope, analysis. AML thus can thus deliver integrated, comprehensive Petrophysical Information Logs (PILs) as a first aid for well evaluation, and facilitates improved monitoring and thus optimisation of drilling operations.
The power of AML will be illustrated with examples from the above mentioned areas, including excellent matches with acquired wireline logs, unequivocally demonstrated added value for drilling operations, both well control and drilling optimization, and AML providing petrophysical evaluation information where conventional systems simply cannot measure the parameters required for a complete evaluation.
With these sorts of technical capabilities, AML has numerous applications, including especially challenging unconventional resource evaluations, where conventional methods just fall short of requirements.
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Constraining Petrophysics with Rock Physics
By M. SamsSummaryIn the context of seismic reservoir characterisation the availability of high quality and consistent petrophysical analysis is essential. Achieving consistency is often compromised by poor data quality, lack of sufficient data and ambiguities in the data. Rock physics modelling can help to improve the consistency by ensuring that the petrophysical interpretations are also constrained by the elastic logs. There are three ways that rock physics can be used. First as a simple quality control, second to provide quantitative feedback to the petrophysics and third in a joint interpretation. The choice of method depending on the confidence achieved in the rock physics model.
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Acquiring Remaining Gas Saturations in a Pilot Hole Drilled from a very Extended Reach Drilling Well in a Mature Field
Authors A. OConnell, H.F. Lee, G. Warrlich and A. MukhopadhyaySummaryAn out-stepping appraisal pilot hole was drilled away from centrally clustered producing wells in a carbonate field operated by Sarawak Shell Berhad. This presentation outlines the planning involved prior to drilling the well which had the rare opportunity to drill below the original gas-water contact in a producing field. Part of the appraisal content of the pilot hole was to acquire residual gas saturations.
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Estimation of the Petrophysical Model through the Joint Inversion of Seismic and EM Attributes
Authors F. Miotti, I. Guerra, F. Ceci, A. Lovatini, M. Paydayesh, G. Milne, M. Leathard and A. SharmaSummaryReservoir characterization objectives are to estimate the petrophysical properties of the prospective hydrocarbon traps and to reduce the uncertainty of the interpretation. In this framework, we present a workflow for petrophysical joint inversion of seismic and EM attributes to estimate the petrophysical model in terms of porosity and water saturation. This study realizes the joint inversion within the probabilistic structure provided by the Bayesian theory. The algorithm is applied to a real hydrocarbon exploration scenario to evaluate its contribution to the interpretation phase. 3D volumes of estimated porosity and saturation, show how the joint inversion of acoustic impedance and electrical resistivity can provide a quantitative description of the reservoir properties and with it a measure of uncertainty, which is consistent with the petrophysical model and observations.
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Rock-typing Using Morphological Descriptors for Laminated Sands
Authors N.I. Ismail and C.H. ArnsSummaryUnderstanding the petrophysical properties of thinly layered sandstones is a longstanding problem in reservoir characterisation. The development of high resolution micro-CT acquisition with helical scanning allows acquiring 3D tomograms of very long cores. It is then of interest to select different regions of these systems where properties are similar, as one can then attempt to model the rock at a larger scale assuming a distribution of these micro rock-types. In this paper we introduce the Minkowski measures (volume, surface area, mean curvature and Gaussian curvature) as powerful discriminators of structure. We show that a classification scheme employing these measures discriminates layers of different morphology in a way that there is also an excellent discrimination between physical properties. In particular, we consider Formation factor and permeability. Thus, an automatic classification scheme with petrophysical relevance based on morphological measures alone is introduced.
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Sand Body Characterization in Tidal Marine Settings – Examples from the Penyu Basin
Authors M. Johansson, S. Faraq and R. LaffertySummaryThe Penyu Basin, as with the Malay Basin is characterized by a shallow marine coastal setting, which comprises various sub-environments ranging from estuaries, distributary channels, tidal channels, sand bars and beaches. The majority of the sandstones form part of a typical facies association, formed by stacked sandstone beds that clean upward. These cycles are considered as 5th order parasequences and are composed of minor smaller scale cycles. The cycle comprises restricted bay mudstones at the base, grading up into tidal shoal silts, overlain by prograding tidal flat/bay margin interlaminated facies, followed by higher energy tidally influenced channel and mouth bar sands, the latter becoming rooted or bioturbated at the top. The Bioturbated/Rooted Sandstone are associated with the abandoned channels and mouth bars. The bioturbation or rootlets destroy the primary depositional fabric, however as the fines are confined to discreet burrows or roots and are not dispersed, some of the original porosity and permeability was preserved. The result of the higher proportion of fines causes the Gamma-Ray to increase, and therefore this high quality rock type is easily misinterpreted through traditional openhole logs.
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Fresh Formation Water in Tight Reservoir Rocks Creates Contention between Petrophysics and Geoscience
More LessSummaryEvaluation of tight reservoir rocks, having low porosity and low permeability, is difficult enough. It becomes even more challenging when the formation water in these reservoirs is either fresh or has low salinity. The combination of fresh formation water and tight nature of the reservoir rocks causes the resistivity logs to read high, resulting in a low contrast in resistivity between fresh water bearing formation and hydrocarbon bearing one. This creates an uncertainty on the type of reservoir fluid and computed water saturation, if the formation water salinity is not known. Consequently, this becomes a source of contention between geoscientists who estimate hydrocarbon resource volumes and petrophysicists who provide the input parameters used in hydrocarbon resource assessment. This problem is becoming more common as wells are being drilled deeper into tighter rocks. Several case histories are presented in this paper, highlighting the difficulties encountered in evaluating fresh water bearing tight formations. Based on all available data, all of these wells have been evaluated as fresh water bearing tight reservoirs, with very small amount of dissolved or residual gas. The challenge here is to perform a conclusive petrophysical evaluation technically acceptable to all parties concerned.
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Comparison of Rock Physics Models to Predict Rock Properties in Carbonate Reservoirs
Authors G.T. Baechle and G.P. EberliSummaryIn this core study, we show the similarities and difference of the two rock physics models. Our motivation is to determine which of the two models is (a) more robust to predict Vs velocities and (b) preferred to understand the rock’s pore structure. We revisit how a differential effective medium model and an thin section image analysis procedure is used to determine the rock’s pore structure (Baechle et al. 2008). Using a differential effective medium (DEM) model with a dual porosity approach, we predict velocity using macro- and microporosity as derived from thin section analysis. A conceptual aspect ratio of 0.1 for micropores and a measured aspect ratio of 0.5 for macropores results in the satisfying prediction of elastic properties of carbonate rocks.
We compare the Dry Rock Approximation (DRA) (Keys and Xu, 2002) and the Extended Biot Theory (EBT) (Sun et al., 2000). Both methods are successful utilized to approximate the DEM velocity trend lines of two endmember aspect ratios for macropores and micropores. Low permeability rocks are uniquely identified by a high compressional coefficient (in EBT and DRA models) in our dataset, hereby emphasizing the potential of improved reservoir characterization using locally calibrated rock physics models
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