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Fifth International Conference on Fault and Top Seals
- Conference date: September 8-12, 2019
- Location: Palermo, Italy
- Published: 08 September 2019
61 - 76 of 76 results
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Parameterising and Modelling Sub-Seismic Fault Structure for Assessing Compartmentalisation and Juxtaposition Risk
Authors T. Manzocchi, C. Childs, V. Roche, A. Heath, I. Telles, V. Papanikolaou, G. Camanni, M. Carneiro and E. DelogkosSummaryPartitioning of fault displacement onto multiple segments within a fault mapped as a single structure on seismic can result in flow paths between seemingly unconnected fault-bound compartments. The problem can be tackled using a quantitative fault zone description underlain by three parameters that have been characterised for a variety of natural fault systems. Methods for deriving these parameters for subsurface datasets are outlined, and a range of analytical and modelling approaches for assessing the likely importance of sub-seismic fault segmentation in an exploration and production context are discussed and illustrated.
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The Three-Dimensional Geometry of Relay Zones within Segmented Normal Faults
Authors V. Roche, G. Camanni, C. Childs, T. Manzocchi, J. Walsh, J. Conneally, M.M. Saqab and E. DelogkosSummaryNormal faults often comprise arrays of fault segments. The boundaries between adjacent fault segments, relay zones and relay ramps can be of crucial importance to fluid migration pathways across and along faults and for across-fault reservoir juxtaposition. However, despite the increased number of studies of faults in high quality 3D seismic data, the three dimensional geometric or kinematic properties of relay zones or the controls on their 3D geometry are still unclear. This contribution investigates the characteristics of three dimensional segmentation based on an extensive collection of normal faults and relay zones in different geological settings. Our analysis shows that relay zones most often develop by bifurcation from a single fault surface but can also arise from the formation of segments which are disconnected in 3D from their inception. Relay zones generally occur between fault segments that step in the dip or strike direction, and intermediate oblique relay zones are less frequent. When combined together, these different geometries can form a complex spectrum of fault segmentation, whose characteristics can be related to underlying geological controls, such as the mechanical heterogeneity of the faulted sequence and the influence of the basement structure.
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Amalgamation of Silt Smears on Normal Faults at Outcrop Scale
More LessSummaryPresentation examines the role of silt smear amalgamation in low permeability fault-rock generation for two different siliciclastic sequences in New Zealand. Data for outcrop-scale normal faults indicate that the geometries and occurrence of smears is highly variable. In sequences where silt smear is common, fault rock is primarily derived from fine-grained beds in the wall rock with frequent smear amalgamation. In these cases published algorithms may provide useful measures of fault-seal potential. In sequences where smear of silt beds is not ubiquitous and the thickness of smears is highly irregular, smears are only rarely amalgamated. In such cases the majority of fault rock appears to be generated by cataclastic processes and existing algorithms may not accurately describe the contribution of low-permeability wall rock to fault zones. The distinction of these two smear models is key for fault-seal analysis and is partly attributed to sequence architecture and silt-bed composition, where higher phyllosilicate content is associated with greater smearing.
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Scaling of Fault Damage Zones and Implications for Naturally Fractured Reservoirs
Authors S. Mayolle, R. Soliva, Y. Caniven, C. Wibberley, G. Ballas, S. Dominguez and G. MilésiSummaryIn this study, we focus on fault damage zones in carbonate rocks. We analyse fracture damage from small-scale outcrops to map-scale analyses, using scanlines adjacent to fault cores ( Figure 1a, b ) far from fault tip zones, and aerial images. This enabled the detailed characterisation of 12 faults, on which we define the Displacement-Thickness relationship. We analyse the resulting scaling laws and discuss their properties with respect to the map scale observations and previous models proposed in the literature. Finally, we propose new explanations based on fault segmentation and linkage and discuss their application to NFR.
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Fault Leakage Rates Estimated In-Situ: Implications for Fault Seal Evaluation
By C. WibberleySummaryThis presentation examines the main controls on Darcian leakage through fault seals and investigates the evaluation of hydrocarbon column heights in such cases. Firstly, case studies are used to illustrate how fault seal permeability may be estimated in-situ from aquifer compartmentalisation data, improving on existing algorithms currently based mainly on empiric relationships. Secondly the quantitative estimation of hydrocarbon column heights is investigated from the dynamic interplay between charge rates into the trap versus seal leakage rates. A particular consideration is placed on the geometric and petrophysical properties of the leak paths, such as across-fault flow through a fault zone barrier or up-fault conduit leakage. Finally, a consideration is made of the relative importance of aquifer hydrodynamics and dynamic hydrocarbon flow on controlling hydrocarbon contacts. It is concluded that both hydrodynamic flow in the aquifer, and dynamic charging and leaking of hydrocarbons in an active petroleum system, can control hydrocarbon column heights trapped against a seal. Whilst an understanding of the pressure distribution is critical to prospect evaluation in such settings, sensitivity to the geometric parameters of the trap and charge / leak pathways such as fault conduits remains a key uncertainty in the quantitative analysis.
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DEM Modeling of Pressurized Fluid Flow within a Fault Zone in Shale Based on In-Situ Tests
Authors F.V. Donzé, A. Tsopela, Y. Guglielmi, P. Henry and C. GoutSummaryFracture interaction mechanisms and reactivation of natural discontinuities under fluid pressurization conditions inside fault zone can represent critical issues in risk assessment of caprock integrity. A field injection test, carried out in a damage fault zone at the decameter scale i.e. mesoscale, has been studied using a Distinct Element Model. Considering the complex structural nature of a fault zone, the contribution of fracture sets on the bulk permeability has been investigated during a hydraulic injection. It has been shown that their orientation for a given in-situ stress field plays a major role. However, if homogeneous properties are assigned to the fracture planes in the model, the limited irreversible displacements cannot be reproduced. Despite these limited displacements (40 μm maximum), the transmissivity increased by a factor of 10–100. These results provide insights in fracture-controlled permeability of fault zones depending on the geometrical properties of the fractures and their resulting hydro-mechanical behavior for a given in–situ stress field.
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Validation of Fault Seal Prediction Tools, a Case Study in the Permian Rotliegend, Dutch North Sea
Authors K. Van Ojik, A. Silvius, Z. Shipton and Y. KremerSummaryTwo case studies of Permian Rotliegend fields from the Dutch offshore area have been carried out to investigate the validity of property transformation functions estimating threshold entry pressures of fault rock ( Bretan et al. 2003 , Sperrevik et al. 2002 ). These SGR (Shale Gouge Ratio) based functions have been calibrated to Jurassic, Brent type of rock and field data, with clay smearing as the dominant fault sealing mechanism. The theoretical foundation for these algorithms however does not appear to capture the (cataclastic) mechanisms likely to be at play in the fault rocks observed to be present in core at Permian Rotliegend level. One case study is presented here in which the estimated threshold entry pressures are compared against actual pressure data from two wells on either side of a partly-sealing fault, both on a geological and a production timescale. Conclusions from this case study are a.o. that the two functions tested appear to predict required threshold entry pressure levels accurately, within an uncertainty range, which was somehow unexpected in view of the above.
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In-Situ Stress and Fault Reactivation in Bozhong 34-2 Oilfield of Huanghekou Sag, Bohai Bay Basin
By Y. JinSummaryThis study have applied Fault Analysis Seal Technology to the Bozhong 34-2 oilfield, located the relative risk areas of faults, and try to guide water injection in the process of oilfield development. The “Huang model” is used to obtain the in-situ stress. The stress magnitudes indicate a normal faulting regime in the study area, and the direction of maximum horizontal principal stress is N70°E. The fault stability is controlled by fault orientation obviously, and the faults with strike near east-west, dip angle close to 60° have a relatively high risk. All faults are stable under the hydrostatic condition, but the processes of injection and production have a strong influence on the pressure. Therefore, for accurate determination of fault risk, it is necessary to simulate the current pore pressure distribution.
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Fracture Stratigraphy and DFN Modelling of Tight Carbonates, the Case Study of Monte Alpi (Southern Italy)
Authors A. Giuffrida, F. Agosta, P. Castelluccio, E. Panza, V. La Bruna, A. Rustichelli, E. Tondi, M. Eriksson, S. Torrieri and M. GiorgioniSummaryRecent geological and structural analyses of the Monte Alpi carbonate massif focused on the dimensional properties and growth mechanisms of large-scale, high-angle fault zones. In this work, we focus on the role played by primary heterogeneities on the vertical growth of high-angle structural elements such as joints, sheared joints, persistent fracture zones, and small faults. By combining traditional field structural analyses with 3D photogrammetric analysis, we are able to document the attitude and height distribution of individual structural elements. Data are statistically elaborated in order to assess their multi-scale dimensional properties, which are discussed in light of the abutting and crosscutting relationships with respect to the primary heterogeneities. Results of this work fill the gap that exists between the in situ and seismic resolution analyses, and provide new insights into the mechanical stratigraphy of tight, platform-related carbonates of the Inner Apulian Platform.
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Imbricated Structure and Hydraulic Path Induced by Strike Slip Reactivation of a Normal Fault in Carbonates
Authors I. Aubert, J. Lamarche, P. Richard and P. LeonideSummaryFault zones strongly impact basin reservoir properties as they can act as drains or barriers depending of their structural and diagenetic properties. In the case of reactivated faults, newly develop fracture and fault systems reworked and cross-cut preexisting structures generated by the first fault activity potentially result in new fluid pathways. The study focalized on the polyphase Castellas fault affecting Barremian calcarenites (Urgonian facies). We performed a 870m-long high resolution mapping along the Castellas fault zone with a data of 586 measurements, including 56 fault planes, 460 fractures and 70 bedding planes. We realized a geological map and a stratigraphic log and fifteen cross-sections perpendicular to the fault zone, to capture fault architecture variations. The Castellas fault structure, observed on map and cross-sections exhibit large lateral variations of fault core and fault geometry. It is composed of a complex anastomosed architecture made of 8 main fault planes striking from N047° to N078°, with secondary fault planes, horse tail structures and imbricated lenses. Fault zone hydraulic signature change from a porous fault rock with a tight damage zone during normal faulting to a fracture network and fault core enhanced permeability during strike-slip deformation.
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The Cause of Hydrocarbon through Salt in Kuqa Basin, Northwest China: Evidence from Mechanics Laboratory Results and Oil-Gas Exploration Verification
By Z. Qin-GongSummaryBoth anhydrite rocks and salt rocks have embrittlement at low temperatures and ductility at high temperatures. The brittle-ductile transition depth of evaporites in Kuqa Basin is 3000m or so. In the late tectonic active period of Kuqa Era, the strong tectonic compression from South Tianshan will generate fractures and faults in evaporites to let hydrocarbon immigrate upward if burial depth shallower than 3000m. However, after evaporites were continuously buried deeper than 3000m, previous faults would be welded to keep good seals. so early oil accumulations were destroyed and late high mature coal gas accumulations were preserved.
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Fault Seal Analysis (FSA): Benefits and Limitations in Recent Wintershall Drilling Projects
Authors J. Chevallier-Messbacher and P. BretanSummaryShould fault rock attribute analysis be wider implemented within Wintershall Dea and if so, under which data conditions should it be recommended to estimate fault seal potential using Shale Gouge Ratio (SGR) and when to compute hydrocarbon column heights? This question has been addressed through a comprehensive and detailed project, evaluating Pre-Drill and Post-Drill data analysis and results, run on existing Wintershall prospects. The pre-post drilling comparison of fault seal analysis results demonstrates that understanding the sedimentology is equally important as understanding the structure. It is important to be aware that uncertainties in the input will directly be reflected in the predictive capabilities of the fault seal analysis. For this reason, the integration of a fault seal analysis results in the prospect assessment needs to be decided in dependency of the quality and completeness of the input data. And as each variation of the prospect, will have an impact on the fault seal prediction, the fault seal analysis needs to be in very close cooperation with the prospect geologist to ensure consistency between the prospect model used for prospect evaluation and the fault seal analysis model.
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The Impact of Faults on Fluid Flow in Travertine
Authors D. Drayton and Q. FisherSummaryUnderstanding continental carbonate deposits is of increasing importance due to their great hydrocarbon reservoir potential, particularly with the development of continental carbonate plays within the ‘pre-salt’ of the South Atlantic ( Carminatti et al., 2008 ). However, these deposits possess significant heterogeneities related to complex depositional and diagenetic processes ( Delle Piane et al., 2017 ). The nature of faulting within continental-type carbonates and its impact on fluid flow is crucial when considering reservoir characterisation and quality. Unlike established concepts of fault and fluid flow models within clastic rocks ( Knipe 1992 ; Yeilding et al., 1997 ; Fisher & Knipe, 1998 ), the heterogeneous nature of carbonates means that faulting within these deposits is difficult to model and predict (Michie et al., 2017) . To this end, we have carried out an integrated petrophysical and geomechanical study of shallowly buried travertine samples from Italy. The study aims to characterise heterogeneities, examining their control on fault chracteristics and, ultimately, the impact on fluid flow.
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A Strategic Company Approach towards Understanding Sealing Mechanisms and their Impact on the E&P Value Chain
Authors J. Schmitt, F. Schaefer, S. Aartmrg, J. Chevallier and R. HeldSummaryWintershall Dea has kicked off a strategic initiative towards a better handling and fit-for-purpose application of the various seal related topics, including fault seal as well as top, base and intraformational seals. The project targets at establishing a holistic view to seal risk as basis for more informed discussion between the technical community and management. An improved understanding of fault sealing aspects will impact projects throughout the E&P lifecycle. Anchoring fault seal analysis with all its components and tasks such as de-risking exploration prospects, clarification of maximum sustainable hydrocarbon column heights or compartmentalization will create value at relatively low costs as it is involving merely standard data sets.
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Assessment of Fault Sealing in the Nanbaxian Area of Qaidam Basin, Western China
By Q. LiSummaryFault sealing is mainly restricted by many factors, such as lateral sealing and vertical sealing. Based on the structural characteristics of faults in the northern margin of Qaidam Basin, the evaluation methods of fault sealing are analyzed and summarized.
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Seal Integrity in the Uplifted Basins in the Greater Hoop Area on the Northern Barents Shelf
Authors R. Paulsen, S. Grundvåg, K. Senger and E. StuelandSummaryThe geological evolution of the northern Barents Shelf is complex, and the area has undergone several phases of tectonic activity leading to a mosaic of several deep and shallow basins, platforms, salt-cored domes and structural highs. The area is highly gas prone with some very few commercial oil discoveries, and only two fields currently in production. Deep burial and subsequent Late Cretaceous–Cenozoic exhumation and isostatic rebound following the last glaciation have strongly influenced the petroleum system This have in particular lowered the cap rock integrity over large parts of the northern shelf. Thus, we wish to evaluate the regional cap-rock properties in the area in order to lower future geological exploration risk. Additionally we aim to establish a robust structural framework and sequence-stratigraphic models, highlighting the tectonic and stratigraphic evolution of regional cap-rock units on the northern Barents Shelf.
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