Multi-fault analysis is an ExxonMobil stochastic tool for analysing the impact and sensitivities of stratigraphic uncertainty and variability on cross-fault leakage of hydrocarbons in faulted traps. This juxtaposition-based method provides quantitative prediction of hydrocarbon contact levels through a complex system of structural spills and juxtaposition leak points in traps with stacked reservoir systems and one or more faults. Validation of the Multi-fault analysis technology was carried out by comparing pre-drill predictions to post-drill results from 41 faulted exploration prospects drilled from 1994-2001. Of the 41 prospects, 29 were valid tests in which we made 22 successful predictions. Of the 22 successful outcomes, 11 were discoveries and 11 were dry wells. Some of the dry wells were drilled assuming the presence of sealing fault-zone material to trap hydrocarbons despite a Multi-fault analysis failure prediction. The seven Multifault failures comprise four predicted successes that were failures and three predicted failures that were successes. Most of the Multi-fault prediction failures can be attributed to data quality and uncertainty; however, some may be associated with sealing fault-zone material. Other considerations in fault seal analysis (i.e. dip leak along faults and sealing fault zone materials), model input uncertainties, and using drill-well learnings are also discussed.Fault seal analysis has been used since the 1960s to predict the impact of faults on the flow or storage of fluids in hydrocarbon reservoirs. Initial attempts at fault seal analysis concentrated on defining pressure or hydrocarbon column height differences across faults and using those observations to infer the sealing behaviour of faults (e.g. Smith 1966). Such studies used cross-sections constructed at high angles to the strikes of faults to understand the connections of permeable units across the faults. If disparate pressures or hydrocarbon fluid contacts were observed where a cross section provided evidence of a potential sand-to-sand juxtaposition, then it was assumed that the fault zone itself sealed in order to isolate the sands on each side of the fault from each other. However, the cross-section approach gives only a one-dimensional look at a fault (i.e. a single profile view along the fault), and the sand-to-sand juxtapositions across it, and as such, failed to define possible juxtapositions everywhere along the strike length of a fault. As well, early attempts at fault seal analysis were hampered by map quality and accuracy. In the 1960s and 1970s, depth-structure maps were constructed from variable quality two-dimensional seismic data and/or from well penetration data (formation or sequence tops), making derivative analyses, such as fault seal analysis, of suspect quality.With the development by Allan (1989) of a method for making fault plane profiles (so-called Allan diagrams), sand-to-sand juxtapositions along the length of faults could be defined in much better detail. Fault plane profiles are cross-sections ...
A microstructural investigation of cataclastic fault rock evolution from a quartzite with an original mylonitic microstructure is reported. The fault rocks produced range from clast dominated microbreccias to matrix dominated ultracataclasites. The recrystallized grain size and the sub-grain size in the original mylonite appear to control the development of the fine-grained matrix in the microbreccias and cataclasites by focusing fracture along sub-grain and grain boundaries. The ultracataclasite generation involves further grain size reduction which is dominated by transgranular fracturing. The host rock clasts present in the fault zones show a significant increase in dislocation density indicating that a component of low temperature crystal plasticity is associated with the faulting. In addition the fault rocks show evidence of partial cementation by the growth of quartz and carbonate cements. The evolution of the fault rocks studied in terms of the clast size and the clast/fine-grained matrix ratios are not a simple function of the displacement magnitude.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.