Geological modeling of gas reservoirs with rich water in the Permian Lower Shihezi Formation,A well area,Dongsheng gasfield
For reasons of fine characterization on favorable belts available for adjustment of tight gas reservoirs rich in wa-ter and making clear reservoirs'spatial distribution,the gas reservoirs of the Permian Lower Shihezi Formation,A well ar-ea,Dongsheng gasfield,Ordos Basin,were taken as objectives to analyze their modeling tools.In addition,a 3D geological model was established for the Lower Shihezi reservoirs by virtue of Petrel software based on core,well-logging and geologi-cal data.Results show that(ⅰ)the overall study area is just a wide and gentle monocline with northeast high and southwest low.There developed two normal faults,small nose-like uplift and anticlinal structure;(ⅱ)massive deposits of both chan-nel and composite channel bar in the first member of Shihezi Formation(Shihezi 1 Member)represent the pattern of"mud-stone-wrapped sandstone",while those in the Shihezi 2 and Shihezi 3 Members are smaller in size with the"sandstone-wrapped mudstone"pattern.In this study area,mudstone interbed accounts for 50％,and both siltstone and tight interbed of 30％,respectively;and(ⅲ)data from the established model is relatively accordant with drilling practice,so the natural gas in place here can be calculated from the model rapidly and efficiently.The calculated ending in the Lower Shihezi res-ervoirs is 341.16×108 m3.Three conclusions are made.First,subdividing stratigraphic microstructure based on fine single-layer division of horizontal wells makes it possible to build a fine structure model for the whole area.Second,creating a sedimentary microfacies model and a barrier-interbed model under the control of horizontal well configuration can effective-ly improve the accuracy and effectiveness of physical parameter models.Third,the parameter modeling under the con-straint of influential factors(such as sedimentary microfacies,lithofacies and faults)can also enhance the model's accuracy and effectiveness,so as to make it well applicable to the tight gas reservoirs rich in water with"multiple,thin,narrow,tight,strong and complex"reservoir space.
Ordos BasinDongsheng gasfieldPermian Lower Shihezi FormationTight gas reservoir with rich waterGeo-logical modeling
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