Research He8~shanxi Group On Tight Sandstone Gas Reservoir Characterization Yanqi-2Gas Well Block

This paper based on oil and gas reservoir geology, sedimentary petrology, structuralgeology,logging geology and other theories, with core observation, sampling and analysis test,log interpretation and other information in the study area, for the Yanqi-2gas well block oftight sandstone gas reservoirs conducted a small layer of fine gas reservoir contrast, structuralcharacteristics research, sedimentary facies research, analysis of reservoir characteristics andother exploration research, conducted a comprehensive evaluation of tight gas reservoirs.By fine-scale stratigraphic correlation,The group from He-8to Shanxi is subdivided into18single layers with their sedimentary subfacies as delta front. The sedimentary microfaciesare distributary channel, channel margin and interdistributary bay. The mouth bar and alluvialfan are relatively less developed. The distributary channels of He-8~Shanxi Group areextending along north-south direction with3~4channels between1km~3km in width. Atthe intersection area of those channels, the superposition width reaches to5km~10km whilethe sand thickness is5~10m. The braided or anastomosed features are formed due to thedistributary channels intersecting in different areas. The gas bearing sand is not only controlledby the extension of sedimentary microfacies, but also the effect of diagenesis. Therefore, thereservoir is severely affected by sedimentary environment, diagenesis, physical property andgas accumulation level. The research indicated that Shanxi Group subdivided layer Shan23ismainly formed inⅡ、ⅢType Formation while some portions develop Type ⅠShan22,Shan21,Shan13Layers are mainly developing Ⅳ Type Formations, secondly ⅢType. Shan11,He82and He81Layers are type Ⅲ、 ⅣFormations. The delta sedimentary system and barrier barswhich form the lithological traps provide an effective migration pathway and accumulationspace for the nearby natural gas. The regional tectonics characteristics are of no controllingeffect on natural gas distribution since gas has been produced from both the high and lowposition of the geological structure. The local structures also do not play a controlling role ongas distribution since both the uplifted and low areas have produced natural gas. However,only the formations with better physical properties have become the natural gas-rich regions.