Reservoir Characteristics Of Platform Margin Reef Of Changxing Formation, Eastern Sichuan

Reefs which are built by the biological fixation of situ deposition is a carbonate construction, Reef carbonate reservoirs as a special kind of oil and gas reservoir rocks, has significant exploration potential. However, The geological characteristics of reef carbonate reservoir is complextive.The Features of reef carbonate reservoir is that storage space is unique and complexity,the reservoir is strong heterogeneity and other features.Guided by carbonate reservoir sedimentology, petroleum geology, structural geology, diagenesis, and other theories as the guiding mechanism. By means of the combined methods of indoor ,outdoor and outcrop,microscopy drilling core data , based on the previous research results, The research from the study area is start by detailed description and anatomy of platform margin reef of Changxing Formation and gas reservoir geological characteristics of reef. a systematic research was made on Characteristics of growth and development of reefs and their relationship with the sedimentary environment changes, the internal structure of reefs, reef location of reservoir development and reservoir control factors,The conclusions are reads as follows:1) Studies suggest that tectonic activities are frequent in the east of Sichuan.In the early Permian,Hercynian sport make the Upper Yangtze Platform overall decline,in the region received the most extensive transgression,forming a shallow sea platform of sedimentary environment in Changxing formation.The sea level is rising most of the time during the period. The characteristics of sedimentary facies of Changxing Formation in wubaiti area were studied sysmatically by drilling,field profile,thin section, and outdoor and outcrop data. Sex depositional facies were developed in Changxing Formation,including restricted platform, open platform, platform-margin reef, platform-margin shoal, foreslope and intraplatform troughThe depositional model was established.The platform-margin reef and shoal facies are the most favorable reservoirs.2 )Based on core description and rock-mineral analysis, the main reef reservoirs are dolomite,Representative rock types including bioclastic dolomite, dolomicrite, Reef dolomite,fine-middle crystal dolomite, Bioclastic algal laminated dolomite, Brecciated dolomite. According to the texture-genetic characteristics,they could bedivided mainly into penecontemporaneous replacive dolomitization and buried dolomitization.3)The characteristics of reservoirs in Changxing Formation were studied intensively and sysmatically,it could be determined that the most effective pore space are intergranular pores and intergranular dissolution pores,the minor are outsized solution pores and intragranular dissolution pores. Combined with reservoir properties, pore structure parameters and other indicators, the reef-beach reservoirs in Changxing Formation were classified and evaluated, and the controlling factors for the reservoir development and distributions were discussed intensively. the reef-beach facies controlled regional distributions scales of the reservoirs,Extent and distribution of reservoirs was controlled by dolomitization of the degree of development, developmental stages and output features of the development. burial dolomitization and dissolution is the most important contribution on the formation of favorable reservoir space.