Analysis On Sedimentary Reservoir Under High-resolution Sequence Framework In Baijiahai Salient Of Junggar Basin

Baijiahai Salient in Junggar Basin has good reservoir conditions,which is surrounded by many hydrocarbon-generation sags,and Baijiahai Salient is always to be the important exploration area in Junggar Baisn.In recent years,direction of oil and gas exploration is changed from structural reservoirs to lithologic reservoirs,and sands are well developed in Sangonghe Formation that is the exploration object for lithologic reservoirs.Previous analysis have confirmed that high-resolution sequence stratigraphic is one of the effective ways to search for lithologic reservoirs.It is hard to divide sequence and make clear understanding on distribution of sands in multi-tectonic movements time,and previous sedimentary facies and reservoir characters in sequence framework have not satisfied modern exploration accuracy,all of above problems hinder deeper oil and gas exploration of Sangonghe Formation.Based on previous research,sedimentary and reservoir characters of Sangonghe Formation are detailed analysed under high-resolution sequence framework by research on comprehensive data composed of core,logging,seismic and experimental analysis,then make summary of controlling factors and comprehensive eveluation on reservoirs,and finally predict distribution of favorable reservoirs,which supply guidance for exploration of Sangonghe Formation.Based on observation on geology profile in field and drilling cores,tracing on sesmic profile and analysis on logging curves,interfaces of every grade sequence are recognized in study area.Based on sequence division of single well and sequence comparison between wells,high-resolution sequence framework is built in whole area.Through heavy minerals and detrital composition analysis,provenance of Sangonghe Formation can be judged.Sedimentary facies are recognized by analysis on core face,logging face and seismic face under high-resolution sequence framework,based on faces division of single well,vertical and horional face characters are searched by face comparison between wells and distribution of sedimentary face under mid-term base level cycle,and sedimentary model is summarized at last.Lithology,diagenesis and physical properties of reservoirs under mid-term base level cycle are analysed by many technologies like section and SEM,then make summary of controlling factors and divide favorable diagenetic facies through analysis of sedimentary facies,and make comprehensive eveluation on reservoirs by many parameters composed of sedimentary face,diagenetic face,physical property,pore throat,sorting and lithology,finally,predict distribution of favorable reservoirs.Result shows that Sangonghe Formation can be devided in one long-term base level cycle,three mid-term base level cycles and nine short-term base level cycles.The provenance of Sangonghe Formation in study area is northeast direction,and mainly develop braided river delta and lake sedimentary system.Frond-delta mainly is developed in MSC1 and MSC2,and shallow lake is mainly developed in MSC3.It is showed that reservoir sand type mainly is lithic sandstone,and second is feldspathic clast sand.Content of interstitial material is low,and sorting is middle with rounding is bad to middle,and pore types mainly is original intergranular pores.Reservoir types of Sangonghe Formation in study area mainly are low porous and extremely low permeable reservoirs,and low porous and middle permeable reservoirs are developed regionally from characters of porus-permeable relationship.Sedimentation and diagenesis are controlling factors of Sangonghe reservoirs,and sedimentation is the main controlling factor with the best physical property in subaqueous distributed channel sand body.Compaction and cementation break physical property of sand body,while dissolution improve.Diagenetic facies can be divided into three types depend on affection of different digenesis,and weak-mid compaction-weak corrosion-weak cementation face and mid compaction-mid corrosion-mid cementation face are favorable for development of reservoirs.Reservoirs have three types,and Ⅰ and Ⅱ type reservoir have large pore throat and good physical property,and diagenetic facies are weak-mid compaction-weak corrosion-weak cementation face and mid compaction-mid corrosion-mid cementation face which is favorable for reservoir development.Sandbodies in SSC6 have better physical property than other short-term base level cycles in MSC2 which mainly develop Ⅰ and Ⅱ type reservoirs,but MSC1 mainly are Ⅲ type reservoirs.