The Study Of Reservoir And Hydrocarbon Accumulation Characteristics Of The Middle-Lower Jurassic In K Block Of Indonesia

The K block is located in the north of the Bom Peninsula of West Papua in Indonesia.It structurally belongs to the secondary structural belt of Bintuni basin,and it is under the control of the two strike slip faults in the south and north.The North adjacents to some big oilfields which have producted a large number of oil and gas including WOS,VOR,WIR and so on,this suggests that the block is rich in oil and gas resources.The K block is in the early stage of oil and gas exploration,the level on the exploration and research is relatively low.Although we have obtained certain knowledge of geology,but there are still a lot of problems to be solved,including sedimentary facies,reservoir and hydrocarbon reservoir system,which are the main factors to control the oil and gas exploration.This paper takes the middle-lower Jurassic R formation in the K block as the research object,On the theoretical foundations of sedimentology,petroleum geology and reservoir geology,combined with the core analysis,logging and formation testing data and certain technical means,we can systematacially research the sedimentary phase,reservoir lithology and physical property,flow unit and hydrocarbon accumulation characteristics.By the analysis of petrology,sedimentary structures,electrofacies and other facies marks,the types of sedimentary facies of R formation is shore deposits,it mainly develops the foreshore and Shoreface subfacies.By well contrast analysis,it shows that the foreshore-Pro Shoreface sand body of R formation develops well,the thickness of sand is large,it extends far,locally interbedded thin mudstone.The thickness of R formation is large,and gradually thinning to the northeastward and southwestward.Reservoir rocks are dominated by pure quartz sandstone,with part of the tuffaceous sandstone,dolomitic sandstones and siderite sandstone,particle sorting better,roundness mainly by sub-rounded,subangular-rounded,tecture maturity is high.The pore type is mainly composed of primary pores,and there are also some intergranular and intergranular dissolution pores and fractures.The reservoir porosity is distributed in 10-12%,and permeability is generally 10-100md,so R formation has better reservoir properties.The physical property of reservoir is influenced by some factors,among which the deposition and diagenesis are the main factors controlling the reservoir physical properties.On the basis of reservoir physical properties analysis,we use the FZI method to divide the target formation into seven types of flow units.The reservoir physical properties of different flow unins vary a lot,among which Flow Unit-6 and 7 are the best reservoir types in the study area,and they are mainly located in the upper of the target formation.on the contrary,the properties of lower layer are poor by the influence of sedimentary environment and diagenesis,which mainly have Flow Unit-1 to 4.By the study of the distribution,we know that the heterogeneous in the south of the study area is strong and become weak in the north area,meanwhile,Flow Unit-6 and 7's thickness increase from south to north in study area.By the analysis of hydrocarbon accumulation fluid,we can know that the type of formation waters is CaCl₂ and it blongs to oilfield water type.The degree of reservoir biodegradation is low,and the preservation condition of reservoir is good.The hydrocarbon accumulation condition is good in the study area.The types of hydrocarbon reservoir have anticline,fault-block and fault nose reservoirs.The factors of structure and reservoir physical property are the main controlling factors for the hydrocarbon accumulation in the area.