Sedimentary Characteristics And Hydrocarbon Accumulation Of Fuyu Oil Layer In 401 Block, Sanzhao Depression,songliao Basin

Sanzhao depression is an important area of rich hydrocarbon accumulation in Songliao Basin, and has made great contribution to production of Daqing oil field. The exploration and evaluation of Fuyu oil layer, which plays the role of replacement production layer, has become increasingly significant. Nowadays both the use rate of proven reserve and drilling success rate are low, and the main reason is the unclear understanding of the sedimentary characteristics and hydrocarbon accumulation pattern of Fuyu oil layer. According to this exploration situation, this thesis selects Zhou 401 block of Sanzhao depression as study area and deeply analyzes the structural features, sedimentary characteristics, tectonic evolution characteristics, hydrocarbon migration and accumulation patterns of the study area based on well logging, mud logging, cores, oil test and 3D seismic data, etc. The main achievements include:(1) According to the research of cores, well logging and seismic data, etc, combine with regional geological conditions and results of previous studies, Fuyu oil layer is divided into 5 short-term cycles, respectively corresponding FⅢ, FⅡ, FⅠ3, FⅠ2, FⅠ1.(2) Through 3D seismic interpretation in detail, the plane and section characteristics of T2 tensile fracture system in Sanzhao depression is described. Moreover, structural sedimentary evolution characteristics has been figured out by the analysis of sedimentary filling characteristics according the structure characteristics of the bottom and top of each oil layer group in Fuyu oil layer.(3) Sedimentary environment and facies distribution are studied based on the analysis of well logging, cores and seismic. Furthermore, the main sedimentary face of FⅢ, FⅡ, FⅠ3 and FⅠ2 is considered as the shallow delta plain deposits by the prediction of sand body distribution based on RMS amplitude inversion. While delta front mainly developed in F Ⅰ 1. The distributary channel controls the sand both distribution.(4) The controlling role of tectonic evolution on the reservoir is revealed through the integrated analysis of tectonic evolution characteristics, tectonic deformation features, fault activity characteristics and each accumulation event, and that the critical period of Fuyu oil layer accumulated at the late Nenjiang and late Mingshui group is clarified. Moreover, the dynamic of the reservoir is illustrated by deep investigation of oil and gas migration and accumulation of each period.(5) The roles of different faults on hydrocarbon accumulation are deeply discussed and the controlling effects of the faults are revealed through the analysis of hydrocarbon accumulation and reservoir dynamic characteristics of late Nengjiang and late Mingshui group. The faults are classified into two catalogs, including inherited large scale faults and small scale faults which only developed nearby T2 axis. Large scale faults promoted the hydrocarbon accumulation at late Nenjiang period while destroyed the reservoir at late Mingshui period; small scale faults promoted at both periods so they are considered as “favorable faults” to the hydrocarbon accumulation in Fuyu oil layer.(6) The distribution pattern of oil is clarified through detailed study and three hydrocarbon accumulation patterns are concluded, which are horst, step and graben mode. The oil rich zones are identified according to the study on favorable faults and finally the favorable accumulation area is figured out.