A Study On High-resolution Sequence Stratigraphy And Rule Of Hydrocarbon Accumulations Of Lithologic Reservoirs In Meandering River Delta

Taking high-resolution sequence stratigraphy theories and fine sedimentology theories as guidance, this study comprehensively used full and accurate well core, well logging and the 3-D seismic data, etc in higher exploration degree area. Through depositional dynamic analysis of different grades base level cycle and identification of interface, method of high-resolution sequence stratigraphic fine division and correlation is presented which is fit to meandering river delta. It is a method that correlation of base level cycles interfaces are come near under the control of gradual marker chronohorizon. By the method, Fuyu oil layer of Liangjingdong-mutounan area is divided into one long-term base-level ascending cycle, four medium -term base level cycle, Thirteen short -term base level cycles for the first time, established high-resolution sequence stratigraphic framework, and proposed sequence stratigraphic model of step thinning to basin that it is controlled by inherited paleo uplifts.Within the fine sequence stratigraphic framework of the sag, sources of sediments, depositional system and distribution of sedimentary facies are analyzed. The shallow lacustrine fluvial-dominated delta system of Fuyu oil layer is presented which is controlled by the end river system of southeast Baokang depositional system and the branching river system of southwest Changchun-huaide depositional system. It is realized that (submerged) distributary channel sandbodies as sand body framework of this delta system is abundant, closely and narrow. It is continual than original understanding and it extends to the far underwater, until disappearing into thin sheet sands. (submerged) distributary channel sandbodies is mainly reservoir sandbodies of Fuyu oil layer. Banded (underwater) distributary channel sandbody and fluvial-dominated banding with their distributions being multiple and independent in plane as well as narrow-banded in source direction is immediate reason of complicate and versatile reservoirs.Based on understanding of Sedimentary Background and sedimentary characteristics and sedimentary facies types of Fuyu oil layer of Liangjingdong-mutounan area, Sedimentary mode of shallow lacustrine fluvial-dominated delta is established, and Sedimentary mode of six subfacies is further divided. Shallow lacustrine fluvial-dominated delta outer front is mode of tide-dominated sheet sand; Transition region of inner front and outer front is mode of fluvial-dominated sheet sand; Inner front is mode of fluvial-dominated banding; Transition region of front distributary plain is mode of inshore;Delta distributary plain subfacies is mode of fluvial-dominated banding. Based on sequence stratigraphic framework and distribution of its inner monosandbody, through systematically analyzing types of found reservoirs and its distribution characteristics, The controlling factors of hydrocarbon distribution in lithologic reservoirs area are investigated. The distribution of reservoirs is mainly controlled by five geological factors: (1) Distribution of mature source rocks control ranges and styles of hydrocarbon migration; hydrocarbon is mainly vertical migration in mature source rock; and laterally migration in crudity source rock. (2) The distribution of (submerged) distributary channel sandbodies control spatial distribution of quality reservoir, quality reservoir formed by channel sandbodies accounted for more than 95%. (3) Overpressure of Qingshankou formation is power of petroleum migrating down, controlling layer of hydrocarbon accumulations. (4) Fault is predominant transporting pathway of hydrocarbon migration; the combination of faults and sandbodies controls ranges and distribution of hydrocarbon migration. (5) predominant direction of hydrocarbon migration is controlled by Tectonic evolutionary characteristics. It induced oil and gas migration at a critical period of hydrocarbon accumulation and formed oil-gas accumulation area.Using analytic hierarchy process, three levels hydrocarbon accumulation rules in lithologic reservoirs area are proposed. The first level is regional hydrocarbon accumulation rules with characteristics of"key-factor controlling oil, multi-factor coupling for controlling hydrocarbon accumulation", and it revealed hydrocarbon accumulation zones. The second level is hydrocarbon accumulation rules of tertiary structure with characteristics of"tertiary structure controlling direction, single trap controlling hydrocarbon accumulation", and it revealed local distribution characteristics of the oil and water. The third level is hydrocarbon accumulation rules of single trap with characteristics of"local structure controlling boundary, monosandbody controlling layer", and it revealed mechanism of hydrocarbon accumulation in single trap. Spatial complicated superposition of vertical multi-layer and planar multi-branch monosandbody traps and mis-traps is essential reason of complicated distribution of oil and water. Local structure, single distributary channel sandbody and their array mode is main controlling factors on complicated distribution of oil and water. It is supported an important realistic significance to complicated exploration and development of lithologic reservoirs.Based on the first and second level hydrocarbon accumulation rules, it is predicted that favorable hydrocarbon accumulation zones is axis, wings and slope closing sag of nose structure(Qian60, Liangjing, Qian48). Based on the third level hydrocarbon accumulation rules, 16 favorable traps are predicted, and 21 exploration wells or evaluation wells are deployed, and 3500×104t geological reserve are submitted. a handsome sum of economically valuable is produced.