Discussing Lithostratigraphic Reservoir Controlled By Slope Break And Shore Line In Depression

China has already been the second largest petroleum input country in the world. The contradiction of petroleum requirement and production stands out gradually, which involves in the national energy security. At present, the exploration of oil and gas gradually focuses on lithostratigraphic reservoirs other than the structural's. The exploration of lithostratigraphic reservoirs, for example, in the Songliao, Ordos and Bohai Gulf basins, has broken through in large extent and became the main exploration domain in these basins. With the development of lithostratigraphic reservoirs exploration, some new theories, such as the source-controlled theory, slope break-controlled theory and facies-belt of delta front controlled theory and technologies such as reservoir prediction and hydrocarbon detection have been formed. But at present, we have not mastered the macro distribution regularity of lithostratigraphic reservoirs and have different understandment for research approaches, exploration thinking and technologies. All of these are attributed to two neck-puzzles. The first is lack of related theories which deeply make us understand the distribution and accumulation regularity of lithostratigraphic reservoirs. The second is lack of systematic approaches which make us identify the lithostratigraphic traps and judge the effectiveness. In the paper, the author takes the Qingshankou and Yaojia Formation (the middle oil-bearing formation) of the west slope of the South Songliao Basin for an example to discuss these two problems. The west part of Songliao basin is a whole slope dipping to the east. Large to medium structural traps have already been drilled in this region, but have little achievement of petroleum reserve. The fan-delta and coastal lacustrine facies deposited in Qingshankou and Yaojia period alternately distribute in the slope break,which the vast remained petroleum reserves exists in this position. With the instruction of modern sedimentology and petroleum geology, using the analysis methods of sequence stratigraphy and petroleum system, we systemically researched the backgrounds of regional geology and kinetics of petroleum accumulation of Songliao Basin and deeply anatomize the feature of sequence stratigraphy and sedimentary evolution. Then we mainly discussed the petroleum accumulation regularity of lithostratigraphic reservoirs and the control models of petroleum. At last, we pointed out the prospecting exploration zones and targets of lithostratigraphic reservoirs and established new theories and related technologies of lithostratigraphic reservoirs exploration. 1.This paper Provided the view that slope break of depression basin controls oil in large scale for the first time. This paper's basic points: ①the slope break in depression basin may be divided into flexure slope break and glacis slope break. ②the contain capacity of flexure slope break is large and abundance in sediment source. The fan-delta, coastal lake facies, eroded valley and lowstand fan formed by under-water fluvial channel are located at the third level sequence boundary. The mouth bar of fluvial channel,coastwise bar and shore sandstone body developed in different sequence tract are favorable reservoir for petroleum accumulation. ③The flexure slope breaks are good position for lithostratigraphic traps, which is in good condition of generation, reservoir and seal. ④ In large scale, the flexure slope break controlled the distribution of lithostratigraphic reservoirs. 2. This paper submitted the concept that shore line of lacustrine controls oil and the view that for the first time. This paper pointed out basic points: ① Abundance sandstone developed in shore and shallow lacustrine, which can form various lithostratigraphic traps. ② Cycle and periodicity of shore lines provide good conditions for reservoir and seal formation. ③ Various lithostratigraphic traps may form different oil reservoir, such as stratigraphic overlap, stratigraphic offlap, coastwise bar, shore sandstone and stratigraphic unconformity etc.. ④Oil migration system includes faults in longitudinal and unconformity and ditch-valley in transversal, and the large fluvial channels are the most effective expressway conduction system. Therefore, we may seek reservoirs beyond the region of source rock.⑤The distribution of lithostratigraphic reservoirs along the shore line is in belt and scale. The reservoirs of stratigraphic overlap mainly scatter near the shore lines of LST and TST and the reservoirs of stratigraphic unconformity mainly scatter in the nearby of sequence boundary. The stratigraphic offlap reservoirs mainly scatter near the shore line of RST. But the reservoirs of shore matting sandstone bodies, coastwise bar, lacustrine bay sandstone and cut valley may occur in each tract. The reservoirs formed within the coastwise bar and lacustrine bay with sandstone bodies should be paid more attention to. 3.This paper generalized a set of SSL method,which can predict, identifiy and evaluate lithostratigraphic reservoirs. Under the instruction of sequence stratigraphy,it mainly can seek shore line and identify lithostratigraphic traps and judge the effectiveness by the combining seismologic technique and logging information...