The Study On Sedimentary Microfacies And Reservoirs Characteristics Of Shahejie Formation Of Gaoyang Oilfield In Lixian Slope

With the development of exploration and exploitation in these years, the exploration direction of Gaoyang oilfield has turned from structure reservoirs to lithologic reservoirs. Gaoyang oilfield has entered the high-water stage. With the contradiction of “water above while oil underneath”, the present research result of sand-body distributions and connectivity is outdated to guide the present oilfield production. Combined with the principles of sedimentology, on basis of core, thin section observation, logging, laboratory testing and production data, the paper did micro-facies judgments and micro-facies analysis on unit of fine single sand body. And on this basis, the paper analyzed the reservoir characteristics which should be as accurate to the level of single sand body.Studies have shown that rock types of Sha1 and Sha2 formation are mainly fine-grained lithic feldspar sandstone and the rock types of the lower Sha1 formation are biological limestone and oolitic limeston. The paper summed up and improved the micro-facies identification scale of terrigenous clastic rock and carbonate rock in research area, and the result shows that in the study area, delta plain sediments was developed in Sha2 formation and the upper Sha1 formation. In lower Sha1 formation, sediments accumulated, forming shore-shallow lacustrine beach bars, which include sandy bars and carbonate bars. The carbonate bars developed into grain beaches on high position underwater, and formed into dolomitic limestone lake-bays in lower places. And on this basis, the paper established facies models of Sha1 and Sha2 formation.Thin section analysis has revealed that there are two types of diagenetic environment-Acidic and Alkaline. The stressful catalysis of oolith and quartz, and the quartz corrosion are the represents for alkaline diagenetic environment. The phenomenon of secondary enlargement of quartz, feldspar corrosion and calcite dissolution are the indication of acidic diagenetic environment.The compositions, structure of original sediment are the main factors which influence and control the reservoir diagenesis, and in the study area medium compaction diagenetic facies mainly developed. The reservoir space is mainly secondary pores, which are primarily dissolution pores between particles and pores inside. Pore structure with characteristics as poor throat, poor sorting, and high expulsion pressure. The physical property of reservoirs is absolutely controlled by sedimentation and diagenesis. The reservoir physical property of upper sha1 section, which develop beach bar facies, is better than that of sha2 section and under sha1 section, which developed delta facies. The paper also did comprehensive assessment focusing on Sha1 and Sha2 formation and the result shows that, low permeability reservoirs which distributed in branch river edge, dam lateral margin and beach deposition mainly developed in the area.The differences of reservoir physical properties are the main factors that affect oil-water relationship of the study area. Based on the core description and physical analysis, with the contrast of sand bodies of the single well with that of the connected well, 2 kinds of genetic models of single well with illogical location of “water-oil” and sand body correlation patterns have been established. The result shows that the shoreline twists and turns degree is the important factor which affects the research area. Gao 44 fault block, with Poor oil-bearing property, is in the relatively structural high part to the gao30 and gao14 fault blocks which are adjacent to research area.According to the research result, the ooid of Gao 44 fault formed as pseudo-oolith, developed in weak hydrodynamic condition of the closed lake bay. At the same time, the ooid of gao30 and gao 14 fault block formed in normal formation, which developed in strong water energy of open lake situation. The differences of sedimentary position result in that gao30 and gao14 fault block had better reservoir physical property compared with Gao 44 fault block. Inconclution, gao30 and gao14 fault block has better reservoir physical property.