Carbonate Reservoir Characteristics Of The Fourth Member Of Shahejie Formation In Shaojia Sag

Lacustrine carbonate rocks are common in Shahejie formation of the Paleogene in Bohai bay basin. High productive lacustrine carbonate reservoirs were found in Dongying Depression, Chezhen Depressin and Zhanhua depression. Study area is located in the southwest of Zhanhua depression, where the deposition pattern of the lacustrine carbonate reservoirs in the fourth member of Shahejie formation(Es4) is complex. It is difficult to probe the potential reservoirs. In this thesis, starting from the geological studies, geological characteristics of lacustrine carbonate are fine described. Then a depositional model that can explain the depositon process and the causes and the differences between different carbonate reservoirs is established.Follow the principle that the oil and gas reservoirs are products of geological processes. Comprehensive technology is used for evaluation and prediction of reservoir. The classification and evaluation of carbonate reservoirs use the combined data that from geological characteristics and physical properties of reservoir testing and commissioning of oil reservoir. Then the well-logging data is used for prediction of carbonate reservoir. The research can provide guidance for the oil exploration and development.The Es4 stratum is divided into system tracts with the data of core, logging, well-logging and seismic based on the elder research. It shows that the lacustrine carbonate rocks are mainly developed in the transgressive systems tract and highstand systems tract, while sediment thickness and filling pattern were controlled by accommodation space.Emphasis on the detailed study of carbonate rocks shows that the distribution of carbonate rocks is strict controlled by the sedimentary facies, the ancient landscape, the source of clastics and the water body condition. Sedimentary face which is the significant geological factor that can explain the distribution of carbonate rocks mostly. Based on the comprehensive study of lacustrine carbonate rocks about petrology and sediment types and developmental characteristics of the study area, the lacustrine carbonate rocks sedimentary facies are summarized as three kinds: reefs, far-shore beach and near-shore beach. Then an explanative depositional model of lacustrine carbonate rocks is established. Reservoir geology study shows that the lacustrine carbonate reservoir development is controlled by the native factors as depositional environment, rock type and secondary factors as diagenesis, structure, sequence etc. There are significant differences between the processess that the carbonate reservoir with different facies suffered. To overcome the shortcomings that caused by the complexity of the porosity and permeability of carbonate systems and the low density of core physical property test data, the classification and evaluation of carbonate reservoirs use the combined data which from geological characteristics and physical properties of reservoir testing and commissioning of oil reservoir in this paper. Reservoir types are linked with the petrography. Geological characteristics are directly used in Classification and evaluation of carbonate reservoirs.To fine geological conditions as constraints, the model that distinguish reservoir from different facies with well-logging data is establishment. Then the well-logging data can be used to distinguish lacustrine carbonate reservoir among the study area. The result shows that the classâ… reservoir developed discontinuously in Yidong fault zone , which is the thickest and best quality among the whole area. The classâ…¡reservoir develops in the near-shore beach by the Shaojia fault. The classâ…¢reservoir develops in Luojia area. The result shows that Yidong fault zone and part of the far-shore beach are the classâ… favorable zone. The near-shore beach near the Yi'nan fault with dolomitization and fault is the classâ…¡favorable zone. The southeast part of far-shore beach is the classâ…¢favorable zone.