Evaluation And Prediction Of Mesozoic Reservoir In Fulin Subsag

Buried hill reservoirs in Fulin sub-sag are getting more and more attention with the development of oil and gas resources because of its typical characteristic of Jiyang depression.Currently, there are the following problems in this region: ① Unclear distribution of Mesozoic strata;②Low Seismic resolution, no obvious characteristics of internal seismic reflection and low velocity contrast between the layers; ③ Poor correspondences between velocity interface and lithologic interface which causes the hard reservoir tracking and interpreting from seismic data. Thus improving the accuracy of reservoir prediction have become the key of petroleum exploration in Mesozoic in Fulin sub-sag.This study had focused on the integrated description of Mesozoic reservoir in Fulin sub-sag. And at the same time the study made accurate description of the Mesozoic reservoir(Weathering crust and Inside cracks) under the theoretical guidance of Reservoir Sedimentology and Reservoir Geology.And,along with comprehensive utilization of datum from geology, geophysics and analytical experiment as well as systematic study of the Mesozoic strata and its tectonic characteristics the study above could be finished.Through the study we had gotten the following points: Mesozoic strata was divided into four groups from bottom to top: Fangzi group, Santai group, Mengyin group, Xiwa group, which had lots of unconformity; Fractures were well developed in Fulin sub-sag.Fulin sub-sag developed four major faults, including Kendong and Kendong 6(South End) NNE fault zone, Kenli NEE fault zone, and Guxi NW fault zone. The intersections of three groups of strike fault systems made Fulin sub-sag be cut into a series of fault blocks and faulted noses;There were igneous rocks as well as clastic rocks,which contributed to the complexity of the formation lithology in the study area.And the tufa could be used as reservoirs because of being oily.There were two kinds of reservoir types: crust of weathering and buried hill interior.And fractures were the main reservoir space in both of them.There were different methods and techniques in predicting these two kinds of reservoirs because of their different geophysical response.Seismic attributes were mainly used in reservoir prediction of crust of weathering, while the methods of the relation of geology and geophysics were well used in reservoir prediction of buried hill interior.The prediction results showed the following points: the fracture development was closely related to the distribution and date of the fault;The confluence of two groups of faults of different natures was fracture development zone;The fractures which were formed in the early faulting were easy to be filled,which were unfavorable to hydrocarbon pool-formation.But the late fault reconstructions were positive to hydrocarbon pool-formation.