Distribution Regularities And Major Controlling Factors Of Stratigraphic Reservoirs In Ke-Xia Structural Belt

Based on seismic data, well logs, cores and geochemical analysis, characteristics and spatial distribution of unconformities in Ke-Xia Structural Belt have been studied in this thesis. Combined with structural setting and sedimentary system, the thesis also studied the vertical and horizontal distribution of stratigraphic reservoirs and the controlling factors to the accumulation of stratigraphic reservoirs in Ke-Xia Structural Belt.According to the reflection characteristics of seismic, the unconformities in Ke-Xia Structural Belt have been classified into structural and depositional types, and the spatial distribution and differences within the bases of Cretaceous, Jurassic and Triassic have been revealed. On the basis of comprehensive logging data, the thesis summarized the lithology combination of the Triassic unconformity emphatically. The physical property analysis indicated that the rock above the unconformity and semi-weathered rock could serve as medium-quality reservoir; the latter owned better porosity, both of which showed decreasing trend from mountain to depression.Statistics of detected stratigraphic reservoirs suggested unconformity near the source rock could be the most favorable position, in Ke-xia which was the base of Triassic. According to the reservoir distribution in unconformity structure, structural position and sedimentary system, the thesis pointed out that stratigraphic reservoirs tended to locate in multi-truncation and truncation unconformity near the structural ridges; nearly half of the reservoirs were discovered in fault-fold belt; and submarine fan and alluvial apron appeared to be the favorable facies for stratigraphic reservoirs. In overlapping region and fault-fold belt, unconformities and faults played a significant role in controlling the formation and distribution of stratigraphic reservoirs, while in the slope unconformities and sedimentary facies did so.Based on the research above, the controlling effects of unconformity, structural setting and deposition was also discussed separately. Structural setting controlled the development of unconformities and faults and, as a result, controlled the spatial distribution of stratigraphic reservoirs. Fluctuation of base level during regression and transgression formed the overlapping and truncation trap, and sedimentary faces controlled the distribution and lithology of deposition. Take unconformities’ surface morphology, physical property and the property of crude oil and groundwater into consideration, a formula has been established to assess the conduction efficiency of unconformity quantitatively, and major migrating paths were confirmed due to the assessment.