Distribution Regulation Of Effective Reservoir Sandbody In Major Gas-bearing Interval Of Upper Paleozoic In Sulige Gas Field

According to the theory and methods of Sedimentology, high-resolution sequence stratigraphy, reservoir geology, mineralogy, geochemistry, geophysical, petroleum geology and reservoir evaluation, taking full advantage of data of core, outcrop, logging and seismic, on the basis of predecessor's achievements, along the main line of basin evolution, sedimentary evolution and distribution regulation of effective reservoir sandbody, and according the evaluation process of prediction on effective reservoir sandbody of lithology reservoir, which is five-step and block decided by graphic and table, distribution regulation of effective reservoir sandbody of major gas-bearing interval in Sulige gas field was studied systematically, several creative achievements as follow were obtained.①According to research idea of provenance direction controlled by tectonism and provenance location determined by analysis and measurement, based on the study on tectonic evolution of Yinshang old land and Yimeng upheave and the analysis of the response between provenance basement and sediment in basin, the influence on sediment supply in study area by both was definited firstly. With combination of Dickinson triangular diagram, distribution character of basement rock type, detrital component character, heavy mineral distribution character, rock detrital character, quartz cathodeluminescence character, REE character and Zircon dating, it is revealed that the provenance of upper Paleozoic major gas-bearing interval in Sulige gas field was from Yinshang old land.②Based on provenance analysis, according to the research route of single well facies, cross-well facies, plane facies, sedimentary evolution and sedimentary model, with combination of sedimentary setting of upper Paleozoic in Ordos basin, and according to basin evolution and formation mechanism of shallow water delta, it is concluded that shallow water delta system developed in Sulige gas field during period of Shan1 and He8. It is first proposed that the sedimentary environment is blanketed shallow water braided river delta in He8 member of Sulige gas field, and the sedimentary model of shallow water meandering river delta in Shan1 member and the model of blanketed shallow water braided river delta in He8 member were built firstly, which were used to guide reservoir evaluation and prediction in Sulige gas field.③According to the theory and methods of high-resolution sequence stratigraphy, which is guided by the Cross's base level cycle, with combination of stratigraphy classification plan of major gas-bearing interval in Sulige gas field, sequence character and sequence configuration of major gas-bearing interval were studied carefully, seismic framework and high-resolution sequence stratigraphy framework of mid-term cycle were built. It is clear that there are regional progressive and regressive cycles in most long-term cycle of sequence framework, two types of reservoir sandbody developed in the long-term cycle, one of them developed on two sides of sequence boundary, the other one developed within sequence. The position of sandbody developed on sides of sequence is relatively stable, the thickness is great, they usually stacked continuously in vertical direction, and they stacked in shape of blanket or wide belt in horizon direction, where are the best position for developing reservoir sandbody. No matter the supply in horizon or vertical, with the increase of accommodation, the thickness in every mid-term cycle, especially the thickness of fine flooding sediment increased synchronously, meanwhile, the thickness of reservoir sandbody and the developing position showed reverse regression and reduction, part of them were affected by paleotopography.④Based on the systematical study on character of reservoir mineralogy, diagenesis, geophysical, pore configuration, nonhomogeneity and reservoir sandbody genetic type, parameter and standard of reservoir evaluation are established to evaluate by sorting and synthetically. TypeⅠreservoir with high production without any fracturing and typeⅡreservoir with high industrial gas flow after fracturing mainly located in He8 member, part of typeⅡlocated in Shan1 member, typeⅢreservoir and typeⅣnon-reservoir with industrial gas flow after fracturing can be both found in Shan1 and He8 member.⑤Based on the forenamed studies, particularly combined with results of sedimentary character of effective reservoir, sequence stratigraphy character and reservoir evaluation, referenced the main control factors of effective reservoir, the distribution regulation of effective reservoir of Shan1 and He8 member of upper Paleozoic in Sulige gas field is explicit. The sandbody of Shan1 member distributed in shape of belt, effective reservoir sandbody distributed isolatedly, the ones of He8 member distributed in large area like blanket, effective ones mostly distributed isolatedly or regionally in shape of belt. Respectively enrichment blocks located in sandbody of main braided distributary channel, the most favorable typeⅠblocks and second most favorable typeⅡblocks should be key area for next exploration, the middle favorable typeⅢblocks also have high value for exploration.