High-resolution Sequence Stratigraphy And Reservoir Modeling

High-resolution sequence stratigraphy,raised by Cross in Corolado mine school in 1994,was introduced to China by Deng Hongwen in 1995.It plays more and more important roles in exploration and development of oil and gas in continental basin in China. We may set up systematical concept of strata forming and evolution by analyzing high-resolution sequence stratigraphy, which helps for the detailed description and correlation of strata. Especially, To the complex of forming and distribution of strata in continental basin in our country, it seems more important to divide and correlate strata , and construct framework of strata through high-resolution sequence stratigraphy. Based on the study of high-resolution sequence stratigraphy, 3-D model of reservoir forming and ditribution is set up through the technology of stochastic modeling,which is a good way of prediction of the distribution of sand-body.In this paper, On the basis of the basic principles of high-resolution sequence stratigraphy, the hierarchies of the changes of the base-level cycles , and strata records preserved during the changes of different base-level cycles are analyzed, and the characters of development and distribution of different hierarchical base-level cycles are discussed on the basis of hierarchical surfaces and hierarchical bodies. At last, identification marking of different hierarchical base-level cycles and study procedure are concluded. Based on above analysis, Chang4+5-Chang6 can be divided into 6 microfacies as follows: subaqueous dirtibutary channel, subaqueous natural leveel, subqueous creveas, distributary mouth bar and so on through outcrop, core of wells and the well log data in Pingbei oil field in Ordos basin. Through the analysis of different types of sequence surfaces, microfacies assembling and stacking stratigraphic pattern, different hierarchical base-level cycles can be divided. The Chang4+5-Chang6 can be divided into 2 kinds of the fifth hierarchical base-level cycles, 3 kinds of the fourth hierarchical base-level cycles and 16 kinds of the third hierarchical base-level cycles. The framework of the 5-th and the 4-th hierarchical base-level cycles are achieved through different hierarchical base-level cycles correlation in Pingbei oil field. Using maximum flooding surface and local explosure erosion surface as the correlation framework surface in the 4-th hierarchical base-level cycles, sand-body in the 3-th hierarchical base-level cycles formed in the 4-th hierarchical base-level cycles may be correlated layer by layer. The law of the sand-body and the characters of reservoir heterogeneity formed in the 4-th hierarchical base-level cycles are discussed. The study shows: (1) During early period of the 4-th hierarchical base-level cycle rising, subaqueous distributary channel formed, continuously stacked vertically, and migrated in limit range laterally, and channel sand-body stretches farther longitudinally, and lacks interbeds of mud rock and siltsand in sand rock, reservoir heterogeneity is relatively weak. (2) During mid-period of the 4-th hierarchical base-level cycle rising, subsaqueous distributary channel migrated actively, channel divided and converged strongly to form netted sand-body and sand sheet mainly, but interbeds of mud rock and siltsand increases gradually in sand-body, reservoir heterogeneity increased. (3) During later period of the 4-th hierarchical base-level rising andearly period of the 4-th hierarchical base-level falling, reservoir sand-body was poor, and only form thin sand-body of subsaqueous distributary channel, subsaqeuous creveas and distal mouth bar, sand-bodys are surrounded by mud and silt rock. Reservoir heterogeneityies are strong.On the basis of above synthetical study, the reservoir geological knowledge base has been founded, and reservoir geological modeling has been proceeded using the 4-th hierarchical base-level cycles as modeling unit. 6 microfacies were integrated to 3 microfacies before modeling and then the rock frame model has been constructed by the Sequential Indicator Simu...