Hydrocarbon Accumulation Dynamics Of Hu-Qing Fault-step Belt In Dongpu Depression

Hu-Qing Fault-step Belt, which lies in the middle area of western slope in the Dongpu Depression, is one of the important hydrocarbon exploration areas in Zhongyuan Oilfield . Shahejie formation is the main exploration layer system in the study area, which has the characteristics of more oil-bearing layers, widely distributing faults and complicate structures. Based on the modern petroleum geology theories and the existing research results, this paper has systematically studied on the dynamics of hydrocarbon accumulation and favorable directions of hydrocarbon exploration in the study area by using new technology and new approaches as well as doing integral, systematic, dynamic and quantitative research.The main results and knowledge of this study are as follows:1) On the basis of the analysis of sequence stratigraphy cycles, mudstone compaction and organic geochemistry, associating with sealing conditions and features of formations in salt lake basin, the study area can be divided into five hydrocarbon accumulation dynamic systems from top to bottom on the guidance of hydrocarbon accumulation dynamic theories, which are the top allogenic nomal-pressured semi-opened hydrocarbon accumulation dynamic system(I), the upper commingled normal-pressured semi-opened hydrocarbon accumulation dynamic system(II), middle commingled weakly abnormal-pressured semi-closed hydrocarbon accumulation dynamic system(III), the lower authigenic abnormal-pressure semi-closed hydrocarbon accumulation dynamic system(IV), the bottom authigenic abnormal-pressured closed hydrocarbon accumulation dynamic system(V).2) Based on the data of drilling, seismic, other relevant analysis and tests and so on, the evolution history of fluid kinetic field in study area are recovered and rebulit by dynamic numerical modeling technique, which suggest that the fluid kinetic field has different response features in different formations, different benches and different fault blocks on the same bench, also indicat that the fluid kinetic field has close relationship with hydrocarbon accumulation, and it is of great significance to hydrocarbon generation, physical property of reservoir, preservation condition and hydrocarbon migration and accumulation in study area..3) Associated with geochemistry, sand body, formation test and geological data, the hydrocarbon accumulation dynamic course including geohistory, thermal history, hydrocarbon generation history and expulsion history is recovered by using the dynamical numerical modeling of BasinMod. And then the oil and gas-filled history is dealed with fluid inclusion. They reveal the complexity and differences of hydrocarbon accumulation processes in this paper.4) The paper reveals properties and distribution rules of crude oil by comprehensive application of drill stem test. Type I: low density, low viscosity and light crude oil, distributed in step I; type II: medium density, medium viscosity and medium crude oil ,distributed in step II; type III: high density, high viscosity and medium heavy crude oil ,distributed in step III and Block-Hu19, And the oil is water flushed heavy crude oil in Block-Hu 19,which is different from the degraded crude oil on step III.5) On the basis of analyzing and comparing the different hydrocarbon accumulation patterns of typical ramp region in China, three hydrocarbon accumulation patterns are summed up: authigenic-sand body parallel migration and accumulation, commingle source-sand body-fault parallel-vertical migration and accumulation, allogenic-sand body-fault-unconformity surface parallel-vertical stepping migration and accumulation. According to the above mentioned three hydrocarbon accumulation patterns, it points out that commingle source-sand body-fault parallel-vertical migration and accumulation pattern together with lower hydrocarbon accumulation dynamic subsystem is of great exploration potential and the favorable exploration aspects are blocks or fault-lithology compound reservoirs in step II and lithology or lithology-fault compound reservoirs in step I.