Studies On The Conduit Systems And Its Control On Hydrocarbon Accumulation In Nanpu Depression

This paper firstly analyzed pathway elements such as fault, sand body and unconformity through comprehensive use of geological, geophysical and geochemical new theories and methods. On the base of discussion above, the space-time match between pathway system and conditions of hydrocarbon accumulation were analyzed. At last, the paper summarized the factors that control hydrocarbon distribution, established the modes of pathway system that controls reservoir-forming in Nanpu depression.Through the study of pathway elements of research area, the distribution of sand body, faults and unconformities of Nanpu depression were ascertained, the activity characters of main faults of the depression were analyzed. Results showed that the sand body of main structural belt were relatively developed, the properties and connectivity of Dongying Formation and Upper Tertiary sand body were better than the third member of Shahejie Formation. The main oil and gas structures commonly developed with oil source faults which were mainly active in the third member of Shahejie Formation, Dongying Formation and Minghuazhen Formation.Through analyzing oil source characteristics, wave impedance inversion, hydrocarbon accumulation period and the match of pathway system with accumulation conditions, we evaluate the time-space effectiveness of pathway system in the study area carefully. By the study of Oil-source Correlation, source rocks in the Depression are divided into three groups and crude oil is divided into four groups. By analyzing wave impedance inversion profiles and the match of faults with sand bodies on the plane, there is a good match of faults with sand bodies in the Depression. Based on geological and geochemical comprehensive research method, it is considered that the accumulation period mainly includes two stages, dongying stage and minghuazhen stage, and there are different accumulation periods in different area. There is not only a good match between the time of faulting and hydrocarbon generation and expulsion period in the Depression, but also the spatial combination relations between faults and sand bodies. All of that are beneficial to hydrocarbon migration and accumulation.The lateral pathway of the shallower Nanpu depression was fluvial sand body whose connectivity was poor because of the cutting of upper faults. Sand body of Dongying formation is of large scale, good lateral connectivity and a good matching with the fault. The sand body scale and connectivity of Shahejie formation was inferior to that in Dongying formation. The space combined features of pathway system make the hydrocarbon generated by resources of Shahejie formation and Dongying formation to migrate to the faults through lateral pathway, and then the hydrocarbon were migrated to superficial layer sand bodies by vertical pathway system and accumulated in reservoirs. Oil and gas experienced a"deep migration and shallow accumulation"process.