| Wenmingzhai oilfield is one of the important old oilfield in Zhongyuan which has explored and developed for about forty years since 1975, it has found many oil-bearing strata and multiple oil-bearing structure and its high capacity has made positive contribute to economic construction. Though the high water, it is still a important block. The oilfield is located in the junction of Qingfeng, Henan province and Shenxian, Shandong province. It belongs to dome structure in secondary structure of central uplift belt in the northern of Dongpu sag on the Bohaiway basin. It is a horst caused by two groups of NNE dip and its opposite normal faults. The main basin type belongs to fault depression and depression of Meso Cenozoic continental facies. The main depositional sequence are Paleogene, Neogene and Quaternary and its main oil-bearing series found are Shahejie formation of Paleogene.Wenmingzhai has been developed for many years, it has formed a set of complicated fault block reservoir description and stimulation technology and realized efficient development, but with the extent improved, it needs further research in order to maintain a good development situation. The study of Wenmingzhai oilfield has been in structure, not in phase of Shahejie formation, and sedimentary system has been long disputed, proposed delta, shallow water delta, fan delta, terminal fan, lake and other various types. It is imminent to take a further research on the sedimentary system.This study systematically collects seismic, logging, well logging, laboratory analysis, and comprehensive use sedimentology, reservoir geology principle and the methods, takes research on reservoir sedimentology and provides the theory basis for the remaining oil in Wenmingzhai oilfield.Relying on core, seismic, logging data, we identify the formation interface. Based on the former, we divide the Shahejie Formation into third level, fourth member, lower part of third member, middle part of third member, upper part of third member, lower part of second member, upper part of second member, first member.Synthesize tectonic background, characteristics of heavy minerals, fault activity and paleogeomorphogloic, Wenmingzhai oilfield is mainly controlled by northeast, northwest source. Based on the rock and mineral characteristics, the study area is far from the source, and it is also influenced by the southwest source, due to further, it less influenced. In different periods, activity intensity of different fault influence the different directions of the source supply, and the fault strike influence the form of sediment distribution.The detailed description of core wells in study area, identify the tabular cross bedding sandstone facies, parallel bedding sandstone facies, small wavy or intermittent hummocky cross stratification siltstone facies, deformation of silty sand facies, massive bedding silty sand facies, dark mudstone facies, variegated mudstone facies, shale, nagelfluh and so on. According to the characteristics of phase combination, it mainly develops meandering river delta and lake, mainly locates in the end of delta front, strongly influenced by lake, identify the subaqueous distributary channel, river overflow, subsea distributary bay, mouth bar, sheet sand, the mud among sheet sand, prodelta mud.Based on the influence of the paleoclimate, faults and source, combined with well connection, analyse the sedimentary facies distribution and evolution in each period. During the deposition of the fourth member, with the northeast source, develop delta front from the northeast to southwest. During the deposition of the lower part of third member, with the northeast and northwest source, develop delta front in middle and northern area, develop underwater distributary channel and overlap. During the deposition of the middle part of third member, the northeast source regression, the northwest mainly develop, the delta front size reduce. During the deposition of the upper part of third member, inherit the northwest source, the northeast source also influenced, develop the delta front, and the underwater distribution channel is wide. During the deposition of the lower part of second member, inherit the northwest source, the west and north source influenced, develop three delta lobes. The northwest and north lobe caused by the northwest and north source, and Ming 15 area caused by the west source. By contrast, the north area is nearer the source than the southwest area, underwater distributary channel scale larger. Besides, the lake influence enhanced, sand mat more serious. During the deposition of the upper part of second member, inherit the lower part of second member source, mainly develop delta front and promote the lake, underwater distributary channel extend farther. During the deposition of the first member, inherit the upper part of second member source, supply weaker, the lake influence more enhanced. The delta is not continuity and the sand body refinement degree is serious.Based on the evolution of sedimentary, we sum up the sedimentary model. The main factors of distribution are tectonic activity, ancient landform and climate evolution. The study area has experienced fault depression and depression which form different stages and levels of faults. The main direction of sand body is consistent with fault trend. Liuta on the western part of the study area, Chenying on the northeast and Guancheng on the northwest provide detrital material under the interaction of active faults and higher land in different period. The climate affect rainfall and sediment type. When the climate is humid, rainfall is relatively large, lake basin expand, delta atrophy, delta front and lake develop. When the climate is dry, rainfall decrease, lake basin shrink, delta front develop and underwater distributary channel are wide... |
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