Dissolution mechanism and favorable reservoir distribution prediction are the key problems restricting oil and gas exploration in deep-buried layers.In this paper,the Enping Formation and Zhuhai Formation in Baiyun Sa...Dissolution mechanism and favorable reservoir distribution prediction are the key problems restricting oil and gas exploration in deep-buried layers.In this paper,the Enping Formation and Zhuhai Formation in Baiyun Sag of South China Sea was taken as a target.Based on the thin section,scanning electron microscopy,X-ray diffraction,porosity/permeability measurement,and mercury injection,influencing factors of dissolution were examined,and a dissolution model was established.Further,high-quality reservoirs were predicted temporally and spatially.The results show that dissolved pores constituted the main space of the Paleogene sandstone reservoir.Dissolution primarily occurred in the coarse-and medium-grained sandstones in the subaerial and subaqueous distributary channels,while dissolution was limited in fine-grained sandstones and inequigranular sandstones.The main dissolved minerals were feldspar,tuffaceous matrix,and diagenetic cement.Kaolinization of feldspar and illitization of kaolinite are the main dissolution pathways,but they occur at various depths and temperatures with different geothermal gradients.Dissolution is controlled by four factors,in terms of depositional facies,source rock evolution,overpressure,and fault activities,which co-acted at the period of 23.8–13.8 Ma,and resulted into strong dissolution.Additionally,based on these factors,high-quality reservoirs of the Enping and Zhuhai formations are predicted in the northern slope,southwestern step zone,and Liuhua uplift in the Baiyun Sag.展开更多
The gravity flow deposit were mainly developed in the lowstand systems tract（LST） of the first member of Upper Miocene Huangliu Formation（Ehl1） in Dongfang area, Yinggehai Basin, has become a valuable target for g...The gravity flow deposit were mainly developed in the lowstand systems tract（LST） of the first member of Upper Miocene Huangliu Formation（Ehl1） in Dongfang area, Yinggehai Basin, has become a valuable target for gas exploration and production. The gravity flow sedimentary characteristics of lithofacies associations, sedimentary texture, seismic facies and logging facies were described in detail on the basis of integrated analysis of cores, logging and seismic data. The sedimentary microfacies types composed of neritic sandbar, continental shelf mud, main channel, bifurcated or cross-cutting distributary channel, overspill, and natural levee are revealed under the constraint of high resolution sequence stratigraphic framework in the Ehl1. The gravity flow deposit system in the LST is divided into three evolution stages corresponding to periods of three parasequence sets. The gravity flow deposit was induced in the early LST, expanded rapidly in the middle LST and decreased slightly in the late LST. But its developing scale decreased sharply in the transgression systems tract（TST） and finally vanished in the highstand systems tract（HST）. This spatial evolution rule is constrained by the integrated function of sediments supply of the Vietnam Blue River in the LST, the development of local gradient change in sea floor（micro-topography, i.e., flexure slope break）, and the fall in relative sea level. On the basics of the deep study of the coupling relationship among the three main control factors, the sedimentary model is established as an optimal component of ＂source-channel-sink＂ for shallow marine turbidite submarine fan.展开更多
基金The National Natural Science Foundation of China under contract No.42202157the China National Offshore Oil Corporation Co.,Ltd.Major Production and Scientific Research Program under contract No.2019KT-SC-22。
文摘Dissolution mechanism and favorable reservoir distribution prediction are the key problems restricting oil and gas exploration in deep-buried layers.In this paper,the Enping Formation and Zhuhai Formation in Baiyun Sag of South China Sea was taken as a target.Based on the thin section,scanning electron microscopy,X-ray diffraction,porosity/permeability measurement,and mercury injection,influencing factors of dissolution were examined,and a dissolution model was established.Further,high-quality reservoirs were predicted temporally and spatially.The results show that dissolved pores constituted the main space of the Paleogene sandstone reservoir.Dissolution primarily occurred in the coarse-and medium-grained sandstones in the subaerial and subaqueous distributary channels,while dissolution was limited in fine-grained sandstones and inequigranular sandstones.The main dissolved minerals were feldspar,tuffaceous matrix,and diagenetic cement.Kaolinization of feldspar and illitization of kaolinite are the main dissolution pathways,but they occur at various depths and temperatures with different geothermal gradients.Dissolution is controlled by four factors,in terms of depositional facies,source rock evolution,overpressure,and fault activities,which co-acted at the period of 23.8–13.8 Ma,and resulted into strong dissolution.Additionally,based on these factors,high-quality reservoirs of the Enping and Zhuhai formations are predicted in the northern slope,southwestern step zone,and Liuhua uplift in the Baiyun Sag.
基金supported by the National Natural Science Foundation of China (NSFC) (Nos. 41272122, 41202074, 41172123 and 40702023)the National Twelfth Five-Year Major Projects of Oil and Gas (No. 2011ZX05025-002-02-02)+1 种基金the Key Laboratory of Tectonics and Petroleum Resources (CUG)of Ministry of Education open issue (No. TPR-2013-08)the China University of Geosciences (Wuhan) Teaching Labor atory open funded projects
文摘The gravity flow deposit were mainly developed in the lowstand systems tract（LST） of the first member of Upper Miocene Huangliu Formation（Ehl1） in Dongfang area, Yinggehai Basin, has become a valuable target for gas exploration and production. The gravity flow sedimentary characteristics of lithofacies associations, sedimentary texture, seismic facies and logging facies were described in detail on the basis of integrated analysis of cores, logging and seismic data. The sedimentary microfacies types composed of neritic sandbar, continental shelf mud, main channel, bifurcated or cross-cutting distributary channel, overspill, and natural levee are revealed under the constraint of high resolution sequence stratigraphic framework in the Ehl1. The gravity flow deposit system in the LST is divided into three evolution stages corresponding to periods of three parasequence sets. The gravity flow deposit was induced in the early LST, expanded rapidly in the middle LST and decreased slightly in the late LST. But its developing scale decreased sharply in the transgression systems tract（TST） and finally vanished in the highstand systems tract（HST）. This spatial evolution rule is constrained by the integrated function of sediments supply of the Vietnam Blue River in the LST, the development of local gradient change in sea floor（micro-topography, i.e., flexure slope break）, and the fall in relative sea level. On the basics of the deep study of the coupling relationship among the three main control factors, the sedimentary model is established as an optimal component of ＂source-channel-sink＂ for shallow marine turbidite submarine fan.
