梁平地区二叠系长兴组台缘礁滩储层演化——来自天东110井岩石学及地球化学证据

Evolution of platform margin reef beach reservoir of Permian Changxing Formation in Liangping area:petrological and geochemical evidence from Well Tiandong 110

天东110井是川东地区长兴组近年来获得的高产稳产井之一,该井的不同类型储层成因研究及模式建立对梁平地区长兴组勘探具有重要指示作用。基于天东110井长兴组丰富的取心资料,文中对其开展了岩石学、地球化学分析,建立了不同储集空间的演化模式,提出了高产井储层分布模式。结果表明:1)天东110井长兴组发育孤立状洞、溶洞、孔隙(包括针状孔及晶间孔)、高角度构造溶蚀缝。2)天东110井长兴组针状孔分布于礁滩体的颗粒云岩中,准同生期大气淡水溶蚀成孔、渗透回流白云岩化起关键保孔作用。3)缝洞形成受晚三叠世诺利期地层水溶蚀及瑞提期热液溶蚀作用控制,前者被沥青及巨晶方解石全充填,储集性能较差,后者部分被方解石、白云石、萤石等充填,充填程度低,孔渗性能好。下一步勘探应注重台地边缘的白云岩礁滩体微地貌高点与近晚三叠世瑞提期断裂及裂缝的热液溶蚀叠合发育区,可望获得更大突破。

Well Tiandong 110 is one of the high and stable production wells obtained in Changxing Formation in eastern Sichuan area in recent years.The study on the genesis and model establishment of different types of reservoir in this well is of great significance to the exploration of Changxing Formation in Liangping area.Based on the rich coring data of Well Tiandong 110 in Changxing Formation,the paper carried out petrological and geochemical analysis,established the evolution model of different reservoir space,and put forward the reservoir distribution model of high production wells.The results show that:(1)Isolated caverns,karst caverns,pores(including needle-shaped pores and intercrystalline pores)and high-angle structural corrosion fractures are developed in Changxing Formation of Well Tiandong 110.(2)The needle-shaped pores of Changxing Formation in Well Tiandong 110 are distributed in the granular dolomite of reef-shoal bodies,and the atmospheric fresh water dissolved into pores in the penecontemporaneous,and the seepage reflux dolomitization played a key role in preserving pores.(3)The formation of fractures and caverns was controlled by formation water and hydrothermal corrosion in the Late Triassic Norian and Ruetic,and the former was fully filled with bitumen and macrocrystalline calcite,with poor reservoir performance.The latter was partially filled with calcite,dolomite,fluorite,etc.,the filling rate was low,with good porosity and permeability.The next exploration should pay attention to the microgeomorphic high point of the dolomite reef-shoal bodies at the platform edge and the hydrothermal solution superposition development area of the Ruetic faults and fractures in the late Triassic,which is expected to get a bigger breakthrough.