新疆塔中油田中古58井寒武系芙蓉统白云岩储层特征

RESERVOIR CHARACTERISTICS OF LATE CAMBRIAN DOLOMITES IN THE WELL ZHONGGU-58, TAZHONG OIL FIELD,XINJIANG, NW CHINA

塔里木板块广泛分布的寒武系白云岩储层具重要的油气勘探潜力。塔中油田I号断裂带的中古58井寒武系芙蓉统下丘里塔格群白云岩在区域上有代表性,具有孔隙规模大且储层物性好的优势。储集空间类型包括小型溶洞、溶孔、晶间孔、晶间溶孔及裂缝等,常充填石英、隐晶质硅质、白云石、萤石、黄铁矿、闪锌矿、方解石并呈现明显的充填次序;有效储层包括原生孔隙及准同生成岩阶段—浅埋藏阶段的溶蚀和白云化作用所形成的次生孔隙;中—深埋藏成岩阶段的热液溶蚀在改造部分储集空间的同时,也表现为多种矿物充填过程。

The wide-spreading Late Cambrian(Furongian) dolomites have served as essential petroleum reservoirs in Tarim Block of NW China, and are of great significance for petroleum-gas explorations. The Well Zhonggu-58, situated in the Fault 1 of the Tazhong Oil Field, is a regional representative case of reservoir studies. In the well, crystalline dolomites of the Lower Qiulitag Group(Furongian of Cambrian in age) are well developed, and therefore provide important information for insight into the porosities and their evolution. Our analyses show that these reservoirs are of very high porosity and permeability. The types of reservoir spaces include small solution vugs, dissolution pores, intercrystalline pores, intercrystalline dissolution pores, and fractures. In the reservoir space, the filling sequence of minerals seems to be quartz, cryptocrystalline silica,dolomite, fluorite, pyrite, sphalerite and calcite, respectively. Effective reservoirs include primary pores and secondary pores formed by dissolution and dolomitization during the penecontemporaneous diagenesis stage and the subsequent shallow burial stages. The physical properties of the reservoirs were modified, in the diagenetic stage of middle-deep burial, by hydrothermal dissolution accompanied by precipitation and filling of various minerals.