沉积盆地流体活动及其成岩响应

Basin Fluid Flow and Associated Diagenetic Processes

盆地流体活动通过改变成岩场的温压和孔隙水介质条件,进而影响到盆地内成岩作用序列、水—岩相互作用以及储层孔隙变化。对于碎屑岩而言,流体活动仅能导致母岩中少部分矿物的溶蚀以及孔隙内溶解与沉淀作用发生,富含二氧化碳和有机酸的流体活动为次生孔隙发育提供条件,超压环境下流体幕式释放既可导致超压体内次生孔隙的发育,又可以导致热流体活动影响区域内浅部储层的成岩异常;对于碳酸盐岩而言,由于碳酸盐岩具有很强的溶解性,盆地流体活动导致碳酸盐岩储层组构及空间发生巨大的变化,其中天水的下渗以及与深部热液或热流体沿断裂或裂缝释放均可导致碳酸盐岩成分、组构、储集空间发生根本性变化,故与盆地流体活动密切相关的风化壳型岩溶储层和构造热液白云岩储层构成碳酸盐岩中最为重要的储层类型。然而,盆地流体活动及其成岩响应研究仍存在许多亟待解决的难点问题,急待深入的研究探索。

Basin fluid flow will change a diagenetic condition including temperature, pressure and fluid geochemistry in a pore space of host rocks, and result in the variation of sequential diagenetic processes, interaction of water and rock, and porosity of reservoir. Viewing in siliciclastie rocks, fluid flow only results in dissolution of minor mineral and modification of pore space due to mineral dissolution and precipitation. Fluid with plentiful of CO2 and organic acid will provide an available condition for the development of secondary porosity. Fluid episodic expulsion in overpressured environment not only results in the formation of secondary porosity in the overpressured compartment, but also results in the occurrence of abnormally diagenesis due to perturbations in temperature in shallow reservoirs with a hydrostatic environment. Viewing in carbonate rocks, because of strong dissolution of carbonate rocks, basin fluid flow can result in an essential variation in fabric and pore space in carbonate reservoirs. Expulsion of metroric inleakage and deep volcanic or hydrothermal fluids along faults or fractures will result in an essential variation in composition, texture, reservoir space in a vast realm in carbonate rocks. Hence, weathering karst typed and structurally controlled hydrothermal dolomitization typed reservoirs related closely to basin fluid movement are taken as main reservoir in carbonate rocks. However, basin fluid flow and associated diagenetic process has remained a matter of controversy, much more research are needed in the future.