摘要:
碳酸盐岩早成岩岩溶作用可发育溶蚀孔洞或具有规模的溶洞,这对于认识我国塔里木盆地、四川盆地碳酸盐岩内幕岩溶区孔洞成因与分布具有重要参考价值。然而碳酸盐岩早成岩岩溶在我国现代岩溶发育较少,研究程度低。文章通过总结国外在碳酸盐岩早成岩岩溶形成机理及孔洞发育特征的研究成果,探讨早成岩岩溶的油气地质意义:(1)成岩早期碳酸盐岩胶结程度差,岩石疏松,孔隙度、渗透率极高,介质空间较均匀;(2)早成岩岩溶作用与海平面升降具有明显的关系,尤其海岛或滨岸地区的淡水-海水交互带,以混合水岩溶为特征的岩溶作用较强烈;(3)早成岩岩溶孔洞发育分布具有一定特点,岛屿岩溶以发育侧面边缘洞穴为特征,而滨海岩溶以发育混合带管道为特征;(4)孔洞的发育主要受淡水中 CO 2含量、水流通过混合过渡带的水动力及海平面变化速率控制;(5)早成岩岩溶为研究我国地质历史时期碳酸盐岩短期暴露岩溶作用提供借鉴,对其孔洞发育分布特征的认识,将促进碳酸盐岩内幕区孔洞型油气储层形成机理研究,指导内幕区孔洞储层分布预测和油气勘探。
Abstract:
Solution caves or big karst caves can be generated in carbonatite by eogenetic karstification,which is very important for the study of distribution and genesis of such caves in karst areas of the Tarim and Si-chuan basins.However,young carbonate karst is few in amount and poorly studied in China.So,a large number of foreign literature about this issue were collected and reviewed in this paper.The purpose is to present features of the caves by eogenetic karst and their corrosion mechanism,and the petroleum geological significance.(1)Young carbonatite is characterized poor cementation,loose structure,and high porosity and permeability,with uniform medium space.(2)Eogenetic karst is obviously associated with rise and fall of sea level.Especially in islands or coastal areas with fresh-salt water interaction zones,the karstification fea-tured by mixed water is relatively intense.(3)Holes or caves which formed by eogenetic karst have such patterns that flank margin caves develop in islands while channels of mixed zones appear in coastal karst.(4) Development of karst caves depends on the CO 2 content of the freshwater,hydrological power of the mixed transition zone,and the change rate of sea level.(5 )Eogenetic karst provides a theoretical reference for studying the short-term exposure of karstification during geological times.Such research will help under-stand formation mechanisms of hole-cave type carbonate reservoirs in internal karst areas and guide the dis-tribution prediction of hole-cave type reservoirs in carbonatite regions.
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