塔里木盆地奥陶系边缘相分布及储层主控因素

Distribution of marginal facies and main controlling factors of reservoirs in the Ordovician,the Tarim Basin

赵宗举 周新源 王招明 沈安江

Zhao Zongju Zhou Xinyuan Wang Zhaoming Shen Anjiang

通过对塔里木盆地奥陶系层序地层及其沉积相、碳酸盐岩储层等方面的研究,探讨了盆地奥陶系台地边缘相分布及储层的主控因素。识别出分布位置不同的下奥陶统下部蓬莱坝组、下奥陶统上部-中奥陶统下部鹰山组、中奥陶统中上部一间房组及上奥陶统中部良里塔格组4期台地边缘高能相带。认为该边缘相带碳酸盐岩形成有效储层的主控因素为:高能滩相颗粒灰岩是有效储层发育的主要物质基础,而障积礁与灰泥丘次之;高频与三级海平面下降造成的同生暴露所产生的淡水溶蚀作用、混合水白云石化作用及混合水溶蚀作用是有效储层的主要建设性成岩作用;志留纪—泥盆纪期间奥陶系边缘相碳酸盐岩的古潜山岩溶作用进一步造就了次生溶孔洞;二叠纪期间的深部埋藏有机酸溶蚀作用和岩浆热液流体溶蚀作用以及与主压应力平行或低角度斜交的开启断裂-裂缝带对奥陶系边缘相碳酸盐岩有效储层的形成具有建设性改造作用。

Through research on the Ordovician sequence stratigraphy,sedimentary facies and carbonate reservoirs in Tarim basin,this paper discusses the distribution of platform marginal facies and main controlling factors of reservoirs in the Ordovician.Four stages of platform marginal high-energy facies belts are identified,including the Penglaiba Formation of the lower Lower Ordovician,the Yinshan Formation of the upper Lower Ordovician to the lower Middle Ordovician,the Yijianfang Formation of the middle to upper part of the Middle Ordovician,and the Lianglitage Formation of the middle Upper Ordovician.The main factors controlling the effective formation of carbonate reservoirs in these marginal facies are that the high-energy bank facies grainstone serves as the main material basis for the effective formation of reservoirs,followed by the barrier reefs and micrite mounds;the fresh water dissolution,mixed-water dolomitization and mixed-water dissolution,caused by contemporaneous exposure of marginal carbonate due to Milankovitch or the third-rank sea level dropping,are the chief constructive diagenesis for the formation of effective reservoirs;secondary vugs and cavities were generated by the karstification of the Ordovician marginal carbonate during the Silurian and the Devonian;and the organic acid dissolution and magma hydrothermal fluid dissolution during deep burial of the Permian and the open fault-fracture system parallel or small-angle obique to the major compressional stress are constructive for forming effective reservoirs in the Ordovician marginal carbonate.

10.11743/ogg20070606