黔南石炭系层序地层格架中碳酸盐岩成岩作用研究

Study on diagenesis of the carbonate rocks in the Carboniferous sequence stratigraphic framework of South Guizhou

在三级层序地层格架内,从体系域及层序界面的角度对黔南石炭系碳酸盐岩的成岩作用进行了研究。结果表明,与LST有关的成岩作用主要为范围广泛的暴露溶蚀作用;与TST有关的成岩作用主要发育于海底成岩环境和混合水成岩环境,其中后者会随着海平面的不断上升而向大陆迁移;与HST有关的成岩作用主要包括发育于海底成岩环境的胶结作用及高位晚期的大气淡水成岩环境中的溶蚀、胶结和白云石化作用。与Ⅰ型层序界面有关的成岩作用主要有溶蚀作用、胶结作用和白云石化作用,成岩时间长、强度大,并且在黔南可进行区域对比;与Ⅱ型层序界面相关的成岩作用发育规模小,对碳酸盐岩的改造能力较弱。与HST有关的成岩作用及与Ⅰ型层序界面有关的成岩作用对碳酸盐岩储层的改造能力强,往往可形成厚层的白云岩及规模较大的溶蚀孔洞体系,因此,可以作为有利储层追踪对比及预测的有力地质依据之一。

This paper studies the diagenesis of the Carboniferous carbonate rocks in the sequence stratigraphic framework of South Guizhou and draws the following conclusions. The main diagenesis developed during the LST period is fargoing karstification in the exposed area. The diagenetic environments with respect to TST are mainly marine and mixed-water environments, and the latter will transfer toward to the continent with the sea level continuously rising. During the highstand of sea level （HST）, the platform carbonate sediments are subject to the marine （for the earlier period） and meteoric water （for the later period） diagenesis environment, in which rapid marine carbonate cementation and meteoric erosion, cementation and dolomitization will occur respectively. The diagenesis correlative to Ⅰ -type sequence boundary, with the characteratics of long-time process and high intensity, mainly includes erosion, cementation and dolomitization which can be correlated throughout South Guizhou area. While those diageneses correlative to Ⅱ-type sequence boundary occur relatively at a limited scale and have less ability in rebuilding the carbonate strata. The diageneses correlative to HST and Ⅰ-type sequence boundary can produce thick dolomite and large scale pore space. So they can be considered as the effective geological evidences for predicting favorable reservoirs.