川西北地区双鱼石区块栖霞组沉积微相特征

Characteristics of sedimentary microfacies in Qixia Formation, Shuangyushi block, northwestern Sichuan Basin

近年来,以双鱼X131、双鱼X133井为代表,川西北地区双鱼石区块部署的多口井在中二叠统栖霞组钻遇厚层的孔隙型白云岩,并获得超过百万方的高产工业气流,展示了该地区栖霞组良好的勘探前景。研究区栖霞组储层的发育情况受沉积相控制明显,为明确川西北地区双鱼石区块中二叠统栖霞组沉积微相类型及有利相带分布,提高油气勘探效益,本次研究主要利用野外剖面测量、岩心描述、铸体薄片鉴定、成像测井分析等方法对栖霞组沉积相特征进行详细分析,研究结果表明:①建立微相识别模板,将栖霞组划分出4种亚相、5种微相并分析对应特征;②结合9口单井的微相划分及连井相剖面分析,认为滩核、滩缘微相为最有利相带,纵向上主要分布于栖霞二段,横向分布稳定;③结合相对海平面变化,应用趋势面法恢复川西北地区双鱼石区块中二叠世栖霞期古地貌,并进一步得出沉积微相平面展布特征。以上研究为该区栖霞组后续的优质储层研究及井位部署提供了地质依据。

In recent years, thick porous dolomites have been found when drilling into Qixia Formation for multiple wells with both Shuangyu X131 and Shuangyu X133 wells as the representatives deployed in Shuangyushi block, northwestern Sichuan Basin, and high-yield industrial gas flow over one million cubic meters have been also produced from these wells, which indicates the promising exploration prospect of Qixia Formation in this block. It’s found that for this formation, its reservoir development is obviously under the control of facies. In order to determine the types of sedimentary microfacies, figure out the distribution of favorable facies zones, and improve oil and gas exploration benefits in the Lower Permian Qixia Formation, Shuangyushi block, this paper studied some characteristics of sedimentary facies in the Qixia Formation by means of many approaches of field section measurement, core description, casting thin-section identification, and imaging logging analysis. Results show that(1) one template to identify microfacie is established, the Qixia Formation can be subdivided into four subfacies and five microfacies, and their corresponding characteristics are analyzed;(2) after the microfacies classification and profile facies analysis for nine single wells, it’s indicated that the microfacies of beach core and beach margin are the most favorable facies zones, and they are vertically deposited mainly in Qixia 2 Member and laterally distributed stably;and(3) combined with relative sea-level change, the palaeogeomorphology of Qixia Formation is restored by means of a method of trend surface, and the planar distribution characteristics of microfacies are made further clear. These results may provide the geological basis for subsequent study on high-quality reservoirs and well deployment on Qixia Formation in Shuangyushi block.