川西洛带气田上侏罗统遂宁组天然气富集主控因素分析

洛带气田遂宁组主要为三角洲前缘斜坡亚相和浅湖亚相沉积,其物源区为龙门山隆起区。大多数产气层均处于浅湖砂坝、河口砂坝、水下分支河道及远砂坝等有利沉积微相较厚的砂体分布范围内。沉积微相的发育控制了砂体在平面上的展布,进而控制天然气富集区的分布区域与范围。产气层段砂体在纵向上的厚度与砂岩粒度受控于不同微相在纵向上的叠置关系,产能的高低与储层的孔、渗条件和孔隙结构特征有更直接的联系。自深层运移上来的天然气至上侏罗统遂宁组储层中占高点运移和聚集,形成构造-岩性复合型次生气藏,原生裂缝的发育对产量的增加起着至关重要的作用。因此,寻找构造适当部位有利沉积微相内的优质储集体和原生裂缝发育区,应为洛带气田今后的重点勘探方向。

The dominative factor of gas abundance zone of Suining Formation, Upper Jurassic in Luodai gas fields, West sichuan basin

Delt-frong acclivity and shallow lake are a major type of sedimentary sub-facies of the Suining formation of Upper Jurassic,and the provenance is uplifted area of Longmenshan.Most of gas-producing formation are located in favorable sedimentary microfacies,such as shallow lake sandbar,river mouth bar,underwater distributary channel and distal sandbar with thick sand body.These sedimentary microfacies control the distribution of sand body,and moreover,they control the area and bound of gas accumulation.The sand body thickness and sand grain of gas-producing horizon are lies on incumbent relation of different microfacies.The production has direct affiliation with porosity,permeability,porosity texture.The gas migrated from deep formation to structural high of Suining formation and formed compound gas pools of structural-lithology,and syngenetic fracture is crucial to gas production.The further exploration should look for reservoir of high quality located at appropriate structural and developed area of syngenetic facture.