四川盆地东部涪陵—巴南地区茅口组储层特征及预测

Predicting reservoir characteristics of Maokou Formation, Fuling-Ba’nan area, eastern Sichuan Basin

四川盆地南部下二叠统茅口组储层油气勘探开发历史较为久远,取得了丰硕的成果,其储集类型丰富多样。近年川西北部和川东地区二叠系勘探也获得了突破。而位于四川东南部的涪陵—巴南地区受不同方向的应力发育多组系构造,茅口组储层的储集类型、主控因素及展布特征是不清楚的,导致前期钻井虽有显示但产量不高。因此,通过分析川东涪陵—巴南勘探区内及邻区的钻、测井资料,进行茅口组古地貌特征研究、地震相分析及含油气异常的地震反射特征判别,识别出储层有利分布区。研究结果表明:①茅口组储层是富含生物碎屑、溶孔、裂缝的综合型储集层;②储层在地震剖面上具有“下拉式弱反射”“眼球状”“斜亮点”“同相轴错断”“同相轴分叉及合并”等特征;③储层分布横向变化较大,主要受古构造位置及断层展布控制;④探区西部古地貌位置较高,是岩溶较发育的有利区域,地震异常较为集中,具有良好的勘探潜力。

The reservoirs of Lower Permian Maokou Formation,southern Sichuan Basin,are of diverse types.Their exploration and development undergo a long time,and rich achievements have been obtained.Recently,Permian exploration has also been made breakthrough in northwestern and eastern basin.Especially in Fuling-Ba’nan area of eastern basin,it is found there are multiple structures developed with different-oriented stress.However,the reservoir types,main influencing factors,and distribution characteristics of Maokou Formation have not been made clear,resulting in lower production despite gas show discovered in the early drilling.So,some drilling and well-logging data of this area and neighboring areas was analyzed.Then,the palaeogeomorphic characteristics of Maokou Formation were investigated,the seismic facies was analyzed,and the seismic reflection characteristics of hydrocarbon-bearing anomalies were discriminated.At last,the distribution belt of favorable reservoirs was identified.Results show that (1) Maokou Formation is composite reservoirs containing abundant bioclastics developed with dissolution pores and fractures;(2) in seismic sections,these reservoirs represent the features of "push-down weak reflection","augen","oblique bright spot","faulted event",and "event divergence and convergence";(3) the reservoir distribution is characterized by considerably lateral change and mainly controlled by paleo-structure position and fault;and (4) the western study area,also higher palaeogeomorphic position in Fuling-Ba'nan area,is just a favorable one with more developed dissolution pores and seismic anomalies,also indicating stronger exploration potential.