川西坳陷雷口坡组气藏勘探远景区预测

川西坳陷中三叠统雷口坡组顶面是一个风化面,目前在雷口坡组还没有发现大型的溶蚀孔洞缝型气藏。从雷口坡组的成藏地质条件、岩相古地理演化、沉积相和地震相等方面探讨了雷口坡组发育优质储层的可能性，预测了洛带气田、新场气田和马井构造雷口坡组气藏的勘探远景区。雷口坡组优质储层发育的基础是潮坪沉积相的藻屑滩和古岩溶形成的各类溶蚀性孔隙，区域岩相古地理分析认为，沿着中坝—安县—新场—洛带印支期古斜坡环带可能发育藻屑滩，且受到过暴露剥蚀作用。洛带地区雷口坡组地震相表现为丘形反射，两侧存在斜交反射带，顶部呈削蚀面特征，可能存在溶蚀沟和古潜山，预测发育有经过暴露溶蚀作用的藻屑滩；新场气田雷口坡组顶部存在地层圈闭和斜交反射带，有明显的削蚀面特征；马井构造存在连片的丘形地震异常。结合露头剖面的藻屑滩特征，分析认为洛带气田和新场气田的雷口坡组为有利勘探远景区，马井构造雷口坡组为远景勘探区。

Prediction of exploration potential area of Leikoupo formation in Western Sichuan Depression

The top of Leikoupo formation at middle Triassic (T2l) in Western Sichuan Depression is an erosional surface.At present,gas reservoir with large-scale caverns and corroded fissures has not been found in T2l.Aiming at this problem,through analyzing the geological conditions of reservoir formation,lithofacies-paleogeographic evolvement,sedimentary facies and seismic facies,etc,we discussed the possibility of developing favorable reservoirs,and predicted the exploration potential area in Luodai gasfield,Xinchang gasfield and Majing gasfield.The algae clastic beach deposited in the tidal flat and corrosion pore caused by ancient karst are the bases of favorable reservoir of T2l.by analyzing regional lithofacies palaeogeography,we found that algae clastic beaches might develop and be exposure to erosion in Indosinian paleo-slope annulus along Zhongba,Anxian,Xinchang and Luodai gasfield.The seismic facies of T2l in Luodai field is mound configuration;oblique reflections exist in both side,and the top is truncation.All this phenomena indicates that there may be corrosion ditch,buried hill and algae corroded clastic beaches.There exist stratigraphic traps and oblique reflection on the superface of T2l in Xinchang gasfield,which shows obvious truncation characteristic.There also exist mound seismic anomalies in Majing gasfield.According to all these data,combined with algae clastic beaches on outcrop section,T2l of Luodai gasfield and Xinchang gasfield is taken as favorable exploration area,and T2l of Majing gasfield is taken as the exploration potential area in next step.