川西坳陷三叠系雷口坡组顶部白云岩储层分布预测_甯蒙

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2015年5月

第20卷 第3期

中国石油勘探

CHINA PETROLEUM EXPLORATION

DOI : 10.3969/j.issn.1672-7703.2015.03.004

川西坳陷三叠系雷口坡组顶部白云岩储层分布预测

甯 濛1 刘 殊2 龚文平1

(1长江大学地球科学学院;2中国石化西南油气分公司勘探开发研究院)

摘 要:川西坳陷中三叠统雷口坡组顶部发育古风化壳型储层,近期PZ1井在该风化壳层再次获得高产工业气流,显示雷口坡组具有较大油气潜力,但TS1井的失利又显示了气藏的复杂性。川西坳陷雷口坡组顶部雷四上亚段具溶孔的颗粒白云岩是主要储层,优质储层以白云岩坪相为基础,后期发生白云岩化成岩改造。但由于断层及膏岩夹层的干扰,难以根据地震反射结构预测储层。研究发现,川西坳陷雷口坡组顶部表现出独特的断层相特征:坳陷内发育两个弧形小断层带,表现为强断裂变形白云岩相;断层带后方为断层不发育的完整背斜,表现为弱断裂变形白云岩相;坳陷东坡为揉皱膏岩相。利用这一特殊的断层相特征,依据地质力学原理,预测两弧形小断层带为刚性、单层厚度较薄的地层,为白云岩坪边缘相带,储层厚度较薄但裂缝发育;断层带后方完整地块为刚性、单层厚度较大的地层,为白云岩坪中心相带,储层厚度大;小断层带东侧的揉皱带为膏岩发育区。

关键词:川西坳陷;三叠系;雷口坡组;地质力学特征;白云岩坪;断层相中图分类号:TE112 文献标识码:A

Prediction of Dolomite Reservoir Distribution on Top of Triassic Leikoupo

Formation in Chuanxi Depression

Ning Meng 1, Liu Shu 2, Gong Wenping 1

(1 School of Geosciences of Yangtze University; 2 Exploration and Development Research Institute of

Sinopec Southwest Oil and Gas Company)

Abstract: The weathering crust reservoir developed on the top of Triassic Leikoupo Formation in Chuanxi depression. Recently, a high-yield industrial gas fl ow was acquired from Well PZ1 drilled at this weathering crust, indicating a great oil and gas potential of Leikoupo Formation, but the failure of Well TS1 also shows complexity of the gas reservoir. The grained dolomite with dissolved pores is the main reservoir in the 4th member of Leikoupo Formation in Chuanxi depression. Based on the dolomite fl at, the high-quality reservoir came under dolomite diagenetic transformation in the later period. However, thanks to interferences of faults and gypsum in Leikoupo Formation, it is dif fi cult to predict reservoirs by means of seismic re fl ection structure. The study indicates that the top of Leikoupo Formation in Chuanxi depression is characterized with unique fault facies. Two small arc-shaped fault belts developed in the depression, which are dolomite with strong fault deformation facies. The complete anticline with the faults undeveloped was behind the fault belt and in the form of dolomite with weak fault deformation facies. The eastern slope of the depression is crumpled gypsum facies. Based on the unique characteristics of fault and geo-mechanical principles, the two small arc-shaped fault belts are predicted as rigid formations with the single layers being thin and dolomite fl at marginal facies. The layers of reservoir are relatively thin but with development of fractures. The complete block behind the fault belts is the rigid formation with the single layers being thick and dolomite fl at central facies. Thickness of the reservoir is large. The crumpled zone east of the small fault belts is gypsum development zone.

Key words: Chuanxi depression, Triassic, Leikoupo Formation, geo-mechanical characteristics, dolomite fl at, fault facies

第一作者简介:甯濛(1991-),女,四川德阳人,在读硕士,研究方向为石油构造。地址:湖北省武汉市蔡甸区大学路特1号长江大学武汉校区,邮政编码:430100。E-mail:342850128@

收稿日期:2014-10-22;修改日期:2015-04-10

四川盆地位于扬子板块北缘,为一个大型含油气叠合盆地,主要经历了两个构造演化阶段:震旦纪—中三叠世的被动大陆边缘构造演化阶段,沉积巨厚的海相碳酸盐岩;晚三叠世—始新世的前陆盆地演化阶

段,沉积陆源碎屑岩。中三叠统雷口坡组(T 2l)是四川盆地海相碳酸盐岩演化阶段的最后层系,主要沉积相为局限台地、蒸发台地,发育云坪、膏岩盆、砂屑滩等微相[1,2]。

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