川中地区中二叠统构造热液白云岩的发现及其勘探意义  

Discovery and exploration significance of structure-controlled hydrothermal dolomites in the Middle Permian of the central Sichuan Basin

作　　者：陈轩[1,2] 赵文智 张利萍[1,2] 赵宗举 刘银河[5] 张宝民[5] 杨雨[1] 

机构地区：[1]长江大学油气资源与勘探技术教育部重点实验室,湖北荆州434023 [2]长江大学地球科学学院,湖北荆州434023 [3]中国石油勘探生产公司,北京100011 [4]中国石油学会,北京100724 [5]中国石油勘探开发研究院,北京100083

出　　处：《石油学报》2012年第4期562-569,共8页Acta Petrolei Sinica

基　　金：国家重大科技专项(2008ZX05004-001);中国石油天然气集团公司重大专项(2008E-0702)资助

摘　　要：综合地震资料解释、岩石矿物学观察以及地球化学分析结果,认为四川盆地中部中二叠统栖霞组、茅口组白云岩为构造热液白云石化成因,具有以下典型特征:①白云岩单层厚度较大,多呈透镜状产出,横向连续性差,钻遇井附近多伴有走滑断裂发育,白云岩层段在对应的地震剖面上见"下凹"反射特征;②基质白云岩多呈中-粗晶,其缝洞中见具有波状消光特征的填隙鞍状白云石,并发育大量的角砾岩,角砾岩间充填白色的白云石,形成斑马构造;③基质白云岩与填隙鞍状白云石的均一温度较白云石化作用时地层的温度要高5℃以上,分别为105.8～159.6℃及113.2～138.6℃,同时二者还具有偏负的氧同位素特征(-7.64‰～-7.95‰)以及高87Sr/86Sr值(0.708 369～0.709 684)。构造热液白云岩的发育和分布受走滑断裂控制,若与上覆致密灰岩地层有机配置,可以形成良好的岩性圈闭。Integrated with seismic profile interpretations, Petro-mineralogic observations and geochemical analyses, the present paper proposed that dolomites in the Middle Permian Qixia Formation-Maokou Formation of the central Sichuan Basin are of a structure- controlled hydrothermal origin. The characterization of the dolomites showed that.. 1） they are relatively thicker in a single layer, commonly in lenticular form, poor in lateral continuity, sometimes accompanied with developed strike-slip faults and having a ＂con- cave-down＂ reflection in seismic sections corresponding to dolomite intervals concerned; 2） matrix dolomites composed mainly of me- so- or macro-crystalline grains have the saddle-shaped dolomite with undulatory extinction stuffed in their fractures and rugs, where a large amount of breccias with white dolomites filled between them develops, forming zebralike fabrics; and 3） homogenization tem peratures of matrix and interstitial saddle-shaped dolomites are commonly 5℃ higher than those of strata during dolomitization, ran- ging between 105.8-159.6℃ and 113.2-138.6℃ ,respectively. In addition, they show lighter oxygen isotopes （ - 7.64‰ - 7. 95‰） and higher ^87 Sr/^86 Sr ratios （0. 708 369 - 0. 709 684）. The development and distribution of structure-controlled hydrothermal dolomites are dominated by strike-slip faults. There would be a good lithologic reservoir if hydrothermal dolomites combine well with overlying tight limestones.

关 键 词：热液白云岩 白云岩储层 锶同位素 栖霞组 茅口组 中二叠统 四川盆地 

分 类 号：TE112[石油与天然气工程—油气勘探]