塔里木盆地温宿凸起吉迪克组成岩与成藏过程——以古木1油藏为例

Diagenetic and hydrocarbon accumulation process of Jidike Formation in the Wensu uplift: A case study of Gumu 1 reservoir

近年来塔里木盆地西北缘温宿凸起在新近系吉迪克组不断获得油气突破,展现出较大的勘探潜力,但吉迪克组砂岩储层物性和含油性非均质性强,其成岩与成藏过程不清.本文以古木1井为例,运用包裹体岩相学、阴极发光(CL)、显微测温、扫描电镜矿物定量分析(QEMSCAN)以及碳酸盐U-Pb定年等技术,分析了吉迪克组砂岩储层的成岩-成藏演化过程和非均质含油的成因.研究结果表明:吉迪克组砂岩储层成岩阶段处于早成岩A期,方解石差异化胶结作用影响了储层物性,方解石原位U-Pb定年确定方解石胶结物形成于(17.1±2.8) Ma.储层内原始孔隙好的区域方解石连晶胶结,储层变得致密,面孔率仅为2.76%,而原始孔隙较差的区域方解石未胶结—弱胶结,加上后期溶蚀作用改造,面孔率达12.64%.温宿凸起本地不发育烃源岩,油源来自于北东部的阿瓦特地区,结合邻区乌什凹陷油气成藏过程,推断古木1井成藏时间为5 Ma左右.研究指出,靠近油源方向的温宿凸起东侧且相对远离古木别孜断裂的构造-岩性圈闭为有利勘探方向.

In recent years, Wensu uplift in the northwest margin of Tarim Basin has continuously made oil and gas breakthroughs in the Neogene Jidike Formation, showing a great potential for exploration. However, the Jidike sandstone reservoir has shown a strong heterogeneity of both physical and oil-bearing properties, with the process of its diagenetic and hydrocarbon accumulation process unclear. This study takes well Gumu 1 as the object of study, analyzed the diagenetic and hydrocarbon accumulation process and thus the origin of heterogeneous oil-bearing in the Jidike Formation sandstone reservoir. The methods utilized in the analysis process include and was not limited to: fluid inclusion petrography, cathodoluminescence(CL) image, microthermometry, QEMSCAN analysis, and carbonate U-Pb dating. The results show that the Jidike sandstone reservoir is in the early diagenetic stage A.The differential cementation of eogenetic poikilitic-cemented calcite affects physical properties of the reservoir. The carbonate U-Pb dating confirms that the calcite cement was formed at(17.1±2.8) Ma. A part of the reservoir with good original pores was continuously cemented by calcite and became dense with a plane porosity of 2.76%, while the part with poor original pores was weakly cemented by calcite and later reformed by dissolution, thus became better reservoir with a plane porosity of 12.64%. There is no source rock in Wensu uplift, and the oil is migrated from Awat area in the northeast. Referencing the oil and gas accumulation process in the adjacent Wushi Sag, it is likely that the oil accumulation period of Gumu 1 reservoir was around 5 Ma. The study indicates that the structural lithologic traps close to oil source and relatively far from the Gumubizi fault in the east of Wensu uplift are favorable exploration targets.