哈拉哈塘地区热液岩溶形成演化与油气分布

哈拉哈塘油田奥陶系碳酸盐岩油藏为塔里木油田高产稳产的主力油藏,其缝洞型储集层成因机理、形成时期和油气分布一直是研究难点。基于地球物理资料,结合岩心和薄片观察、地球化学分析、生产特征分析等手段,研究了哈拉哈塘地区热液岩溶的特征,厘定了热液岩溶时期,明确了海西运动期活动断裂与加里东运动期走滑断裂对热液岩溶和油气分布的控制。研究认为,岩浆活动、海西运动期活动断裂形成、热液岩溶和油气成藏均主要发生在二叠纪,时间相近并具有成因上的继承性。海西运动期活动断裂与加里东运动期走滑断裂在力学性质、产状、规模、分布以及对热液岩溶的发育和控制方面存在差异。加里东运动期走滑断裂上热液岩溶体可以有效成藏,而海西运动期活动断裂由于在油气成藏期存在开启和间歇活动,导致热液岩溶体不能成藏或成藏能力差,从而造成哈拉哈塘地区奥陶系东西部油气分布差异巨大。在进行油气勘探和井位部署时应区分海西运动期活动断裂和加里东运动期走滑断裂,以寻找加里东运动期走滑断裂上热液岩溶体作为勘探目标。

Formation and Evolution of Hydrothermal Karst and Hydrocarbon Distribution in Halahatang Area

The Ordovician carbonate reservoir in Halahatang oilfield is the primary contributor to high and stable production of Tarim Oilfield Company. However, it has been difficult to study its forming mechanism, forming period, and oil and gas distribution. Based on geophysical data, core and slice observation, analysis of geochemical and production data, etc., the characteristics of the hydrothermal karst in the Halahatang area have been studied, the forming period of the hydrothermal karst has been determined, and the controls of the active faults formed in the Hercynian movement and the strike-slip faults formed in the Caledonian movement on the distribution of the hydrothermal karst and hydrocarbon are clarified. The study results show that magmatic activities, active faults in the Hercynian movement period, and hydrocarbon accumulation in hydrothermal karst mainly occurred in the Permian, and they are similar in timing and successive in origin. There are differences between the Hercynian active faults and the Caledonian strike-slip faults in terms of mechanical properties, occurrence, scale, distribution, and controls on hydrothermal karst. Hydrocarbon can effectively accumulate in the hydrothermal karst on the strike-slip faults in the Caledonian movement period, while hydrocarbon can not or poorly accumulate in the hydrothermal karst on the active faults in the Hercynian movement period due to the influences of the openning and intermitting of faults during the hydrocarbon accumulation period. As a result, the distribution of the hydrocarbon in the Ordovician strata in the east of the Halahatang area greatly differs from that in the west. During petroleum exploration and well allocation, it is necessary to differ the Caledonian strike-slip faults from the Hercynian active faults, and then take the hydrothermal karst on the strike-slip faults as the exploration target.