库车坳陷博孜—大北地区油气充注期次、成熟度及其对构造圈闭形成时序的指示

Hydrocarbon charging periods and maturities in Bozi-Dabei area of Kuqa depression and their indications to the structural trap sequence

塔里木盆地库车坳陷博孜—大北地区是近年来深层—超深层油气勘探的主战场之一,具有构造变形强、断裂体系复杂、构造圈闭密集排布的特征。目前的勘探结果显示,研究区不同圈闭内的油气相态、成熟度存在明显差异,并在平面上呈现明显的递变规律,但其成因机制尚不明确。此外,研究区还存在油气充注期次不明、构造圈闭的演化时序不清的问题。基于流体包裹体技术、埋藏史-热演化史模拟、三维地震资料解释和油气碳同位素测试结果,分析了研究区巴什基奇克组的油气充注期次及其对构造圈闭形成时序的指示。研究结果表明:①巴什基奇克组的流体包裹体主要为烃包裹体所伴生的盐水包裹体,发育少量气液两相包裹体和气态烃包裹体,主要赋存在石英颗粒或石英的愈合裂隙中;②研究区整体存在3期油气充注,博孜地区的油气充注以第1期和第3期为特征,而大北地区的油气充注以第2期和第3期为特征且整体晚于博孜地区;③结合油气充注期次、成熟度及气油比分析认为,大北地区可在其后缘(北部)优先形成圈闭,并逐渐向前缘(南部)扩展,而博孜地区由于受温宿古隆起遮挡,会优先在其南缘和北缘形成圈闭,进而向中部逐渐扩展。

In recent years,Bozi-Dabei area in Kuqa depression of Tarim Basin has become one of the main fields for deep and ultra-deep oil-gas exploration in China,which is characterized by strong structural deformation,complex fault system and dense arrangement of structural traps.The current exploration results show that the traps have significant differences in the oil-gas phases and maturities in the study area,showing obvious grading regularity on the horizontal level.However,the genetic mechanism is not yet clear.Meanwhile,some other problems exist in the study area,e.g.,the hydrocarbon charging periods and the evolution sequence of structural traps are still unclear.Based on the fluid inclusion technology,burial-thermal evolution history simulation,three-dimensional seismic data interpretation,as well as carbon isotope test of hydrocarbon,the paper analyzes the charging periods in Bashijiqike Formation and their indications for the structural trap sequence.The research results show as follows.(1)The fluid inclusions are dominated by saline inclusions associated with hydrocarbon inclusions in Bashijiqike Formation,where a small amount of gas-liquid two-phase inclusions and gaseous hydrocarbon inclusions are developed,and mainly occur in quartz grains or healing cracks.(2)Overall,there are three oil-gas charging periods in the study area.The oil-gas charging in Bozi area is mainly characterized by the first and third stages,while the charging in Dabei area is mainly characterized by the second and third stages and is generally later than that in Bozi area.(3)Based on the analyses of hydrocarbon charging periods,maturities,and gas-oil ratios,it is believed that the traps in Dabei area could be preferred to form in the rear margin(northern part)and gradually expand towards the front margin(southern part),while the traps in Bozi area should be preferred to form in the southern and northern margins due to the obstruction from the Wensu paleo-uplift,and then gradually expand towards the central part of Bozi area.