塔里木盆地奥陶系油气成藏规律与勘探方向

塔里木盆地奥陶系碳酸盐岩油气显示普遍,但发现的油气田(藏)少.针对目前在塔里木已经发现的一批以奥陶系为主要产层的油气田(藏),总结油气成藏规律和富集主控因素,有利于分析有利勘探方向和领域.从塔里木盆地奥陶系地层结构、储层类型、盖层条件和含油气系统(烃源岩、主要生排烃期、含油气系统划分)分析入手,解剖了目前已发现奥陶系油气藏油气平面分布和纵向分布特征,认为塔里木盆地奥陶系以碳酸盐岩缝洞型油气藏为主,具有大面积连片或成带分布的特征.进一步结合前人认识总结了塔里木盆地奥陶系碳酸盐岩成藏规律为:与烃源岩生排烃期相匹配的、发育在古隆起、古斜坡背景上的岩溶缝洞储集体,或受深大断裂带控制的多成因类型的缝洞型储集体,具有大范围富集成藏的特征,储集体发育程度是控制油气成藏差异的关键因素.同时提出,需要用动态的视角认识奥陶系的成藏过程和用辩证的思维优选碳酸盐岩勘探领域与目标.在此认识下综合分析认为,塔河油田奥陶系深层和顺南-古隆地区奥陶系是当前发现大、中型油气田(藏)的最现实目标.

Hydrocarbon accumulation patterns and favorable exploration areas of the Ordovician in Tarim Basin

Oil and gas shows are common in the Ordovician carbonates in Tarim Basin, but few oil and gas fields (reservoirs) have been found. Based on the current Ordovician oil and gas fields (reservoirs)in Tarim Basin, summarizing the hydrocarbon accumulation patterns and main controlling factors of enrichment is helpful to identify potential exploration target areas. According to the analysis of the Ordovician geology conditions, reservoir types, sealing conditions and petro-leum system (source rocks, the main hydrocarbon generation and expulsion period, petroleum system division), we analyzed the areal and lateral distribution characteristics of the Ordovician reservoirs. The results show that fractured-vuggy carbonate reservoir is the main reservoir type of the Ordovician in Tarim Basin, which are characterized by large scale continuous distribution or zonal distribution. In combination with the previous understandings, we summarized the regularity of the Ordovician carbonate reservoirs in Tarim Basin: fractured-vuggy karst reservoirs that matched well with hydrocarbon generation and expulsion period and were development on paleo-uplifts and paleo-slopes, and/or fractured-vuggy carbonate reservoirs of multiple origins that were controlled by deep faults are characterized by large scale hydrocarbon enrichment and the development of reservoirs is the key factor controlling differential hydrocarbon accumulation. It is proposed to understand the hydrocarbon accumulation process from a dynamic perspective and to identify carbonate exploration targets via dialectical thinking. According to the comprehensive analysis, the deep interval of the Ordovician in Tahe oilfield and the Ordovician in south Shunnan-Gulong area are the most favorable target for discovering large and medium sized gas fields (reservoir).