塔里木盆地塔中北坡构造解析与油气勘探方向

Structural interpretation and petroleum exploration targets in northern slope of middle Tarim Basin

通过塔中北坡三维地震资料的解析,对主要断裂带的变形特征、活动期次与控储控藏特征进行了研究,认为该区主要发育8排NNE或NEE走向的左行走滑断裂带,主要活动期为加里东中期(中奥陶世末)与海西早期(中泥盆世末)。海西早期张扭性走滑断裂是在加里东中期压扭性走滑断裂的基础上继承性发育的,受控于先存基底薄弱带与构造应力的不均衡作用,属于典型的被动型走滑断裂;断裂系统形成的裂缝及后期发生的热液活动,对奥陶系碳酸盐岩溶蚀孔洞-裂缝型储集体发育具有重要的控制作用。该区经历了加里东晚期、海西晚期与喜马拉雅期3个主要成藏期,古生代的构造格局与走滑断裂活动控制了本区油气纵向分布的差异与富集,形成了中下奥陶统以干气气藏为主、下志留统以油藏为主的成藏特征。塔中北坡奥陶系碳酸盐岩是寻找天然气规模储量与产量阵地的现实领域,走滑断裂附近分布的串珠状地震反射异常体是最有利的勘探目标;同时志留系柯坪塔格组中段泥岩覆盖下砂体的"甜点"发育区,是柯坪塔格组下段油藏的有利勘探区带。

Based on the 3D seismic interpretation of the northern slope of the middle Tarim Basin, the evolution features, activity phases and their controlling on reservoirs of main faults were studied. There were 8 rows of NNE-or NEE-trending sinistral strike-slip faults in the study area, and the faults were active mainly during the middle Caledonian （ the end of the Middle Ordovician） and the early Hercynian （ the end of the Middle Devonian） . The early Hercynian tense-shearing strike-slip faults developed based on the middle Caledonian compressive-torsional faults, and were controlled by previous basement weak zone and disproportion tectonic stress, hence belonged to typical passive strike-slip faults. Fractures and hydrothermal activities played important roles in the generation of fracturedand vuggy reservoirs in Ordovician carbonate rocks. 3 main reservoir charging episodes were conclu-ded including the late Caledonian, the late Hercynian and the Himalayan. Paleozoic tectonic frameworks and strike-slip fault activities controlled the longitudinal distribution and enrichment of hydrocarbon, featured by dry gas in the Middle and Lower Ordovician and oil in the Lower Silurian. The Ordovician carbonate rocks in northern slope of the middle Tarim Basin are actual domains for the industrial production of natural gas. The beaded seis-mic reflection anomalies near to strike-slip faults are most favorable exploration targets. The“desserts” in sands under mudstones in the middle Kepingtage Formation are also favorable targets.