反向断裂下盘较顺向断裂上盘更易富集油气机理的定量解释

为了研究含油气盆地中断裂对油气成藏与分布的控制作用，在断层侧向封闭机理及影响因素研究的基础上，对反向断裂下盘较顺向断裂上盘更易富集油气的机理进行了定量解释。结果表明，无论是反向断裂还是顺向断裂，均源于断层岩封闭油气，断层岩油气运移方向排替压力是影响其侧向封闭油气能力的主要因素。在断裂埋深、断裂倾角和地层岩性、地层倾角相同的条件下，理论上反向断裂断层岩泥质体积分数大于顺向断裂断层岩泥质体积分数，即反向断裂断层岩油气运移方向排替压力大于顺向断裂断层岩油气运移方向排替压力，反向断裂侧向封闭能力强于顺向断裂侧向封闭能力，造成反向断裂下盘较顺向断裂上盘更易富集油气。歧口凹陷板桥断裂下盘沙一段下部断层岩在反向条件和顺向条件下油气运移方向排替压力的实例研究结果表明，反向条件下较顺向条件下在油气运移方向有更高的排替压力，侧向封闭能力更强，更有利于油气在板桥断裂下盘沙一段储层中富集。

Quantitative Explanation of Mechanism About Lower Wall of Antithetic Faults Accumulating More Oil-Gas than Upper Wall of Consequent Faults

To study the control effect of faults to oil-gas accumulation and distribution in oil-gas bearing basins, based on the study of mechanism and influence factors of faults lateral sealing, we made a quantitative explanation of mechanism about foot wall of antithetic faults accumulating more oil-gas than hanging wall of consequent faults. Antithetic faults and consequent faults both sealed oil-gas by fault rock and displacement pressure of fault rock in oil-gas migration direction, which were the main factors to influence its lateral sealing oil-gas ability. Under the similar conditions of faults buried depth and dip, layer lithology and dip, theoretically, the shale content of antithetic faults was larger than consequent faults, which mean that displacement pressure of antithetic fault rock in oil-gas migration direction was larger than consequent fault rock, and lateral sealing ability of antithetic faults was stronger than consequent faults, thus, the foot wall of antithetic faults accumulated more oil-gas than the hanging wall of consequent faults. We made an investigation on fault rock displacement pressure in oil-gas migration direction from foot wall of Banqiao fault under conditions of antithetic and consequent, in lower Es¹ of Qikou sag. It indicated that, displacement pressure in oil-gas migration direction of antithetic fault rock was larger than consequent fault rock in foot wall of Banqiao fault in lower Es¹, with stronger lateral sealing ability, which was favor of oil-gas accumulating in Es¹, foot wall of Banqiao fault.