Abstract: The vertical sealing ability of fault is mainly determined by the displacement pressure of filler in fault,while the displacement pressure has some relation with the diagenesis grade being controlled by the positive pressure exerted on the fracture surface.A quantitative method for evaluating the vertical sealing ability of fault was proposed.The positive pressure in the break point and the buried depth of strata corresponding to the pressure exerted on the fracture surface are calculated according to the relationship between geostatic pressure and buried depth of strata.The displacement pressure of filler in the fracture corresponding to the buried depth of strata is determined according to the relationship between the displacement pressure of caprock and buried depth.The vertical sealing ability should be the combination of displacement pressure of fillers in the fractures and porous fluid overpressure of strata.The filling degree of oil and gas in trap can be predicted by comparing the vertical sealing ability of fault and closure altitude of trap.This method is applicable to Kuche Depression.

Key words: fault, vertical sealing ability, caprock, fracture, filler, displacement pressure, quantitative evaluation method

摘要： 断层垂向封闭性主要取决于断裂充填物的排替压力,而排替压力的大小与充填物的成岩程度有关,成岩程度又受控于断面所承受的正压力大小。据此提出了定量评价断层垂向封闭性的方法,其基本原理是:首先计算断点处断面正压力;根据地静压力与地层埋深关系计算该断面压力所相当的地层埋深;最后,根据研究区所建立起来的盖岩排替压力与埋深关系,确定该地层埋深下断裂充填物的排替压力。如果所断移的盖层段内存在地层孔隙流体超压,断层的垂向封闭能力应是断裂充填物排替压力与孔隙流体超压之和。用断层垂向封闭性研究结果同研究区与断层有关的圈闭的闭合高度比较,可预测圈闭的油气充满程度。该方法在库车坳陷得到了成功应用。

关键词: 断层, 垂向封闭性, 盖层, 断裂, 充填物, 排替压力, 定量评价方法