砂泥岩薄互层段中断层封闭性的定量研究

砂泥岩薄互层段内断层是否具有封闭性取决于断层岩与储层的排替压力差。断层岩的排替压力又取决于断层岩泥质含量和成岩程度，断层岩的成岩程度取决于断层岩承受的断面压力，断面压力的大小与断层倾角和断层岩埋深有关。而储层排替压力与其泥质含量和埋深有关。根据岩石的排替压力封闭原理，提出了砂泥岩薄互层段中断层封闭性的定量评价方法。操作步骤如下：①视断层岩的泥质含量等于断移地层的泥岩层厚度与地层厚度的比值；②建立不同泥质含量岩石排替压力随埋藏深度的变化关系；③计算断点处断面的正压力；④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；⑤在不同泥质含量排替压力与埋深关系图上确定断层岩排替压力；⑥根据储层的泥质含量及埋深，确定储层的排替压力，用断层岩排替压力减去储层排替压力，得到两者排替压力差，该排替压力差即为所研究断层点处的断层封闭能力。在海拉尔盆地贝尔凹陷已知封闭能力断层的验证表明，该方法具有非常好的可行性。

Quantitative study on fault sealing ability in sandstone and mudstone thin interbed

The sealing ability of faults in the sandstone and mudstone thin interbed is mainly determined by the displacement pressure contrast of fault rock against reservoir, while the displacement pressure of fault rock is controlled by shale content and diagenetic grade of fault rock. The proportion of mudstone thickness in faulted formation decides the shale content of fault rock, and the posi-tive pressure exerted on the fracture surface determines the diagenetic grade of fault rock. The positive pressure of fractured surface has relation with the fault dip and buried depth of the fault rock, while the displacement pressure of reservoir is controlled by the shale content and buried depth of reservoir. A new quantitative method for evaluating fault sealing ability is proposed on the basis of sealing rule of displacement pressure contrast in the sandstone and mudstone thin interbed. The evaluating procedure is as follows: ①regarding the shale content of fault rock as being equal to the proportionality of mudstone thickness to faulted formation thickness; ②setting the alternation relationship between displacement of different shale content rock and burial depth; ③calculating the positive pressure on the fracture surface;④calculating the positive pressure in the break point and the buried depth of strata corresponding to the pressure exerted on the fracture surface according to the relationship between geostatic pressure and buried depth of strata; ⑤de-fining the displacement pressure of fault rock according to the relationship between displacement pressure and buried depth of strata; ⑥calculating the reservoir displacement pressure on the objective plate according to the shale content and buried depth of the reser-voir, and determining the displacement pressure contrast to the reservoir displacement pressure using the fault rock displacement pressure. The displacement pressure contrast expresses quite right the sealing ability of the fault in the break point. This method is feasible by means of actual verification in Beir Depression of Hailar Basin.