Abstract:

In order to study the oil-gas distribution law with fracture zone in the oil-gas bearing basin, based on the mechanism of oil-gas leakage out through mudstone caprock by active and static faults, the geological conditions and recognition methods of oil-gas leakage out through mudstone caprock along the active and static faults were studied, and the research indicated that: the geological condition of oil-gas leakage out through mudstone caprock by active fault is the active fault connected up and down in mudstone caprock, which becomes the oil-gas transportation pathway through mudstone caprock, and the condition of oil-gas leakage out through mudstone caprock by static fault is in which the oil-gas residual pressure of underlying reservoir is larger than displacement pressure of still fault rock. Through comparison between oil-gas residual pressure in underlying reservoir and still fault rock displacement pressure, and between fault connected thickness in mudstone caprock and minimum necessary fault connected thickness of oil-gas leakage out through mudstone caprock by active fault, recognition method is set about whether oil-gas leaks out through mudstone caprock by active fault or still fault, which is applied into recognition of whether gas from Es₃ and Es₁ source rocks leak out through Ed₂ mudstone caprock by active fault in Nanpu sag, Bohaiwan basin. The results show that :In faulting period, nature gas can leak out through mudstone caprock of Ed₂ by active NP5-2 fault in lines L₂ and L₈, and in the rest place(L₁、L₃、L₄、L₅、L₆、L₇、L₉) can’t. However, in fracture static period, nature gas can’t leak out through mudstone caprock of Ed₂ along the NP5-2 fault. The recognition result coincides with present gas distribution under mudstone caprock of Ed₂ in the Nanpu Structure 5, which indicates that these two methods are feasible to be applied into recognition of whether oil-gas leak out through mudstone caprock by active and static fault.

Key words: oil-gas, mudstone cap rock, active fault, still fault, leakage out, geological condition, recognition method