关键词: 珠江口盆地, 珠一坳陷, 断层封闭性, 断层圈闭, 钻探风险, 断层岩, 钻探成功率

Abstract:

Many fault traps occur in the Zhu Ⅰ Depression in the Pearl River Mouth Basin because of well-developed faults. Researches on drilled fault traps in the depression revealed that both the lateral seal and the breakdown intensity of faults in the oil source province and its vicinity mainly determined how risky the drilling was. This paper used arithmetic products (SDD) of the shale content in fault rocks, the burial depth of fault rocks and the cosine of fault dip to quantitatively express the lateral sealing of faults indirectly, and applied products of the quotient derived from the division of the fault throw resulting from re-activities after the reservoir formation of fault traps by the ancient fault throw during the reservoir formation of fault traps and the frequency number of fault activities to quantitatively express the extent to which fault rocks were destroyed. By drawing a scatter diagram revealing the correlation of the success rate of drilling with the SDD and the breakdown intensity of fault rocks, the paper determined critical values of both the SDD and the breakdown intensity of fault rocks, which were required by a successful drilling of fault traps in various zones of interest. Consequently, a risk assessment plot of drilling in undrilled fault traps was worked out based on these two critical values in order to predict the drilling risk of undrilled fault traps. The prediction result showed that among the twelve fault traps to be drilled in the zone, five of them were less risky if drilled and the rest were too risky to be drilled.

Key words: Pearl River Mouth Basin, Zhu ⅠDepression, fault sealing, fault trap, drilling risk, fault rock, success rate of drilling