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

摘要：

珠江口盆地珠一坳陷发育众多断层圈闭。对已钻断层圈闭的研究表明，在油源区及其附近，断层侧向封闭性及断层岩的破坏强度是决定断层圈闭钻探风险大小的主控因素。利用断层岩泥质含量、断层岩埋深及断层倾角余弦的乘积SDD间接定量表征断层的侧向封闭性，用断层圈闭油气藏形成之后断层再次活动形成的断距除以断层圈闭油气藏形成时的古断距与断层圈闭油气藏形成之后断层再次活动形成的断距之差,再乘以断层的活动频数定量表征断层岩破坏强度。通过绘制断层圈闭的钻探成功率与SDD、断层岩破坏强度关系散点图，确定研究区各目的层段断层圈闭钻探成功所要求的SDD和断层岩破坏强度的临界值；再根据此二临界值绘制断层圈闭钻探风险评价图版，来对未钻断层圈闭进行钻探风险评价。预测结果表明，研究区可供钻探的12个断层圈闭中，有5个钻探风险较小，是近期重点考虑实施钻探的目标，有7个钻探风险过大，不建议实施钻探。

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