珠江口盆地文昌A区圈闭类型以断层圈闭为主,断层是油气运移的主要通道,断层封堵性是影响该区断块成藏的主控因素.首先通过Allan图快速评价断层侧向封堵性,结合实际钻井情况分析Allan图的适用性和研究区的断层封闭类型;然后选取影响断层封闭属性的主要参数,断层泥比率(SGR)和泥岩涂抹系数(SSF),依据中新统珠江组二段已钻井圈闭的SGR和SSF数据,结合测井解释成果,建立了SGR-SSF判别图版,定量研究文昌A区断层侧向封堵能力.结果表明:SGR>0.32且SSF≤3.2,断层封堵性相对较好;SGR≤0.25,或SSF>4.2,断层封堵性最差,可排除成藏的可能性;0.250.32且3.2

Fault sealing is the main factor of hydrocarbon accumulation in Wenchang A area, Pearl River Mouth Basin, where faulted traps developed. The Allan map is used to quickly evaluate the lateral sealing property of the faults, and with the actual drilling results, the applicability of the Allan map and the type of fault sealing are analyzed in the study area. It is shown that the Allan map can't completely evaluated the lateral sealing character. Then the main parameters, SGR and SSF, are selected to setup SGR-SSF discrimination chart for quantitative study. According to seismic interpretation, SGR and SSF of the faults related to the drilling traps in Member-2 of Miocene Zhujiang Formation are obtained, and the SGR-SSF discrimination chart is set up combined with logging results of oil and water. It is shown that when SGR＞0.32 and SSF≤3.2, the fault sealing property is relatively good; when SGR≤0.25, or SSF＞4.2, it is the worst, with little possibility of oil accumulation; when 0.25＜SGR≤0.32 and SSF≤4.2, or SGR＞0.32 and 3.2＜SSF≤4.2, it is in the unproven area, with a certain potential. According to the charm, the lateral sealing feature of faults in E1 and W1 blocks of Wenchang A are analyzed. It is proved that the oil formation of ZJ2-3U、ZJ2-3M、ZJ2-3L、ZJ2-4U in high position of E1 block, and ZJ2-1L、ZJ2-3U、ZJ2-3L、ZJ2-4U of W1 block are relatively good in fault sealing condition, which could be the favorable targets for further exploration.