四川盆地磨溪区块龙王庙组气藏流体分布控制因素

随着勘探开发的深入,对四川盆地磨溪龙王庙组气藏流体分布的认识发生变化,由早期的无水气藏或无边底水气藏转变为存在边底水、局部封存水,表现出复杂的气水关系,这制约了气藏的高效开发。为此,本次研究综合现有录井、岩心、测井、地震、测试及生产资料,识别出溶蚀孔洞发育区,在此基础上,采用印模法恢复研究区龙王庙组古地貌格局,结合现今构造特征,综合分析认为:(1)油气分布既受现今构造圈闭控制,又受有利岩相控制,也受古地貌影响;(2)古地貌控制了早期油气聚集,在地势较高的缓坡区聚集油气,在局部洼陷区滞留地层水,在地势变陡的低部位形成富水区;(3)在现今构造圈闭范围内,由于物性、闭合度和海拔高差存在差异,导致东、西部井区含气性不同,西区富气程度优于东区;(4)结合古今构造格局,在古地貌地势低部位(地势低于-300m)、现今构造低部位(海拔低于-4385m)广泛分布边水;(5)当古地貌地势低于-300m时,在现今构造和古地貌相对凸起部位存在局部油气聚集。

Controlling factors of fluid distribution in the Lower Cambrian Longwangmiao Formation, Moxi area, Sichuan Basin

With further exploration and development,the understanding of fluid distribution has changed compared with the previous conclusions on the Lower Cambrian Longwangmiao Formation of the Moxi area in Sichuan basin,which has affected the efficient development of gas reservoirs.To this end,based on data of drilling wells,cores,well logging,seismic survey,tests and production,the moldic methods are used to reconstruct the karst paleogeomorphy of the Longwangmiao Formation,combined with current tectonic features.The results show that(1)the distribution of gas and water are controlled not only by present-day structural traps,but also by the favorable facies,and by paleogeographic framework.(2)The paleogeography controlled early accumulation of oil and gas,thus oil and gas accumulated on the higher terrain of gentle slopes,formation water remained in the low-lying areas,and water-rich regions formed in the low-lying parts of the steepening areas.(3) Owing to differences of physical property,closure degree and altitude,east and west hydrocarbon degrees of aggregation are different in present structural traps.West is richer than east.(4) Edge formation water is widespread when paleogeographic terrain is lower than-300m,and current tectonic elevation is lower than-4385m.(5)Oil and gas accumulation occurred only in relatively protrusions localities of today's structure and paleogeography when the paleogeographic terrain is lower than-300m.