南盘江坳陷JZ 1井目的层未钻遇油气原因探析

Analysis on the causes of undrilled oil and gas in formation of interest of JZ 1 well in Nanpanjiang depression

JZ 1井是部署在南盘江坳陷秧坝凹陷JZ构造高点的一口区域探井,目的为探查二叠系丘台及生物礁、滩灰岩的含油气性。通过对南盘江坳陷及局域秧坝凹陷地质构造特征研究,结合邻井测试成果,认为JZ构造位于丘台相古地貌边缘局部构造小高点,具备形成礁、滩相沉积格局模式的地质条件,且JZ构造圈闭形成期要早于烃源岩生烃高峰期,有一定勘探潜力,但实钻全井未钻遇烃类异常显示。为查明其原因,打开后期勘探布署局面,从烃源岩、储集层、沉积及构造等条件综合分析认为,JZ 1井区受火山活动影响,烃源岩生烃能力的有效性降低,孔渗性变差,储集性能变差,沉积格局的变化及贯穿性大断裂对油气运移、存储条件的破坏作用,是造成 JZ 1井二叠系未钻遇烃类油气的重要原因。

JZ 1 well is a regional exploration well deployed at the structural high of JZ structure in Yangba sag of Nanpanjiang depression,with the purpose of exploring the oil-gas bearing properties of Permian hilly platform,organic reef and shoal limestone.Based on the study of the geologic structure characteristics of Nanpanjiang depression and local Yangba sag and the test results of adjacent wells,it is concluded that JZ structure is located at minor structural high of local structure at the edge of hilly platform facies palaeogeomorphology and has the geologic conditions to form the reef and beach facies sedimentary pattern models.Moreover,the formation period of JZ structural trap is earlier than the peak period of hydrocarbon generation in source rocks,which has certain exploration potential,but no hydrocarbon anomalies have been drilled in the whole well.In order to find out the causes and open up the situation of late exploration and deployment,the comprehensive analysis of hydrocarbon source rocks,reservoirs,sedimentary and structural conditions shows that JZ 1 well is affected by volcanic activities.The effectiveness of hydrocarbon generation ability of hydrocarbon source rocks decreases,porosity and permeability become worse,and reservoir performance becomes worse.The change of sedimentary pattern and the destructive effects of penetrating large fracture on hydrocarbon migration and storage conditions are the important reasons for the undrilled hydrocarbon in the Permian of JZ 1 well.