轮南油田深埋风化壳储集层地质条件对地层水混合的控制作用

Geology of Deeply Buried Weathering Reservoir in the Lunnan Oilfield and Its Controls on the Mixing of Formation Waters

碳酸盐岩深层风化壳油气藏普遍出水,严重影响油气的开采,因此地层水赋存规律及其与储集层的关系对于油气的勘探开发具有重要意义。本研究以轮南风化壳油气藏为例,选取构造位置具有明显差异的轮古7和轮古2井区进行地层水的对比研究,并对地质条件与地层水特征的关系进行了讨论。在14个月的跨度内,对研究区各开采井地层水进行了6次采样及分析测试工作。结果表明,同轮古2井区相比,构造高部位的轮古7井区各钻井同一时间出水特征相对集中,且不同时间各钻井出水特征的变化不大;同时具有明显偏高的氯溴比及脱硫系数。表明构造高部位的轮古7井区储集层连通性更好,同时开放性更强,与上部地层盐岩溶解水的混合作用更为明显。不同构造位置的地层水特征明显受地质条件的控制,并反映出地层水所在储集层埋藏越深,石炭系砂泥层厚度越大,储集层的开放性及连通性越差。

Formation water invasion is common in production wells,which rise concerns about future production potential of hydrocarbon resources.Thus,the preservation regularity of the formation water and the relationship between the reservoir and hosted formation water are very important.A comparative study of the variation of formation waters in Lungu7 （LG7）and Lungu2（LG2）wellblocks are conducted in order to address relationship between the characteristics of formation water and geological setting.These two wellblocks are located at structural location of the Lunnan Oilfield：The LG7 well-block is located at the tectonic high position with Carbonaceous layer partly wedge out,whereas the LG2 wellblock is loca-ted at the tectonic lower position with thicker Carbonaceous layer.The formation water in all producing wells at LG7 well-block have similar chlorine concentration over time,suggesting that the producing wells in LG7 wellbolck have good con-nectivity.On the contrary,the formation water in producing wells at LG2 wellblock are highly variable in composition,in-dicative of poor connectivity of LG2 reservoir.Formation water in LG7 wellblock has higher Cl/Br ratios and coefficient of desulfurization than that in LG2 wellblock.These results show that the carbonate reservoir in LG7 wellblock is more open, and is apparently affected by salt dissolved water compared with that in LG2 wellblock.Thus,it is concluded the reservoir connectivity is controlled by the geological setting.Distance to the wedge line of the Carboniferous layer and the thickness of Carboniferous sand-mudstones have negative correlation of openness and connectivity of the reservior.