川西北部双鱼石区块栖霞组气藏水侵特征及开发技术对策

Water-invasion characteristics and countermeasures on gas reservoirs of Qixia Formation, Shuangyushi block, northwestern Sichuan Basin

近年来,双鱼石区块二叠系栖霞组气藏已快速成长为川西北部地区主要产能贡献区,但已经陆续出现气井产水现象,对气井及气藏的稳产造成威胁,急需准确认识水侵特征以采取相应对策。由于该气藏构造复杂、储层非均质性强,导致水侵特征认识不清,制约气藏开发。为此,通过离子分析法、G_(p)-W_(p)关系曲线法、Stiff图版法等多种方法分析生产井的产水类型,明确产水为地层水的几口井,并结合静态、动态资料分析其水体来源、水侵通道和水体大小,提出开发技术对策。研究结果表明:(1)双探F、双探E、双鱼G共3口井产地层水,其中2口井(双探E、双鱼G)产出水为栖霞组地层水;(2)双探E、双鱼G的产水来源为同一水体,来自(3)、(4)号条带之间的构造低洼处;(3)两井产水动态特征不同(双探E为地层水沿储层均匀推进,双鱼G为地层水沿高导裂缝水窜),是由于所在位置的断层及裂缝发育特征有所不同;(4)双探E井区、双鱼G井区的水侵量分别为26.04×10^(4)m^(3)、30.50×10^(4)m^(3),水体能量中等偏弱;(5)针对水侵特征,分析认为目前(3)号条带井网密度合理,但采速过高,故提出气井合理配产方案,对目前配产作出调整;(6)针对水侵特征,建议(2)号条带部署2口开发井,提高(2)号条带储量动用率,以实现气藏均衡开采,降低水侵风险。

In recent years, gas reservoirs of the Permian Qixia Formation in Shuangyushi block have rapidly become the major contributor to productivity in northwestern Sichuan Basin. However, successive water from many gas wells endangered their stable production. It is urgent to make clear the characteristics of water invasion for making countermeasures. Due to both complex structure and strong heterogeneity, the characteristics have not been unclear yet to condition reservoir development. So, water-produced types in producers were analyzed by employing three methods of ion analysis, Gp-Wp relation curve, and Stiff chart. For several wells where water was produced from formation water, their water source, invasion channel, and aquifer size were analyzed by combining static and dynamic data. In addition, some countermeasures were made. Results show that(1) formation water is produced from Shuantan F, Shuangtan E and Shuangyu G wells, and that in the latter two is from Qixia Formation;(2) the produced water in these two wells roots in the same aquifer located at the low-lying structure between(3) and(4) strips;(3) for both Shuangtan E and Shuangyu G wells,dynamic characteristics of water production are different: the water in Shuangtan E well from formation water advances evenly along reservoirs while that in Shuangyu G well also from formation water flows along high conductivity fractures mainly because of various features of faults and fractures extended at their location;(4) the water influx in these two is 26.04×10^(4)m^(3) and 30.50×10^(4)m^(3), respectively, presenting moderate to weak water energy;(5) the analysis on water-invasion characteristics illustrates proper well spacing density in(3) strip but extra-high production rate. As a result, a reasonable proration plan has been proposed to mend the current one;and(6) it is recommended to deploy two development wells in(2) strip to increase the production rate of reserves, further to conduct the balanced exploitation in Qixia gas reservoirs and reduce the risk of water invasion.