高产水平井的突破与四川盆地深层常规气藏巨大的勘探开发潜力

四川盆地西北部地区(以下简称川西北)深层海相碳酸盐岩气藏天然气资源丰富,该区双鱼石构造中二叠统栖霞组气藏属于超深、高温、高压的构造—岩性复合圈闭气藏,受滩体发育、成岩作用及构造作用等的影响,其储层非均质性强、单井测试产气量差异较大。为了提升天然气勘探开发效益,实现"稀井、高产",利用岩心分析、测井、地震等资料,基于油气勘探开发一体化、地质工程一体化的工作思路,综合分析并确定了该区栖霞组气藏天然气富集高产的关键因素;进而利用三维地震资料,明确了栖霞组气藏优质储层的平面分布规律;同时大力推广应用新工艺新技术,连续在该构造获得了SYX131、SYX133两口高产水平井,栖霞组气藏测试天然气日产量分别达123.97×10~4 m~3和142.51×10~4 m~3,创造了该区天然气高产的新纪录。研究结果表明:①该区栖霞组溶孔、溶洞型白云岩储层厚度、裂缝发育程度与天然气产能之间具有明显的正相关性;②地震剖面上表现为栖霞组顶部"复波"或中上部"弱波峰"反射特征,储层越发育,"复波"或"弱波峰"特征越明显;③水平井钻井及大规模裸眼分段酸化改造等新工艺、新技术是实现该区天然气高产的重要工程保障。结论认为,两口高产水平井的突破,揭示了川西北深层海相碳酸盐岩气藏具备常规气规模效益勘探开发的巨大潜力。

A breakthrough in high-yield horizontal gas wells and great exploration and development potential in deep conventional gas reservoirs in the Sichuan Basin

There is a huge potential of natural gas resources in deep marine carbonate gas reservoirs in the northwestern Sichuan Basin, where the structural–lithological Middle Permian Qixia Formation gas reservoirs in the Shuangyushi structure are characterized by ultra depth, ultra high temperature and ultra high pressure. Due to the effect of beach body development, diagenesis and tectonism, the reservoirs in this area are of strong heterogeneity and the tested single-well gas production rate varies greatly. In order to improve natural gas exploration and development benefit and realize "sparse well and high yield", we comprehensively analyzed the key factors influencing the enrichment and high yield of natural gas in Qixia Formation gas reservoirs in this area through core analysis, logging and seismic data. Then, based on 3D seismic data, the "complex wave" and "weak wave peak" in the seismic profile of Qixia Formation were depicted precisely and the areal distribution laws of quality reservoirs in the gas reservoirs were figured out. Meanwhile, with new technologies having been thoroughly applied in this study area, two implemented horizontal wells (SYX131 and SYX133) have been drilled into thick dolomite reservoirs with their tested daily natural gas production rates of Qixia Formation being 123.97×104 m3 and 142.51×104 m3, respectively, which set up a new record of high-yield gas rate there. And the following research results were obtained. First, natural gas productivity in this area is in obvious positive correlation with the thickness of dissolved pore type and dissolved cavern type dolomite reservoirs of Qixia Formation and the fracture development degree. Second, the seismic profile presents the reflection characteristics of "complex wave" at the top of Qixia Formation and "weak wave peak" in the middle and upper parts. The more developed the reservoirs, the more obvious the characteristic of "complex wave" or "weak wave peak". Third, such new technologies as horizontal-well drilling, large-scale open-hole staged acidizing stimulation, are important engineering support in this study area. In conclusion, such a breakthrough made in these two high-yield horizontal wells demonstrated that there is a huge potential in the deep marine carbonate gas reservoirs of northwestern Sichuan Basin.