7000 m以深复杂断裂成组气藏开发早期评价技术--以川西北双鱼石构造栖霞组气藏为例

Early-stage development evaluation technology for complex fault group gas reservoirs below 7000 m:A case study of Qixia Formation gas reservoir in Shuangyushi structure of northwestern Sichuan Basin

四川盆地西北部(以下简称川西北)双鱼石构造中二叠统栖霞组气藏天然气勘探开发潜力大,尚处于开发早期阶段,由于该区地质条件特殊、动静态资料缺乏,导致对该气藏认识不足,尚未实现整体规模效益开发。为了有效预测开发早期复杂气藏的开发前景并给后续气藏整体效益开发提供支撑,基于新钻井及其试采资料,结合数字岩心、灰色关联法及大数据分析等技术的应用,系统评价了双鱼石构造栖霞组气藏的地质及气藏工程特点,总结了控制气井高产的影响因素,评估了气藏的开发前景。研究结果表明:①川西北双鱼石构造栖霞组气藏具有明显“分带分层”特征,由西向东划分的6个构造高带共发育局部圈闭14个,圈闭面积共计246.4 km^(2),总体为台地—台地边缘沉积,角砾状白云岩和砂糖状白云岩为有利的储集岩相;②储层具有特低—低孔隙度、低渗透率特征,裂缝—孔洞型和裂缝—孔隙型是主要的储渗空间类型;③该气藏具有统一的压力系统和天然气性质,整体发育大型构造—岩性复合圈闭,为超深复杂断裂成组气藏;④采用容积法估算该气藏地质储量超过1000×10^(8)m^(3),试采井总动态储量为150×10^(8)m^(3),气井产能差异较大,水平井(大斜度井)井型提产效果显著,基于灰色关联法明确了控制高产井的主要地质因素为沉积相;⑤基于大数据分析技术,预测双鱼石构造栖霞组气藏采气速度为2.61%,稳产年限为11.34年,采收率为60.5%。

Gas reservoir of Middle Permian Qixia Formation in the Shuangyushi structure of northwestern Sichuan Basin has great potential of natural gas exploration and development,and it is still in the early stage of development.The geological conditions in this area is special and there is lack of dynamic and static data,so this reservoir has not been understood sufficiently and its overall large-scale benefit development has not been realized.In order to effectively predict the development prospect of the complex gas reservoir in the early stage of development and support its subsequent overall benefit development,this paper systematically evaluates the geological and gas reservoir engineering characteristics of Qixia Formation gas reservoir in the Shuangyushi structure by using digital core,grey correlation method and big data analysis,based on new drilling and testing data.In addition,the influential factors controlling the high yield of gas wells are summarized and the development prospect of the gas reservoir is evaluated.And the following research results are obtained.First,the Qixia Formation gas reservoir in the Shuangyushi structure of northwestern Sichuan Basin has the obvious characteristics of"stratification and zonation".Fourteen local traps are developed in 6 structural high belts from west to east,with a total trap area of 246.4 km^(2).On the whole,it is a platform-marginal platform deposit.Breccia dolomite and saccharoidal dolomite are favorable reservoir lithofacies.Second,the reservoir is of ultra low-low porosity and low porosity and its reservoir and percolation space is mainly fracture-vug type and fracture-pore type.Third,this gas reservoir has a unified pressure system and natural gas properties,a large structural-lithologic trap is overall developed,and it is an ultra deep complex fault group gas reservoir.Fourth,the geological reserves of this gas reservoir estimated by the volumetric method exceed 1000×10^(8)m^(3),and the total dynamic reserves of production test wells are 150×10^(8)m^(3).Gas well productivity is more different,and the production rate of horizontal well(highly deviated well)is improved significantly.It is confirmed based on the grey correlation method that the main geological factor controlling high-yield wells is sedimentary facies.Fifth,it is predicted by virtue of big data analysis technology that the gas recovery rate of Qixia Formation gas reservoir in the Shuangyushi structure is 2.61%,the stable production time is 11.34 years and the recovery factor is 60.5%.