四川盆地龙王庙组气藏储层改造技术及其应用效果

Reservoir stimulation techniques and their application to the Longwangmiao Fm gas reservoirs in the Sichuan Basin

四川盆地中部磨溪构造下寒武统龙王庙组气藏具有高温、高压、含H2S等特点,视均质中高渗储层厚度是气井高产的地质基础,天然缝洞良好搭配是气井高产的关键因素.过平衡钻进导致天然裂缝开启,易发生钻井液漏失,储层伤害严重,实验评价结果显示,钻井液对储层天然裂缝岩样伤害率为82.2％～89.2％,严重制约了气井产能的发挥.基于此,有必要深化实验评价技术和方法,以此来提升工艺技术参数设计的针对性.研究结果表明：①优选的胶凝酸和转向酸具有缓速、解堵效果且能够有效形成酸蚀蚓孔,充分解除钻井液污染堵塞;②研制的纤维转向剂和可溶性暂堵球能够起到转向效果,井底处理压力增加5～15 MPa,实现非均质储层的均匀改造;③基于酸液穿透和酸岩反应等实验评价,推荐出解堵酸化合理的施工排量为3.0～3.5 m3/min,用酸强度为3.0～5.0 m3/m;④形成的解堵和转向酸化技术现场推广应用20余井次,增产效果显著,充分发挥了气井自然产能,同时降低了用酸规模.上述技术措施有效提高了该气藏的开发质量与效益.

The Longwangmiao Fm gas reservoirs in the Moxi tectonic structure in central Sichuan Basin are featured by high temperature,high pressure and high H2 S content.The thickness of such high permeable reservoirs with great homogeneity is recognized as the geologic basis of the high productivity of a gas well,and the good arrangement of natural fractures is also the key factor to high well productivity.Over-balance drilling results in the cracking of natural fractures,which will lead to the leakage of drilling fluids and severe damage of the reservoir.The experimental evaluation displayed that the damage rate of the drilling fluid to the rock sample is be tween 82.2 and 89.2％,which severely restricts the productivity of a gas well.Therefore,it is necessary to deepen the experimental evaluation technologies and methodologies to promote the design pertinence of processing technical parameters.The following findings were concluded.First,the optimized gelled and steering acids can retard and resolve the blockage problem,and acidizing wormholes can be formed to effectively eliminate the blockage effect caused by the drilling liquid pollution.Second,the developed fiber steering agent and soluble temporary blocking ball can realize direction turning and the processing pressure at the shaft bottom increases by 5 to 15 MPa,which realizes the even reform of heterogeneous reservoirs.Third,based on experimental evaluations such as the acid liquor penetration and acid rock reaction,it is recommended to take 3.0 3.5 m3/min as the rational construction displacement of acidizing treatment and 3.0-5.0 m3/m as the acid strength for blockage removal.Fourth,the formed blockage removal and steering acidizing technologies have been applied in more than 20 wells with a remarkable productivity-increasing effect,which completely gives full play to the natural productivity of a gas well and decreases the acid application scale.All these technologies and measures effectively enhance the development quality and profit of such gas reservoirs.