深层页岩气水平井多尺度裂缝压裂技术

Multi-Scale Hydraulic Fracturing of Horizontal Wells in Deep Shale Gas Plays

深层页岩气(埋深3 500.00m以深)资源量丰富,但存在压裂施工压力高、加砂困难和压裂后产量低等问题,尚未实现商业化开发。为此,通过模拟地层条件的三轴应力-应变试验分析了深层页岩的变形特征,发现深层页岩具有较强的非线性变形特征,导致深层页岩压裂后平均裂缝尺度偏小;在此基础上,总结深层页岩气井的压裂经验,提出了深层页岩气水平井多尺度裂缝压裂技术:采用酸预处理或中途注酸、粉砂段塞打磨等技术降低施工压力,利用大阶梯变排量、变黏度多级交替泵注模式实现对多尺度裂缝的改造,增加小粒径支撑剂比例实现对多尺度裂缝的长效支撑。该技术在川东南某井进行了现场试验,压裂效果明显改善。这表明深层页岩气水平井进行多尺度裂缝压裂具有可行性,并能提高深层页岩气井的压裂效果。

Shale gas resources are abundant in shale plays deeper than 3500 min China.They have not been commercially developed yet due to high treatment pressure,difficulty in sand pumping and low postfrac production.Rock mechanics tri-axial tests were conducted under simulated reservoir conditions.Testing results showed that the deep shale plays presented obvious nonlinear deformation feature,which would lead to narrow fracture widths after fracturing.Combining our fracturing experiences in deep shale gas wells fracturing,we put forward the technique of multi-scale fracturing in horizontal wells of deep shale gas plays.This technique adopts acid pretreatment,or acid injection during the treatment,and slit slugging and grinding to reduce treatment pressure;step pump with varied pumping rate and multi-stage alternative pump injection mode with varied frac fluid viscosity to stimulate multi-scale fractures;and increases the portion of small size proppant to realize long-term and effective prop of multi-scale fractures.This technique has been applied in a well in Southeastern Sichuan Basin and achieved encouraging fracturing result.It demonstrates the feasibility and availability of this technique in deep shale gas wells,and fracturing results can be improved from this technique's application in deep shale plays.