天然裂缝对页岩气水平井压裂的影响及工艺调整

Influence of natural fractures on fracturing of horizontal shale gas wells and process adjustment

缝网压裂是页岩气"缝控储量"开发模式的具体体现,天然裂缝是影响水力裂缝扩展及压裂后效果的重要因素,国内外学者多采用数值模拟进行研究。基于矿场实践与数据统计分析,利用分类方法研究不同特征天然裂缝对压裂施工及效果的影响,开展了天然裂缝发育储层提高改造效果矿场探索与效果评价。研究结果表明:①前置高黏压裂液+低黏滑溜水携砂可解决细微天然裂缝发育储层加砂难度大、改造体积偏小、改造效果欠佳等难题;②大尺度天然裂缝发育储层压裂后裂缝复杂程度低、改造效果欠佳,与井筒大角度相交的大尺度天然裂缝是诱发套管变形、压裂井间干扰的潜在地质因素,暂堵转向压裂工艺对干扰裂缝扩展、提高改造效果存在一定不确定性;③后续相关研究应集中在大尺度天然裂缝与井筒平行情况下的压裂效果提高,以及与井筒大角度相交情况下的套管变形和压裂井间干扰防治。

Fracture network fracturing is the concrete embodiment of the development mode of "fracture-controlled reserves" in shale gas wells. Natural fracture is an important factor affecting the hydraulic fracture propagation and the post-fracturing effect, which is mostly studied by numerical simulation at home and abroad. Based on the field practice and data statistical analysis, this paper studies the influence of natural fractures with different characteristics on fracturing operation and post-fracturing effect by classification method, and carries out the field research and evaluation of the improvement on reservoirs in which natural fractures are developed. The study results show that:(1) For reservoirs with micro nature fractures, the problems such as difficulty of proppant adding, small stimulated reservoir volume and poor stimulated reservoir effect, can be solved by the method of "pad high-viscosity fracturing fluid + low-viscosity slick water carrying proppants".(2) For reservoirs with large-scale natural fractures, the complexity of post-fracturing fractures is low, and the fracturing effect is not good. The large-scale natural fracture intersecting with wellbore at a large angle are the potential geological factor that induces casing deformation and well interference. There are some uncertainties about temporary plugging diversion fracturing process on fracture propagation interaction and stimulation effect improvement.(3) The follow-up researches should focus on improvement of fracturing effect when the large-scale natural fractures are parallel to the wellbore, and the prevention of casing deformation and frac-hit when the large-scale natural fractures are intersected with wellbore.