柳林地区煤层压裂液伤害评价及应用

Evaluation of Fracturing-Fluid Damage for Permeability in Coal Seam, Liulin Area, Ordos Basin

压裂增产技术是煤层气开发的重要手段之一。针对鄂尔多斯盆地柳林地区煤层具有储层压力低、渗透率低、孔隙度低和含气饱和度低以及煤层吸附性较强等特点,通过使用短岩心(暂堵)酸化流动仪进行了活性水压裂液、线性胶压裂液、冻胶压裂液和清洁压裂液对煤岩的柳林地区煤岩心渗透率伤害评价实验。实验结果表明,活性水对岩心渗透率的伤害程度最低,为9.82%,清洁压裂液的伤害程度为43.49%,冻胶破胶液压裂液的伤害程度为81%,线性胶压裂液的伤害程度为89.3%,对煤层伤害程度依次为:活性水<清洁压裂液<冻胶破胶液<线性胶。使用优选出的活性水压裂液对现场实施压裂10口井,单井的最大砂比不超过30%,平均砂比15%左右,显示出活性水压裂液的携砂能力满足压裂施工要求,施工成功率接近100%。

Fracturing stimulation is one of the key tools for CBM development. In Liulin area,Ordos Basin, most coal seams are characterized by low reservoir pressure, permeability, porosity,and gas saturation, and strong adsorbability. By using short-core(temporary plugging) acidizing flow meter, some evaluation on the core permeability damage of coal rocks caused by fracturing fluid with active water, linear gel, gel, and clean fracturing fluid was carried out. Result shows that the active water has the minimum level of damage which is 9.82% to the core permeability; meanwhile, the damage level of the clean fracturing fluid is 43.49%, 81% for the gel and gel breaking fracturing fluid, and 89.3% for the linear gel one, individually. Therefore, their damage levels to coal bed are, in order, active water < clean fracturing fluid < gel and gel breaking fluid < leaner gel. The selected active-water fracturing fluid was applied to 10 wells, resulting in the maximum sand ratio no more than 30%, and the average sand ratio of 15% in single well. That means its sand-carrying capacity can meet the requirement of fracturing operation. The success rate is approximately 100%.