微裂缝封堵剂评价新方法及强封堵钻井液配方优选

硬脆性泥页岩井壁失稳问题是致密油气等非常规资源钻井过程中的常见难题,目前普遍认为增强对泥页岩微纳米裂缝的封堵,是减少井下复杂的关键。选用一种孔径与泥页岩的微裂缝比较匹配的新型混合纤维素滤膜,替代滤纸做滤失实验,通过对比瞬时滤失量大小,评价了单一处理剂溶液对滤膜的封堵效果。利用该方法进行评价,优选出微纳米粒径的石灰石和二氧化硅复配使用,辅以聚胺、铝合物等抑制封堵剂,构建了一种无黏土相微纳米强封堵钻井液。评价结果表明,该体系在较低表观黏度下,具有较高的动塑比和φ6、φ3读数,有利于水平井井眼净化;具有较低的滤失量,岩屑滚动回收率接近100%,封堵能力远高于常规聚合物体系,可用于致密油气、页岩气等非常规能源的钻进。

Method for Evaluation of Plugging of Nano-micron Fractures

Borehole wall destabilization in unconventional oil and gas drilling has been a problem frequently encountered, and it is widely agreed that plugging of the nano-micron fractures in shale is key to the solution of the problem.A new compound cellulosic filter membrane was chosen to do filtration test.This membrane has pore sizes that are compatible with the sizes of fractures found in shales.By comparing of spurt losses of different additives, the plugging effect of these additives on the membrane can be examined.Using this method, limestone of nano-micron particle sizes and silica of the same size distribution are selected and compounded, producing a clay-free drilling fluid with strong plugging capacity.Polyamine and aluminum compound are also introduced into the drilling fluid to render it inhibitive capacity.At low apparent viscosity, this drilling fluid has high YP/PV ratios, and high φ₆, φ₃ readings.These characteristics are advantageous to hole cleaning.The drilling fluid has low filter loss and high percent cutting recovery(almost 100%).It has plugging capacity much higher than that of the conventional polymer drilling fluids, and is suitable for use in tight oil and gas drilling and shale gas drilling.