纳米微球保护储层钻井液研究及应用

致密砂岩气藏具有特殊的储层特性，在钻井施工中极易受到损害，且损害难以解除。临兴区块是典型的低孔渗-致密、低丰度、不含硫干气气藏。为防止储层损害，在该区块钻井完井液中引入了封堵剂Micro-ball和CARB，API滤失量降至5mL以下，防塌、封堵性能优良，对易坍塌地层的岩屑回收率大于93%。纳米微球聚合物封堵剂Micro-ball是一种纳米级高分子聚合物，能对储层的微小喉道形成暂堵，可形成超低渗透率的内泥饼；多级惰性封堵剂CARB是一种粒径多级分布的可酸溶的惰性处理剂，其粒径范围一般大于储层孔喉，其在井壁表面可快速形成薄而脆的外泥饼，封堵效果好，泥饼易于清除。LX-xx5-1H井水平段采用裸眼-压裂方式完井，施工中该体系保持了良好的润滑性能，有效解决了钻进托压问题，未出现任何黏附钻具的情况；有良好的抗污染能力，性能稳定，维护简单；具有良好的流型和强抑制性，未发生坍塌掉块情况，多次起下钻十分顺利；压裂试气产量达到预期效果。 

Study and Application of Reservoir Protection Drilling Fluid Treated with Nano Spheres

Tight sandstone gas reservoirs have special characteristics that make them quite prone to damage, which is very difficult to remove, during drilling. The dry gas reservoir in the Block Linxing, for example, is such kind of reservoirs, with low porosity, low permeability, low abundance, and no sulfur. To protect the reservoir from being damaged, two plugging agents, Micro-ball and CARB, have been used in the drill-in fluids to reduce the API filter loss to less than 5 mL. The Micro-ball is a high molecular weight polymer nano material able to penetrate into the pores in the reservoir formations to form interior mud cakes with ultra-low permeability, thereby to temporarily plug the micro pores. CARB is an acid-soluble inert spherical material with wide range of particle size distribution. CARB has particle sizes greater than the sizes of the pore throats in the reservoir formations, and are thus able to mud cakes on the surface of the formations. CARB has good plugging capacity and forms mud cakes that are easy to remove. The horizontal well LXxx5- 1H, completed with open-hole fracturing, was drilled with this drill-in fluid, which had good inhibitive capacity (shale cuttings percent recovery in hot rolling test is greater than 93%) and good plugging capacity. The improved lubricity of the drill-in fluid helped solve the problems of being unable to exert WOB during horizontal drilling, and balling of BHA. The drill-in fluid is resistant to contamination, has stable property which is easy to maintain, and good flow pattern. The drilling operation has been successful, and the gas production rate obtained after fracturing job is highly satisfactory.