使用纳米碳酸 钙降低低孔低渗煤层气储层伤害
Reducing Formation Damage to Low-Porosity and Low-Permeability CBM Reservoirs Using Calcium Carbonate Nanoparticles

传统暂堵剂难以封堵低孔低渗煤层气储层中的大量纳米级别孔隙．通过煤岩显微观测、钻井液基本性能测试、泥饼清除 实验、煤岩孔隙分布实验和气体渗透率实验，探讨了纳米碳酸钙降低低孔低渗煤层气储层伤害的效果．结果表明：纳米碳酸钙 材料只有在水溶液中保持纳米级的分散状态，才可能对低渗煤岩起到暂堵作用；基于纳米碳酸钙的可降解钻井液既能封堵低 孔低渗煤岩中微米级别孔隙，也能封堵其中的纳米级别孔隙；经过生物酶和稀盐酸双重解堵后，煤岩渗透率恢复值达 ７７．１７％～９７．９８％，储层保护效果好；煤岩孔隙分布实验可以在纳米尺度上研究纳米材料对低孔低渗储层的暂堵效果．研究成 果可为纳米碳酸钙在低孔低渗煤层和页岩钻完井过程中的应用奠定良好技术基础．
It's di価cult to b1ock a mass of nanoscale pores in the1ow-porosity and1ow-permeability coalbed methane(CBM) res- ervoirs using traditiona1 temporary plugging additives. The performances of reducing formation damage to1ow-porosity and 1ow-permeability CBM reservoirs using calcium carbonate nanoparticles(nCaC〇3) are evaluated in this study through micro- scope investigationof coa1 rocks, the basic performance tests of dri11ing fluid, mud cake remova1 tests, pore size distribution tests and gas permeability tests of coa1 rocks. It is found that only when nCaC〇3 are dispersed to nano-scaled state in water solution could it tempora11y plug the1ow permeability coa1 rocks. However, nCaC01, based degradable dri11ing fluid not only b1ocks themicroscale pores in1ow-porosity andlow-permeability coa1 rock, but also b1ocks the nanoscale pores. With the double unplugging techno1ogy of bio1ogica1 enzyme plus1ow concentration hydroch1oric acid on the nCaC()11 based dri11ing fluid, the permeability recovery rate of coa1 rocks ranges from77. 17% to97. 98%. The reservoir protective effect on reservoir proves good. It is shown that the pore size distribution test could be used in the investigation on tempora11y plugging performance of nanoparticles to1ow-porosity and1ow- permeability reservoirs on nanoscale. This study may offer a technica1 support to facilitate future applications of nCaCC)11 in dri11ing and completion process of 1owporosity and1ow permeability coa1 seams and shale formation