压裂液与煤岩相互作用实验研究

煤层气通常需要借助压裂改造措施来实现经济开采,但常用压裂液与煤岩之间相互作用的规律仍不清楚,这不利于煤层的压裂液选择和压裂施工设计。文中通过开展压裂液(CO2压裂液、活性水)与煤岩相互作用实验,研究了不同压裂液对煤岩性质的影响规律。结果表明:煤岩经CO2压裂液浸泡后,其矿物组成发生变化,方解石质量分数显著降低,黄铁矿次之,石英、有机质及黏土矿物质量分数略微增加,伊利石和高岭石被轻微溶蚀,煤岩溶蚀孔隙数量增多,孔隙度和渗透率增大,抗压强度降低幅度为46.0%;煤岩经活性水浸泡后,其矿物组成基本不变,高岭石发生轻微水化膨胀,煤岩孔隙度及渗透率降低,抗压强度降低幅度为1.6%;CO2压裂液比活性水压裂液更有利于煤层气压裂改造。

Experimental study on interaction between fracturing fluids and coal rock

Coalbed methane usually needs fracturing stimulation to realize economic exploitation.However,the interaction behavior between commonly-used fracturing fluids and coal rock is still unclear,which is not conducive to the fracturing fluid selection for coal seam and the fracturing treatment design.This paper conducts static soaking experiments on the interaction between fracturing fluids(CO2 fracturing fluid and active water)and coal rock to investigate the influence of fracturing fluids on the properties of coal rock.Experimental results show that after the soaking treatment on coal rock with CO2-saturated brine,the content of calcite reduces significantly,followed by that of pyrite,while the content of quartz,organic matter and clay minerals are slightly increased.Moreover,illite and chlorite are dissolved with a limited scale,while kaolinite is scarcely dissolved.The number of dissolution pores increases and the pore size is enlarged,resulting in the enhancement in porosity and permeability as well as the decrement of compressive strength(up to 46.0%).After the soaking treatment with active water,the change in mineral composition of coal rock is negligible.The kaolinite undergoes slight hydration expansion,leading to the decrease in porosity,permeability,and compressive strength(approximately 1.6%).The obtained results show that CO2 fracturing fluid is more beneficial to the fracturing treatment of coal seam than the active water fracturing fluid.