中文摘要：

为解决煤层气开采钻井过程中的井壁失稳和储层伤害问题,以硅酸钠和甲酸钾质量比2∶1比例复配,采用正交试验法,实验因素为成膜剂、增黏剂、降滤失剂、絮凝剂,研究出1种煤层气钻井低密度水基成膜钻井液配方即质量分数为5%成膜剂＋质量分数为2%增黏剂＋质量分数为2%降滤失剂＋质量分数为0.3%絮凝剂等。测试了成膜钻井液和未添加成膜剂钻井液的基本流变参数,进行抑制分散性实验、渗透率伤害实验、动滤失实验。实验结果表明：与未添加成膜剂的钻井液相比较,成膜钻井液的剪切稀释性和抑制泥页岩水化性能较好;新型水基成膜钻井液在接触井壁的短时间内在井壁形成半透膜,薄而韧,且稳定时间长;钻井液滤失量相对较小,阻挡液体及聚合物的侵入,能够有效防止地层水化膨胀并封堵地层。

英文摘要：

To solve the problem of wellbore instability and reservoir damage in the process of coal seam gas drilling,the membrane forming agent was composed of sodium silicate and potassium formate as 2：1 quality ratio.A type of low density water-based film forming drilling fluid for coalbedmethane drilling wasdesigned and studiedusing the orthogonal test.The experimental factors include film forming agent,tackifier,filtration reducer and flocculant.The composition is 5% film forming agent,2% tackifier,2% filtration reducer and 0.3% flocculant.The rheological parameters of the film forming drilling fluid and drilling fluid without film forming agent were tested,and the suppression of the dispersion experiment,permeability damage test,dynamic filtration test were carried out.Compared with drilling fluid without film forming agent,the experimental results show that the shear dilution property and mud shale hydration inhibition performance of the film formingdrilling fluid agent is better.A new water-based film forming drilling fluid forms semipermeable membrane when in contact with the boreholein a short time.The semipermeable membrane is thin and tough and stable for a long time.The filtration of drilling fluid is relatively small and resists the liquid and polymer continuing invasion.Itcan effectively prevent the formation of stratum hydration expansion and blocking the stratum cracks.