大佛寺井田煤层气储层伤害及其原因分析

利用X衍射、电镜扫描等方法，参照行业标准SY/T 5358-2010《储层敏感性流动实验评价方法》，对大佛寺井田主力煤层气储层进行了速敏、水敏和压敏实验评价，以期减小大佛寺矿区煤层气开发过程中对储层的伤害，实现煤层气的高效开发。研究表明，大佛寺井田煤储层速敏损害程度弱偏中，主要是煤粉运移所导致；水敏损害程度极大，高岭石在水中分散、运移和堵塞孔隙喉道，是影响储层水敏性的主要因素；压敏损害程度大，而且一旦受到围压伤害之后，即便围压恢复，渗透率恢复的概率也很小。由此建议，在煤层气井排采过程中，控制降液面强度和产液量，减小煤粉运移而导致的速敏效应，降低近井筒地带压敏伤害，使用接近于原煤层水矿化度的钻井液和压裂液，防止水敏伤害。 

CBM RESERVOIR DAMAGE AND REASONS OF DAFOSI WELL FIELD

This paper, by means of XRD and TEM, conducts tests in velocity sensitivity, water sensibility and pressure sensibility of the major CBM reservoirs in Dafosi well field according to industrial code SY/T 5358-2010, aiming at reducing damages to reservoirs during CBM development and reaching an efficient development. A moderate damage to velocity sensibility comes from coal powder motion. A big damage to water sensibility is derived from kaolin, which disperses and migrates in the water, and blocks pore throats. Also there is a big damage to pressure sensibility by surrounding pressure; permeability is impossible to recover even if the surrounding pressure is restored. This paper suggests controlling liquid level reduction intensity and liquid quantity, reducing velocity sensibility, decreasing damage to pressure sensibility near wellbore zone, avoiding damage to water sensibility by using drilling liquid and fracturing liquid close to the original coal water mineralization degree.