钻井液侵入引起煤岩膨胀对煤储层的伤害

Damage in Coal Reservoir Caused by Coal Swelling after Drilling Fluid Invasion.

在分析了煤层气储层岩性特征和煤层水特征的基础上,通过室内静态实验测定了沁水盆地郑庄3号主力煤层煤样分别在蒸馏水、煤层水和1%KCl盐水中的线性膨胀率;并测定了煤样的水敏性。研究结果表明,煤岩遇水膨胀程度直接受煤中黏土矿物的影响,煤粉膨胀主要发生在开始与水接触的1h时间内,配制钻井液的地表水进入煤层后将造成煤岩膨胀,降低煤储层渗透率,对煤储层造成损害。

Based on the analysis of lithologic characteristics and water feature of coalbed methane reservoir,linear expansion rate of coal samples in main coalbed of Zhengzhuang No.3 in Qinshui was measured by static experiments in distilled water,coalbed water and 1%KCl brine.Water sensitivity of coal sample was measured by core flow experiments.The results showed that the swelling degree of coal was directly impacted by clay minerals in the coal.Expansion of coal dust mainly occurred in 1 hour after contacting with water.The surface water prepared for drilling fluid led to coal swelling,permeability decrease and coal reservoirs damage.