煤层气储层钻井液结垢伤害实验研究

Experimental research on the scaling damage in coalbed methane reservoir caused by drilling fluid

我国煤层气储层渗透率低,有轻微结垢也极有可能导致渗透率大幅度降低。为了深入研究结垢对煤层气储层的伤害,在分析煤层气储层特征的基础上,利用饱和指数法预测了山西沁水郑庄煤层气储层在钻井液侵入时的结垢趋势,然后通过室内静态实验测定了钻井液与地层水在不同混合比、不同pH值条件下的结垢量,并通过岩心流动实验,进一步证实了钻井液侵入产生结垢对储层的伤害程度。研究结果表明,采用地表水配制的钻井液在侵入储层后有碳酸钙垢形成,结垢量随pH值升高而增大;钻井液侵入量越大,煤储层伤害越严重。

The permeability of our country＇s coalbed methane reservoir is low,so,even slight scale is most probably lead to reduce the permeability.The scaling trend of coalbed methane reservoirs in Qinshui zhengzhuang,Shanxi is predicted by the saturation index method based on the analysis of characteristics of coalbed methane reservoir when drilling fluid invade.Then the amount of scale is measured by static experiments under different mixing ratios of drilling fluid and formation water as well as different pH.The damage of formation by drilling fluid invasion is studied by core flow experiments.The result shows that calcium carbonate scale will develop after drilling fluid invasion,the amount of scale will increased with a higher pH value;the more serious the invasion of drilling fluid is,the greater the damage of coal reservoir will be.