盐溶液对煤岩抑制性效果的评价

Inhibitive ability appraisal of salt solution on coal rock

通过室内试验研究了不同种类(NaCl,KCl,CaCl2,HCOONa和HCOOK)和不同质量浓度(5%,10%和20%)的盐溶液对晋城3号煤层煤岩样品膨胀性、滚动回收率、渗透率和钻杆腐蚀性等的影响规律。结果表明:在黏土矿物含量较高的煤层中钻进时,即使是使用清水作为钻井液,也会给煤储层带来伤害;盐溶液可以有效抑制煤基质吸附膨胀甚至使之收缩,在同类型盐溶液中,其抑制效果随其质量浓度的增加而增加;综合技术和经济成本的考虑,HCOONa和HCOOK对煤岩抑制性较好,腐蚀性低,最优加量均为10%。

Employing a lot of lab tests, this paper investigated the impact of salt solution on the expansibility, the roller recovery rate and the permeability of coal rock samples collected from No. 3 coal seam in Jincheng. The impact of salt solution on drill pipe＇ s corrosivity was also investigated. Here salt solution includes various types of salt such as NaC1, KC1, CaC12, HCOONa and HCOOK with the concentration varies as 5% , 10% and 20 %. The results show that ： firstly, fresh water can bring formation damage to gas bearing coal seam when it is used as drilling fluid in coal seams with a high content of clay minerals;furthermore, in presence of salt solution, adsorption and swelling of coal rock matrix can be restrained and even the matrix can shrink, increase of weight percent results in better inhibitive performance when same type of salt is used;finally, with the integrative consideration on technology feasibility and economic cost, HCOONa and HCOOK have better inhibitive performances and lower corrosivity compared with other salts and the optimal concentration are 10%.