川渝地区碳酸盐岩气层钻井碱敏性实验研究

EXPERIMENTAL RESEARCH ON DRILLING ALKALI SENSITIVITY OF CARBONATE GAS R ESERVOIRS IN SICHUAN──CHONGQING REGION

通常认为碳酸盐岩储层由于粘土矿物含量少,其碱敏性弱,但未考虑碱与碳酸盐岩矿物白云石反应生成水镁石这一情况,反应使矿物颗粒分散/运移至细小孔喉处堵塞,从而造成储层损害。文章以川渝地区碳酸盐岩气层为对象,通过实验及相应的标准评价了储层碱敏程度。实验结果表明,该气层碱敏程度强,且损害是不可恢复的。敏感机理包括:碱与白云石相互作用生成水镁石,反应使矿物颗粒分散;碱性介质诱发粘土矿物失稳;阳离子交换吸附;碱液与地层水相互作用生成无机垢等。

It was generally considered that the alkali sensitivity of carbonate reservoir is weak because of a lower clay mineral content. However, the brucite formed by the reaction of alkali to carbonate mineral - dolomite didn't be thought over, and the reaction made mineral paritcles dispersed and moved to the pore throat, thus causing formation damage due to the small passages being blocked by the particles. By taking the carbonate gas reservoirs in Sichuan-Chongqing region as research target, the reservoir alkali sensitivity was evaluated by laboratory experiments and relevant standards, the experimental results indicated that the alkali sensitivity of the gas reservoir was high and the damage was uncovered. The alkali sensitivity mechanisms include: the reaction of alkali to dolomite to form brucite and make mineral particles dispersed; the clay mineral destabilisation induced by alkaline medium; the cation exchange adsorption: and the interaction of alkali lye with formation water to form inorganic precipitates.