气体钻井岩屑遇水黏附现象与对策研究

Adhesion of Cuttings during Gas Drilling and Counter-measures

气体钻井钻遇地层水时,泥页岩岩屑形成黏附岩屑床,导致注气压力升高、钻柱转矩增大,甚至卡钻。通过实验模拟水平段岩屑起动和气体携水过程,研究了岩屑黏附机理、影响因素和控制方法。结果表明:大量岩屑在下井壁缓慢移动,水呈液膜状贴井壁流动并伴随悬浮液滴,部分粒径岩屑受毛细管力黏附导致无法起动;小出水量时,可提高钻速减小液固比,使岩屑床处于固态,不易黏附;大出水量时,可控制钻速使环空液固比升高,则岩屑与水的混合物处于流动状态,以避免黏附。该研究成果为遇水情况下气体钻井的顺利进行奠定了技术基础。

When penetrating water-bearing formations,gas drilling operations were frequent by adhesion of mud shale cuttings.Such adhesions may result in higher gas-injection pressures,enhanced torques of pipe-string and bit sticking in some cases.By simulating movements of cuttings and water-carrying performances of gases in horizontal intervals,researches have been conducted to clarify adhesion mechanisms,influencing factors and relevant controlling techniques for cutting.Research results show large quantities of cutting migrated slowly along sidewalls.At the same time,water flowed along the sidewall in liquid film accompanied by droplets in suspension.Some granular cuttings were incapable to move due to capillary forces.In cases with minor volumes of water production,rates of penetration can be enhanced to reduce liquid/solid ratios.Accordingly,cutting beds may be maintained in solid phase to minimize possibility of adhesion.In cases with massive water production,rates of penetration can be controlled to promote liquid/solid ratios in annular spaces.In this way,mixture of cutting and water may flow,instead to adhesion.Relevant researches may establish reliable technical foundation for proper execution of gas drilling in water-bearing formations.