针对易漏砂岩地层防井漏材料粒径优化设计

为解决易漏失砂岩地层频发的井漏问题,采用巴西劈裂试验研究方法,测试不同粒径组合方式下防井漏材料对于井壁抗拉强度的强化效果。通过对比岩样孔喉尺寸和钻井液中防井漏材料的颗粒粒径,分析砂岩经不同粒径防井漏材料钻井液处理后的岩样抗拉强度测试结果,得到以下结论:相较于水润岩样的抗拉强度,防井漏材料明显起到强化井壁的效果,从而提高地层承压能力;未经粒径优化设计的防井漏材料有可能无法强化井壁,从而造成井漏问题无法缓解和钻井材料资源浪费等问题;钻井液中防井漏材料颗粒粒径范围越广,井壁强化效果越明显;若要达到最佳防井漏效果,使得地层承压能力最高,建议钻井液在进行防井漏材料粒径组合优化设计时,应考虑将防井漏材料的平均颗粒粒径约等于岩样平均孔喉尺寸。研究结果可为维持易漏失砂岩地层的井壁稳定、缩短非生产时间和安全高效钻井提供参考。

Optimization of Particle Sizes of Plugging Materials for Sandstone Formations

Brazilian split tests were conducted on plugging materials with different combinations of particle sizes to improve the tensile strength of a wellbore encountering sandstone formations which is easy to be invaded by drilling mud.The pore throat sizes of the rock sample and the particle sizes of the plugging material were compared,and the tensile strength of the rock sample was tested after treated with the drilling fluid with plugging materials with optimized combination of particle sizes.It is concluded that,the plugging material can improve the tensile strength of the rock sample,compared with the tensile strength of a water-wetted rock sample,thereby improving the pressure bearing capacity of the formation;the plugging material with particles size not optimized may not to strengthen well wall,thus causing lost circulation and the waste of drilling resources;the wider the range of the particle sizes,the more obvious the strengthening effect;to get the best plugging effect and the highest pressure bearing capacity,the average particle size should be approximately equal to the average pore throat size.These findings are helpful to improving wellbore stability,reducing non-production time,and guaranteeing safe and efficient drilling operation in sandstone formations.