小井眼双阶梯水平井摩阻分析及降摩阻技术

Friction analysis and friction reducing technologies of double-step horizontal wells with slim hole

阶梯水平井作为一种特殊水平井,是开采低渗透、薄油藏的有效途径,然而,针对小井眼双阶梯水平井,由于钻具重量有限,定向滑动钻进过程中,钻压的施加极为困难,直接关系到钻井安全。分析了小井眼双阶梯水平井摩阻产生的原因,形成了以改善接触正压力和摩擦系数为主的小井眼双阶梯水平井降摩阻配套技术,并进行了现场应用。结果表明,通过简化井身结构,增加下部钻具的柔性,改善钻具与井眼之间的间隙,优化井眼轨道类型、靶前位移及造斜率,采用强抑制低摩阻低伤害暂堵钻井液体系等配套技术措施,可降低钻井过程中的摩阻,在确保安全钻井情况下,能有效地提高机械钻速,成功实现地质钻探目的,平均砂岩钻遇率为70.4%,为小井眼双阶梯水平井提供借鉴作用。

As a special horizontal well,stairs horizontal well is an effective way to produce low permeability and oil sheet.However,in the slipping orientation drilling,because of limited weight of drilling tools,it＇s extremely difficult to add drilling pressure for the slim hole double stairs horizontal well,which directly results in the safety of drilling.The cause of friction in slim hole double stairs horizontal well drilling was analyzed,and the matching technology to reducing the friction which can improve contact normal pressure and friction coefficient was proposed and applied in field.Results indicated that friction drag can be reduced dramatically by simplifying well structure,increasing flexibility of bottom drill tools,improving the interspace between drill tools and borehole,optimizing well track type,displacement before target and rate of build up,adopting highly inhibitive and low friction and low damage bridging drilling fluid system and so on,which increased the ROP,and made successful geologic drilling when safe drilling.Average rate of sand drilled was 70.4%,which provided reference for slim hole double horizontal well drilling.