地应力场对井眼轨迹设计及稳定性的影响研究  

INFLUENCE OF GROUND STRESS FIELD ON BOREHOLE TRAJECTORY DESIGN AND WELL-FACE STABILITY

作　　者：刘向君[1] 罗平亚[1] 孟英峰[1] 

机构地区：[1]"油气藏地质及开发工程"国家重点实验室.西南石油学院

出　　处：《天然气工业》2004年第9期57-59,共3页Natural Gas Industry

基　　金：CNPC"九五"重大科技攻关项目

摘　　要：井壁的张性破裂和剪切垮塌 ,是钻井过程中经常遇到的井壁稳定性问题 ,严重地影响着钻井的速度、质量及成本 ,对部分新探区还会因井壁不稳定而无法钻达目的层 ,延误勘探开发的速度 ,影响其综合经济效益。文章基于线弹性力学模型计算分析了地应力场对直井、水平井井眼轨迹设计和稳定性的影响。结果表明 ,当垂向应力为原地最大主应力时 ,垂直井眼最不容易发生剪切垮塌 ,其次是沿着原地最小水平主应力方向的水平井眼 ;当垂向应力为原地中间主应力时 ,垂直井眼最不稳定、最容易发生剪切垮塌 ;当垂向应力为原地最小主应力时 ,平行于原地最大水平主应力方向的井眼最不容易发生剪切垮塌 ,平行于原地最小水平主应力方向的井眼最容易发生剪切垮塌。相同钻井条件下 ,与原地三个主应力的中间主应力平行的井眼比沿着原地最大、最小主应力方向的井眼更容易发生张性漏失。因此 ,为预防和减少井下复杂事故 ,井眼应尽可能避开原地中间主应力方向 ,原地应力大小及方向的准确确定对于优化钻井和降低钻井成本都具有重要的现实意义。Wellface tension failure and shear collapse have seriously influenced the drilling speed, quality and cost, and, in partial new exploration areas, the objective formations couldn't be drilled because of the wellface's unstability, thus delaying exploration and development and affecting overall economic efficiency. The influences of ground stress field on the borehole trajectory design and wellface stability of the vertical well and horizontal well were calculated and analyzed by use of the linear elastic mechanical model. The results indicated that, while the vertical stress was the maximum in-situ principal stress, it was most difficult to form shear collapse in the vertical well, then in the horizontal well distributed along the minimum in-situ horizontal principal stress direction; when the vertical stress was the in-situ intermediate principal stress, the wellface of the vertical well was most instable and it was easiest to form shear collapse in the well; and, while the vertical stress was the minimum in-situ principal stress, it was most difficult to form shear collapse in the borehole parallel to the maximum in-situ horizontal principal stress direction and easiest in that parallel to the minimum one. On the same drilling conditions, it is easier to form tension lost circulation in the borehole parallel to the intermediate in-situ principal stress direction than in the borehole parallel to the maximum or minimum in-situ principal stress direction, so that the borehole should avoid the intermediate principal stress direction as far as possible in order to prevent and reduce downhole accidents, and the in-situ stress magnitude and direction's being accurately determined is of great importance to optimizing drilling and reducing drilling cost.

关 键 词：井眼轨迹 水平井 垂直井 钻井过程 井壁稳定性 钻井成本 主应力 原地 方向 最大 

分 类 号：TE21[石油与天然气工程—油气井工程]