实验设计方法在气井完井管柱选择中的应用

当深层高温高压气井采用酸压措施生产一体化管柱完井投产时,既要防止管径太小酸化压裂时摩阻太大导致井口施工压力太大,影响井口的安全性,也要防止管径太大井筒携液能力差,使气井过早停喷,因此需要选择合理的完井管柱或完井管柱组合。通过利用实验设计软件对影响气井井口施工压力的4个主要参数进行优化设计,在优化设计的基础上对设计出的14种参数组合进行了井口施工压力计算,并进一步回归出了井口施工压力计算方程,经与实际计算的结果对比,模型的平均相对误差为0.24%,同时还利用优化设计得到了不同井深不同管柱组合下的井口施工压力曲线图版,可以从图版上很直观地选择管柱。运用该方法可以计算不同参数组合下的井口施工压力并进行敏感性分析,也可以对新井进行管柱优化设计。

Application of Experimental Design in Gas Well Completion String Selection

When the acid fracturing production integrated string is used in a deep well with high temperature and high pressure,it is necessary to avoid the small size or large size pipe diameter.The big wellhead working pressure which is produced by big friction resulted from small tubing size will take wellhead safety risk when the pipe diameter is very small;the poor ability of wellbore loading liquid will make the gas well quit flowing earlier than expected while the pipe diameter is very large.Thus,it is required to select the reasonable selection of tubing string.In this paper,we use the experiment design software to optimize four main parameters of tubing string composition,well depth,construction displacement and fracture propagation pressure gradient which affect gas well wellhead working pressure.Then we calculate the wellhead working pressures based on the designed 14 parameter combination,and get the regression equation for wellhead working pressure.Finally we obtain the wellhead working pressure curve for different parameter combinations by using experimental design.It is advantage to intuitively choose tubing string.The average percent difference is 0.24% between model result and the actual value.So,the experimental design is available to calculate the wellhead working pressure resulted from different parameters,to perform sensitivity analysis,and to design tubing string for new well.