基于机械比能理论的渤海深层钻井参数优化

Optimizing drilling parameters of deep formations in the Bohai Basin based on mechanical specific energy theory

渤海渤中19-6围区北部构造储层埋深超过4500 m,平均钻井深度大于5500 m,目标层位太古界潜山岩性为花岗片麻岩,岩体抗压强度最高超过200 MPa,地层研磨性强,机械钻速仅1~4 m/h,严重制约了区块的高效开发。为提高目标区块钻井效率,基于机械比能理论,从钻进过程能量守恒角度,分别建立了钻压、扭矩、破岩以及摩擦的做功表达式,并进一步建立了破岩过程的能量输入输出平衡方程。实际应用结果显示,该能量平衡方程能够利用待钻地层的基础参数给出合理的钻压区间,推荐的最优化钻压与实钻吻合良好,预测的机械钻速米平均误差为8%,表现出良好的适用性,可为后续深井、超深井钻井作业优化提供设计依据。

In the northern structure of Bozhong 19-6 surrounding area,the Bohai Basin,the burial depth of the reservoir is over 4500 m,the average drilling depth is more than 5500 m,and the target horizon,i.e.,the Archean basement is lithologically composed of granite gneiss,whose maximum compression strength is over 200 MPa,abrasivity is strong and rate of penetration(ROP)is only 1-4 m/h,which seriously restricts the efficient development of this block.In order to improve the drilling efficiency in the target block,this paper established the work expression of weight on bit(WOB),torque,rock breaking and friction,respectively from the perspective of energy conservation in the process of drilling,based on the mechanical specific energy theory.Then,the energy input-output balance equation of rock breaking process was created.The practical application results show that the energy balance equation can provide a reasonable WOB range by using the basic parameters of the formation to be drilled.The recommended optimal WOB is in line with the actual drilling data and the average error of the predicted ROP is 8%,indicating good applicability.The research results provide a design basis for the optimization of subsequent deep and ultra-deep well drilling operation.