修正剑桥模型在深水浅层石油钻井井壁稳定中的应用

THE APPLICATION OF MODIFIED CAMBRIDGE MODEL FOR THE WELLBORE STABILITY ANALYSIS OF DEEPWATER SHALLOW SEDIMENTS IN PETROLEUM DRILLING

深水浅层的压实程度低、结构薄弱,其破坏规律是深水浅层相关问题研究中的关键点之一。目前修正的剑桥模型已经应用于深水浅层的各类研究中,但是在深水浅层的井壁稳定问题中,深水浅层往往仍然被认为是理想弹塑性材料。将井眼周围地层分为3个区域:弹性区、流动区、塑性区。弹性区,地层为线弹性状态;流动区,地层服从修正的剑桥模型及小变形理论;塑性区,地层服从摩尔库伦准则。对各个区域的应力分布进行了求解,并在求解的基础上,结合超级孔隙压力建立了深水浅层的井壁稳定分析模型。通过实例运算,该井壁稳定模型的可靠性得到了验证。

Deepwater shallow sediments are weakly structured and unconsolidated.The deformation and failure is one of the key points in the study of deepwater shallow sediments.The modified Cambridge model was widely used in the studies of deepwater shallow sediments except for the borehole stability analysis,in which deepwater shallow sediments are still regarded as ideal elastic plastic materials.The formation is divided into three parts:the elastic zone,the flow zone and the plastic zone.In the elastic zone,the formation is linear elastic.In the flow zone,the modified Cambridge model is applied.In the plastic zone,the formation obeys the Mohr–Coulomb criterion.In this paper,the stress distribution of each region is solved,and on the basis of the solution,combined with the excess pore pressure,the borehole stability analysis model of deepwater shallow sediments is established.The calculation results agree with actual data,which verifies the proposed model.