井壁稳定性研究中考虑中间主应力强度准则的对比分析

发布时间：2018-10-16 22:23

【摘要】：中间主应力σ_2对岩石强度具有显著影响,在井壁稳定性研究中需考虑σ_2效应。常用中间主应力强度准则有统一强度理论(UST)、Mogi-Coulomb(MG-C)准则、Drucker-Prager(D-P)准则、修正Lade准则、三维Hoek-Brown(H-B)准则和修正Wiebols-Cook(W-C)准则等6种。文中对比分析了上述6种强度准则在σ_1-σ_2平面内的曲线,并进行了井壁稳定分析。结果表明:在σ_1-σ_2平面内,除UST准则为双折线形式外,其他准则均为非线性形式;D-P准则所预测强度最高,其他准则预测结果相近。在当量坍塌压力计算中,UST准则(b≠0)、MG-C准则、修正Lade准则、三维H-B准则和修正W-C准则计算结果相接近,D-P准则所计算当量钻井液密度最低。对于安全钻井方位,UST准则下安全井壁稳定分布区域随着参数b值升高而逐渐减小;D-P准则下井壁稳定分布区域最高;MG-C准则、修正Lade准则、三维H-B准则和修正W-C准则所给出的井壁稳定分布区域相近。对比分析后,在井壁稳定性研究中推荐使用MG-C准则。该准则不仅反映了σ_2对岩石强度的影响,且形式简单,便于在实际工程中应用。
[Abstract]:The intermediate principal stress 蟽 _ 2 has a significant influence on the rock strength, and the 蟽 _ 2 effect should be considered in the study of wellbore stability. There are six kinds of intermediate principal stress strength criteria: unified strength theory (UST), Mogi-Coulomb (MG-C) criterion, Drucker-Prager (D-P) criterion, modified Lade criterion, three-dimensional Hoek-Brown (H-B) criterion and modified Wiebols-Cook (W-C) criterion. In this paper, the curves of the above six strength criteria in the 蟽 _ 1- 蟽 _ 2 plane are compared and analyzed. The results show that in the 蟽 _ 1- 蟽 _ 2 plane, all the criteria are nonlinear except for the UST criterion, and the D-P criterion has the highest predicted intensity and the other criteria are similar. In the calculation of equivalent collapse pressure, UST criterion (b 鈮，

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