عنوان مقاله [English]
نویسنده [English]چکیده [English]
In this study, the deformation of wellbore wall due to creep behavior in the salt rock was investigated during drilling and production operations in one of the oil fields of Iran. Therefore, in this oil field, three wells with the required characteristics were selected. To address this, a numerical ground-well-fluid coupled model was developed by the finite difference method (FDM) in FLAC3D for basis of this research. In the first step, the deformation of the wellbore wall was investigated during the drilling operation without the use of the casing and considering the different mud weight for 10 days. The results showed that increasing the mud weight reduced the deformation and convergence of the wellbore wall. Excessive mud weight will lead to divergent deformations which can cause tensile fractures on the wellbore wall, resulting in the lost circulation and instability of the wellbore. The optimum mud weight for wells A and B was 145 pcf (with the convergence of 3.76 cm and 3.93 cm, respectively) and for well C was pcf 140 (with the convergence of 3.94 cm). In order to investigate the effect of the casing on wellbore wall deformation (wells numbers B and C), the analyses were performed in two states; (1) running the casing in the wellbore without the cementing operation and (2) running the casing in the wellbore with the injection of cement behind it. By considering the cement behind the casing, the maximum stress applied to the wellbore wall B was reduced from 446.90 MPa to 350 MPa. Also for well C, the maximum stress on its wall was decreased from 435.4 MPa to 387.1 MPa. By reducing the stress on the wellbore wall, the deformation rate is reduced and as a consequence, the stability of wellbore is significantly increased against casing collapse.