Numerical Modeling of Behavior of Oil Well in Salty Formation (Case Study: An Oil Well in Kupal Oil Field)

Salty formations are considered as one of the most important petroleum traps. Thus, oil well drilling in salty formations and its support are among the most significant issues in drilling engineering and one of the most important factors in the life of an oil well. Not only does the loss of these wells cause waste of time and money, but it also hinders the exploitation of large volumes of reservoirs. Among the problems which occur during and after the drilling operations in salty formations, we can mention some of the important problems; such as, trapping of the drill string, decrease in the diameter of the well, and crumpling or shearing in the casing. Convergence of the well lining in salty formations is caused by creep. Creep is a time-dependent phenomenon which occurs under constant stress. Initially, the geo-mechanical properties of one of the wells in Kupal oil field were obtained in this study by sampling and laboratory testing. Afterwards, using the results of a creep test on the sample, the creep behavior of a salt layer around the well was modeled by FLAC2D software. The modeling was done in the two states of drilling ((1) during the drilling and (2) after the drilling (in contact with the casing)) by using the Viscoplastic-burger model. Modeling during the drilling illustrated that using drilling fluid with the weight of 18 pounds per gallon controlled the convergence very well. The findings would also demonstrated that casing rupture would not occur if the cement work behind the casing was appropriate.