This paper presents a methodology for designing setting depths of surface and intermediate casing strings in oil wells using the concept of kick tolerance. The methodology was implemented in a microcomputer program written in FORTRAN. The results are plotted to the microcomputer screen through a graphical interface written in C that calls Windows API functions.
The proposed algorithm uses an iterative procedure to define the shallowest casing shoe setting depth employing the kick tolerance concept. It compares the curve of fracture pressure equivalent density with the pressure generated inside the wellbore during a well control operation to estimate the casing shoe setting depth. The kick tolerance concept is applied in two ways: (a) for the well containment and (b) during the gas kick circulation.
In situation (a), the calculation procedure considers the wellbore pressure just after the well closure. In (b), a two-phase flow kick simulator is applied to predict wellbore pressure generated during the gas kick circulation from the well.
Two examples are elaborated to show the application of the proposed methodology and the computer program. The results are presented graphically to illustrate the use of the graphical interface.