| Abstract |
A finite element model was developed for a 1-meter section of a geothermal production well with high total suspended solids. The modelled section contained an isolated pit which was recorded to be the deepest penetration based on the obtained log data of a casing caliper survey. The penetration was assessed to be the results of the abrasive effects of high-velocity solids that impacted the 9-5/8†reline casing overtime. The structural integrity of this casing section was evaluated by modelling the stresses at flowing condition as well as during quenching and air compression using ANSYS® Academic Teaching Mechanical and CFD, Release 19.1 (ANSYS, Inc., 2018) and determining whether the calculated stresses satisfy the von Mises criterion. The obtained results from the numerical modelling showed that a stress concentration has developed at the isolated pit of the 9-5/8†reline casing. At flowing condition, the casing section was evaluated to be generally safe using the von Mises criterion. The simulated von Mises stress at the isolated pit was found to be 44.85 MPa which is less than the assumed ultimate yield strength of steel at 460 MPa. Identical evaluations were obtained for the quenching and air compression scenarios where the von Mises stresses at the isolated pit were calculated to be at 78.22 MPa and 199.49 MPa, respectively. The maximum principal stresses at the isolated pit in both flowing condition and quenching, however, have exceeded the calculated critical burst pressure for the 9-5/8†reline casing at 45.12 MPa. These results indicate that the burst failure of the 9-5/8†reline casing is imminent without the support of the surrounding concretes and outer casings. For the air compression, the principal stresses of the 9-5/8†reline casing were obtained to be compressive suggesting that it has less likelihood of bursting. |