Mechanical Earth Model (MEM): An Integrated Study in Low-Fracture-Gradient and Depleted Fields to Improved Cementation (Case Study)

Abstract

A depleted reservoir in the Tapian Timur field in South Kalimantan, Indonesia, is located at 1,400-mTVD with a 400-psi formation pressure. Drilling through it presents potential threats to operations, including lost circulation during drilling and cementing and borehole instability. Two wells previously drilled and completed in the area suffered long NPT due to stuck pipe and bad cement bond quality. Even though the field has been explored and developed for 43 years, a thorough study of the reservoir characteristics was never done. Improper knowledge of a reservoir like this one cause’s unnecessary lost time during drilling and poor zonal isolation of the target zone, can potentially jeopardize the economic feasibility of a project. For this reservoir, a geomechanical study was applied, and a mechanical earth model (MEM) was built. The model utilized multidisciplinary data across the field (drilling and logging data, core, pressure history) to evaluate wellbore stability and improve drilling practices. The MEM study provided key recommendations for the drilling process and cementing operation. Decisions made based on the study include changes in casing point, mud-weight optimization, and utilization of high-performance lightweight slurry with fiber. A subsequent well drilled in the area applying the recommendation from the study was drilled and completed faster. Cement bond logs from the section also indicated excellent zonal isolation across the reservoir. The recommendations from the study are currently integrated into the standard operation procedures.