Improving Zonal Isolation and Cutting the Water Production with the Help of an Engineered Self-Healing Cementing System: A Case Study Review of the First Implementation of its Kind in Kuwait

Abstract

In one of the prolific fields in Kuwait, achieving zonal isolation posed a big challenge mainly due to setting the production liner shoe close to the oil-water-contact zone. Cement bond logs from the primary cementing jobs were not acceptable due to contamination from intruding water leading to a high water-cut in the produced oil. We review the first implementation of a self-sealing Cementing System in Kuwait to improve zonal isolation and cutting the water production. A comprehensive pre-job study was executed to engineer a suitable cementing system containing a swellable elastomer for oil-water-cuts with proper test in Lab. A novel HPHT multi-function test cell apparatus and procedure were utilized to measure in-situ ability of fractured cement specimens to seal oil-water-flows under the given simulated downhole conditions. Shrinkage or expansion of the set cement was also verified under pressure and temperature with a continuous test method run over several days. Thorough lab tests and Computational Fluid Dynamics simulations were run to enable a fit-for-purpose and robust cement slurry design ensuring proper placement of the cementing system in the well. This paper will describe how this cement was designed and engineered in laboratory. It will also describe how the set up was made simulating a crack in cement specimen and injecting water cut oil reacts and provides desired results. A calculated cement engineering approach was adopted to ensure better cement slurry placement and reduce the chances of slurry contamination. The test conditions were staged to replicate the most appropriate downhole conditions of pressure, temperature and simulated micro channel in the cement sheath. After the successful implementation of the self-sealing cementing system along the 7-in production liner in 2 wells, the corresponding cement bond log images showed hydraulic isolation and the production data from the wells indicated a reduction of nearly 50% in the water cut thus allowing a favorable oil production. This technology is applied in other wells of this field and other fields also with good results. This is being continued to use in critical wells.