Successful Implementation of Improved Cementing Workflow in Heavily Depleted Brown Field through Advanced Integrated Cement Evaluation
Authors: Lau C. , Ahmad Tajalie A. , Wa W. , Abdul Rahman N. , Chabernaud T. J. , Saidin S. , Pasteris M. , Johan Z. J. , Cavallini A. , Abd Rahim A. , Shah Zainudin A. B 
Published: October 2017

A seven-well drilling campaign was carried out in Malaysia brown field targeted for enhanced oil recovery (EOR) purpose. The targeted sands were heavily depleted with pore pressure as low as 4 ppg. Good hydraulic isolation in the annulus is critical to prevent the production of unwanted fluid, i.e. water behind casing. The cement evaluation logs performed in the first four wells revealed presence of microannulus response across the same sands in the field. This microannulus occurrence complicated the decision making on perforation intervals. There was a need to prevent or to minimize the microannulus occurrence in the subsequent three wells that planned to penetrate the same sands. A systematic approach had to be taken to integrate the multiple-domains raw datas and a platform was needed to analyze the data to resolve the problems. Integrated workflow was introduced for the first time in South East Asia region.

Via integrated workflow, a thorough study integrating the data from multiple domains i.e. drilling data, well trajectory, petrophysical evaluation, pore pressure, cementing design and execution, effective mud removal, centralizers’ performance evaluation and cement evaluation logs, was performed on the first four wells, with the key objective to identify the root cause for the microannulus response. The root cause for the microannulus in these four wells was successfully identified, besides verifying the centralizers’ performance and mud rheology in slurry displacement process. The solution was able to be proposed and implemented in the subsequent three wells’ cementing recipe, which include the usage of lightweight cement, fluid loss optimization and formation netting using fiber.

The efficiency of the proposed enhancement on the cementing recipe was verified through the obvious improvement in the cement evaluation logs in the wells that followed the integrated platform recommendations. The microannulus impact was greatly reduced in these wells which penetrated the same problematic sands as in first four wells. The hydraulic isolation evaluation in the planned perforations could be performed with less ambiguity and the confidence on the cement quality for long term well integrity assurance increased. This improvement further verified the key reason identified for the microannulus occurrence.

Integrated workflow could increase the level of assurance on cement evaluation by integrating the data via robust workflow and access to the experts in multiple disciplines. The platform provided valuable information by correlating open-hole formation evaluation logs, surface measurements and cementing data using acoustic logs. A complete database was established for cementing planning in future EOR wells. The production data from these newly completed wells complement the study and confirm the efficiency of hydraulic isolation. This workflow has served as maiden approach to develop the cement evaluation integrated platform in South East Asia region.