Mud Cooler and Chiller Packages in High-Temperature Deep Horizontal Gas Wells: A Case Study from Saudi Arabia

Abstract

Abstract The temperature gradient in a giant gas field in the Middle East shows wide differences from one location to another. The drilling environment in slim single-lateral wells is challenging due to the substantial temperature anomalies resulting to multiple drilling tool failures where recorded downhole temperature exceeded 320 degF. This paper focuses on the first implementation of mud cooler with chiller packages in a gas drilling project and how it affected downhole temperature and well delivery performance. The process that led to the successful implementation of the technology can be summarized in four phases: the analysis of business drivers, preliminary temperature simulations and package design, and compatibility analysis, installation and operation. The identified business drivers included prevention of tool failures, optimization of drilling parameters, reduction of additional trips and the removal of the time-consuming staging procedure. To address these business needs importing HT tools did not seem to be the optimal solution as the temperature anomalies are not experienced in every well; the mud cooler and chiller offered the needed flexibility and cost-efficient solution. The mud cooler and chiller packages were implemented in a series of high-temperature gas wells and proved to be highly effective in rapidly decreasing the temperature of the mud at surface and substantially cooling down the downhole drilling tools. Maintaining a low downhole temperature throughout the section enabled the reservoir laterals to be drilled more efficiently, with less runs, and with no temperature-related tool failure. At surface, the mud temperature was lowered by more than 40 degF. Downhole temperature reduction measured by the drilling and measurement tools was up to 21 degF. Remarkable performance was achieved, such as the drilling of more than 3,000 ft of 5-7/8″ lateral in a single run while keeping the downhole temperature below 280 degF which was decisive in preserving the downhole tools. This project is a notable illustration of successful collaboration between different business units within the integrated service provider's organization to design and implement a fit-for-purpose solution to enhance tools’ reliability in high-temperature environments. The key elements which made the implementation successful in extending the runs and eliminating non-productive time for improved well delivery performance will be presented and described in length in the paper. Integration of the different technologies involved proved to be a key driver of innovation in the project and allowed for faster trials and deployment of new technologies and ways of working. Both the operator and the integrated services provider joined their efforts to achieve step changes in performance in high-temperature gas wells which can be successfully implemented elsewhere with all the main IOCs and NOCs.