This paper describes the importance of pressure transient analysis (PTA) for reservoir surveillance and production optimization of a giant carbonate field during the early stages of production. Multiple field examples are provided which illustrate an improved understanding of well behavior and reservoir response.

The Kashagan field operational procedures during start-up allowed for numerous shut-in and build-up opportunities which lasted from a few hours to several days. The time lapse analysis of short build-ups combined with pressure and temperature data was applied to monitor well performance, identify opportunities for productivity improvement and assess the effectiveness of acid stimulation. It was also utilized to improve the allocation process for production. Extended buildup tests were conducted to evaluate reservoir properties and identify unexpected well / reservoir responses.

Results from multiple buildup analysis in individual wells were critical to evaluate well performance behavior during early production. The time lapse analysis of the build-up data was able to confirm changing downhole conditions. Furthermore, continuous monitoring was helpful in characterizing the nature of the changes and identifying opportunities for improving well performance. Additionally, routine pressure transient analysis helped to resolve challenges faced by the surveillance team with production allocation.

Reservoir parameters determined by pressure transient analysis improved understanding reservoir behavior in various areas of the field and helped to detect outlying well behavior. As a result, the collected and analyzed pressure transient data has demonstrated its importance as an integral component of reservoir surveillance and production optimization.

This paper presents real field examples of pressure transient analysis in a giant carbonate field along with their ability to improve well performance and to better understand the reservoir response. It also describes the challenges and learnings from production pressure transient analysis data which can be useful for other practicing engineers who might face similar issues.

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