Efficient and Cost-Effective Casing Leak Detection Methodology on Offshore Oil Fields

Abstract

Maintaining well integrity is one of the critical factors in the oil and gas industry. It requires close monitoring during the life cycle of the well, especially in offshore fields, to maximize the well life cycle and avoid catastrophic failure. Casing and bonded cement are major components of well completion that secure oil and gas production paths from different overburden formations. However, casing leaks are a common issue that might lead to serious losses in oil and gas production, locked reserves due to formation damage, personnel injuries, and severe environmental impact. Thus, it is important to detect casing leaks in the early stages to prevent such losses, which might induce a high cost of workover operations and well suspension or abandonment. Casing leaks occur due to corrosive fluids in the formations and long-term exposure to corrosive gases. During drilling, cement is set between the casing and the different formations or between the two casings for isolation and well protection. A bad cementing job leads to the failure of well barriers, cracks, and microchannels that allow corrosive fluids to migrate, which slowly corrodes casing and tubing over time. The flow direction determines the type of casing leak, either dumping (downward) or taking (upward). However, both types have a dangerous effect depending on leak severity. The identification of casing leaks, their severity, depth, and flow direction are a crucial task. Well diagnostic using the latest advanced leak detection tools is important in deciding the most appropriate remedial actions. This paper discusses a case study in a well of the Al-Khafji offshore field, where different methodologies were utilized to identify casing leaks. It involves the use of pressure/temperature profiles through downhole memory gauges, annuli pressure surveys, well-testing operations, geochemical analysis, and conventional production logs. The approach used succeeded in identifying casing leaks, flow direction, and the accurate determination of the leak location/depth.