Proactive Casing Leak Detection Methodologies: A Case History

Abstract

Abstract This paper addresses how high resolution electromagnetic induction was used to study, assess and map the overall well casing integrity of offshore wells and to enable predictions of casing leakage based on the extent or severity of the casing corrosion log. The objective of the paper is to show how proactive detection and prevention of leaks before they occur have guaranteed continuous operation excellence, safety and environmental compliance. These studies were carried out to understand the nature of the corrosion observed. In addition, several other technologies were deployed to effectively detect leaks and further sketch out their location. The lessons learnt and experience acquired during the monitoring and evaluation of casing integrity will be shared. The new technology was used as a tool to establish a casing integrity baseline for an entire field and articulated the new strategic corrosion master surveillance plan. Using the new technology has resulted in a significant reduction in the frequency of routine conventional temperature surveys and therefore optimized resource utilization to foresee other essential jobs. Introduction Issues associated with casing leaks can lead to significant losses of oil or gas reserves as well as momentous pollution problems. Therefore, early detection of the leaks as soon as they occur is very crucial. In Saudi Arabia oil fields, casing leaks are of particular importance since the country holds some of the largest reserves of petroleum in the world1. The problem is of variable severity from one field to another, depending on the conditions encountered. The sensitivity increases when the field is mature. A thorough investigation of all factors — influencing the life of the casing — and their correlation with field data has been conducted for a particular field. In addition, over the years engineers have improved their detection techniques. In this paper, the effect of all factors influencing the life of the casing and casing leak detection methods used are discussed. Safety, asset integrity, monitoring, detection and possible maintenance and/or repairs of leaks as a result of corrosion are paramount. The conventional technology to detect leaks is the temperature survey, which identifies either up flow or dumping leaks. The method is executed on quarterly basis to identify any casing leaks in a timely manner. If the temperature profile is suspicious, well head samples are collected to carry out further investigation and testing. Annuli survey is conducted bi-annually in addition to temperature survey. This average production casing life has improved with the new proactive approach to monitor and maintain the integrity of production casing in the field. Other practices that help enhance the strategy include improving cementing practice, selecting chrome 13 casing types across corrosive aquifers, and completing new and workover wells with tubing downhole packers to isolate and protect potable aquifer water from contamination.