Integrity diagnostic has become one of the key prerequisite criteria when dealing with uncertainties in the well completion of mature assets. This is particularly true in Malaysia, where most of the tubing and casing in production wells has aged more than 30 years, and yet some of these wells are still producing beyond their original design life expectancy. Locating the source of integrity issues relies on being able to identify leaks and/or flow behind casing. Typically, conventional technologies have been used for anomaly detection, including spinners and temperature logs, downhole cameras, calipers and noise logs. In general these lack accuracy, with smaller leaks being particularly difficult to identify. Development studies pioneered in the well logging industry have led to a new diagnostic approach utilising high definition ultrasound technology. This has created a fast, accurate and reliable technique which can be used to identify leaks as small as 0.02 litres per minute inside the completion tubing. Field D and Field BN fields are two of PETRONAS Carigali Sdn. Bhd. (PCSB) mature fields where ultrasound technology has been implemented aggressively in order to mitigate complex completion problems involving tubing and annulus leaks. PCSB has successfully implemented this technology since 2008; to date the company has resolved more than 100 wells uncertainties using the method to determine multiple completion leaks and flow channelling behind casing. The ultrasound-based leak detection case histories demonstrate the practicality of the technique in many cased-hole applications. The related ultrasound-based flow-behind-pipe survey detects liquid or gas flow behind casing with a measurement from within the tubing. This unwanted flow can have a variety of negative outcomes, including poor well performance, ground water or reservoir contamination and/or more catastrophic uncontrolled fluid escape at surface. The diagnostic is sensitive to the ultrasound energy created by turbulent liquid or gas flow through small restrictions in annuli. From within the tubing, it can detect and locate undesirable flow behind pipe with great accuracy - even through multiple casing strings. This paper shares some experiences and best practices developed while implementing the technology in Field D and Field BN fields.

When ConocoPhillips (COP) decided to conduct Casing Directional Drilling (CDD) operations from a platform in the Norwegian Sector of the North Sea, the well design required that the drilled in 7–3/4" production casing string be converted into a liner prior to completing the well. There was a challenge in identifying a liner hanger system that would be suitable for CDD operations; that did not require a running tool; would maintain a full internal diameter (ID) for running and retrieving bottom hole assemblies (BHA's) and would act as a barrier against gas migration over the service life of the well. Expandable technology(1) was identified as a potential solution. Once a service provider was identified, a basis of design was established and testing began. The end result after eighteen (18) months of work was a successful field deployment of a 7–3/4" liner hanger that was drilled in from surface; successfully expanded into 10–3/4" casing; had a load capability of over 440,000 lbs (200 metric tons or MT) and a 5,000 psi (345 bar) gas tight seal qualified to ISO 14310:V0. This paper will describe the development, testing and actual deployment that took place between December 2006 and January 2007. Introduction In the well under consideration, COP wanted to casing directionally drill a long string of 7–3/4" casing to the top of the reservoir, cement the casing shoe, then convert the long string into a liner and retrieve the upper section of 7–3/4" casing. This conversion was required for four main reasons: the completion & stimulation design; future sidetrack operations; concerns regarding Equivalent Circulating Density (ECD) while drilling the 6–1/2" reservoir section; and space constraints within the wellhead system. Conventional liner applications typically involve making up a liner with an integral liner top packer and a specific running tool; attaching the liner to the drill string; then running it into a pre-drilled hole section prior to cementing. However, it was planned to drill this well with casing as the drill string; with the casing string extending from Total Depth (TD) back to the rig floor. Bottom hole assemblies (BHA's) would have to be run through the liner hanger (LH) on wireline; the liner hanger would be picked up at surface and needed to be drilled in to approximately 4,800 ft after which it would need to be set and provide a gas tight seal. Therefore a conventional liner hanger assembly was not believed to be a viable solution. It was also important to ensure that the LH could be set at any depth in the well in the event the casing could not reach TD during CDD operations. As it happened, the casing did reach TD and although the LH was positioned across a 10–3/4" casing collar, this had no detrimental affect on the setting of the LH.

This paper is a case study of field data, assessing the impact of a well integrity survey on an on-going development drilling programme, enabling critical management of an unexpected shallow gas risk. The results and conclusions presented are applicable to the diagnosis and risk management of shallow gas zones and their impact on well construction, design and integrity. The well Operator experienced a severe loss of well control during drilling operations in the Western Block of Talang Jimar field in Sumatra. The field is mature and the well was considered routine in a series of more than 200 drilled over the past 50 years. A kick occurring at a relatively shallow depth around 300m was completely unanticipated. It was judged critical to further drilling to investigate the location and extent of the charged interval. This would identify HS&E and operational risks to be mitigated by modification of both the on-going drilling plan and the well design. The clearest and most precise information was required. When active surface gas venting was discovered at an adjacent well, an ultrasonic annular integrity survey was commissioned to determine the subsurface source of the gas. This ultrasonic survey deploys a number of sensors on wireline in the well, the most important being a passive ultrasound detector. The paper describes the survey technique in brief, the results of the successful survey and the modifications made to the well and mud-weight design to manage the shallow gas risk and the benefits for the drilling programme. The new results presented reveal annular flow outside surface casing with clarity, and the paper explores the underlying reasons for this clarity and its potential benefits for shallow-gas applications. Field data is presented to support the conclusions reached. The methods and technology described in the paper will be of interest, as they should be widely applicable to shallow gas integrity diagnosis, whether a surface gas vent or sub-surface cross flow, in both onshore and offshore applications. Such diagnosis may enhance drilling and production HS&E performance, reducing the risk of well-control incidents.