In brownfield developments, prolonging the production life of the wells beyond the 30-year original well design life has been one of the challenges in managing well integrity. This challenge is often compromised by multiple tubing leaks or, in the worst case, by parted tubing caused by metal fatigue, erosion, and corrosion. The issue is often observed in many wells in the S field and usually occurs at a shallow depth between the tubing hanger and subsurface safety valve. The conventional through-tubing repair technique becomes increasingly difficult and ultimately tends to be unsuccessful. Moreover, with the challenge of low oil prices, a simple single-trip system, necessary to reduce costs and increase the success rate, is preferred. Several cost effective approaches to repair production tubing leaks have been available in the market for quite some time. These conventional methods (e.g., stackable slickline straddle, multi-run coiled tubing (CT) conveyed straddle, and tubing patches) come with basic tools, but require difficult manipulation to set and retrieve some of the assemblies, which are permanently installed, that may complicate future well abandonment. For wells with multiple leaks or where the completion tubing has been parted, complete replacement of completion tubing will be the only solution because of the severity of damage. This typically requires a workover rig or snubbing unit at both economically and operationally significant expense. It also typically results in a significant amount time required for well preparation, mobilization, and demobilization of the rig. In addition, the retrieval of this degree of corroded completion is not straightforward because it can come apart piece by piece, which will consume additional time. This paper describes the first customized, through-tubing hanger system installed at the lower master valve (LMV) of its kind. This unique repair method uses a coiled tubing-conveyed swellable packer, a hanging mechanism at the LMV, and through-tubing swellable packer elastomers at both top and bottom of the assembly. A description of the single-trip technology is presented, with a brief description of its engineering development and the installation procedure. The candidate selection process and installation procedure are discussed; information about the economics is provided to demonstrate that this type of repair was economically superior to a rig workover. This paper presents the successful field application of a new well intervention technique to repair multiple shallow leaks in production tubing in S field, an offshore field located in Malaysia. Effective teamwork among various parties through all phases, including engineering design, LMV fabrication, through-tubing hanger customization, swellability laboratory testing, and the execution phase, were key elements to the success of this pioneer project. By demonstrating the operational possibility and a low-cost alternative to an expensive rig workover, this unique technique has created more new opportunities to restore the integrity of shallow leaks and can be run in wells with parted tubing in similar brownfield wells.
One of the challenges for brownfield operators managing over 20 year-old wells is the uncertainties of well integrity impacting the effort to access the remaining oil in place. EnQuest known as the operator of choice for maturing and underdeveloped hydrocarbon assets, sees this challenge as an opportunity to grow by exploring the best approach in the market to meet our objective. This paper presents one of EnQuest’s wells that may have a crossflow interzone between water to the oil bearing reservoir. Well ‘Z’ is a single oil producer completed in 1997 but shut in since 2001 due to a high water cut. This well produces from three zones namely A, B and C. Zone A is expected to produce oil but well test results showed a 100% water cut. Offset well suggest the water bearing is contributed by Zone B. The High-fidelity Distributed Acoustic and Temperature Survey (‘DAS’ and ‘DTS’) was evaluated to determine the possibility of crossflow behind the casing. The unique data solution using a combination of DAS and DTS technology based on engineered fibers, allowed for continuous and wide coverage logging of the well. Real-time data acquisition and displays of the entire wellbore led to a better understanding of the well’s dynamic and transient behavior and ultimately to a rapid and complete well integrity assessment. The abnormal fluid movement detection during shut-in was achieved through the highly sensitive sensor array, within the low acoustic frequency range, something conventional logging techniques would have missed. This service was deployed via a normal slickline unit with additional hardware required for real-time monitoring. Twelve hours of data were recorded, under a baseline shut in condition, followed by a flowing condition and then a hard shut-in. Real-time data processing and interpretation were performed onsite during logging operations by a service provider’s experts. An unexpected result was discovered with the water contribution identified as coming from Zone B through a leaking Sliding Sleeve Door (‘SSD’) which was in a closed position, as cyclic liquid movements inside the tubing originating from Zone B and past Zone A were detected and tracked from a low frequency DAS signal. Moreover, clear acoustic activity was measured at two gas lift orifice valves during the shut-in condition; these were likely allowing the passage of the reservoir fluids into the annulus. Finally, during flowing condition, all production clearly showed that crossflow originated from Zone B to A, by both DTS and DAS measurements. This explained the water production observed at the surface. Results obtained were well received and immediate was planned action to isolate the water source resulting in 0% water produced afterwards establish movement via slow strain DAS and noise logging analysis.
Dulang is one of the aging fields in Peninsular Malaysia that started its first oil production in March 1991. After 10 years in operations, the field started to show a rapid declination in production. Since then, a lot of Production Enhancement & Idle Well reactivation activities have been conducted despite the presence of high CO2 that post challenges for well intervention jobs. The number of activities keeps increasing over the years in hope to boost production and with a time constraint, each job is planned with a very limited window for execution. The engineers constantly have to find more efficient ways to ensure all these planned activities are completed on time despite these challenges. One of the Idle Well reactivation that was successfully conducted at Dulang is at Well A-40ST1. The well was 100% watered out from the lowest zone J-36 and uncertain production from the upper zone J-32. Based on the survey data, there is a potential reserve at a new zone that has been identified in above the current zones, namely upper J-32. Amongst the challenges in this well is the interval of each zone is so close and it is located at the highest slope of the well at 74°. Conventional method to execute such job normally takes 2 months which involved Electric-line and Coiled Tubing packages alternately. The other option is to use electric-coil tubing which can save operation time but with higher cost. Ultimately, field operator has taken fresh new application that can provide more benefits in term of time, cost and deckspace layout. This paper will describe the details of the complexity of the operation which involves milling, water shut-off, cementing, and perforation at remote platform location. Prior to that, detail evaluation is performed to weigh the pros and cons of conventional method and real-time fiber optic application.
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