When operators are faced with issues involving casing leaks, a typical course of action is to pull the tubing and make efforts to identify and locate the source of the leak by logging or other mechanical means. If the leak source can be successfully located, a mechanical method is generally employed to patch the leaking casing. This methodology is time consuming and expensive. Locating casing leaks with the tubing in place using conventional logging techniques has historically been difficult. Where some tools, such as temperature tools, may provide an indication of an anomaly in annuli, the data may be subjective or the leak may be too small to measure. When active, a leak will produce a spectrum of sonic frequencies that may be either audible, ultrasonic or both. Ultrasonic energy will pass through steel but travels relatively short distances. A tool developed around these principles has been successful in accurately locating casing leaks behind tubing. Pressure-activated sealants have been used for a number of years to cure a wide variety of leaks in casing, tubing, control lines, and well heads as well as micro-annulus leaks in cement. For the purpose of repairing a casing leak behind tubing, the liquid sealant may be pumped into the annulus and displaced to the leak site. The liquid sealant will not polymerize until it is exposed to the differential pressure through the leak site. Knowing the leak rate, pressure and precise location of the leak aids in the selection of the sealant formulation and deployment method. This helps to reduce overall repair cost as well as increase the probability of a successful repair. This paper will describe the ultrasonic method of leak detection and the method of curing leaks with pressure activated sealant with tubing in place. Case histories will be presented where these methods were employed to repair casing leaks without removing the tubing. Introduction Perhaps the most challenging well integrity issue with which operators deal with today are casing leaks. Not only are the methods to repair these types of leaks without pulling the tubing limited, but the detection of these leaks using conventional logging methods with the production tubing in place is practically impossible. A common diagnostic methodology is to rely on some fairly subjective logging data and pressure responses to determine where a pressure barrier is leaking. Following this, cement is pumped down the annulus or through punched tubing in an attempt to seal off the leak. This process, along with other hardening sealant methods, can be problematic. Additionally, using this method will also make other operations or future workovers difficult or impractical. Pressure activated sealants have been used on numerous occasions to repair casing leaks with the tubing in place. A major advantage in utilizing this technology is that the sealant will only solidify where the leak is active. In addition, the material is easily removed by mechanical means and will not add difficulty to future workover operations if required. As is true with other remediation methods, a complete understanding of the leak source is critical when planning a pressure activated sealant operation. This is especially true when dealing with leaks behind the tubing. Optimal sealant formulations may be selected along with deployment methods for maximum affect. While rate and differential can be determined by pressure and well bore data, a leak behind casing is more complex. Detection of casing leaks is difficult using conventional logging techniques. These leaks will produce no reading on spinners (for obvious reasons) and may not produce temperature changes that are of a magnitude to confirm a leak point. This is true even with fairly large leaks (>1gpm). Conventional noise logs can detect fluid or gas movement, but must be used in a stationary mode and distant noise sources may confuse interpretation. Tracer logs may be used but can also produce imprecise results. The ultrasonic leak detection method has been proven to be useful in detecting leaks behind casing with a high degree of accuracy. This suggests that it would be a useful tool in evaluating wells for repair using a pressure activated sealant method where accurate spotting of the treatment is critical.

Pressure-activated sealants are used to repair small surface and downhole leaks and have been successful remediating many instances of small pressure anomallies in mature Alaska fields since 1999. The sealants are unique in that the pressure drop through the leak site causes the sealant to polymerize into a flexible solid. Only at this point of differential pressure will the sealant polymerization process occur. As the reaction proceeds, polymerized sealant forms at the edges of the leak site and simultaneously links together to form a flexible bond across the leak site. The remainder of the sealant in the system remains liquid. This paper discusses the history, implementation, and success rate of pressure activated sealants in Alaska including successful deployment methods used to repair small production casing leaks in naturally flowing wells and injectors. The advantage sealant repair has over a conventional RWO for casing repair is that there is no need to pull tubing, resulting in the well being returned to service faster. Typical sealant procedure costs are less than 5% of the costs for production casing repair with a rig workover (RWO). Pressure activated sealants are particularly attractive in areas where RWO cost is high, such as subsea, offshore, remote, or arctic locations. Results will be presented from a study of jobs performed in Alaska from 2005 to 2012. Since 2005, Alaska has performed 56 of BP’s 102 worldwide treatments with a 77% success rate to repair wellhead packoffs, casing, bradenheads, tubing, cement microannuli (Table 1).

fax 01-972-952-9435. AbstractSince the inception of deep water operations, drilling riser seal component failures have been a persistent problem worldwide. Traditionally these failures have required that the drilling riser be pulled, the affected seals replaced and then the drilling riser re-installed; resulting in substantial rig down time and expense to the operators and service companies. Seal-Tite International has developed a unique array of pressure activated sealants able to withstand the high pressure and extreme temperature conditions associated with subsea drilling and production operations. The sealant is polymerized by the differential pressure created through the leak sight. The polymerization process only occurs in the sealant that passes through the leak sight; all other sealant remains liquid and can be circulated out of the well with no damage to any of the well components. Subsequent to extensive testing, pressure activated sealant technology was utilized to repair a leaking joint in a drilling riser choke line at approximately 4200 ft water depth in the Gulf of Mexico. The leak was repaired and the client was able to continue and complete drilling operations with no downtime. The riser was tested to operating pressure every three days for the duration of the drilling operation with no leaks observed.

Pressure activated sealant was used to repair casing leaks in two Prudhoe Bay, Alaska oil wells without the use of a rig workover. The significance of the treatments, development of job screening criteria, and job planning and execution are reviewed.Production casing leaks are a frequent problem in mature oil fields, particularly where there is corrosion. Wells with casing leaks usually do not meet well operating criteria so they must be shut-in, causing a loss in valuable production. Casing leaks normally require a rig workover to repair since the tubing often has to be removed. Rig workovers are very expensive in offshore locations, remote areas, and harsh climates. Special pressure activated sealants, diagnostic tools, and treatment techniques have been developed to find and repair casing leaks without removing the tubing.Case studies of three Prudhoe Bay production wells describe how pressure activated sealant successfully repaired the small casing leaks in two wells without removing the tubing. The third well was not treated because it did not meet the screening criteria. One case study was unusual because the sealant fixed four deep casing leaks with one treatment.The case studies show how refinements in diagnostic techniques, candidate screening, and treatment planning and execution have resulted in the successful application of pressure activated sealant to repairing casing leaks in producing wells and in one case repaired four leaks with one treatment. Using pressure activated sealant to repair casing leaks can result in significant cost savings and return wells to production sooner. The treatment can be particularly useful in mature fields with corrosion problems and in offshore, remote, and arctic fields where rig workovers are expensive and rig availability is limited.

BP policy specifies requirements for well barrier management throughout the life cycle of a well. Well barriers are specifically required to isolate energy sources within the earth from each other, the surface environment, and people. Annulus pressure management is fundamental to maintaining healthy well barriers and active monitoring assures the barriers are in place. In subsea wells, the only annulus that can be monitored in real time is between the tubing and production casing (aka A-annulus). When an anomaly is detected in the A-annulus, then a diagnostics and intervention program must be implemented to repair the suspected well integrity issue. In deepwater environments, repairing a well integrity issue with a rig can be costly and the traditional tools for well diagnostics and repair, such as wireline and coil tubing, are complex to deploy into subsea completions. Alternatives such as pressure-activated sealants have a proven track record repairing well integrity issues in dry tree wells. This technology is now being deployed to repair well integrity issues in subsea wells. This paper presents two case studies where pressure-activated sealants were used to successfully repair tubing by A-annulus (T × A) communication in a subsea wells. BP had utilized this technology with great success in its Alaska fields (SPE Papers10895 and 120978) and saw an opportunity to extend those learnings to subsea wells. These operations utilized innovative delivery techniques to enable sealant injection, placement, and activation downhole. Rigorous testing, simulation, and planning prior to starting the job increased confidence in the operational technique and reduced safety risks to the environment and the wells. Both efforts resulted in a successful repair of the well integrity issue. There were several benefits for using a pressure-activated sealant for these two interventions. The less complex non-rig interventions presented fewer safety and environmental risks and were completed with no HSE incidents. The non-rig repairs were completed for a small fraction of the cost of a conventional rig repair and rig time was kept available for drilling and completing new wells. Given its effectiveness and these benefits, the application of this technology may be especially useful for subsea wells with marginal remaining reserves where the relatively lower cost may help to optimize productive life and ultimate recovery. The integrity of a sealant repair can be monitored during the life of the well just like a conventional rig repair and a sealant repair does not preclude the ability to perform a conventional rig repair in the future.