Perforate, Wash & Cement (PWC) is a method developed over the past few years to remediate cement behind casings, which has been widely applied to the Plugging and Abandoning (P&A) of wells. This technique can also be used to set permanent lateral barriers for slot recovery operations. However, the technique has been mostly applied to smaller casing sizes ranging from 7 – 10 ¾". In the growing slot recovery market across mature fields, the demand is increasing for a reliable and efficient method for achieving shallower lateral barriers, thus facilitating side tracks from bigger casing sizes such as 13 3/8" −13 5/8". For the technology to be successful there are several components that need to be tailored for the specific casing size and borehole diameter. The optimal Tubing Conveyed Perforating (TCP) system needs to be in place to maximize efficiency for the washing and subsequent cementing operation. In order to reduce risk during the washing and cementing operation, it is critical that a suitable area of the wellbore is chosen for the remediation. This area is chosen based on the operational window for the Cup-type PWC technology where annular condition plays an important role. This paper describes the extensive work that has been performed to plan, execute and verify the placement of a lateral barrier across the 13 5/8" casing on the Valhall G-22 Well in the Norwegian continental shelf as part of the slot recovery program for the field. The testing of the TCP Gun system resulted in an optimum Exit Hole Diameter (EHD) and geometry tailored to this specific application. An ultrasonic log was run prior to the PWC operation to determine the status of the annulus to be remediated. The optimal parameters for efficient cleaning of the annular space were simulated, and successfully achieved within the narrow Equivalent Circulating Density(ECD) window for the weak permeable zone below the perforated interval. The cement job was performed flawlessly with no losses, utilizing the Pump and Pull method with the Cup-type PWC system. Moreover, the actual job parameters matched very well with the simulations. The internal cement was drilled out and the annular cement was logged using an ultrasonic logging tool. The interpretation of the log showed perfect circumferential cement coverage across the entire remediated interval. With proper planning and optimized design and execution parameters, successful annular remediation can be achieved in large casing geometries using the PWC technique. This allows for more efficient and cost-effective slot recovery and P&A operations.
Objectives/Scope Creeping shale formations has over the last decade actively been used as permanent barriers for plugging & abandonment of wells across the North Sea. This paper gives an insight in how an innovative one trip system has been used to help qualify the Lower Hordaland formation as a barrier for plugging & abandonment of wells on the Gyda Field on the Norwegian Continental Shelf. The Gyda Field is in the North Sea 280 km southwest of Stavanger in 66 meters of water. The Gyda reservoir is Upper Jurassic shallow marine sandstone at a depth of approx. 4000 meter. The evaluation and integration of data from wells drilled on the Gyda Field has concluded that the following formation groups are potential inflow zones that needs to be isolated in the permanent plugging of the wells Gyda reservoir, Farsund, lower Åsgard, and cretaceous/tertiary Inflow Group Forties/Lista. The permanent plugging & abandonment of the 32 wells on the Gyda Field started in Q-1 2019, and needed an effective approach to qualifying creeping shale as a permanent barrier. Methods, Procedures, Process This approach was based on logging behind the 9 5/8" casing using an ultrasonic logging tool to locate the Lower Hordaland shale creep. The shale was successfully identified on the first wells, and the next phase was to prove, and verify that the creeping shales sealing capability. A one trip tool system consisting of a disconnect tool, by directional cup tool and TCP perforating guns was used to perforated the casing, straddle the perforations and test the hydraulic sealing capability of the Lower Hordaland Shale. Results, Observations, Conclusions The result was 3 successful formation tests qualifying the Lower Hordaland shale as a permanent barrier. This innovative approach has improved the overall efficiency of the permanent plugging and abandonment of the wells on the Gyda Field significantly. This paper describes the extensive work process that has been performed to plan, execute and verify the integrity of the lower Hordaland formation as a permanent barrier for plugging & abandonment.
The Perforate, Wash and Cement technique has been widely applied to remediation of annular cement in recent years. Since 2012, extensive experience in the different technologies currently available on the market has been obtained across ten fields in the Danish and UK sectors of the North Sea and the data obtained has been used to attempt to better understand the effective operational window for the technique, and also further enhance reliability and tool robustness. The run data obtained from several wells has been calibrated against cement bond logging (CBL) responses so that the degree of annular bonding as inferred from the logs may be expressed in terms of the degree to which hydraulic communication or circulation is permitted via perforations and along the annulus. This in turn helps clearer decision criteria to be defined prior to execution that aids in the selection of the most appropriate method for remediating the cement, since Perforate, Wash and Cement may not be the most suitable technique in every case. Given the criticality of cement remediation to the long-term success of zonal isolation, it is important to demonstrate that effective hydraulic communication with the annulus has been established during the washing phase to ensure that the zonal isolation medium (cement) can be effectively placed and the hydraulic seal re-established, resulting in successful remediation. Post-execution verification of the effectiveness of remediation is typically performed via Cement Bond Logging. However, this may not always be a definitive verification step since Cement Bond Logging interpretation does have its limitations (both physical and interpretative), and hence annuli have occasionally been known to develop Sustained Casing Pressure even shortly after positive log interpretations following well-executed cementations. This paper therefore further demonstrates how Sustained Casing Pressure monitoring can be used as a further criterion to verify the integrity of the remediated annulus and hence conclusively demonstrate whether the washing and later cementing of the annulus has been effectively performed. This in turn is used as definitive confirmation that zonal isolation has been performed within the operating limits of the tool and hence qualify Perforate, Wash and Cement as a robust and viable remedial method.
Objectives/Scope Perforate, Wash & Cement (PWC) is a method developed over the past decade to help increase efficiency in plugging & abandonment of wells. The method has helped operators world-wide to save time and cost in plugging and abandonment operations by cutting down time for setting full lateral barriers. This technique can also be used to set permanent lateral barriers for slot recovery operations, and perform well repairs on workovers where there is sustained casing pressure. The technology is used to set lateral barriers to cure the sustained casing pressure, and enable the operator to put the wells back into production. The integrity of the well is restored and significant value is generated. However the technology has previously been limited to setting one barrier at the time. The unique challenge for this well on the Platform Alpha, offshore Malaysia was that two zones had to be isolated in one run. The distance between the two zones was almost 100 meters. A significant challenge, with a significant upside. The execution was using Hydraulic Workover Unit (HWU) and overall 14 plugs completed (for 14 wells). Methods, Procedures, Process The method has several critical success factors that need to be tailored to be able to produce a high quality result, especially with this unique challenge of plugging and abandoning two different zones in the same run. Optimization of the Tubing Conveyed Perforation (TCP) System to be able to balance hole size, geometry and density in order to create the ideal communication path into the external annulus was paramount to the success of the job. The TCP needed to also take into consideration casing size, weight and metallurgy to ensure that downhole conditions are simulated as accurate as possible, increasing the chance of successfully meeting the perforation criteria that has been optimized. Washing parameters needed to be optimized to be able to create high annular velocity for efficient hole cleaning and debris removal. This optimization takes into consideration the fluids density and rheology, ensuring that the mud system has the correct properties to suspend the debris for removal at surface. The compatibility and stability of the fluids and mud condition prior to cementing operation is also critical. The cementing operation on this well was a unique, tailor-fit engineering project, with the end goal and intention of being able to isolate two zones approximately 100 meters apart at the same time. The cement & spacer properties were important here due to possible gas, and high chance of losses into the formation after perforating, and during washing. The volumes, operational parameters and execution were critical to get the two zones efficiently plugged and abandoned in one run. This paper describes the extensive work that has been performed to plan and execute the successful plugging and abandonment of two independent zones using the Perforate, Wash and Cement technology; and in the process, saving several days of rig time, gaining significant value for the customer and setting a new benchmark for efficient plug and abandonment operations for the global market. Results, Observations, Conclusions The system testing of the TCP Gun system resulted in an optimum Exit Hole Diameter (EHD) and exit hole geometry tailored for this specific wellbore size, weight and metallurgy. The washing was efficiently carried out with high amounts of debris over the shaker system and a declining standpipe pressure was observed indicating a very successful washing of the perforations. The cement operation was flawlessly executed according to the planned operational parameters with no losses or operational challenges. The two zones were effectively isolated in 2.5 days. This fantastic result not only significantly lifted the efficiency of the Platform Alpha Plug & Abandonment operations, but also set a new benchmark for the Perforate Wash and Cement Technology globally. By isolating two independent zones in one run using the Perforate Wash and Cement Method, the technology has proven that within an already established methodology, there is still capacity for further progression and evolution of the technology. A one team effort between operator and service companies made this possible and in the process, established a solid blueprint for future efficient, safe and reliable operations.
Objectives/Scope The Perforate, Wash and Cement technique has been widely implemented in the remediation of annular cement in recent years, with the application gaining increasing confidence within the Well Integrity, Plugging and Abandonment sectors. With the increase in confidence in the technique to successfully remediate annulus cement comes the evolution of the process; pushing of limitations to meet new and previously challenging plugging and abandonment projects with confidence. The first attempted and successful ‘Closed System’ type Perforate, Wash and Cement of Dual Annuli is discussed and evaluated in this paper as an effective mean for environmental plugging and abandonment. Methods, Procedures, Process For the dual annuli application to be successful, the perforation of 10-3/4" and 13-3/8" casings must be effective without damaging the 18-5/8" casing to ensure efficient hydraulic communication that allows for washing out of annular debris and placement of cement across both annuli and this was verified by a full system test of the charge. Utilizing a ‘closed system’ (cup tool) perforate, wash and cement method enables constant communication between the isolated swab cups and the annulus behind the perforated casing during the process of washing. As a result of this specific methodology, the amount of annular obstruction is visibly confirmed from surface using standpipe pressure variations long before any debris is seen at surface. The reduction in standpipe pressure over subsequent washing pass is evidence that annular debris has been removed and this is visually confirmed by debris at surface. Dual annuli washing introduces additional uncertainty regarding effectiveness of washing within the second annulus and the effectiveness of this has been verified by both Computational fluid dynamics analyses (CFD), and full scaled yard test. Results, Observations, Conclusions Large volumes of debris consisting of approximately 30% formation cuttings / metal and 70% cement were observed at surface throughout the washing sequence. Cement was efficiently placed using the ‘Pump and Pull’ method. Utilizing the ‘closed system’ benefit of the cup tool, fresh cement was placed across the entire perforated interval ensuring the highest chance of a successful cement bond. Post-execution verification was performed on the cement plug and validation of successful placement of the plug was confirmed. Volumetric analysis verified the effective placement of cement into the 10-3/4", 13-3/8" and 18-5/8" annuli.
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