Abstract Operator's Wells Abandonment & Decommissioning campaign consists of 15 Deepwater subsea wells in Field "C" offshore West Africa. Discovered in 2001, the field is located approximately 80 km west of coastline and about 90 km from Nouakchott, capital of Mauritania. Field "C" is a deepwater field in water depth ranging from 730m to 830m. The field was developed using subsea wells, Hinged Over Subsea Templates (HOST), manifolds, flexible flowlines, umbilicals, and risers tied back to a permanently moored FPSO. In total, the field consists of nine (9) oil producer wells and five (5) water injection wells. During the development stage, one (1) gas injection well was drilled and completed at adjacent Field "B" about 17 km Northeast of Field "C". The water depth at this gas injection well location is approximately 280m. Field "C" reached maturity in 2016. Due to high operating costs, declining production coupled with declining oil prices, the decision was made to cease production, plug and abandon (P&A) and decommission the field. Two phases strategy was engaged by the Operator in order to complete the decommissioning and abandonment of Field "C". In Phase 1, which was executed back in the year of 2017-2018, all the 15 deep water subsea wells were temporarily suspended with two (2) barriers in place. The Floating, Production, Storage and Offloading (FPSO) unit was decommissioned and disconnected. In line with the strategy of dividing the project into two phases, the information on well integrity and conditions acquired during the Phase 1 Temporary Wells Suspension (TWS) was used by the Operator in planning for Phase 2 – Wells Plug and Abandonment (P&A). The operator made full use of temporary well suspension period between Phase 1 and Phase 2 for engineering, procurement, and operations preparation. The same drillship was utilized for the project in both phases. Multiple optimizations and modifications were done on the drillship based on lessons learned in Phase 1 and to cater for the subsea Xmas Tree and subsea structures retrieval in Phase 2. Due to the nature of the remote location and no existing oil & gas operations support base, all equipment required in this project was sent to Mauritania early. Equipment inspection and acceptance were carried out in Mauritania as part of the strategy in ensuring the availability of good quality equipment for offshore operations. The operations on Wells Plug & Abandonment commenced in December 2019. In March 2020, upon declaration of the COVID-19 pandemic, operator was faced with difficulty of continuing operation as the Host Country activated border lockdown. The operator managed to continue operations for remaining well and demobilized drillship and personnel safely. Operator has successfully retrieved three (3) subsea Xmas Trees, P&A three (3) wells and intervened six (6) other wells for tubing cutting before operations was suspended due to COVID-19 pandemic. Operator used the suspension phase to devise a methodology to resume operation in the prevailing COVID-19 pandemic situation. The challenges faced during the COVID-19 pandemic as well as the steps taken for resumption are highlighted in this paper. It is expected that this paper will serve as guidance in highlighting challenges and efforts taken to resume operation in the event of unforeseen suspension due to any reasons. It is also hoped that the details shared in this paper can assist other Operators in better operation planning for remote locations.

Abstract The economic end of the life-cycle of a well is dynamic and it varies with the oil & gas market conditions and advances in extraction technologies. If production declines or the need for a workover arises, plugging and abandonment operations are followed. In case the wellsite has encountered accidental releases, systematic abandonment and remediation becomes even more crucial to avoid further environmental damage and capital investment. This paper analyzes the Baghjan oilfield blowout of the Assam-Arakan basin and provides abandonment practices for gas wells. The mobile workover rig was stationed at the Baghjan Well-5 with the aim to plug the lower producing zone at 3871 m and complete the well in the upper Lakadong+Therria sand at a depth of 3739 m. Baghjan Gas Well No.5 blew during the temporary abandonment which was planned to mitigate the leakage in the wellhead. Improper depth for the placement of cement plug, failure to check the plug integrity, and shortcomings in the regular inspection of annular casing pressure led to the well control situation at the Baghjan gas well. While pulling out the tubing conveyed perforation gun after perforating the Lakadong+Therria I+II sand, Shut-In Tubing Pressure of 4400 psi and 3900 psi Shut-In Casing Pressure was observed which indicated a leak in the Tubing Seal Assembly. The well was killed with a 9.76 lbm/gal sodium formate brine and in the middle of pulling the tubing, leakage in the W.F. Spool was identified which changed the priority of the operations. Therefore, a temporary abandonment operation was planned to mitigate the leakage problem in the primary and secondary seals, during which the well started flowing gas profusely after nipple-down of the blowout preventer. The shortcomings of the abandonment process can be conquered by the selection of an appropriate isolation material such as resin-based sealants or bismuth and thermite, which shall act as a primary barrier and provide enhanced zonal isolation. The isolation material should mitigate micro-fractures, minimize treatment volume and fluid loss, provide ample pumping time, and not degrade in the presence of wellbore fluids. The study discusses resin-based sealants, cement slurry designs, advances in conventional, unconventional, and rigless abandonment techniques, and suggests the most efficient method for the temporary and permanent abandonment operations to avoid further such incidents in the oil and gas industry.

Abstract The project was for part production enhancement project which to cater for brownfield & greenfield project. To cater to the production (oil) increment for the brownfield project, the existing flare tips and separation system need to be upgraded with higher capacity. The inclusive project was upgrading existing. Part of the scope was decommissioning the existing flare tip and associated system, e.g., ignition panel and ignition pipe. The project will decommission the current flare tips and replaced it with new higher capacity flare tips with Low Pressure (LP) & High Pressure (HP) connection. The existing flare panel was a single-type ignition system. The existing flare tip had LP & HP tip with 8″ inch size; the weight for both tip was estimated at 300 kg. The concept selection was discussed on the suitable method to lifting down the decommissioning flare tip at the offshore platform. There were 2 suitable techniques selected at the initial of the concept selection. One was lifting down the decommissioning flare tip directly from flare boom to vessel. Another method was manual rigging of the flare tips from the flare boom to the lower deck. After several discussions and workshops, it was decided to proceed with manual rigging of the decommissioning flare tip to the safe deck area. The removal of the decommissioning flare tip was performed during turnaround. The total days for the overall activity of the decommissioning & installation of the new flare tip was 3 days, 2 days ahead from planned duration 5 days.

Abstract Well abandonment and the associated abandonment expenditure (ABEX) are necessary stages in the post cessation of production (Post COP) phase of the asset lifecycles. There are significant risk factors present, which vary in the frequency and severity based on a multitude of factors pertaining to environment, age, well construction techniques and stratigraphy, to name a few. In the case of well isolation and abandonment operations there are opportunities to innovate through factory project execution techniques and commercial approaches, which are enhanced where standardization and commonality of well architecture is present. These techniques focus on reducing risk factors and creating value where conventional thought suggests there is marginal cashflow benefit, in asset retirement obligation expenditure. Through a reduction in the total cost of ownership (TCO), project financial performance below the estimated provisions, can unlock cashflow from relief adjustments on long term liabilities. The Engineering, Procurement, Services management (EPSm) lump sum partial turnkey contracting approach was developed to assist operators in unlocking cashflow in ABEX provisions, through risk reduction via front end well engineering and integration of service provision, allied to fixed price lump sum contracting to control project cost creep due to unforeseen events. A pilot project was undertaken in South East Asia, delivering 64 permanently abandoned wellbores in 38 consecutive days, representing over 8,300-man hours and over 3,500 operating hours. The EPSm contracting approach delivered lump sum partial turnkey well abandonment services in a high-volume factory well abandonment retirement environment. Operations were executed through a dedicated jack-up drilling rig trimmed to an asset retirement specification to reduce OPEX and increase efficiency. The operational project framework implemented pre-abandonment offline operations prior to rig arrival, then simultaneous operations (SIMOPs) concerning 2 primary worksites: the wellhead platform weather deck and the jack-up rig cantilever. Standalone concurrent Phase I slickline operations comprising of two units, were performed offline on the wellhead platform with pressure control equipment to execute primary reservoir isolation operations. Phase II & III operations were executed above, on the jack-up rig cantilever through the drilling riser and pressure control equipment, executing the overburden and surface isolation operations, minimizing online operating time of the jack-up rig. Key Learnings from the pilot project are presented, along with pilot project key performance indicators. The project learning curve, and human performance factors provide insights to areas where there are synergies and opportunities to further reduce risk and the total cost of ownership through an Engineering, Procurement, Services management (EPSm) contracting approach.

Abstract This paper elucidates the importance of flow assurance transient multiphase modelling to ensure uninterrupted late life productions. This is discussed in details through the case study of shut-in and restart scenarios of a subsea gas well (namely Well A) located in South China Sea region. There were two wells (Well A and Well B) producing steadily prior to asset shut-in, as a requirement for subsea pipeline maintenance works. However, it was found that Well A failed to restart while Well B successfully resumed production after the pipeline maintenance works. Flow assurance team is called in order to understand the root cause of the failed re-start of Well A to avoid similar failure for Well B and other wells in this region. Through failure analysis of Well A, key root cause is identified and associated operating strategy is proposed for use for Well B, which is producing through the same subsea infrastructure. Transient multiphase flow assurance model including subsea Well A, subsea Well B, associated spools, subsea pipeline and subsea riser is developed and fully benchmarked against field data to ensure realistic thermohydraulics representations of the actual asset. Simulation result shows failed restart of Well A and successful restart of Well B, which fully matched with field observations. Further analysis reveals that liquid column accumulated within the wellbore of Well A associates with extra hydrostatic head which caused failed well restart. Through a series of sensitivity analysis, the possibility of successful Well A restart is investigated by manipulating topsides back pressure settings and production flowrates prior to shut-in. These serve as a methodology to systematically analyze such transient scenario and to provide basis for field operating strategy. The analysis and strategy proposed through detailed modelling and simulation serves as valuable guidance for Well B, should shut-in and restart operation is required. This study shows the importance of modelling prior to late life field operations, in order to avoid similar failed well restart, which causes significant production and financial impacts.

Abstract The oil and gas industries are setting a new achievement every day by fulfilling the energy security of almost all the nations. With the continuous rise in the demand of a hydrocarbon, industries are facing many new challenges while fulfilling it. One of the major concerns is the safety of an environment and safety of working professionals that HSE Department is continuously focused in. The industry has been in continuous upgradation since its inception to counter all the challenges. Inverted Umbrella Technique (IUT) is the recent innovation in the industry and this could be further more conceptualized by adding its role into the energy industries. This could turn out as a major breakthrough in the oil and gas domain from HSE perspective. The paper here aimed for providing efficient solution by setting up the system that could help us to drawdown the rising concern in the safety of the environment. Inverted Umbrella Technique (IUT) could roll down the new horizons for the offshore productions system in oil and gas industries. The concept is focused on the minimal loss of methane during exploitation of gas hydrates as well as focused on the prevention of oil spill and reducing the damage that blowout of oil or gas well can make to the environment while making sure that industries do not suffer any kind of major capital loss and making it safe for industries to not face many health, safety, and environment (HSE) norms that are decided by the government and most important is, it will help us to create a safe environment for aquatic species living around the offshore platform and nearby.

Abstract End-of-life production or injection wells may be converted into wellbore heat exchangers for geothermal energy extraction. Whether this conversion is technically and economically feasible depends on several factors such as geothermal potential of the formation, well depth, and working fluid circulation parameters. Here we present a case study where we analyze these parameters and determine their optimum operational brackets. We focus on repurposing active wells that are located in regions with high geothermal potential in the state of Mississippi. Geothermal gradient map of the state of Mississippi was used to select potential candidate wells. Well logs of these candidate wells were used to find formation temperature and other properties such as well diameter and depth. Next, we conducted heat transfer calculations to estimate the temperature rise of various working fluids as a result of circulating inside these wellbores. We ran sensitivity analyses to determine the effect of circulation rate, tubing insulation, and time. Finally, we estimated the power production potential of each well. Our results indicate that geothermal energy production through repurposed end-of-life wells may be viable depending on well depth and geothermal potential of the region. With insulated tubing, the thermal energy delivered by a number of candidate wells is sufficient for a small-scale binary power plant with organic Rankine cycle.

Abstract The current study improved the predictive capability of the biological reefing viability index (BRVI) calibrated using local data. The prediction capability of the BRVI improved from 61% to 76% accuracy out of the 181 locations where the underwater videos available for verification. The BRVI includes corals larvae density, age of larvae at site, sea current, sea temperature, chlorophyll-a, water depth and sediment type to predict biological productivity of an area. Among the parameters, corals larvae density and age of the larvae are the most critical parameters that influent establishment of new biological ecosystem. The BRVI uses settlement of corals larvae as the precursors for the establishment of new habitats in the offshore environment because scleractinian corals is known to be able to form backbone of a new habitat in the environment. In this approach, the BRVI focuses on habitat creation instead of just being a fish aggregating device (FAD) when an artificial reef is deployed in an area. The BRVI can be used as a rapid screening tool to identified potential area for deployment of artificial reefs. The BRVI could reduce the chances of artificial reefs deployment that failed to address its objectives and intended outcomes.

Abstract Uzma was awarded with 1st integrated well abandonment under Provision of Well Abandonment Integrated Services (WAISE) in 2018. Total of 22 wells were plug & abandonment with average 10 to 20 days per well were spent to complete the work. The scope of works is inclusive providing Project Management Team, Hydraulic Workover Unit, Accommodation Work Boat, Supply Vessels, and P&A services. This paper will highlight the practical experiences and capture the lessons learned obtained executing 1 integrated well abandonment campaign in Field A Offshore Malaysia. This paper presents the overall project lesson learnt for 1st integrated well abandonment embarked from early stage of project planning, preparation, acceptance, technical, operation & project close out. The lesson learnt will be beneficial for all Operator & Contractor Company involving with integrated well abandonment. This paper also presents capability of hydraulic workover unit and recommendation for future of low-cost well's plug and abandonment. Plug and abandonment operations with conventional hydraulic workover units have an enormous impact on low-cost plug and abandonment campaign in Malaysia compared with conventional drilling rigs. In essence, the lessons learned and insights gained throughout abandonment campaigns will keep accumulating with time to feed into the knowledge and experience vault. With proper project lesson learnt, many success cases and best practices can be emulated both from technical and commercial point of view. This lesson learnt will be beneficial for all Operator & Contractor Company involving with integrated well abandonment.

Abstract After having been developed in the early 2000's and put on production since then, the deep water (700 M water depth) Field Alpha is now at the end of field life and in the plug and abandonment (P&A) process. Although this field-life phase does not make any money for an E&P operating company, it can be a liability and put the company's reputation at stake, if not done correctly. Therefore, like any other field-life phases, it requires a professional and multidisciplinary integrated approach to deliver it while reducing the company's exposure. P&A campaign involves many stake holders: the local authorities, its technical and operational representative / auditor, the operator's well engineering community, the subsurface team, e.g., petrophysics team, and the operator's management. Understanding all their expectations and KPIs is primordial to prepare and successfully deliver such operations. The P&A process relies on the placement of adequate "barriers" inside the well to guarantee blockade of any potential reservoir fluid communication either within separate reservoirs (to avoid any reservoir re-pressurization through cross flow) or with seabed / surface which could impact the environment. As part of the well barrier, annuli cement quality and efficiency must be checked by cement bond evaluation. The petrophysics team has the responsibility to both define, in collaboration with others team members, the cement quality criteria and then to evaluate the cement quality in timely and efficient manner. In this campaign, which is expected to run for more than a year, with several petrophysicists involved both in the preparation phase and in the operation phase, e.g., execution and results validation, consistency in the process is of utmost importance. This paper presents the workflow put in place by PETRONAS Carigali during the Field Alpha P&A campaign. It emphasizes on the petrophysicist role and responsibilities from the preparation phase, during the operations, and through the results validation. The learnings and experiences acquired during the Deep-Water Field Alpha P&A campaign are now going to be transpose to domestic and international assets by means of corporate guidelines and workflows.