Since the beginning of production, well NA2 and NA3 wells had issues with wellhead integrity due to thermal growth and wellhead tilting. Seepage was observed from wellhead and based on gas chromatography test, the seepage is Synthetic Based Mud (SBM), possibly from B and C annulus (intermediate and surface casing). For well NA3, seepage was observed coming out from the connection of Casing Head and Drive Pipe Housing House (DPHH) while for Well A2, seepage was found between DPHH and conductor. The issues arise from the failed elastomer seals found at the connections of leak of each well suspected due to well growth/shrink and tilting which caused the wear and tear of the seals. The seepage of both wells was rectified by injecting the failed elastomer seals with pressure activated sealant to the P-seal and grease to the elastomer. Both wells managed to produce at the capped production rate without seepage as of today. Another main issue at Field N is the leaking of metal-to-metal seal at Xmas Tree which led to production deferment. Due to the failed barrier at surface, interim philosophy was established to operate the field and rectification plan was implemented to ensure the well is producing safely at the calculated risk. This paper describes the analysis and diagnosis, operating philosophy outline by operator which led to the well safely producing at the desired rate: (1) Standing Instruction (SI) for Well Production Ramp Up and Down based on trending of production and temperature to ensure wellhead growth and tilting will not affecting the integrity of sealant, (2) Finite Element Analysis (FEA) and Wellhead Growth Study to develop operating limit and maximum allowable growth, correlated with well production and temperature, (3) logging and survey for well leak detection and echometer survey, (4) Wellhead Seal Injection for corrective maintenance upon seepage observed, (5) manual measurement of growth and tilting and utilizing laser sensor for automation, (6) External Slip Lock Brace Support (ESBS) Installation to mitigate abnormal relative growth and (7) risk assessment for well integrity. The holistic approach in diagnostic, monitoring and operating philosophy enabled the well to be ramped up to higher production despite the threat of losing the gas production. PCSB also avoided the utilization of rig to rectify the well which resulted in cost avoidance for the company.
Utilization of chemical treatment to isolate or shut off zone is not uncommon in this industry. Cement will normally be chosen as candidate to perform the job as it is more permanent and more economically effective. With recent advanced technologies, cement particles are now designed to be in smaller particles yet still be able to develop sufficient amount of compressive strength for effective zonal isolation and hydraulic seal. Magnesium based Ultrafine Cement System was chosen as chemical candidate to be used in Sarawak West Oil Field. The primary purpose of using this cement system is to penetrate through Wire Wrapped Screen with Mesh Size of 20/40 in the completion. The utilization of Ultrafine Cement in the operation was incorporated with Calcium Carbonate and Cement G slurries. Calcium Carbonate will act as the suspension fluid while Cement G slurry will be pumped to fill up the inside volume of Wire Wrapped Screen after Ultrafine Cement being pumped to occupy the outside volume of Wire Wrapped Screen. Compatibility test between Ultrafine Cement and the two slurries had been tested in the laboratory and it was reported that there was no significant change of viscosity value when they are mixed together. Application of Ultrafine Cement in Sarawak West Oil Field indicated that all Ultrafine Cement pumped during the operation was managed to pass through the 20/40 Mesh Size. Tubing Clearance Check (TCC) by Slickline showed high held up depth (HUD) but Coiled Tubing was used to run in hole to confirm on the HUD depth. It was reported that there was no significant weight loss when Coiled Tubing passing through Slickline HUD. Coiled Tubing stopped run in hole at Top of Calcium Carbonate to avoid disturbing the suspension fluid. Based on this situation, it is also known that there was no presence of Ultrafine Cement settle on top of Calcium Carbonate at all due to its efficiency in penetrating the Wire Wrapped Screen.
Abandonment is becoming a major focus as an operator and also by regulators with a single prominent objective – to reduce its overall operation expenditure. From an operator's perspective, striking balance between abandonment expenditures asset integrity, regulator's requirement and funding for growth projects is key to ensure safe & reliable operations, sustained growth and profatibility. Sarawak Oil (SK Oil) is a brownfield operator with a huge number of legacy asset; some reaching more than 40 years of age. These assets are constantly being monitored closely for any integrity issue that might emerge due to assets operating beyond their original design life. There is also major development project currently on going which requires huge investments each year. These projects are vital to sustain the positive cash flow for SK Oil operations. Thus, there is a need to diligently balance between the expenditure for growth projects, routine operations and abandonment activities. In view of the business & operational requirements, a comprehensive abandonment execution outlook, stretching out until the end of field life was developed. The main consideration is the total free cash flow taking into account investments for development projects. The basic formula isOperating Cash Flow minus Capital expenditure where the balance will be used to fund abandonment activities. Another key consideration is the stakeholder management, agreement and consensus have to be met with these partners as well. Thus, the phasing strategy is crucial in determining the prioritization of the candidates which are due for abandonment to ensure minimal cash outflow for a non-cash generating activity. SK Oil has developed an abandonment roadmap which narrows down to the next five (5) years abandonment outlook. This roadmap has been presented to the regulator and has been agreed upon. Thus, this five (5) years abandonment outlook will be a guiding principle to plan for the actual abandonment execution. This paper is intended to highlight the approach in developing an abandonment database and key criteria that has been considered to phase out the abandonment activities. This paper is beneficial to operators that manage a huge high number of assets with mostly aging facilities, which need to be abandoned in order to reduce the operating expenditure in the long run.
A prolific gas producer in Sarawak waters was shut-in and idle due to a tubing leak resulting in a significant decline in the total hub production. The well remained idle and required immediate remedial action to meet the contractual sales target. Hence, an expandable tubing patch was proposed to isolate the leak and reactivate the well faster. This paper presents data gathered to identify leak location, tubing patch design, and installation using real-time coil tubing. Several logging surveys were performed to detect leak depth including caliper log, leak detection log (LDL), and downhole camera run; since no pressure build-up was observed post bleed-off tubing and casing, while SCSSV was in closed-state. Running caliper log could not indicate severe metal loss of 7-inch tubing, hypothesizing that the leak could be of a smaller dimension. Therefore, LDL was conducted, indicating temperature gradient and acoustic energy changes at a single depth location of 247 ft.THF, above SCSSV. Utilizing the leak depth marker from acoustic log, a downhole camera was staged to verify geometry of tubing leak. Root cause failure analysis (RCFA) was carried out for this tubing anomaly using diagnostics data to determine the possibility of UHP-17Cr-110 tubing failure. The likelihood of tubing failure is attributed to two main causes namely oxygen corrosion cracking and stress corrosion cracking. Based on RCFA outcome, Hastelloy C276, a nickel-molybdenum-chromium superalloy with the addition of tungsten was selected for the patch material, which is V0 rated, internal gas-tight qualification for temperatures up to 150 degrees Celsius and 5,000 psi. Moreover, this patch material satisfies the well conditions at approximately 20% CO2, 200 ppm H2S, 1000 mg/L salinity, and varying Hg concentrations from 800-2,000 ug/Nm3. The design of patch has been improved by adding AFLAS elastomer for the whole exterior of patch to eliminate contacts between the two metals: reducing the risk of galvanic corrosion. Real-time coiled tubing application was selected for setting the patch to ensure accurate depth-sensing control. Additionally, patch is a rig less intervention technique that will not disrupt the production from the existing wells sharing the same drilling platform. Generally, for high-rate gas wells, economic indicators seem lucrative with tubing patch application, where the payout can be achieved within a month of continuous production. The first step in ensuring the success of tubing patch is by running right diagnostics tools such as leak detection logging and downhole camera run, since multi-finger caliper analysis alone would not locate the leak depth and the leak geometry precisely. Valid design inputs are quintessential for the fitting recommendation of tubing patch design which includes accurate reservoir and fluid properties to ensure sustainability of the expandable tubing patch application.
In 2020, PCSB implemented the first permanent Plug & Abandonment (P&A) campaign for three Subsea wells in a gas field offshore Malaysia. The main objective of the campaign was to establish two (2) barriers for every movable hydrocarbon or overpressure bearing sand by placing laterally extended cement plug across impermeable formation with enough formation strength to handle the pressure of the formation to be isolated. The unique case of this operation was the challenges to execute PCSB's first subsea P&A operation in gas field Malaysia during pandemic situation. In March 2020, the Malaysian government imposed Movement Control Order (MCO) to curb the spread of the COVID-19. A semi-submersible rig was on-hired a week after government initiated the MCO, resulted in the rig preparation being badly hampered due to manpower management and material fabrication and delivery. PCSB was exposed to expensive rig daily rate that had to be managed. Four (4) main challenges were encountered during operation: safe protection for workers, expensive standby cost, manpower management and material fabrication and delivery. This paper, from the ‘project management’ point of view, describes the journey of managing rig operation during PCSB's first subsea wells P&A in Malaysia efficiently amidst the pandemic by reducing the impact of COVID-19 on project cost. With the experience of managing rig for subsea well operation, a complex operation in Malaysia, amidst pandemic, PCSB sharing on the experience is beneficial to provide context setting and benchmark on maintaining the efficiency of operation. Wells successfully met the objective of operation with no incident occurred, negotiated reduction on standby cost and managed to bring critical manpower on time during operation.
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