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.

Underground storage of CO2 in depleted gas reservoirs is a greenhouse gas reduction technique that significantly reduces CO2 released into the atmosphere. Three major depleted gas reservoirs in Central Luconia gas field, located offshore Sarawak, possess good geological characteristics needed to ensure long-term security for CO2 stored deep underground. Long-term integrity of all the wells drilled in these gas fields must be ensured in order to successfully keep the CO2 stored for decades/centuries into the future. Well integrity is often defined as the ability to contain fluids without significant leakage through the project lifecycle. In order to analyze the risk associated with all 38 drilled wells, that includes 11 plugged and abandoned (P&A) wells and 27 active wells, probabilistic risk assessment approach has been developed. This approach uses various leakage scenarios, that includes features, events, and processes (FEP). A P&A well in a depleted reservoir is a very complex system in order to assess the loss of containment as several scenarios and parameters associated to those scenarios are difficult to estimate. Based on the available data of P&A wells, a well has been selected for this study. All the barriers in the example well have been identified and properties associated with those barriers are defined in order to estimate the possible leakage pathways through the identified barriers within that well. Detailed mathematical models are provided for estimating CO2 leakage from reservoir to the surface through all possible leakage pathways. Sensitivity analysis has been carried out for critical parameters such as cement permeability, and length of cement plug, in order to assess the containment ability of that well and understand its impact on overall well integrity. Sensitivity analysis shows that permeability of the cement in the annulus, and length of cement plug in the wellbore along with pressure differential can be used as critical set of parameters to assess the risk associated with all wells in these three fields. Well integrity is defined as the ability of the composite system (cemented casings string) in the well to contain fluids without significant leakage from underground reservoir up to surface. It has been recognized as a key performance factor determining the viability of any CCS project. This is the first attempt in assessing Well Integrity risk related to CO2 storage in Central Luconia Gas Fields in Sarawak. The wells have been looked individually in order to make sure that integrity is maintained, and CO2 is contained underground for years to come.

Leveraged on the abundant weight data comprised of more than 200 offshore platforms, a smart digitalized analytical tool called i-WEIGHT, an integrated weight control tool consisting of three (3) main modules: centralized multi-discipline weight database module for all offshore platforms, seamlessly linked with Insights dashboard module in providing actionable insights, and weight predictive module supported by Machine Learning (ML) model was developed. This paper discussed the Minimum Viable Product (MVP) Phase 1 development outcome, using a close-loop weight control ecosystem for continuous update of validated weight data in Module 1, and eventually improve & enhance capability of both the EDA and Predictive module. Using a supervised machine learning algorithms, the identified target variables were observed to provide weight prediction between 16% to 38% of Mean Absolute Percentage Error (MAPE), using Extreme Gradient Boosting Regressor (XGBR) algorithm. Top 10 important features were identified for each target variable, which provide insights to the operators on critical data required for topside with identified missing equipment weight data for future i-WEIGHT improvement. Based on more than 200 integrated platform topside data gathered for this study, consolidated insights from the data enabled operators to identify the threat of current data quality and thus bringing forward a promising opportunity to enhance platform weight data management system. Having a centralized and automated platform weights data, this tool has the potential answers for United Nations’ Sustainability Development Goals, in particular Goal 9.4, where the study represents a small but crucial step to upgrade from an existing conventional process into a digitally driven operation, introducing a sustainable ecosystem in offshore structure weight management, thus fostering sustainable growth within the industry.

Carbon sequestration is the process of capturing and storage of atmospheric carbon dioxide. The objective of any carbon sequestration project is to store CO2 safely for hundreds or thousands of years with a goal of reducing global climate change. A depleted hydrocarbon reservoir is one of the potential storage sites being considered for long-term CO2 storage. The dynamic, geochemical, and geomechanics changes that occur during CO2 injection are inter-related. For example, when injected CO2 causes dissolution of reservoir rock, on one hand, porosity increases while rock strength decreases. On the other hand, reduced rock strength could cause additional compaction thus reducing porosity, whereas increase in pressure due to injection could cause dilation. Hence, it is critical to have an integrated model that captures effect of all changes on the storage capacity and integrity of the reservoir. Three major depleted gas reservoirs in Central Luconia field, located offshore Sarawak, are being evaluated for future CO2 storage. A 3-way coupled modelling approach that integrates dynamic model, geochemistry model, and geomechanics model is utilized to obtain cumulative effect of all three changes. This integrated model provides a more accurate estimate of 1) CO2 storage capacity, 2) Caprock integrity evaluation, 3) CO2 plume migration path, and 4) Volume of CO2 stored through different storage mechanisms (viz. hydrodynamic trapping, capillary trapping, solubility trapping, and mineral trapping). Apart from providing storage capacity, this model also provides inputs for evaluating integrity of caprock, fault reactivation study, MMV (Measurement, Monitoring, and Verification) planning, and estimating potential leak rates through plugged and abandoned wells. Using a 3-way coupled model, it is estimated that there is an average reduction in porosity of 5-10% (of initial porosity). This translates to an equivalent reduction in CO2 storage capacity of 5-10% compared to dynamic model. It is observed that pore collapse as a result of pressure depletion is primarily responsible for this reduction in porosity. It has also been observed that the injection can be continued till initial reservoir pressure is reached without breaching caprock integrity. CO2 plume migration path significantly affects MMV planning. Potential leak rate estimation is critical in mitigation and contingency planning.