Mature Field Subsurface Integrity: Formulation of New Paradigm Through Hollistic Diagnostic Approach for D-Field, Malaysia

Adherence to prudent implementation of subsurface integrity assurance activities, as one of the crucial responsibilities of the field operators, has often been sidelined due to the obscure nature of potential hazards in the wellbore. With the previous Gulf of Mexico oil spill incident still fresh in mind, immense attention in safety should be given to the integrity assurance of subsurface apparatus in the field operation philosophy.

As a field matures, to sustain production over the life span of the field, there is a crucial need to focus on integrity related issues such as hazard prevention and mitigation. The necessity to properly acknowledge and execute subsurface integrity assurance activities, are crucial in order to avoid such incident from happening within the wellbore by routinely ensuring the reliability of multiple downhole safety barriers in place.

The main challenge for D-field in Malaysia is related to CO₂ corrosion as the field contains up to 70% of CO₂. During the initial field development, the well design has been made as fit for purpose to cater the production need as per the reservoir data obtained from series of appraisal wells. However, extension of production requirements contrary to the early plans, together with production driven operation philosophy, and irregular well integrity surveillance, have exacerbated the integrity issues.

Diagnostic surveys and integrity logging were conducted to evaluate the current condition of completion strings, casing and cement. Furthermore, severe internal and external corrosion was observed from the retrieved completion strings during workover.

Consequently, production deferment as a result of the aggravated integrity problems has impacted the field’s revenue from the oil sale.

A series of concrete steps were taken as part of the field redevelopment such as: utilization of 13 chrome completion strings for all producers, carbon steel lined galvanized reinforced epoxy (GRE) with rice wrap, and 25 chrome accessories for injectors, upgrading water injection facility to achieve zero ppm oxygen in injected water and executing scheduled diagnostic surveys.

These steps have successfully ensured the longevity of the wells and reduce the production deferment. This paper will further expound on the journey of integrity assessments conducted, formulation of new production philosophy by the team in order to sustain production and ensuring the health and safety aspects of D-field operation.