Abstract
This paper presents overall challenges and experiences that the team were facing during offline well unloading campaign recently. On paper, offline well unloading is more favorable as an option to minimize environmental impact, economize rig days and reuse produced clean-up oil. This practice is not new. The implementation of this practice to a 40-year-old brown fields led to successfully bring adopted for two drilling campaign. The well unloading to the existing facilities requires substantial strategies to be adapted and possibilities to handle drilling fluids and solid/debris are extensively discussed within multi disciplinary team whereby risk evaluation was conducted ensure the good progress of this operation. The assurance part to handle production of solid/debris along with produced fluid to surface within 12 hours operation with the assitace from Hook-Up and Commissioning (HUC) work barge initially and resumed later by daily trip via boat to offshore site will be discussed in this paper. Almost 90% of this activity is carried out with crews mobilized with 45-minute boat trip from Bintulu to site, highly depended on weather condition. This paper also will share the major challenges that resisted the good progress of unloading for four wells such as limitation associated setting of the surface Hi Lo Pilot safety switch that cannot handle the transient flow condition, huge pressure drop exerted by the inline surface strainer that temporarily installed to filter any solid production, unintentional jammed close of Tubing Retrieveable Surface Controlled Subsurface Safety Valve (TRSCSSV), unanticipated low performance of gas lift compressor that restricted the wells to continuously flow to the test separator and temporary high H2S gas release throughout the well unloading operation. Due to daily tripping, the crew left with constrained time of 4 - 5 effective hours only per day in attempts to kick off and flow the wells. On paper, offline well unloading indeed offered 70% cost saving compared to clean up with rig. However, in actual it resulted to increase 3 times in well cost and delay in achieving first production target which was 6 months later from the plan due to unanticipated causes that prolong the unloading activities.
