Mahakam block has supported Indonesia's Oil and Gas production with over 40 years of deliverability. Presently, along with its maturity cycle, comes the challenge of a steeply declining matured field with indicators of marginal reserves, included unconsolidated sand reservoirs as one of the main contributors which required sand control. In addition, future offshore platform development emerged the urgency of light deployment and robust sand control.
Deep dive into the methodology, it was mandatorily to revisit what techniques available on the shelves and what is the current technology has to offer. Mahakam subsurface sand controls were classified into gravel pack, open hole stand-alone screen, chemical sand consolidation (SCON), and thru-tubing metal screen. These also respectively account for the highest to the lowest of operational investment, associated production contribution, and its reliability.
Thru tubing screen methodology in cased-hole application showed weakness by plugging and erosion issue resulting on minimum utilization as lowest end subsurface sand control means. Several normative elements factored into it, with the root cause of screen placement. It was avoided to install metallic screen in front perforation due to direct jetting during the natural sand packing (NSP) process, causing an installation at slightly above perforation with the absence of stable NSP and screen size selection complexity. Thru-tubing screen with higher strata of material, silicon carbide or ceramic, was selected as a pioneer on new installation philosophy to tackle erosion issue. It was combined with the developed Mahakam sand grain size map as a screen size selection guideline. A confidence pseudo-straddle thru-tubing ceramic screen (TTCS) installation campaign in front of perforation interval was explored on swamp (Tunu) and offshore (Peciko) gas wells. This technique adopts open hole SAS with retrievable concept optimizing slickline intervention.
Perfection of the techniques is a process that continues. However, based on the current study and trial results on wells installation throughout 2020 to 2021, positive results were achieved:
Operation simplicity with minimum operation HSE risk, Sand free production delivery addressing highly unconsolidated reservoir with widely distributed sand grain by mitigating the risk of screen erosion, The average cost savings were 66% in delta and 76% in offshore compared to allocated SCON budget, Cummulative gas deliverability increased by more than 200% compared to previous thru-tubing metal screen performance, Performance exceeded average SCON production rate and in-situ gas velocity limit at several installations, The installation method had a 100% retrievability success ratio from all retrieval attempts on inactive wells installation, It had no damaging effect to the reservoir when remedial by SCON was required, The installation concept adoption has been proven on highly deviated and unique completion configurations.
This enlightenment boosted confidence in both the assessment technique and installation philosophy. This initiative would enable the production of Mahakam marginal sandy reservoir while sparking to a wider application as an alternative robust and light sand control solution.
