Handil Field is a mature oil and gas field located in Mahakam Delta, East Kalimantan, Indonesia, developed since 1975. Handil reservoirs were deposited in a fluvio-deltaic environment. Oil reservoirs mainly located in shallow zone, whereas gas bearing reservoirs are mainly located in lower main until deep zone. Handil shallow zone consists of multi layer reservoirs located at depth 200 to 1500 m TVDSS. This zone is penetrated by different kinds of completion well techniques: gravel pack well for shallow zone and tubingless and dual string well for main and deep zone. The oil production from shallow zone is supported by gas lift system. The characteristic of shallow reservoir is poorly consolidated to unconsolidated sand with strong aquifer support. Due to sand prone reservoir, sand control technique is mandatory to prevent sand production when producing the oil. Gravel pack is commonly used as completion technique. Yet it still has limitation in number of reservoir coverage. As an alternative solution to produce remaining uncovered oil reservoirs, resin sand consolidation (SCON) is chosen. As the impact of bottom-up perforation strategy applied in Handil field, SCON implementation in ex-main and ex-deep zone wells are continuously emerging. Currently, several wells start producing from shallow reservoirs. Extensive preparation should be performed such as gas lift installation, tubing integrity, cementing, and site preparation in order to perform SCON in these types of wells. In terms of SCON target selection, several assesment should be performed to deal with SCON chemical limitations. SCON technique in Handil shallow oil reservoir was put on pilot project in 2011. Until End of 2018, 19 jobs have been implemented in different type of well architectures. In term of production gain, SCON jobs have been delivering ~1,100,000 bbls cumulative oil production with 100% success ratio on job execution and durability of the resin (no early sand breakthrough on surface). In 2018, 11 SCON jobs were performed with an average production gain 400 bopd and reserves 80,000 bbls. Due to its profitability, robustness, and applicability, SCON remain the main option to unlock oil potential of the remaining unperforated shallow reservoir in Handil Field.
Mahakam block with one of its gas fields, Tunu, has been developed for decades. Hundreds of wells were drilled to unlock layered sand reservoirs ranging from unconsolidated to consolidated reservoirs. Through field experience, well architecture is actively developing. The latest architecture, targeting shallow reservoirs only, is called Shallow Light Architecture (SLA). The well is completed with 3.5in production tubing cemented inside a 8.5in open-hole reservoir section. SLA is the default architecture for chemical sand consolidation (SCON) or thru-tubing screens as subsurface sand control. Perforation is performed by deep penetration (DP) hollow-carrier guns deployed with double-density to maximize open area and reduce sand production risk. DP charges were used based on the requirement to bypass near-wellbore damage, which is the same practice used in consolidated sand reservoir perforating. As more marginal reservoirs need to be unlocked, big entrance hole (BEH) perforation was initiated for the current sand control optimization alternative by SCON chemical reduction with shorter perforation intervals; and for thru-tubing metal screen performance improvement by placement in front of perforation entrance tunnels with minimum erosion risk. BEH was then studied as it has never been used previously in Mahakam with thru-tubing applications. Simulation and pilot well trials were explored to ensure that a short penetration would not significantly impact reservoir delivery on SLA wells. Inflow performance relationship (IPR) analysis resulted in slight additional drawdown compared to the calculated drawdown using DP at 2.5 MMscfd as an average gas rate in current thru-tubing sand control, which was considered acceptable from the operating envelope perspective. In total, BEH perforation was executed on ten wells with reservoir permeability range from 220 millidarcy (mD) to an extreme case of 3000 mD. Various SCON treatments were injected at optimized perforation lengths by cutting chemical costs up to 60% with sand-free production at a particular parameter and chemical type. On the other hand, in the application using screens, evaluation was not conclusive due to screen sizing issues for some installations. However, in-situ gas velocity could be reduced to the theoretical erosion velocity limit for a metal screen. This new approach to BEH charges utilization has a potential solution optimizing current SCON costs while also reducing erosion risk for the through tubing screen application to improve its performance. By using short penetration of charges, this approach was successfully implemented without jeopardizing reservoir's deliverability.
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.
Tunu is one of Mahakam fields with majority gas production. The depositional nature of fluvial with minimum tidal influence results in the signature of delta sedimentation by hundred layers of gas-bearing sand lenses as pay zone. They are constructed of unconsolidated clean and shaly sand reservoirs at the shallower burial and higher consolidation at deeper burial due to compaction and diagenesis. The unconsolidated section requires sand control as mandatory means to unlock it safely. The combined challenge of numerous sand layers and marginal reserves makes it economically impossible to perform regular detailed physical sand grain assessment by individual conventional coring completed with Laser Particle Sieve Analysis (LPSA). An economic approach is through performing sand bailing. However, the bailed sand dry-sieve results were confusing with wide particle size distribution (PSD) curve variation from several well samples. Referring to this PSD uncertainty, installing straddled thru-tubing screen in front of the reservoir as sand control resulted in good production and plugged indication at the beginning of the initiative by utilizing a similar screen opening size. Thus, a new fit-for-purpose methodology was required. A study to predict sand grain size on each reservoir target was initiated by analyzing three available shallow reservoir cores in Mahakam, which could cover most of Tunu's shallow sedimentation type. The result was that most of the sand grain size distribution on each sample core correlated with their calculated shale volume content (v-shale). Lower v-shale is respected to larger sand grain size. Unconsolidated Tunu Shallow reservoir doesn't contain any specific radioactive minerals. Thus, v-shale could be easily calculated from gamma-ray logs, which are always available on each reservoir target at any drilled wells. The relationship between sand grain size and v-shale was gathered on a single map. The map was then validated by historical screen installation. Positive results were seen when screen size selection respects specific patterns on the generated sand map at the v-shale value of perforation intervals. Thru-tubing screen installation campaign was continued following the new sand map reference. It could deliver more than 80% successful installation with no plugging or sand at a new perforated reservoir when no screen integrity issue due to erosion was encountered. This novel approach allowed better prediction of thru-tubing screen opening size requirements and perforation interval selection in Tunu unconsolidated reservoir and was successfully expanded in offshore Mahakam field at similar facies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.