Optimized Multizone Single-Trip Gravel-Pack System Deployed in Brownfield
Authors: Carpenter Chris 
Published: October 2024

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 214914, “Deployment of Novel Optimized Multizone Single-Trip Gravel-Pack System,” by Emmanuel J. Mogga, SPE, SLB, and Afiq Ismail, SPE, and Adebayo Adeyeba, SPE, Shell, et al. The paper has not been peer reviewed.

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The operator constructs many wells that require active sand control for multiple zones in cased-hole environments with the option for zonal selectivity and the possibility of watered-out zones to be isolated through well intervention. The most frequently used tubing in these wells is 3½-in. tubing, which poses a selectivity challenge when used in the standard 9⅝-in. multizone single-trip (MZST) gravel-pack system. An optimized MZST gravel-pack system alternative was developed and implemented successfully in Brunei and across the industry.

Background

Many brownfield development projects in Brunei use existing platform assets that target multiple sand layers. One of these projects consists of gas infill wells drilled from an existing platform as a sidetrack to target the crestal gas accumulation in sandstone reservoirs to support hydrocarbon-maturation delivery. To develop these shallow gas reservoirs, which have low unconfined compressive strength and high fines content, gravel-packing has become critical for effective sand control downhole for sand-free production. These gas-cap developments target the shallow gas caps and are aquifer-driven, requiring multizone water control and breakthrough management.

Functional well requirements of this project are defined as follows:

- Robust Sand Control—Based on the offset well history, most offset wells targeting the same reservoir were completed with sand control, predominantly using a gravel-pack technique. As part of competitive scoping, standalone screens were considered but deemed unsuitable because of the high risk of fines plugging and hot spotting. Previously, three wells were completed with casing and perforation without sand control that later required retrofitting with through-tubing sand screens because of sand production.

- Zonal Isolation—This is critical because the targets are aquifer-driven and the in-between intermediate reservoirs are filled with water. Thus, a high risk of water breakthrough exists.

- Zonal Selectivity—This is required for water shutoff and zonal data acquisition and optimization. Cased-hole completions with selective perforation will ensure the zonal selectivity required for the well, while reservoir and facility management and the gravel pack will control sand production. Considerations for openhole gravel pack or external gravel pack with swell packers do not fully assure zonal isolation upon swelling in a gas-dominant contact environment.

- Non-Smart—Permanent downhole gauges and inflow control devices are not required, which reduces the overall project cost. Instead, scheduled wireline operations are used when required.

Based on the functional requirement, a cased-hole gravel-pack design was essential. The cost implications were significant for the project because the value drivers were to maximize estimated ultimate recovery and minimize capital expenditures. Thus, the optimized MZST gravel-pack system was considered and matured through the design phases.