Challenge: Demonstrate the economic and technical feasibility of reversing declining production from the billion-barrel Samarang oil field offshore Malaysia

Solution: Deploy a modular intelligent well completion inside AllFRAC® cased hole frac-pack screens run in tandem with MZ Alternate Path® gravel-pack shunt tube technology multizone packers across four unconsolidated sands in one well—an industry first

Results:

• Increased oil production by 90% and reduced water cut to 20% in first 3 months.
• Saved USD 3.2 million in rig costs, proving the viability of prolonging the life of the field

Enhance completion efficiency and production in brownfield

Samarang oil field offshore East Malaysia had entered a production decline phase, and a new approach was needed to improve reservoir productivity. With limited reserves still in place, PETRONAS was seeking cost-effective completion techniques to revitalize the field, which consists of several stacked reservoirs, some partially depleted and some with a strong water drive from aquifers. Traditionally, dual-string completions with multiple stacked cased hole gravel packs had been installed to maximize the number of layers produced from each well. These designs lacked independent zonal flow control and thus could not optimize commingled production and water cut, limiting oil recovery. Integrating gravel packs with an intelligent completion was needed.

PETRONAS worked with SLB to find a solution for increasing hydrocarbon recovery by targeting previously unattractive marginal reserves and commingling them to bundle the production into economically attractive opportunities. Completion installation efficiency was crucial for controlling costs. In the workover well selected as a candidate, oil production had declined below economic levels and water cuts for the various producing layers had reached 90% to 100%. The Samarang asset management team decided to abandon the watered-out layers and perforate four shallower oil-bearing zones.

Deploy multizonal sand control and modular intelligent completion

AllFRAC screens use shunt tubes and nozzles to ensure a complete pack. The screens were deployed in tandem with MZ shunt-tube multizone packers, which are sealed inside the casing to provide isolation between the closely spaced reservoir zones. Stacking conventional gravel-pack packer assemblies, which are longer, would have restricted the perforation intervals to much shorter lengths and negatively impacted production. During the single pumping operation, the top two zones (treated as a single interval) were packed conventionally while the middle and lower zones were packed via the shunt tubes extending through the packers. ClearPAC™ polymer-free viscoelastic surfactant gravel-pack fluid was used to prevent formation damage and ensure packing of perforation tunnels.

Because of the different pressure regimes between the producing layers, selectivity and control of each target zone was needed to prevent the more prolific layers from watering out and suppressing low-productivity layers. This first installation of an intelligent completion inside a shunt-tube multizone cased hole gravel pack necessitated reengineering and testing of downhole and surface equipment in a timely manner, all within the tight cost-benefit constraints.

Increase recovery and reduce water cut and rig time

Eliminating traditional stack packs and a dual-string completion installation saved PETRONAS 8 days of rig time, equivalent to approximately USD 3.2 million. Production in the first 3 months increased approximately 90% while water cut dropped to 20%. The intelligent well completion provided the ability to choke back intervals exhibiting a high water cut without shutting them off completely and without disturbing oil production from other intervals. The flow control valves also enabled reservoir engineers to optimize production from each zone despite uneven depletion rates. Simulations have predicted recovery will increase by 8% from this well compared with the use of sliding sleeves to shut off production when water cut from a layer reaches 90%. Continuous, real-time monitoring of each layer via downhole gauges provided additional benefits by minimizing production inefficiencies and downtime.

Pleased with the results, PETRONAS completed a second well with the same design and has planned more in Samarang and other fields. Additional operators in the region are considering adoption of the completion design for their fields. See SPE 171477 for more details.

AllFRAC and Alternate Path are marks of ExxonMobil Corp.; technology licensed to SLB.