Abstract

Water and gas injection are widely used techniques to alleviate pressure decline and improve sweep efficiency in brownfield reservoirs. When variable reservoir properties exist, such as permeability, pressure, and thickness, the requirements for real-time monitoring and control become crucial to ensure zonal injection target rates and volumes are achieved.

The Bokor Field is located in the Baram Delta area of the South China Sea, 45 km from the shore of Sarawak, Malaysia, in a water depth of approximately 70 m. This marks the initial use in Malaysia of a distributed temperature sensing (DTS) fiber optic cable installed and cemented behind casing in a multizone immiscible water alternating gas (IWAG) injection well. Injection profiling was monitored via the DTS across multistacked reservoirs having different horizontal permeabilities. The DTS detected injection profile patterns within each zone and enabled identification of high permeability streaks and thief zones. Inflow control valves (ICV) were then used for injection management and control.

For Bokor well, offshore Malaysia, an intelligent completion system was chosen. The well comprised downhole flow control valves with 8 choke positions, permanent downhole gauges, and a DTS cable to enable optimum injection conformance. DTS provides real-time temperature measurements along a multimode optical fiber encased in a ¼-in control line. Enhanced measurement accuracy can be achieved by placing the DTS cable as close as possible to the reservoir by installing it behind the production casing in direct contact with the reservoir formation.

Deployment of the DTS in such a way presents several challenges in the design and operational phases. The first challenge is to ensure the integrity of the cable while running and cementing the casing in a highly deviated trajectory. Special equipment was designed to ensure mechanical protection of the fiber while safeguarding the quality of the cement-to-casing bond. An innovative TCP perforating technique and cable detection system had to be developed to prevent damage to the DTS when perforating the casing. Several design interfaces and system integration tests were identified and carried out between multiple providers to guarantee a smooth and successful installation.

Preliminary results demonstrate intelligent technology for real-time monitoring of the actual injection profile behind casing, and for controlling it remotely via an RTAC (real-time acquisition and control) software solution.

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