Field X consists of 17 scattered clusters of more than hundred oil wells producing from different reservoirs. The produced fluids from these reservoirs vary considerably in PVT properties, but all are of relatively average GOR and light oil API.

Gaslift is the dominant lifting system in clusters A, B and C for field X. The clusters are very scattered and far from each other. Long surface pipelines to transport lifting gas are built across the field and a compressor is installed with a total throughput of 90 MMSCF/D at a discharge pressure of 1,280 psi.

As the field expands, two major factors are contributing into the reduction of the Gaslift network efficiency; the rapid expansion of the network which is a result of the dynamic drilling operations. This makes the lifting network extremely busy and full of low lifting gas rate ends. The second factor is the water aquifer which increases produced watercut% dramatically resulting in heavier fluid column gradient to be lifted which again causes lifting inefficiency.

The easy solution to overcome these challenges was to increase lifting gas utilization, but this was an expensive option. A more economical option was; based on proper engineering to restructure the gaslift surface pipelines by rerouting surface network in order to reduce network branching and accordingly enhancing lifting gas pressures and rates across the network while maintaining same lifting gas utilization. A numerical simulation model was built based on rigorous physics and nodal analysis to integrate between well production model and gaslift surface network model to enable the engineer to evaluate the impact of rerouting the network on individual wells production.

This paper will describe the following process which was adapted to build and solve the integrated model to obtain an economical optimization approach for any scattered clusters field:

  1. Clusters field model building phase:

    • Characterize reservoirs PVT samples and match to equation of state EOS. Build material balance models. Build well models and entire surface production and gas lift injection networks.

    • Integrate fluid models, reservoir models, well models and surface production and gas lift injection network.

  2. Clusters field model solving phase:

    • Link the production model and gas lift injection model.

    • Solve the gas lift injection network to identify the weak injection rate ends. Restructure Gaslift network by rerouting the pipelines. Solve again the network to obtain optimized lifting gas rates based on actual gas lift injection depths.

    • Run network optimizer to enhance lifting gas injection depths based on available injection gas rates and pressure.

      Oil production gain of 15% was achieved from rerouting the gaslift network in three clusters wells in field X by enhancing lifting gas rates and avoiding unnecessary network branching.

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