Gas Lift Nodal-Analysis Model Provides Economical Approach to Optimization

Topics: Artificial lift
Fig. 4—Production gain per well.

Field X consists of 17 scattered clusters of more than 100 oil wells producing from different reservoirs. Rapid expansion of the network has made the lifting network extremely busy and has resulted in many low-lifting-gas-rate ends. An easy solution is to increase lifting-gas use, but this is expensive. A more economical option is to restructure the gas lift surface pipelines, on the basis of proper engineering, by rerouting the surface network to reduce branching and enhance lifting-gas pressures and rates while maintaining the same level of lifting-gas use.

Introduction

The main gas lift 4-in. line connects Clusters A through C with the compressor. The main line is branched with 2-in. lines to every well in the cluster to deliver the required gas for lifting. As the number of wells increased dramatically, more low-rate and -pressure branches of the 2-in. lines were built. This was the main reason behind the loss of lifting efficiency. An increase of water cut in these clusters was another reason for loss of vertical-lift efficiency.

Considering the operational challenges of the field, the easy yet expensive solution was to increase the volumes of lifting gas, knowing that 30 MMscf/D of gas already was used for lifting. A more-practical and -economical approach was, first, to build a numerical optimization model that could identify the low-pressure and -rate ends in the gas lift network on the basis of nodal analysis. The next step was to modify the gas lift network by rerouting the surface pipelines to help reduce any network branching and enhance lifting-gas pressures and rates accordingly across the network while maintaining the same volume of gas being used.

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 171345, “Gas Lift Nodal-Analysis Model—Economical Optimization Approach,” by Mustafa Al Lawati, Occidental Petroleum, prepared for the 2014 SPE Artificial Lift Conference and Exhibition—North America, Houston, 6–8 October. The paper has not been peer reviewed.
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Gas Lift Nodal-Analysis Model Provides Economical Approach to Optimization

01 July 2015

Volume: 67 | Issue: 7

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