Equalize Method: A New Method for Optimizing Gas Lift Spacing Design

Abstrak

In gas lift unloading process, killing fluid depth is often represented using static fluid model. An innovative method is proposed to optimize gas lift design by considering the fluid movement into the reservoir. The objective of this paper is to present this new equalized method in order to minimize the number of unloader valve and optimize the gas lift design.
The equalized gas lift spacing design method is started by determining reservoir parameters, reservoir pressure, and productivity index. Well testing data provides necessary data to determine static bottomhole pressure, indicating reservoir pressure in a static condition, as well as productivity index. Afterwards, combining Darcy law and hydrostatic pressure equation, actual killing fluid depth for a set of time can be obtained until it reached equalized condition. This equalized condition is the starting point for gas lift spacing design.
The following study used well-X in ONWJ field which plans to target depleted reservoir. To enhance the production, a gas lift system is required to maintain oil production. The conventional gas lift spacing method yields a total of eight unloaders. By utilizing this new method until the pressure reached equilibrium condition, the number of unloaders used can be reduced significantly to a total of four unloaders. In addition, the equalized method will allow higher test rack opening pressure that result in higher gas lift operating pressure and higher injected gas capacity. In the end, equalized method will achieve higher oil productivity and will generate greater profit compared to conventional method.
The novelty of this paper involves the application of a new method for gas lift spacing design. For future implementation, most well cases with gas lift system can use this method for higher well production capacity and better economic feasibility.