Abstract
Drag reducing agents (DRA) have been used in the oil and gas industry for decades to increase flow capacity of pipelines transporting petroleum products or crude oil over long distances. Injection of DRA reduces the flow turbulence, thereby reducing the frictional pressure drop in the pipelines and increasing pipeline throughput. Most of the time DRA is used in single phase flows, but application in multiphase flow conditions is growing. The surface gathering system of Tengiz oil field is complex and consists of more than 300 km of gathering lines and trunklines, some of which are bottlenecked due to their smaller diameter or high flowrates from the wells. TCO decided to implement continuous injection of DRA in parts of the production system to lower the frictional pressure drop in the bottlenecked pipelines and increase production from the wells.
The selection of DRA chemical was based on laboratory testing of the additive's compatibility with other liquids (such as caustic solution, produced water, corrosion and hydrate inhibitors) used in the field and plant processes, and on field trials. The obtained field test data was used to calibrate the network model in IPM GAP to simulate the reduction in pipeline friction losses due to DRA injection, and this approach helped to find future locations for continuous injection of the additive. As a result, continuous DRA injection was implemented at four injection points, which increased the total oil production from the field by 3%.
The purpose of this article is to share TCO's experience with the application of DRA injection in a multiphase flow system and describe all stages from selection of DRA and laboratory testing to modelling and actual execution of DRA injection in the pipelines of the Tengiz oil field. The paper discusses an overview of the current status of the DRA project, results obtained, best practices and lessons learned from field applications.
