Improving Artificial Lift Design Through Dynamic Simulation

Abstract In a low commodity price environment, the quickest and most cost efficient way to increase production is by optimizing the existing well stock. The objective of this paper is to describe the successful use of transient flow and dynamic simulation to optimize artificial lift systems in tight gas wells. The most economical way to produce natural gas wells for the field in this study (Field A) is on a plunger lift system. However, optimal plunger lift relies heavily on certain wellbore conditions (e.g. liquid to gas ratio, differential pressure between the sand face and flow line, and annular and fracture volume). Dynamic simulation helped understand the optimal wellbore conditions for maximum plunger performance, optimized plunger lift cycles, and allowed engineers to develop a consistent plunger lift strategy across the field. Improved knowledge of the dynamics of the plunger lift system resulted in a few million dollars in cost savings by refining the selection criteria for candidate wells and reducing risks in well intervention execution. Dynamic simulation was also utilized for rod pump optimization for a 40 well rod pump pilot program. Preliminary results of the pilot program suggested that the initial rod pump design performed below expectations. The pilot well produced at a low gas rate with a high annulus liquid level. Dynamic simulation was used to test and improve the existing rod pump design and best practices. Understanding the downhole dynamics of the system allowed the engineers to identify a choke in the system resulting in a false-high fluid level reading while simultaneously causing the pump to gas lock. An optimized rod pump design was created from the learnings and the design was executed in the field. As a result, the rod pump was able to fully pump off the annulus volume and the gas production was increased by 50%. This paper discusses the methodology to match actual field data and investigate the downhole dynamics for plunger and rod pump operation using a commercial transient flow application. The learnings and observations from this study allowed engineers to answer key technical questions, to reduce project execution risks, and to increase gas production. In the end, dynamic simulation provided a quick way to improve existing designs, test new ideas, and refine operational procedures without the time and cost of field implementation.