Study Evaluates Ability of Tailpipe Systems To Optimize Artificial Lift in Horizontal Wells

Abstract

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 190938, “Evaluating Tailpipe Systems Designed To Optimize Artificial Lift Performance in Horizontal Wells,” by C.R. Humphreys, SPE, B.N. Vangolen, SPE, A.P. Allison, SPE, D. Yin, SPE, and C. Yicon, SPE, Occidental Petroleum, prepared for the 2018 SPE Artificial Lift Conference and Exhibition–Americas held in The Woodlands, Texas, USA, 28–30 August. The paper has not been peer reviewed. The performance of artificial-lift systems on horizontal wells is greatly influenced by both the volume of gas produced and the tendency for gas slugging. With a sucker rod pump (SRP) system, gas slugging leads to gas interference at the pump, reducing system efficiency and equipment run life. With an electrical submersible pump (ESP), gas slugs can cause cycling of the ESP, which may shorten run life significantly. A trial project was launched to evaluate the performance of two tailpipe systems that could be applied to both forms of artificial lift. Introduction The two tailpipe systems were tested in a number of wells using SRPs, and one well was tested using an ESP. The goal was to Reduce the frequency and magnitude of slugging behavior seen at the pump Reduce the flowing bottomhole pressure without having to land pumps past the kickoff point (KOP) Improve separation of free gas from the produced fluid before it reaches the pump intake The two systems differ in both separator design and packer location. The first uses a conventional packer-style gas separator with a reduced-inner-diameter (ID) tailpipe extending below the separator and past the KOP. The second uses a special cyclonic separator with a reduced-ID tailpipe, and the packer is located at the lower end of the tailpipe. The authors examined the differences between the two systems regarding the isolation location, whether at the top or bottom of the tailpipe, to aid in designing future systems. A comparison of the two separators was attempted, and various operational challenges are discussed in the complete paper to improve the design, installation, startup, and operation of these systems. Some installations were outfitted with downhole gauges (DHGs) measuring pressure and temperature at several points along the tailpipe. The DHGs recorded pressure at the tailpipe inlet and outlet, pump intake pressure, and pump discharge pressure. This surveillance package allowed for real-time monitoring of the performance of both the tailpipe and the artificial-lift system while also providing data for modeling the flow regime through the tailpipe. The modeling results were used to forecast long-term performance of the system as well production declines over time. Results from the field trial show the performance of each system from a variety of standpoints: changes in flowing bottomhole pressure, flowing behavior through the tailpipe, separation effectiveness, and changes in production.