Artificial-Lift-System Selection Guidelines for Horizontal Gas Wells
Authors: Wilson Adam 
Published: July 2017

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 181229, “Defining the Artificial-Lift-System Selection Guidelines for Horizontal Wells,” by J. Valbuena, E. Pereyra, SPE, and C. Sarica, SPE, The University of Tulsa, prepared for the 2016 SPE North American Artificial Lift Conference and Exhibition, The Woodlands, Texas, USA, 25–27 October. The paper has not been peer reviewed.

Many different artificial-lift systems (ALSs) are used in horizontal gas wells. Basically, most of them were adopted and evolved from those used in oil wells. This study presents a methodology to define the most-adequate artificial-lift technique on the basis of technical limitations, a suitability coefficient (based on an attributes table), and economic analysis toward horizontal well configuration. 

Introduction

The objective of the ALS in gas wells is to remove liquid from the wellbore, which is referred to as deliquification. The ALSs or deliquification techniques can be categorized into two groups, passive systems and active systems. Passive systems take advantage of reservoir energy. These ALSs include velocity strings, plunger lift, and foam lift. These methods are used when the gas velocity is insufficient to carry liquid naturally from the wellbore but sufficient energy remains in the reservoir to operate the method. The active systems include sucker-rod pump, progressing-cavity pump, electrical submersible pump, jet pump, and wellhead compressors. These methods add energy to the system and are generally used when the reservoir is depleted.

Recommended Guidelines

The development of the recommended guidelines is based on physical limitations of each ALS, well and field constraints, and a quantitative assessment of the attributes involved in the selection processes. Three main screenings are performed in the decision-making process. The first screening is based on the ALS’s limitations, including depth, flow-rate constraints, gas requirements, pressure requirements, well-integrity issues, and field conditions. The first screening rules out the unsuitable methods and leaves possible methods. The second screening is based on an attribute table that assigns a score for each attribute considered. In this screening, an average suitability factor is calculated for each feasible artificial-lift option, and the artificial-lift methods are ranked. The third screening is an economic assessment of the methods being evaluated. The net present value (NPV) and other economic parameters are calculated in this screening.

Technical Limitations of Methods.

Several parameters affect the ALS selection process, and they need to be considered to accomplish the main goal of the first screening, which is to rule out the unsuitable choices and provide a list of remaining methods that can be candidates for implementation. The strategy is based on defining simple rules to conduct the elimination process. These rules include limitations listed in typical-attribute tables, quick calculations, common reasoning when selecting an ALS, and typical “rules of thumb” based on experience for specific field conditions.