A Practical Approach to Removing Gas Well Liquids
Authors: Hutlas Edward J. , Granberry William R. 
Published: December 2007

This paper reviews various methods used in the past for removing liquids from gas wells, discusses some of the latest approaches and results obtained with them, and presents a practical way of evaluating gas wells as candidates for liquid removal.

Introduction

In the past few years the burden of fulfilling a larger and larger proportion of our energy requirements has been given to natural gas. At the same time, as a result of depletion, many wells are declining to low deliverabilities. The combination of these two factors has turned attention as never before to means of increasing gas well deliverabilities. One of the numerous factors that can decrease the deliverability of a gas well is the accumulation of liquids in the wellbore. Liquid accumulation and associated decreased deliverability can occur in wells that have never made large quantities of liquids. This paper will discuss various means of removing liquids and of recognizing and evaluating liquid-removal candidates.

History of Gas Well Liquid Removal

The history of efforts to remove liquid from gas wells can be illustrated by tracing the various devices used in the Hugoton field in Kansas. These gas wells, averaging approximately 2,500 ft in depth, were completed with 5 1/2- or 7-in. production casing. Initially, rates were adequate to develop the velocities needed to carry liquids to the surface, but as bottom-hole pressures declined and, in some cases. as more water pressures declined and, in some cases. as more water was being produced, it became necessary to blow the wells periodically at atmospheric pressure to unload the water. When it became impossible to unload the wells by blowing them, 1 1/4-in. siphon strings were run. The normal procedure was for the pumper to unload the well from time to time by opening the siphon strings to atmospheric pressure. Sometimes small holes were drilled in the siphon strings to aid in lifting the water; these "weep holes" enabled gas to enter the tubing at intervals uphole, providing additional lift toward the surface.

The installation of time-clock intermitters to open the siphon string automatically at predetermined time intervals was the next step in the history of liquid removal. The equipment consisted of a clock and a motor valve installed on the tubing at the surface. Weep holes were also used in these installations. This method was less time-consuming and more efficient than manually blowing the well. However, the optimum interval between blows and the length of each blow had to be arrived at by trial and error. Also, the method left much to be desired in that the gas was not used efficiently and maintaining liquid levels below the producing intervals was difficult.

The next step was the differential-pressure intermitter. This more sophisticated device measures the difference between tubing (siphon string) and casing pressure, determines the amount of water in the pressure, determines the amount of water in the siphon string, and blows the well when an adequate load of water is detected. After liquid is unloaded, the siphon string, is shut in (gas is being produced up the tubing-casing, annulus). Then gas is slowly bled from the siphon string to lower the pressure and cause the water in the wellbore to move into the tubing. The gas is bled by notching the seat of the motor valve mounted on top of the tubing.

JPT

P. 916