Lease Pumper's Handbook Published by the Commission on Marginally Producing Oil and Gas Wells of Oklahoma, First Edition 2003 Written by Leslie V. Langston Table of Contents Introductions A. Cover Sheet Book Title B. Publishing Information First Edition, 2003
 




The Lease Pumper's Handbook

Published by the Commission on Marginally Producing Oil and Gas Wells of Oklahoma, First Edition 2003 Written by Leslie V. Langston Table of Contents Introductions A. Cover Sheet Book Title B. Publishing Information First Edition, 2003

 

Written by Leslie V. Langston

 

Publishing Information. First Edition, 2003. C. Foreword. Rick Chapman, Executive Director (1996-2000) Commission on Marginally Producing Oil and Gas Wells, State of Oklahoma. D. Dedication. John A. Taylor, Chairman (1992-1998) Commission on Marginally Producing Oil And Gas Wells, State of Oklahoma. E. Author’s Introduction. Leslie V. Langston, Author, First Edition F. Commission Introduction. Liz Fajen, Executive Director, Commission on Marginally Producing Oil and Gas Wells, State of Oklahoma.

 

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 The Lease Pumper’s Handbook

 CHAPTER 18 GAS WELLS A. INTRODUCTION TO NATURAL GAS WELLS. 1. Understanding the Gas Well. 2. Wellheads and Christmas Trees. 3. Reservoir Characteristics of Gas Wells and Gas Production. 4. Producing the Gas Well. 5. The Wellhead and Safety Devices. · The tubing safety valve. · The surface safety valve. B. FLUID SEPARATION. 1. The High-Pressure Gas Well Separators. 2. Three-Stage, High-Pressure Separation and Indirect Heating. 3. Vertical Separators That Do Not Require Heat. C. GAS DEHYDRATION. 1. Gas Dehydration. 2. Operating the Dehydration Unit. · The inlet scrubber. · The contact tower. · The glycol pump. · The dual-action pumps. · The heat exchanger surge tank. · The three-phase gas, glycol, and condensate separator. · The reboiler. 3. Tank Batteries for Gas Wells. D. GAS COMPRESSION AND SALES. 1. Natural Gas Compression. 2. Natural Gas Measurements. 3. Testing Gas Wells. 4. Pipelines and Pipeline Problems. · The removal of liquids from pipelines. 5. Treating and Drying Natural Gas. 6. Transporting Natural Gas Long Distances. · Cross-country gas lines. E. NATURAL GAS SYSTEMS. 1. The High-Pressure Gas Line System. 2. Controlling the Pressure in the Separators and the Heater/Treater. 3. The Well Testing Gas Measurement System. 4. The Gas High Pressure Gathering System. 18-ii 5. The Low Pressure Gas Line System and the Vapor Recovery Unit. · The vapor recovery unit. 6. The Flare and the Gas Sales System. 18A-1 The Lease Pumper’s Handbook Chapter 18 Gas Wells Section A INTRODUCTION TO NATURAL GAS WELLS Many people will casually refer to all the wells in a field as oil wells. When it is necessary to specify exactly what type of hydrocarbons are being produced from a designated well, the designations may become oil well or gas well. A-1. Understanding the Gas Well. The typical production from a gas well is primarily natural gas, often accompanied by liquid hydrocarbons and water. The hydrocarbon liquid is usually referred to as condensate or distillate. · Condensate implies that the liquid was already in a vapor form, and only one step is required—condensing—to change the fluid from a gas to a liquid. The condensing may have occurred as the vapor was leaving the formation, as it flowed up the tubing, as it passed through the processing equipment, or even as it traveled through the gas transmission pipeline. The condensed liquid may be as clear as tap water. · Distillate implies that a two-step process occurs where the liquid is transformed from a liquid state to a vapor, then condensed back to a liquid form. This is a common purifying process that results in the production of a crude or casing head gasoline that contains little or no oil. A-2. Wellheads and Christmas Trees. A typical medium- to low-volume gas well has a double master gate and a safety valve next to the wing gate. The wellhead valves are often referred to as gate valves, which is often referred to merely as a gate. The upper master gate is always used when it becomes necessary to shut in the well. The lower one is in reserve so that if the upper valve fails, the lower one can be closed to make it possible to safely close the well in to repair the upper valve. A gas well may or may not have a packer installed, depending on how the tubing string is installed. A-3. Reservoir Characteristics of Gas Wells and Gas Production. A gas well is any well that produces a lot of gas and very little oil. The oil is usually a very light crude with a high viscosity or API gravity rating—that is, the weight of the crude as compared to the weight of a similar volume of water. An oil well usually produces a heavier crude with a lower viscosity and produces a higher percentage of oil versus gas. The gas produced from an oil well may be low or high volume, depending on the placement of the well in the reservoir and where the well is drilled. Condensate may leave the formation as a liquid or as a gas. If it leaves the formation as a gas, it may begin condensing to a liquid 18A-2 as it travels up the hole and the pressure and temperature decrease. The fluid falling back down the hole can affect production dramatically. Gaseous condensate with a lower hydrocarbon content may remain a gas. Plunger lift is widely used to assist in moving these liquids to the surface. A-4. Producing the Gas Well. Production in gas wells is measured in cubic feet. A well may be capable of producing less than a hundred thousand cubic feet of gas a day or have a potential of over one hundred million cubic feet a day. Each well is different in volume of production, pressures, condensate, and water production. The support equipment will change according to need. In most cases, gas from the well is delivered to a transportation pipeline operated by a gas purchasing company. The gas purchasing company will accept gas as long as a market is available. In the event of oversupply or in emergency situations, the gas purchasing company representative may close the well in as needed. Occasionally a gas well may be shut in for an extended period of time. This seldom occurs with an oil well or the gas produced in conjunction with producing oil. Thus, producing natural gas as a by-product along with crude oil is a more stable product sales market. A-5. TheWellhead and Safety Devices. A typical medium- to low-volume gas well as pictured in Figure 1 has a double master gate and a safety valve next to the wing gate. The upper master gate is always used when it becomes necessary to shut in the well. The lower one is in reserve so that if the upper valve fails, the lower one can be closed to make it possible to safely close the well in to repair the upper valve. A gas well may or may not have a packer installed, depending on how the tubing string is installed. Figure 1. A gas well with a dual or double master gate valve, safety valve, wing valve, and variable choke. A gas well may have two types of safety shut-in controls. Each serves a different purpose, although the results can be similar in that both systems shut the well in. The tubing safety valve. The safety valve installed downhole in the tubing will shut in the well in the event the line should break and a large volume of gas is being discharged. This safety valve is checked on a regular schedule to ensure that it will close in the event of an emergency. A wireline company sets, services, and retrieves these valves. Many companies do not install the downhole safety valve for medium- and lowvolume wells. A hydraulically opened valve can be installed such that the well automatically shuts in whenever this pressure is reduced. This system has been used extensively offshore, even for flowing wells. 18A-3 The surface safety valve. The surface safety valve signal to shut in the well is usually controlled at the high-pressure separator. A hi-lo valve with hi-lo pilot and bypass will shut the well in on either high or low pressure of the sales line. A small stainless steel tube leads from the safety valve on the Christmas tree to the control valve at the separator. The picture of the gas wellhead in Figure 1 shows the surface safety valve. Both Figure 2 and Figure 3 show the same type of control. Figure 2. A small gas well with a threephase separator and compressor in the background. Figure 3. A high-volume gas well. The gas well shown in Figure 4 has no safety valves or even dual master gates. It has been completed like any typical flowing well. This indicates very low production. Figure 4. A low-volume gas well. 18A-4