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.
The Lease Pumper’s Handbook
Motors, Engines, Pumps, and Compressors
CIRCULATING PUMPS AND AIR COMPRESSORS
Pumps are used for many purposes on oil and gas the leases, and there are many styles of pumps. Pumps can be classified by their pressure rating: high, medium, or low. Some pumps will pump only very clean liquid, while others are capable of pumping liquids containing mud, small rocks, and other emulsions with very little or minimum pump damage. There are two basic styles of pumps: the centrifugal pump and the positive displacement pump.
C-1. Tank Battery Circulating Pumps.
The most common pump that the lease pumper operates is the tank battery circulating pump. For medium- and highvolume producing tank batteries, this pump is often permanently installed and the prime mover is an electric motor (Figure 1). On leases where no electricity is available at the tank battery, a single-cylinder gasolinepowered engine is common. When the oil is difficult to treat, the automated electrical pump may circulate the bottom of the tank into which fluid is being produced. This happens for a few minutes every hour. For marginally producing oil wells, the circulating pump may be a portable model that is gasoline powered and moved from battery to battery as needed. In this event, the pump is either trailer mounted or needs to be small enough to be carried easily with one hand. This is because it must be moved, installed, and operated by one person. The most convenient style pump is the one with the pump mounted to the motor because skid-mounted units are too heavy for one person to hand load on a regular basis. Figure 1. A permanently installed, electrically driven circulating pump with an adjacent control box.
C-2. Installation and Maintenance.
Circulating pumps are located in the system with the inlet connected to the drain system and the outlet piped back to the production line after the separator but ahead of the treating system. If no treating vessels are in the system, the outlet is connected into the oil system just ahead of the stock tanks for circulating. The ideal arrangement in some tank batteries is to install the pump in the middle of a loop system where it can pump in either direction. Most transport trucks are piped in this manner so that the tanker can both load and unload itself as needed. There can be many reasons for the pumper needing to pump in either direction at the tank battery. The maintenance of the pump includes lubricating the bearings or changing the shaft packing as needed. The maintenance of the circulating pump engine consists primarily of changing the oil as scheduled, keeping the belt tension correct, and gapping or changing the spark plug as needed. Many of the problems in the carburetion system are caused by allowing water or trash to enter the gas tank—for example, from storing fuel in a rusty and dirty container.
C-3. Understanding Gas Pressure.
One characteristic of gases is that they try to fill all the space in any container into which they are placed. The force that a gas exerts on the walls of its container is referred to as gas pressure. If the container is made smaller or if more air is forced into the same volume, then the gas pressure increases. This is referred to as compressing the gas, and it is the same action that occurs when the piston moves up the cylinder, making the volume of the cylinder smaller and compressing the fuel/air mixture. An air compressor simply pumps more air into a container, leading to greater air pressure. Normal atmospheric pressure at sea level is approximately 14.7 psi. This is basically the pull of gravity or weight of a column of air 1 inch x 1 inch and all the way into outer space. As one goes to a higher elevation, there is less air above each square inch, so atmospheric pressure decreases with altitude. Any container open to the atmosphere will have an inside pressure the same as atmospheric pressure at that location. Gases tend to move from areas of high pressure to areas of low pressure, and this phenomenon can be used to do work. For example, compressed air has a pressure that is greater than that of the surrounding air. Thus, compressed air can be used to move objects, including control valves. In a similar way, if there is an area with a pressure less than atmospheric, the surrounding air will try to move in that direction. These areas of lower pressure are referred to as vacuums. Vacuums are often used to move gases and liquids. For example, as the piston moves down a cylinder in an engine, a vacuum is created in the cylinder. Because the fuel/air mixture from the carburetor is essentially at atmospheric pressure, when the intake valve opens, the mixture flows into the cylinder where the pressure is lower. Gas pressure is measured through the use of gauges. Gauges used to measure compressed gases and sometimes vacuum typically provide readings in pounds per square inch (psi). Vacuum gauges usually provide readings as inches of mercury (in. Hg), though it is often referred to as inches of vacuum. This measurement scale is based on the movement of liquid mercury within a glass column. At sea level, absolute vacuum is considered to be 29.92 inches of mercury. This is the greatest vacuum that can be created. Figure 2. Comparison of vacuum and absolute pressures. When dealing with gas pressures on an oil lease, there are two common ways of referring to the pressure. PSIG, or pounds per square inch, gauge is the pressure inside vessels and lines. The accuracy of the pressure reading depends upon the gauge itself. PSIA, or pounds per square inch, absolute, is the pressure on the outside of the vessels and lines—that is, normal atmospheric pressure.
C-4. Air Compressors.
Air compressors (Figure 3) are installed at tank batteries to supply air to operate automated equipment. Even though automated valves can be controlled by natural gas, several problems can be encountered that will cost the lease operator many times the price of installing and maintaining an air compressor. Figure 3. A tank battery air compressor used to provide clean air to operate automation valves and controls. Natural gas can contain corrosive compounds that are not easily removed by using a scrubber. Expensive controllers can become contaminated, plugged, or corroded by using some natural gases. Air compressors in the field are usually operated by using an electric motor. Maintenance usually involves maintaining correct belt tension, checking the oil level in the compressor, keeping air filters clean, draining accumulated water from the air tank, and lubricating the bearings.
C-5. Air Compressor Maintenance.
Air compressors are easily maintained because they are fully automated and pump air on demand as it is consumed. One of the maintenance tasks is to make sure that there are no air leaks in the system. Leaks can cause the system to run longer to make up for lost air. The inlet air filter will need to be checked and cleaned on a maintenance schedule. The oil in the compressor will also need to be checked on a regular basis. The oil will need to be changed according to manufacturer’s specifications and be refilled with the recommended oil. Hydraulic or compressor oil is not the same blend as engine oil.
C-6. Gas Compressor Operation.
Tank batteries located near or within city limits or oil storage tanks that vent large quantities of natural gas may include gas compressors. These gas compressors are automatically turned on and off by low pressure controls. The unit is referred to as a vapor recovery unit. This unit takes the low-pressure gas from the tanks, compresses it, and injects it into the high-pressure sales system. As the gas leaves the tank battery, just ahead of the compressor, it passes through a tank (scrubber) that removes the distillate. This distillate is pumped back into the stock tanks periodically. Low-pressure gas compressors will usually have vane-type compressors that require a lubricating system. The compressor will probably have an oiling lubricator on it to provide oil for lubrication. The lease pumper must regularly fill this lubricator with oil and keep basic records on oil consumption. This is done to track how much oil is being consumed and to know how often oil must be added. The sight glasses on the lubricator are filled with a water-soluble glycerine solution. As the oil enters the pump and travels upward through the glass, the number of drops of oil being injected per minute can be counted because the oil is lighter than the glycerine.