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
Testing, Treating, and Selling Crude Oil
METHODS USED TO TREAT BS&W
B-1. Overview of Treating Methods.
Separation is the procedure whereby a mixed fluid of gas, oil, and water separates into these different components. Many factors influence the separation of water and oil, and often work at the same time with various degrees of success. Some of the more important factors include: · Gravity · Time · Movement · Chemicals · Heat · Electricity. A knowledgeable pumper understands all factors and combinations of factors that result in a good pipeline oil separation with a minimum drain on time and expensive chemicals. As wells become marginal and production is from the final stripping of the reservoir, the oil can become much more emulsified and difficult to treat.
Gravity causes the separation of crude oil and water. Water will slowly separate from the crude oil from the time it is produced until it is sold. The water can be free water, which falls out rapidly, or it can be emulsified with oil, paraffin, and other elements and compounds, become very difficult to separate, and require a lot of time. This natural separation also occurs at an ever slower rate. Gravity affects larger droplets of water more forcefully, causing them to sink to the bottom more rapidly. Smaller droplets fall slower than larger droplets. Crude oil is lighter than salt water, and gravity will cause the water to work toward the bottom. The smaller the droplet of water, the less the gravity pull and the harder it is to remove. If the heavier water can be broken loose from the oil and paraffin, then gravity will cause the water to work its way down through the liquid to the bottom of the vessel. Paraffin and other compounds form a strong surface tension around these droplets, and with low gravity oil the tension cannot be reduced without assistance by the use of time, movement, chemical, heat, electricity, or a combination of procedures. Flash and slow water gravity separation in treating crude oil. To successfully treat crude oil and make it sellable, the pumper needs to consider what needs to be accomplished and the best way to proceed to achieve that goal. Two concepts to fully understand are flash separation and slow separation. If separation occurs within a few minutes, it is referred to as flash separation. Slow separation requires hours or days. After these fluids have separated, they are usually removed from the vessels through different lines.
B-3. The Use of Time in Treating Oil.
It takes time to break the water out of the oil. Some produced water will separate so slowly that it would require far more time than is available, so action is taken to begin this process as soon as a last tank of oil is sold. If a pumper waits until a tank of oil is almost full before treatment, the ability to use time is lost. Many decisions concerning time are governed by how much oil is produced and the treating problems anticipated. If oil is sold every few days from a tank battery and has treating problems, the pumper should begin treating the oil as soon as it is taken off the sales line. More chemicals than usual can be used because, with frequent sales, income is higher and funds are available. If the wells are marginal producers, production is low, and there can be several weeks or even months between sales. The pumper will have a lot of time but not much chemical available because of the low income. The pumper will learn how to use time and movement and natural separation to an advantage.
B-4. Separating Crude Oil and BS&W by Movement.
Total separation is not feasible. As emulsion falls out, it accumulates near the bottom of the tank. The emulsion must be recirculated with crude oil from the stock tank back through the separation cycle to assist the process and keep tank bottoms clean. Movement is the cheapest of all treating processes after time alone. If a small amount of oil is regularly circulated from the stock tank through the heater/treater or wash tank (gun barrel), this movement alone will treat much of the water out of the oil.
B-5. The Effects of Chemicals in Treating Crude Oil.
Chemicals are one of the most effective and common methods of treating water out of crude oil. An oil soluble surfactant can be added to the crude oil either at the wellhead or just ahead of the separator or first tank battery vessel. This oil soluble chemical is usually a form of soap that reduces the surface tension in paraffin and water droplets. This allows the water to separate by breaking apart from the hydrocarbons. Figure 1. A chemical reservoir tank, electric pump, and lines for chemical injection at the wellhead. Note that chemical identification information has not yet been added. Treating oil is just one of many reasons for using chemicals on the lease. The pumper should know the functions of all chemicals and how to apply them properly.
B-6. The Effects of Heat in Treating Crude Oil.
Heater/treaters (Figure 2) are used extensively to heat and treat crude oil. Heat is applied to the crude oil by both the sun and by burners in heater/treaters. Figure 2. Chem-electric heater/treater for treating crude oil. When possible, flow lines are left on the surface in order to take advantage of summer heat. During this time, heat is turned off and the vessel becomes a large three-stage separator. As little heat as possible is used to treat oil. Some oil companies have set up an objective of eliminating all use of heat and fire boxes in treating oil. This is an extremely aggressive approach that will result in a dramatic reduction in lease gas consumption. However, technology to completely eliminate heating from the treating process is several years away.
B-7. Treating Oil by Chemical-Electrical Processes.
The electrical heater/treater is the most effective method for treating high volumes of crude oil. Because of the cost of electricity, this method is not practical for extremely low producing wells. One chem-electric heater/treater will outperform several standard vertical heater/treaters. Consequently, it is very popular where there are large volumes to treat as well as offshore where platform space is extremely expensive to build.