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
Well Servicing and Workover Section B PULLING THE ROD STRING AND PUMP B-1. Rod String Records. When performing well servicing work, it is important to have access to the latest well records, including the last pulling record that shows what is currently in the hole. An illustration of a pipe tally is shown in Figure 1. Figure 1. A tubing record and a rod record must be maintained on every well. B-2. The Strength of the Rod String. If the well is 2,000 feet deep or less, all equipment made to go downhole will meet the strength requirements of the installation. Little attention is given to tensile strength. If the well is 10,000 feet deep, rods and tubing capable of supporting a 10,000-foot string with a satisfactory operation and safety margin must be used. Satisfactory records of the API tensile strength must be maintained and must include the API rating of every rod in the hole. Companies that manufacture sucker rods use API designations such as C, D, and K to identify the quality of the rod, including tensile strength and corrosion resistance. This letter is also stamped on the flat side of the pin. Class C rods are used in light to medium applications, and D is used in medium- and high-tensile strength applications. An example of an API Class D sucker rod is shown in Figure 2. Figure 2. API Class D sucker rod. (courtesy of Trico Industries, Inc.) Pipe Tally 17B-2 When a string of rods or tubing has been exposed to severe service and the well begins to have excessive problems such as parting rods or breaks, a new or better quality string will be run in the well. The used string will usually be downgraded one step and re-used in a well that requires a lower tensile strength since they should never be graded back to their original level of service. When these used rods are transported to the storage yard, they should be stored and recorded with their lower rating. Common sense must be used when placing them back in service. The lease pumper should accept the inventory classification record, not the stamped designation. Thus, when purchasing used rods or tubing, the lease pumper should make sure that the downgrade practice has been followed. B-3. Straight and Tapered Rod Strings. The API has guidelines for identifying the rod system in the well. Rod diameter measurements are in fractions of an inch, with numbers assigned based on eighths of an inch. The table below shows the numbering system. The first line shows a rod with a one-half inch diameter body. Since one-half inch contains four one-eighth increments, this rod is designated with a 4 and is referred to as a number four rod. Number four rods will work in a water well, but are not usually found in the oil field. ½ = 4 1/8"-increments, or a # 4 string. 5/8 = 5 1/8"-increments, or #5. 3/4 = 6 1/8"-increments, or #6. 7/8 = 7 1/8"-increments, or #7. 8/8 = 1 inch or 8 1/8"-increments, or #8. 9/8 = 1-1/8 inch or 9 1/8"-increments, or #9. 10/8 = 1¼ inch or 10 1/8"-increments, or #10. With this method of identification, it is easy to represent the rod string with just a few numbers even if it is a tapered string. Rod string identification numbers are as follows: API Rod Rod Dia. API Rod Rod Dia. 44 = All ½" 86 = 1", 7/8", ¾" 54 = 5/8", ½" 87 = 1", 7/8" 55 = All 5/8" 88 = All 1" 64 = ¾", 5/8", ½ 96 = 1-1/8", 1", 7/8", ¾' 65 = ¾", 5/8" 97 = 1-1/8", 1", 7/8 66 = All ¾" 98 = 1-1/8", 1" 75 = 7/8, ¾, 5/8" 99 = All 1-1/8" 76 = 7/8", ¾" 107 = 1¼", 1-1/8, 1", 7/8" 77 = All 7/8" 108 = 1¼", 1-1/8", 1" 85 = 1", 7/8", ¾", 5/8" 109 = 1¼", 1-1/8" Figure 3 illustrates a method of identifying the rod quality to be used at a well site. Figure 3. Sign at well specifying rod quality. 17B-3 Some rod strings are tapered. Tapered rod strings do not actually use tapered rods. In this context, tapered means that top of the string has larger rods and that smaller rods are used in lower portions of the string. When going in the hole, a selected number of the smallest rods are run immediately after the pump is set in the hole. A changeover coupling is then added and the next larger size is run. A selected number of this size is run, and, if a third size is used, a second change-over coupling is added so that the next larger size can be run. There are several advantages to this approach: · It lowers the string weight and, thus, reduces the weight load. · A smaller gearbox or pumping unit can be used. · The horsepower or electrical energy needed is reduced. This is a common practice in deeper wells. The tensile strength, stretch, strokes per minute, and other parameters are limiting factors and must be considered when designing tapered strings. When designing tapered strings, the pumper should always consult with qualified engineers who understand sucker rod installations B-4. Pulling and Running Rod Strings. Some lease pumpers with small oil companies may be in charge of well servicing when the owner is not present. At other companies, the lease pumper is not only in charge but runs the well servicing unit or physically assists as a member of the crew. With larger companies, the pumper may only be a spectator who must return the well to service after the job is completed. When pulling and running rod strings, always handle rods in a manner that will run them back into the hole in the same order that they were pulled. The use of a rod elevator (Figure 4) is recommended. Since the boxes are allowed to break at either side on some rigs, this saves problems with double or no boxes when running them back in the hole. Figure 4. A rod elevator. (courtesy of Trico Industries) When making up rods, always use the correct make-up procedures. This includes using proper tools, such as special hand wrenches (Figure 5). The rods can be damaged by over-tightening just as easily as not being tightened enough. Make-up charts are available and should be followed. 17B-4 Figure 5. Typical hand rod wrenches. (courtesy of Trico Industries) When laying rods down on a rack, care should be taken at all times to prevent damaging or kinking the rods. Extreme care must be used when picking up the pump; sometimes a center bridle support must be used. Power rod tongs. Many companies prefer that their rods be made up with power tongs. When correctly used, the rods are made up exactly to manufacturer’s specifications. The correct torque should be used to prevent stretching the neck of the pin, which can cause the rod to break under load. Pulling stuck pumps. Rods are normally pulled through the use of a rod hook (Figure 6). Normally, the rods will come out without excessive problems. However, sometimes the rods will bind or a pump will get stuck. Figure 6. A snap-in spring lift rod hook. (courtesy of Trico Industries) One of the most difficult decisions the lease pumper may have to make occurs when a pump refuses to be pulled out of the seating nipple. If the rods are new, they hang in an even row at the bottom in the derrick. The bottom pins line up. When pulling tension on the rods, the rods always stretch as the operator pulls a tension. If pulled too hard, their ability to return to the original length can be exceeded. The stretch 17B-5 is permanent. When these rods are hung in the derrick, it is obvious to everyone that they have been stretched. If the supervisor has placed the pumper in charge of overseeing the well servicing operation, the pumper has to decide whether the maximum recommendation on the weight indicator has been reached. There are several options if a pump is stuck. The operator could be allowed to pull more tension but at the risk of stretching the rods beyond their ability to return to the original length. Alternately, the pumper could begin a stripping job, which means stripping out the rods and tubing and extending the pulling time and cost. If there is a safety joint in the rod string, the pumper may decide to disconnect the rod string at this point, and pull the rods and tubing separately. For wells that develop pump sticking problems, many options are available that do not involve stretching the rods or having oil spilled on the location. A supervisor should be contacted for a final solution before risking damaging the rod string or beginning a more expensive stripping job. B-5. Running the Rod String into the Hole. If the pumper oversees running the rod string into the hole, a careful listing should be made as everything goes in. Even for a pump change, there may be differences in pump length. As the rod string is run in, the following should be listed: · Gas anchor. Many production people recommend that the gas anchor be long enough to contain 1½ times the capacity of the pump. When very little bottom hole space is available, the gas anchor may be as short as six inches and contain many small holes along the sides and bottom. The pumper must know company policy and must know how long the tubing mud anchor is to make the gas anchor length decision. · Downhole pump. When changing out a worn pump, the pump is taken out of the hole, laid beside the replacement pump, and the bottom of the no-go sections are lined up. If the new pump is eight inches longer than the one being replaced, the clamp on the polished rod will need to be lowered approximately eight inches, so that the pump will have the same spacing. This can be determined by comparing the pumps. Occasionally, the differences in pump lengths will necessitate removal or addition of a pony rod, or exchanging one length for another of a different length. The length of the stroke should be compared and noted on the replacement pump record. A complete description of the new pump needs to be entered in the record. This information will be essential if the pump needs to be fished out of the hole. · Pony rods and the pump record. The first pony rod installed is the lift pony rod between the downhole pump and the rod string. It is listed in this position. New and rebuilt pumps are delivered with a description tag. This is always sent to the office attached to the rod tally sheet. If no changes are made in rods or tubing and the pumps are identical, no new tally sheets are necessary and the tag is simply attached to a sheet of paper giving the date and a brief explanation of where it was installed. · Safety release tool. A safety release tool is next installed if one is to be used. Release instructions should be noted in the report. 17B-6 · Rod string. The number of rods run needs to be counted and entered into the record. If it is a tapered string, the number of each size should be listed separately. Although a length is given, permanent rod stretch may change the length of the string by many feet. · Pony rods. Additional pony rods are used just before the polished rod is reattached as needed to space out the well. Pony rods are available in two-foot lengths from two to twelve feet. Other special lengths may be encountered. · Polished rod and lift pony rod. The polished rod is installed last, and the lift pony on the top may be left in position or removed. If it is removed, a coupling needs to be left on the polished rod to protect the threads (Figure 7). Figure 7. The threads of polished rods need to be protected if the lift pony is removed. Shown from left are 5/8-, 3/4-, 7/8-, and 1-inch rods. · Polished rod liner. If used, a polished rod liner is placed over the polished rod. It needs to be at a minimum of 2-3 feet longer than the stroke length. This allows the rods to be lifted a small distance without pulling the liner out of the stuffing box and also allows a wicktype lubricator to be added. The longer the stroke of the pumping unit, the more polished rod liner is needed below the stuffing box to be able to pick up the string. It also needs to be long enough that the stroke length of the pumping unit can be extended. After the rod job is finished. Before the rod record is sent to the office, a second copy is made. On this report, the listing order is reversed. This final sheet has rods listed in correct order from the top down, just as they are in the hole, and will be retrieved the next time that the well is pulled. This sheet will be forwarded to the office. A copy of this record is entered in the lease pumper’s lease record book for future use. Returning the well to service involves much more than just turning on a switch. Close attention must be given to the well when the fluid reaches the stuffing box so that packing tension may be adjusted, the polished rod liner checked for leaks, all valves opened to the battery, and all equipment set properly. B-6. Fishing Parted Rod Strings. Fishing parted rods is often required when the rod string has corrosion and pitting. The break usually occurs in the rod but can occur anywhere along the string. When fishing, rods are pulled, one additional rod and the fishing tool are added, and all are sent back down the well to “catch the fish.” If the pump unseats and starts out, the brake is adjusted as needed to prevent grabbing or bouncing action of the well servicing unit 17B-7 brake when they are applied. Jarring may cause the overshot to release and drop the fished rods, possibly corkscrewing all of the dropped rods and parting the tubing. Pulling tubing after dropping a rod string requires special considerations to prevent stripping parted tubing from over the rod string and leaving a loose rod string in the casing. These are especially hard to fish. When fishing parted rods, the pumper will need proper fishing tools. One of the typical fishing tools is illustrated in Figure 8. There are several other styles that may be needed. There are several styles of rod boxes, and these may require special considerations. If the pumper’s company owns its own fishing tools, they should be kept well greased and in a waterproof storage location. Appendix A addresses typical fishing problems. Figure 8. Typical sucker rod fishing tool. (courtesy of Trico Industries) B-7. Fiberglass Rods. Fiberglass rods have become widely accepted because their quality has dramatically improved over the years. Fiberglass rods are usually 37½ feet long, so instead of pulling rods in triples on a telescoping well servicing unit as with steel rods, the lease pumper pulls them in doubles. When installing fiberglass rods, a part of the string requires steel rods at the bottom to hold the string in a constant tension condition. These steel rods are installed immediately above the pump. This prevents the fiberglass rods from being operated in a compression mode. Since fiberglass rods weigh one-third the weight of steel, a smaller gearbox can be placed on the pumping unit. With the use of fiberglass rods, the travel length of the pump is dramatically increased and the weight of the rod string is decreased. When laying fiberglass rods down or picking them up during a well servicing job, the lease pumper should always tail the rods by carrying them in or out rather than letting them drag or scrape on the rack. If fiberglass rods are used, the lease pumper should obtain from the manufacturer or supplier a booklet of instructions for care and handling of fiberglass sucker rods. Fiberglass rods are stored and handled much like steel rods, although a few special considerations should be taken. Fiberglass rods should be stored inside a warehouse, under a roof, and/or covered to prevent fiber bloom from occurring while they are in storage. While in storage for three months or longer, these rods should be shielded against ultraviolet rays by storing them inside or with a protective tarp. The rods should never be thrown or dragged. When they are lifted, they need be 17B-8 tailed in. Wooden sills are less damaging than steel. When nicked, rod damage is permanent and the joint may need to be replaced. If a rod is cross threaded, a tap and die (Figure 9) should be run, the threads lubricated, and the joint screwed back together correctly. Figure 9. A tap and die for two rod sizes. B-8. Downhole Pump Problems. The most common reason for well servicing is to replace the pump because of valve wear or because the barrel and plunger clearance has worn excessively. This will occur on a fairly regular schedule and, by referring to the pump replacement record, the next service job can almost be predicted. By studying the pump failure and understanding why each one failed, the pumper can occasionally make small changes such as using a better adapted metallic content or changing the pump arrangement. This may extend the life of the pump dramatically. Occasionally, double valving a pump may extend its life. The shop doing pump repairs must also perform them accurately each time. Many repair shops may not be the most appropriate one for a job. They may not know the correct repair procedures or may not have the proper parts for servicing. For example, if a replacement barrel has been used that is too long it can place additional space between the two valves and promote gas locking. Sometimes when a pump is repaired on a “while-you-wait” basis, substitutions may be made for the correct replacement repair parts. This can cause shorter pump life. These types of repairs should be avoided. The pumper should always search for ways to reduce the necessity of pulling rods and try to lower lifting costs. This section contains only a small sampling of the information that is needed about rods and pump repairs.