Investing In Quality Pumps for Saltwater Disposal in the Oilfields, a Primer

Hi Alex, Thanks for your time today!

1-Can you tell our readers about your company and background? 2-With respect to SWD wells what should operators keep in mind?

M and M Pump and Supply consists of three companies: 1. M and M Pump and Supply Inc., Clay City and Mattoon, Illinois selling Oilfield Tubulars and Sucker Rods, Tanks both steel and fiberglass, downhole oilfield pumps, positive displacement and centrifugal pumps, pipe, valves and fittings and just about anything that is used to drill, complete, or equip an oil or gas well. We also service and repair natural gas engines, salt water pumps and have a complete inventory of fibergass pipe and fittings for salt water injection lines. 2. PD Service Co., Clay City, Illinois furnishing oilfield trucking, oilfield construction crews, tank trucks, tubing and casing testing and inspection crews, frac and swab tank rentals, steamers and oilfield threading services. 3. McCoy Machine and Gear Co., Flora, Illinois furnishing complete oilfield machine shop, new and rebuilt pumping units and mobile service trucks for field repair of pumping units and salt water pumps and manufacturing Miller Sand Pumps.

With regards to salt water disposal and injection wells I would recommend running a good string of Sealtite Plastic or CPVC lined tubing to protect against internal corrosion and being sure to protect the anular space between the casing and the outside of the tubing with a good corrosion inhibitor, oxygen scavenger and biocide in either liquid or pellet form. If you are water flooding be sure to choose a good producer for your injection well as these seem to make the best injection wells with the best waterflood results. Needless to say have a petroleum engineer analyze your field for recoverable barrels of oil and desired injection rates per injection well to improve you odds of the best results from your waterflood. Establish a good chemical program for your injected water for control of corrosion and scaling tendencies. Starting this program immediately is vital to minimizing problems down the road that could lead to excessive pulling of both producing and injection wells in a waterflood. Be sure to have a chemical company analyze injected and produced water for compatibility to prevent possible severe scaling and corrosion down the road.

3-What type of pumps work best for SWD wells? How do they work?

Everything with regards to pump selection for a salt water disposal or injection well is defined by barrels per day of water to be injected and maximum pressure required to inject the water at that rate. Because most injection wells require anywhere from moderate(300 to 700PSI) injection pressures to very high pressures(over 2000PSI) a positive displacement pump such as a plunger or piston pump or a diaphragm style pump is usually required. All positive displacement pumps require good water supply at the pump intake and it is very important to be sure this is achieved either by oversizing and flooding the pump suction or charging the pump suction with a properly sized centrifugal pump. Pumps of this type are usually powered by either an electric motor or gas engine with adequate horsepower to handle the maximum flow rate and pressures that the pump will be subject to. Brake Horsepower requirement is calculated by the following formula: Gallons per minute times Maximum Pressure times a constant of .000648 equals Maximum Brake Horsepower Required.

4-I’ve heard much about Hydra-Cell and Cat pumps, are there any other brands to consider?

Some of the more common brands of Positive Displacement Pumps are Gaso, Wheatley, Oilwell, Gardner Denver, Bethlehem(B-Master), Kerr, Myers, Union, Ingersoll Rand, Cat, Hydracell among others. The key to choosing which pump works best for your application once again depends on barrels per day to be injected and the pressure needed to accomplish this. Another key consideration would be having a distributor that stocks parts for and services the brand of pump you are going to purchase so that downtime for pump servicing and repairs can be kept to a minimum. Hydracell Pumps are in most cases less expensive than plunger pumps if you can find one that meets your volume and pressure requirements. These pumps will also probably require completea replacement after 5 to 10 years in service. Big plunger pumps such as the Gaso, Wheatley, Oilwell, Gardner Denver, Kerr, B-Master can run for 40 to 50 years if properly mainained and rebuilt every 3 to 10 years depending on service conditions.

Cat pumps fill the niche for low volume, very high pressure applications particularly well at a reasonable cost, but replacement part costs tend to be quite expensive when the pump needs serviced. Probably the most important thing you can do for any of the above pumps is to develop a good preventative maintenance program with particular attention being paid to the condition of the oil in the power end of the pump. Pumps in this service frequently run 20 hours a day or more so it is imperative that a daily preventative maintenance inspection is made and that fluid change intervals are followed religiously.

5-Do certain brands have pros and cons?

6-Any maintenance or ongoing usage precautions to take with these type of pumps?

#5 and #6- I partially answered these questions when responding to question #4. Other maintenance considerations. Be sure you purchase a packing gland wrench for tightening plunger packing on plunger pumps as well as a hammer style valve cover wrench for pumps with threaded valve covers. Some pumps use a deep socket packing gland wrench and some require a spanner wrench. In addition to daily power end gear oil inspection, plunger packing should be tightened if plungers are leaking more than 3 to 5 drips per plunger per minute, however it is imperative not to overtighten plunger packing as ceramic plungers which are usually used in salt water service will break if subject to heat over 150F and this can occur if packing is overtightened. It is usually best to let plungers run for several minutes after tightening packing, turn the pump off and then feel the ceramic part of the plunger and make sure it is not hot to the touch, if it is your packing is probably too tight.

If you have an injection well that goes on vacuum and want to suck your tanks dry, install a check valve with a heavy spring which will not allow the well to suck your tanks down. This will prevent plunger breakage due to the pump going on air and sucking any BS on top of your water into the pumps valves. I would also recommend installing a Y-strainer on the intake line to the pump to prevent debris from plugging the pumps valves. Be sure to inspect this strainer on a regular basis and after the initial hour of pump operation and after 24 hours of initial operation, as there is likely to be debris in newly assembled lines that could plug the strainer. When running Hydracell Pumps check the gear oil daily as if you poke a hole in one of the diaphragms salt water will have direct access to the pumps powerend. Finally be sure to oversize the pumps intake(suction) line and use as few 90 degree els as possible to insure adequate fluid supply to the pump. Remember the old adage that 6-90degree els nearly equals a bull plug!!

7-Should an operator over compensate and buy a pump that is much higher Horse Power than is indicated?

A certain amount of safety factor needs to be built into all pump and motor design in the event injection volumes exceed original estimates or more pressure is required to dispose of injected water than was originally estimated. It is also wise not to run any pump at its maximum recommended RPM as this will lead to higher maintenance and rebuild costs than a pump being run at 80 to 85% of its maximum capabilities. I would recommend designing your pump system at 75 to 80% of a pumps volume and pressure capabilities. This will allow for some additional volume and pressure if needed without causing maintenance headaches down the road.

8-What is a common problem you see in the field?

Frequent problems which I see in the field are: A. Failure to properly maintain powerend oil quality leading to expensive powerend overhauls. B. Failure to oversize pump suction lines and allow for adequate water supply to the pumps intake valves leading to premature valve failure. C.Failure to install a bypass valve on pump discharge lines leading to catastrophic falure such as a broken pump crankshaft is someone forgets and turns the pump on against a closed valve. D. Failure to screen incoming water to pump and failure to regularly inspect screen in suction Y-Strainers, particularly when water is being hauled into the lease by tank trucks(Note; A settling tank is best used when water is being hauled into the lease by tank trucks.) E. Failure to install a bleeder valve on pump discharge line to allow for bleeding any trapped air out of the pump. Failure to religiously follow a daily and weekly pump inspection and maintenance schedule.

9-Please Tell our readers about how to handle corrosive fluids in the pump?

In order to properly prevent corrosion in a salt water pump, the fluid end of the pump should generally be cast from either aluminum bronze or 316 Stainless Steel which are highly corrosion resistant. In some brines which are not too corrosive and where pressures are not to high a bronze fluid end will provide satisfactory service at a price which is significantly less expensive than aluminum bronze or stainless steel. However, standard brass has limited resistance to hydrogen sulfide and will often wash out quickly when handling brines that carry H2S. It is also a good idea to chemically treat injected water for both corrosion and scaling tendencies as this will prevent your injection well from plugging off and protect your downhole tubulars.