Water injection, or waterflooding, is the oldest enhanced recovery method. Waterflooding was born over 125 years ago near Pithole City, Pennsylvania. As is often the case with new technology, the earliest water injection for enhanced recovery was almost certainly an accident. Water from a shallow aquifer leaked into an abandoned well, or possibly leaked around an early packer, entering the oil bearing rock formation (pay zone). While this was disastrous to future oil production from the affected well, it was noticed that oil production rates increased in nearby wells. In a published report in 1880, John F. Carll had already observed that water injection not only increased oil production rates, but appeared to increase ultimate oil recovery. By the 1890s, waterflooding was very successful in the Bradford, Pennsylvania area. Water injection for enhanced recovery was slow to expand outside Western Pennsylvania, in part because the practice was rendered illegal in many jurisdictions by early oil conservation laws. This gave rise to some clandestine waterflooding during the first quarter of the twentieth century. But waterflooding slowly gained in popularity with many pilot projects started in the 1940s, and by 1955, there were nearly 2,300 water injection projects in 17 states.A Few Tips
We have over 30 years of experience with shallow waterfloods in the Illinois Basin, some less than 300 feet deep. Here are a few things we have learned along the way.| Home | PBS Tech & Tips | AnaLog Tech & Tips | UIC |
Water Meters are necessary to effectively and properly operate a waterflood. See our Water Meter Trivia page, with its links to additional water meter service notes pages, for some useful information on water meters. If pressures are not too high, it is possible to use relatively inexpensive domestic (household) meters. It is a trivial matter to modify these low pressure meters to read out in 42 gallon barrels. There are also some newer multi-jet meters on the market in various pressure ratings that look promising for waterflood applications.
PVC Piping has long been used for oil flow lines, but it is an attractive injection line piping material if operating pressures permit; it is essentially immune to corrosion. One inch Schedule 40 PVC will safely work to 450 psi conveying cold water, and one inch Schedule 80 PVC pipe will safely work to 630 psi conveying cold water (published industry numbers). If you can find it, the bell end pipe is much more dependable than the stuff with factory glued on couplings. We like Oatey brand All Purpose Cement (red label); it does a better job under adverse conditions than any other solvent cement we have tried. Use PVC pipe cleaner for best results, but the primers (often purple) are a waste of time and money (and try not to get too high off the glue and cleaner fumes).
Copper Tubing makes a nifty connection from the water supply line to a water meter attached to the well head. Rather than hard plumbing the well head to the water supply riser pipe, we use a loop of 1/4 inch OD ACR (Dry Seal) copper refrigeration tubing connected with flare fittings. 1/4 inch OD ACR copper tubing is good for 1,406 psi up to 100 degrees F, and good for 1,125 psi at 200 degrees F. This approach simplifies the pipe fitting job, but it has another big advantage. In the event of a water meter or other mechanical failure associated with the well, the loop of small diameter copper tubing will limit water flow to some extent, preventing the complete collapse of the injection system, but still allowing easy detection of individual well problems for wells taking no more than a couple of hundred barrels per day (shallow injection wells often take less than 100 barrels per day). Incidentally, copper pipe used in the air conditioning industry is always referred to by its outside diameter, but copper pipe made for use by plumbers is referred to by its nominal inside diameter (do not bother asking why).
Plastic Tents make a cheap and effective injection well cover. Kenneth Ingle, our good friend and "poor boy" oil field innovator, began using polyethylene contractor plastic film as an injection well cover over two decades ago. The idea is to drape 6 mil black polyethylene film, available at any builders supply store, over the injection well and to anchor the perimeter on the ground with a few shovels full of dirt. We often make a slit that fits tightly around the top of the water meter so readings can be taken without uncovering the well. This scheme provides just as good freeze protection as fancy boxes placed over the well (short of a heater in the enclosure, no cover will protect against freezing if the waterplant fails on a cold night). Do not use clear plastic or you will create the greenhouse from hell, and it does not weather well absent the carbon pigment.
100 Barrels Per Day (BPD) is close to 3 gallons per minute (gpm). The actual conversion factor is 2.917, but for most practical purposes the 3 gpm approximation can be used. This incredibly handy "rule of thumb" conversion factor is helpful in estimating injection rates, production rates, and just about any situation involving flowing liquids in the oil patch.