What Is Hydro Fracturing?

Hydro fracturing is a process by which water is injected into a low yield water well at a high pressure and volume opening up and cleaning out the existing fractures found in the rock. This process is designed for hard rock wells (i.e. if the well will stay open without the need of being cased after drilling it is a candidate for hydro fracturing).

Before and after hydro-fracturing: new cracks connect with water bearing cracks in the bedrock for a more productive water well.

There are two types of hydro fracturing that we perform Standard Hydro Fracture and Zone Hydro Fracture. 

Standard Hydro fracture:

Consists of a single packer that water passes through and pressurizes the whole well. This method is used to develop a greater production rate for low yielding wells. 

The single packer set is the most common method used. It is designed to be used in circumstances where a minimal improvement is needed. After a well has been drilled silt and deposits may start to build up in the water producing fractures causing a decrease in overall well yield

A packer is lowered down the well to pre-determined depth (Usually 20' below the casing or a minimum of 60' whichever is deeper), and water is injected into the well at high rate of volume and pressure. This will remove the obstruction and open up the water producing fractures

Now that the obstructions have been forced out of the water producing fractures, more water is able to flow into the well increasing the overall yield of the well.

Zone Hydro fracture:

Consists of two packers that are set either 60 or 80 feet apart. Water is then forced in between the two packers creating pressure to be forced in between the 60 or 80 foot zone rather than pressurizing the whole well. This method has a greater success rate and more productive results. However it is also the more costly of the two types and used as a last resort to raise the wells productivity, in most cases standard hydro fracture is sufficient.

When maximum yield is needed, "Zone" or straddle fracturing is utilized. Two packers are lowered down the well isolating a specific "zone" to be Hydro-Fractured.

Once that zone has been freed of its obstructions, the process is repeated at even intervals until the entire well has been Hydro-Fractured.

By concentrating the injection to where it is most needed, zone-fracturing insures optimum yield

Well Development by Hydro fracturing 
Hydro fracturing, commonly referred to as hydrofracking, is a well development process that involves injecting water under high pressure into a bedrock formation via the well. This is intended to increase the size and extent of existing bedrock fractures, thereby enlarging the network of water bearing fractures and size of the area supplying water to the well. 

The procedure is often used to increase well yields of new deep drilled wells with marginal or inadequate production rates. It may also be applied to older existing wells that have progressively diminished recovery rates over time usually caused by mineralization and incrustation of rock fractures. 

History
Hydro fracturing was originally developed in the oil fields to increase production volumes and is a relative newcomer to the drinking water well industry. It is now the method preferred by most contractors for developing bedrock wells because it is a controlled process. Older methods included blasting with dynamite and more recently, the application of dry ice to a capped well was used. These methods were somewhat uncontrolled and sometimes resulted in well failure. 

The use of dynamite frequently caused wells to collapse from the force of the blast rendering the well useless. The use of dry ice was common only a few years ago and was a much less violent approach to applying high pressure to the bedrock formation. The phase change from solid carbon dioxide (CO2) to gaseous CO2 results in a large increase in volume. The well is capped immediately after the introduction of dry ice into the well. The CO2 gas is trapped in the well as it expands and the result is an extreme increase in pressure. The pressure generated theoretically has the same affect on bedrock fractures as the hydro fracturing process does today. Unfortunately, in some wells the increased pressure on the well casing forced the casing in the upward direction causing the drive shoe seal to lift consequently breaking the seal and allowing surface water into the well. At least in one instance the well casing actually shot out of the ground into the air. 

The hydro fracturing process eliminates this problem by controlling the pressure with packers below the well casing. 

The Hydro fracturing Process
The procedure involves the installation of an inflatable or mechanical packer which is placed in the well bore at lease 20 feet below the well casing and drive shoe seal and at least 60 feet below the ground surface to insure that the process does not “break” the seal or allow surface water contaminants to enter the well. The packer is inflated or locked into position and water is pumped through the packer under pressure. Most applications require between 500 and 2000 pounds per square inch (psi) pressure and in some cases 3000 psi pressure may be needed in tight rock formations. 

If successful, pressure will steadily rise to a maximum level as the rock formation resists flow then will suddenly drop off and stabilize at a lower pressure. The drop in pressure indicates that the formation is accepting water and the resistance to flow is diminished. Water is pumped into the formation for 5 to 30 minutes. Injection pump delivery rates of 80 to 160 gallons per minute (GPM) have proven successful. Generally, 2000 to 3000+ gallons of water or more are pumped into the bedrock formation. 

One or two packers may be sued for hydro fracturing. When utilizing one packer, it is set near the top of the well but at a minimum safe distance below the drive shoe. After the initial frac sequence, the packer is deflated or unlocked and lowered further into the hole and the process repeated as many times as necessary. Commonly two hydrofrack sequences are performed. 

Zone fracturing utilizes a two packer system where the packers are placed in series and water is pumped into the zone between the packers. This system can be more effective because it concentrates pressures within a small area, typically 30 to 60 foot intervals, and individual fractures can be isolated and hydraulically fractured. With this method, the procedure starts within a specified section of the well targeted by the Water Well Contractor. Each successive frac sequence stresses one interval higher than the last. In this way, all potential water bearing fractures or fracture zones are worked independently within the section being hydrofracked. This differs from, the single packer, one or two frac sequence method which probably only affects the weakest, least resistant point(s) in the well but still may produce adequate results for private wells serving individual households. 

Zone fracturing is a much more expensive and time consuming procedure and is generally used only on very difficult wells or public supply wells or if a larger flow of water is desired. 

Yield and Yield Testing
Well yield increases, if successful, are generally modest but may constitute a significant increase if the original well yield was very low. Occasionally, large increases in well recovery rates are realized. Overall the hydro fracturing industry reports a success rate in excess of 90% to 95%. A typical well yield rate after hydro fracturing is 1/2 to 5 gallons per minute. 

A yield test should be conducted no sooner than 24-48 hours following hydrofracture to determine actual water production. Generally, hydrofracturing is less expensive than drilling another well and should be considered a viable option if water production is inadequate.