What the Frack is Fracking? Part 2: Down the Hole
Welcome to your second installment in the three-part series, “What the Frack is Fracking?” Part one began by defining the term fracking, also known as hydraulic fracking or fracturing, and discussed why hydraulic fracking is an important process being used by oil and gas companies worldwide. It then went into a brief history of hydraulic fracturing and examined the things needed to begin the process, starting with the materials, equipment and logistics required up on the ground’s surface before any drilling takes place below ground.
Once oil or gas is determined to exist underground at a certain location and the construction site needed to support the fracking operation has been built, it’s time to start drilling down. The wellbore, which is the term used for the vertical hole that’ll be made into the earth, will eventually be topped with a wellhead. This wellhead becomes the support anchor needed during pumping and extraction. The wellbore will be surrounded by a casing, constructed before drilling commences.
How Far Down For Successful Hydraulic Fracking?
Hydraulic fracking, although in use commercially for more than 65 years, has become more precise and efficient as new technologies continually improve the process. It’s called hydraulic fracking because water is used as the active agent for producing the fractures needed for the retrieval of hidden oil and gas resources. Typically, a horizontally-running shale bed is the best candidate for hydraulic fracking. Shale commonly has gas and oil locked within its structure, the release of which is the goal of hydraulic fracking.
The fracking process involves drilling first vertically to the depth of the expected rock formation believed to be holding oil/gas resources. Many shale deposits exist at depths of between 2,000 and 10,000 feet, although they’re considerably shallower in some areas. As the wellbore is being drilled to the required depth, a steel-pipe casing is inserted into the hole a section at a time and cemented into position. This cement isolates the casing, protecting surrounding groundwater from any gas or oil leakage from the well.
From Vertical to Horizontal
Once the correct vertical depth has been reached, the drilling efforts are then turned to a horizontal drilling process, meant to follow parallel to the natural horizontal fracturing of the shale deposit, or “play.” The length of this horizontal run can basically be any distance desired, and may often be as long or longer than the wellbore is deep. The metal casing continues to surround this horizontal hole being drilled and, once set in concrete, is ready to be perforated. Small charges are set to blow small holes through the casing and cement and into the shale. Fracking fluid, previously described in part 1, is then pumped under high pressure into the well. This fluid makes its way out through the perforations (perfs), causing the shale to fracture.
This fracking fluid is approximately 90% water, 9% sand (or ceramic beads) and 1% chemicals used to increase viscosity, kill microorganisms, reduce friction and inhibit metal corrosion. The sand, called a propant, serves the function of getting into the fractures caused under high-pressure fluid injection and “propping” them open once the pressure has been relieved. Oil and gas freed up through this hydraulic fracking process then flows back up through the wellbore and out the wellhead.
Why Hydraulic Fracking?
Hydraulic fracking is a means for gas and oil producers to retain maximum return for their investment. As we slowly use up the fuels easily obtained from underground sources, fracking provides an effective, efficient means of recouping lost stocks that would, otherwise, remain untapped. Stay tuned for Part 3, “The Results.”