As with any hot-button issue, it is generally easy to find opinions on hydraulic fracturing, also known as “fracking.” It’s harder to find unbiased information, and most of us don’t really want to seek out opinions we disagree with. This leads to reinforcing our own view, just as the people we disagree with are having their views reinforced as well.
We all understand that fracking consists of pumping a slurry of water, sand, and chemicals into the ground to crack rock substrates and let trapped oil and gas escape. Most of us know that there’s fracking going on in Carbon County now and there are plans for more of it. We’d like to help everyone develop a better understanding of what that actually means.
This is a three-part article:
Hydro-fracturing, an Overview
by Al Bloomer, retired Certified Petroleum Geologist, Red Lodge
Once an initial borehole has been drilled, the operator makes a determination whether there is sufficient evidence for further testing and the possible economic production of hydrocarbons. In some cases the potential reservoir will hold hydrocarbons but the permeability is insufficient for commercial production. Traditional completion and stimulation techniques have been ineffective in the unconventional oil shales such as the Bakken, Marcellus, Barnett and Utica Formations. To be economically viable these unconventional reservoirs have required horizontal drilling and induced fracture techniques.
Induced fracturing (fracking) enhances the reservoir rock’s natural fracture system. Fracking techniques are commonly applied to unconventional low permeability reservoirs such as hydrocarbon bearing shales, coal seams as well as low permeability limestone and sandstone reservoirs. Fracking is a reservoir stimulation process in which a high pressure fluid carrying sand and chemicals is injected into the reservoir to enhance naturally existing fractures. The induced fracture width is about 0.2 cm (pencil point) and is propped open with sand grains. Typical hydro-fracture mixture is comprised of 90% water, 9.5 % sand grains and 0.5% chemical additives. Environmental concerns have been raised regarding the amount of water used and the re-use or disposal of the recovered fluids (flow back). Although it varies, a hydro–fracturing process typically uses 1 to 3 million gallons of water. Another issue with the frack fluid is the presence of carcinogens in the chemicals used. Although they are in relatively low percentage in parts per million, they are a concern and they must be monitored and accounted for.
A horizontal portion of the well bore often exceeds 2,500 feet. A single induced fracture interval is limited to 500 feet, requiring several procedures to cover the total reservoir exposed to the borehole. Injection pressure can be as high as 15,000 psi, injecting up to 100 barrels of fluid per minute. The distance from the bore hole (frack radius) that the frack fluid reaches varies, but rarely exceeds 300 feet. It is confined by the weight of the column of rock above the frack interval (overburden), the thickness of reservoir and the maximum pressure that can be induced. The hydrostatic gradient is about 0.433 psi per foot. Due to this gradient, induced fractures below 2,500 tend to move laterally not vertically. Induced fracture procedures in these unconventional reservoirs are typically at a vertical depth range of 3,500 to 13,000 feet. Fresh water aquifers are above a vertical depth of 2,500 feet.
History of Hydro-fracturing
The first recorded fracture stimulation attempt in the United States was in 1947 by Stanolind Oil Co, in Grant County, Kansas. The first commercial production from hydro-fracturing was in Oklahoma recorded in 1949. Since that time the induced fracture process has been improved and developed. The application to unconventional reservoirs is fairly recent.
Directional drilling technology has been utilized dating back to the 1960s. Most of this technology was developed in exploring around buried salt domes in the Gulf of Mexico. Applying this technology to onshore exploration and development is fairly recent dating back to late 1980s early 1990s. Since the mid 1990’s horizontal drilling technology has allowed operators to drill more accurately and to greater lengths. Mitchell Energy and Continental Resources are credited with developing the induced fracturing technology in unconventional reservoirs. Economic application in unconventional reservoirs was established in 2006-2007. The current “shale oil boom” began shortly thereafter.
The first recorded well drilled in Carbon County was in 1890 at the Cruse Seep 7 miles south of Roscoe. Since that time, in Carbon County, there have been approximately 648 wells drilled and to date 100 are currently recorded as productive. The application of horizontal drilling and induced fracturing in Carbon County is rare. There are two horizontal tests at Golden Dome, both plugged and abandoned. Elk Basin has recorded one horizontal test that is also plugged and abandoned. MacKay Dome southwest of Roscoe recorded initial production in 1960. The first horizontal well was drilled in late 2009. The field currently has one shut-in horizontal well and has recorded four currently producing horizontal wells. Records indicate that the four producing wells that have been fracked are producing between 30 and 69 barrels of API 12 degree oil per well per day.
Alternatives to Hydro-fracturing
At Mackay Dome the horizontal wells were fracked using an established technique called the carbon dioxide frack. The fracture fluid consists of sand mixed with liquefied carbon dioxide. At Mackay Dome the frack fluid contains about 48,000 pounds of sand and 70% carbon dioxide. The total cost to drill and complete these wells to a 3,400 foot vertical depth and then go laterally another 1000 feet is about $3.5 million. The obvious advantage to this method is the reduced use of water. Excessive use of water can damage some reservoirs, especially those with some clay content. However, they are not as effective as the hydro-frack at depths of greater than 5000 feet. In other parts of the country nitrogen has been used instead of carbon dioxide. As stated previously, initial production at Mackay Dome was established from vertical wells in 1960. These wells were stimulated with what is referred to as steam soak (huff and puff).
Water-free fracking is in the early stages of development. Presently, water-free fracks using a propane gel and butane are more costly. GasFrac, a Canadian company, has been working to develop this technique since 2008. Using propane involves risks dealing with high pressure gas and pumping highly flammable fluids. Marathon has reportedly used guar (a small bean that can thicken water) to reduce the total amount of water needed in a traditional hydro-frack.
Development and production of oil and gas from unconventional reservoirs has certainly had an economic, political, cultural and environmental impact on this area as well as the county as a whole. Theories of environmental disaster and negative impact on community infrastructure spawn dozens of rumors that suggest lack of government oversight, along with corporate environmental irresponsibility. Public opinion insists and expects regulatory agencies and industry representatives to be credible and accountable. Yet this same public allows many of the rumors and accusations to stand without basis in facts. Hearsay and opinion cannot be the standard for opposition to drilling and production.
The number of environmental incidents relative to the total amount of drilling and production has been very small. One can argue that one is too many, especially when it happens in our community. Many of the recent accidents have occurred while transporting hydrocarbons. Others have occurred due to surface spillage or leakage. In Montana there were no reported violations directly associated with drilling or down-hole production in 2012, 2013 and so far in 2014. The question remains: should development of unconventional reservoirs using horizontal drilling and induced fracture techniques be shut down? Perhaps a better approach is to have and enforce rules and regulations that reduce the risk, diminishing the chances of environmental accidents. Montana Oil & Gas Commission has rules and regulations in place. They were reviewed and updated in August 2011. Continued responsible citizen oversight is very important in this process.
Let us reduce the drama and the emotional rhetoric. Evaluate the process based on what we know and what is scientifically sound. Propose additions and changes to the drilling permit application and operation regulations. Once regulations are in place we must make sure there is strict review and enforcement.