By: Andy Maslowski
“Macaroni stop, water go.” Substitute the words “frac sand” for “macaroni” and this old Italian expression for draining pasta in a colander describes how sand behaves during hydraulic fracturing operations. Sand and frac water are pumped down a wellbore under pressure and out through perforations or pre-drilled holes in the pipe. After the formation accepts the fluids, some frac water flows back to the surface and the sand grains stay behind in tiny fractures as proppant. The frac sand stops! Hopefully, hydrocarbon production will soon follow.
During the past 60 years, billions of pounds of frac sand have been used to augment oil and gas production, creating even more businesses that service the petroleum industry with valuable products and employment opportunities. Numerous companies are involved, mining or transporting sand to the wellsites where it is needed.
Quarries and mines
Hydraulic fracturing (also called hydrofracking or fracking) has become one of the major topics of conversation of the mainstream media since the popular shale plays have come into the limelight. This is especially true near populated areas, where oil and gas activity is new, or where various groups and governmental agencies are monitoring frac water content, use and disposal.
Since the late 1940s, more than one million oil and gas wells in this country have been safely completed, using various hydrofracturing techniques. Normally each frac job requires a lot of sand — from a few tons to more than two million pounds for a multi-stage completion. So there is a healthy market for the tiny grains of quartz or silica that have such a big, supporting role.
The American Petroleum Institute (API) sets frac sand specifications. These consider the physical properties of the sand, such as grain size, sphericity and roundness, crush resistance and other factors. The most widely used frac sands fall in the 20 to 40 mesh size, or about 0.42 millimeter (mm) to 0.84 mm in diameter. They also include sands made up of 99 percent quartz or silica, and this includes sands that have been washed or scrubbed to remove silt and clay size particles, carbonate cement, iron coatings and other minerals.
A fact sheet from the API further describes the connection with hydraulic fracturing, a technology that “makes it possible to produce oil and gas in places where conventional technologies are ineffective. It uses water pressure, under tight controls, to create fractures in rock that allow the oil and natural gas it contains to escape and flow out of a well. Hydraulic fracturing is well regulated and safe and has a proven track record. Even though America has abundant natural gas resources, most cannot be produced without this technology. Studies estimate that up to 80 percent of natural gas wells drilled in the next decade will require hydraulic fracturing.”
Too bad sand is not an energy source! According to U.S. Geological Survey (USGS), America is the world’s leading producer of industrial sand and gravel, which includes sand for hydraulic fracturing. In 2009, American mines, quarries and sand pits produced more than 27 million metric tons of industrial sand and gravel, the USGS reported. An estimated 10 percent of this was mined for frac sand, although not every mine identifies it as such. Some mines also wash and process silica sand for well-packing for water wells, glass making, filtration and other purposes.
Over the years, numerous sand deposits across the country have been mined for pure silica sand. This includes formations such as the Berea (from Ohio), Clinch (Virginia), Oriskany (Pennsylvania and West Virginia) and the Sylvania (Michigan). But these are not ideal frac sands under API guidelines.
The most popular sands for fracturing are found in the mid-section of the nation, and are derived from older Ordovician and Cambrian units. It’s as if geologic time has aided in the removal of impurities and weak grains from these sands, or reworked them into a more rounded structure.
The best frac sands are derived from the St. Peter and Jordan formations in Minnesota, Missouri, Wisconsin and Illinois, the Oil Creek formation in Oklahoma, and the Hickory and Riley sandstones in Texas. Consequently, the major frac sand producing mines and quarries are in these states too. Some refer to the Jordon or St. Peter sands as the “Northern White” or “Ottawa sands,” a reference to the main, St. Peter sand producing area near Ottawa, Illinois that has quarried sand for more than 100 years.
Most sand mines are open pit quarries. The loosely cemented, somewhat friable sand is normally removed by large excavators or power shovels, transported by trucks or conveyor belts to processing plants where it is screened, washed and/or dried for eventually transport to market by railroad, barge or truck. At the wellsite, sand trucks arrive with their loads, typically consisting of about 50,000 pounds or 25 tons of sand, ready to unload for a completion treatment. Since many hydraulic fracturing treatments require more than one truck load of sand, these sand trucks are a familiar site at most shale well completions.
The following companies include some of the biggest players in frac sand mining and processing: Texas Silica in Brady, Texas; Preferred Sands, LLC, in Radnor, Pennsylvania; Unimin Corporation in New Caanan, Connecticut; and U.S. Silica, headquartered in Frederick, Maryland.
Company literature from Texas Silica states its frac sand comes from open pit mining sources near Brady and Voca, Texas. The company specializes is sourcing “high quality, API RP 56 compliant silica sand proppant for the oil and gas services industry” and also offers “logistical solutions for bringing frac sand to storage facilities, shipping ports and wellsites.”
During a frac job, a horizontally drilled shale well with a potential pay zone a few thousand feet in length can take in a lot more sand than a vertical well with a productive zone only a few feet, or even a few hundred feet thick. Actually, the true, vertical pay thickness would be the same in any given area. But stretching out a lateral well through the sweet spots provides more areas to complete. Most operators would like a shale zone to be at least a couple of hundred feet in thickness since the drill bit falls some by the time it reaches measured total depth. The bottom of the well, the end of the hole, can be a few thousand feet away, laterally, from the original, vertically drilled starting point. That’s why a lateral well can take in more sand.
To feed the need, new sand mines are opening or being planned in many areas. Yes, some are even calling it a bona fide “sand boom!” Not as romantic as a silver or gold rush, but a boom to some nevertheless. Naturally, some people are fighting against new sand mines in their respective areas. For example, in southeastern Minnesota and western Wisconsin some town hall meetings have been scheduled not to discuss the 2012 presidential candidates but new sand quarrying operations in their local communities. In this regard, the meetings are similar to ones held in the past regarding hydraulic fracturing in new prospective shale producing regions, such as those associated with the Marcellus Shale in upstate New York and Pennsylvania, the Bakken Shale in North Dakota, and in Barnett and Eagle Ford areas in Texas.
“The issue of frac sand mining is one of the most dangerous and hazardous components of the hydraulic fracturing process,” one opponent warned. “People living in or near areas where a frac sand mining operation is taking place should be aware of the risks to health and safety it poses, as well as to the natural environment.”
Some legitimate complaints about truck traffic, road repair, dust and noise reduction, water usage and the aesthetics of sand mining operations have been addressed by sand quarrymen and trucking companies. They also point out that each new sand mine may create up to 50 new full-time jobs, generate new work for local trucking and construction contractors, increase local and state tax revenue, and support for local businesses. It really can be an economic boom to a rural community.
Anyone who has ever participated in or watched a multi-stage fracturing completion knows what a highly choreographed performance it really is. It is truly a petroleum engineering work of wonder and awe. Dozens of vehicles at the surface, unloading and mixing thousands of gallons of fracking solutions and thousands of pounds of sand, then pumping them thousands of feet through cemented steel pipe. Thousands of gallons, thousands of pounds, thousands of feet!
The results from hydraulic fracturing are impressive too! During the past 60 years, this technology has helped produce more than 7 billion barrels of oil and 600 trillion cubic feet of natural gas in the USA, according to the API. Just think of all this life-sustaining energy! Natural gas for heat, cooking, hot water and electricity. Liquid fuel for transportation, food production, medicine. Freedom to travel and a high standard of living. Sustainability? Nothing sustains American life better than crude oil and natural gas! It’s good to know how some tiny grains of sand contribute to the program.