A clean operationMarch 9th, 2012 | Posted by in TH60
A water well driller may encounter customers concerned about well contaminants, but nothing like Peterson Drilling and Testing’s customers. The company specializes in drilling environmental wells at contaminated sites. Sites include petroleum production, refining, distribution and industrial and commercial sites.
All types of contaminants are encountered on different sites. Peterson Drilling serves clients in Texas, New Mexico, Oklahoma and Kansas.
How many drillers would think about putting on latex gloves when handling cuttings? Or capturing the first water and all the cuttings from a 400-foot (122 meter) well? Both are common practices for Peterson’s crew. Not all the time, of course, but when it could mean protecting all the fluids, everything is important. The general rule on all jobs is to “keep it clean,” said Drilling Superintendent Roy Wedell.
Peterson Drilling operates multiple drills in its environmental drilling business. Most of the work is done with a newer Atlas Copco TH60, but the company also operates a Classic model TH60 and auger drills.
Environmental wells for Peterson include recovery wells, injection wells and monitoring wells, but the practice is similar in each case. Peterson’s crew captures all the cuttings and occasionally the fluids recovered from the well while drilling. They use roll-off containers or a vacuum truck to capture cuttings that their customers use for various types of testing.
Wells range from 100 to 450 feet (30.5 to 137 meters) in depth with the deepest that Wedell can remember being 540 feet (165 meters). They are generally 6-inch (152 millimeters) wells but can go up to 16 inches (406 millimeters) in diameter.
The company even owns its own cement mixing truck to make concrete. Often it’s required to pour a pad around the well head to provide a surface seal to protect the well from surface contamination as well as protect it from physical damage. The cement truck is also used to make cement slurry to provide an annular seal above the bentonite plug.
The bentonite plug serves as a buffer between the filter pack and cement seal. When backfilling a well, most drillers use various aggregates required for proper water flow. Peterson orders washed silica sand by the pallet that will be used for packing their wells. “The slot size needed on the casing can be .010 to .020 to keep out natural fines,” said Wedell. In some instances larger slot sizes are used, depending on the formation.
The casing is not your normal PVC either. Because bonding agents like PVC cement contain contaminants that may be detected in the monitoring process, the company uses threaded casing and no glue in the casing connection.
At times it is necessary to monitor various aquifers within the same boring. We protect the aquifers from cross contamination by drilling a large diameter hole and cementing the casing in place in the upper aquifer. A smaller diameter hole is then drilled through the larger casing and a smaller diameter well is installed in the lower aquifer. Samples can then be taken from the lower aquifer without cross contamination, said Wedell.
The company’s new TH60 works well for Wedell because he says it’s user friendly with comfortable controls. “It just makes more sense how things like the winch controls are positioned,” he said. He also thinks the full-speed hydraulics at idle are a benefit because they save fuel, while allowing full function.
The jib’s boom swings and operates faster than his last TH60. He also said maintenance is easier than his previous rig. “I will let you know in the future, but right now not having to grease the sheaves because they are sealed is much better,” Wedell said.
Peterson Drilling Vice President Lee Peterson is open about sharing his company’s knowledge about environmental well development. “Everything we do is out there; there are no secrets,” he said. The company has become an expert at what they do because they have the equipment to get the job done and be successful, Atlas Copco is happy to be part of that fleet.