Throughout the United States, hundreds of companies work every day to discover and develop onshore oil and natural gas fields. Thousands more drill deep into the earth to bring water to the surface for commercial, industrial and residential use. Some of these firms are just a few employees in size, while others are among the nation’s largest corporations, with thousands of employees and tens of thousands of wells. Common to all of them is the need to cleanly and efficiently manage the spent drilling mud that is a necessary by-product of their work.
Drillers—whether producing oil, natural gas or water—use a fluid containing bentonite clay to lubricate drill bits as they cut boreholes through soil, sand and rock. The lubricant is pumped into the well, and as drilling takes place, the used (“spent”) mud is circulated out of the bore hole to a holding tank, cellar or open reserve pit near the well. The contents of the spent drilling mud depend on the formation being drilled, the type of drilling being done and the compounds used in the well bore. However, it often consists of drilling water, mineral oil or diesel; accumulated storm and wash water; bentonite clay; weighting agents and other chemicals; plus well cuttings such as pulverized stone, sand, sediment, coral and other gritty substances.
Spent drilling mud is a heavy slurry that is often left in the reserve pits for emergency reuse or to settle out and dry. After evaporation, the solids are encapsulated within synthetic liners in the reserve pits or carried away for treatment, disposal or recycling. According to the American Petroleum Institute, about 1.2 barrels of drilling waste is produced for every foot of well depth drilled; the U.S. Fish and Wildlife Service estimates that about 402 million barrels of drilling waste were produced in 2008. The size of the reserve pits can range from a small tank to more than a half-acre containing 15,000 or more barrels of spent mud. Under extremely tough conditions, the used drilling mud must be pumped into and out of the reserve pits.
Until recently, drilling rig operators had typically used cast-iron wastewater submersible pumps to move the spent drilling mud in and out of the reserve pits—but with very high failure rates. Because of the weight and high solids content of the mud, pumps often ran dry or against closed discharges. Shafts and impeller bolts broke, impeller keyways loosened and seals failed. Across the country, including at many of the shale gas plays in Oklahoma and North Texas, operators and drilling-equipment rental companies have replaced their wastewater pumps with KZN Heavy Duty Submersible Slurry Pumps from BJM Pumps. Because these are top-discharge pumps, the KZNs are more forgiving of low fluid-level conditions. They also have agitators to fluidize settled solids back into slurry for efficient pumping.
Because key components of the KZNs—including the impeller, wear plate and agitator—are made of high-chrome iron to withstand abrasion and the bearings are both tough and oversized, these pumps are performing better and lasting far longer than their standard wastewater predecessors in the harsh oilfield environment. The Oklahoma site pictured uses a 7.5-horsepower KZN55 pump. It has run reliably for 24 hours a day, seven days a week for more than a month a time—even while running dry regularly. Of approximately 80 pumps that BJM sold through its Oklahoma distributor in 2007, very few have had problems, most requiring only replacement power cords, worn from the constant movement of the pumps from one location to another.