U.S.-derived fossil fuels are known as the “cleanest” in the world! If everybody drove an electric car, we could achieve zero emissions! Can both statements be true or are we cherry-picking the facts?
For fossil fuels, the waste stream from drilling operations is known as “exploration and production” (or E&P) waste. E&P wastes are derived from spent drilling mud, rock fragments (“cuttings”), and fluids generated from underground materials that come to the surface during drilling operations. These wastes may sometimes contain environmentally unfriendly contaminants and trace metals. Appropriate management of the wastes in environmentally sensitive areas, such as the North Slope of Alaska, requires newer techniques and technologies. These new measures have changed the way the oil and gas industry manages E&P wastes to reduce long-term risks to the environment.
The North Slope of Alaska holds vast proven reserves of oil and gas in five large oil fields, including Prudhoe Bay – the largest oil field in North America, encompassing 5,000 acres. E&P operations on the North Slope commenced in the 1950s. Operators historically managed wastes by constructing rectangular gravel berm-enclosed pits on top of the frozen tundra and adjacent to each well site to discard cuttings, mud, solids, and drilling fluids.
Environmental Liability
By 1980, hundreds of reserve pits, several acres in size, dotted the Alaska landscape – making them not only eyesores, but also a risk of melting the underlying permafrost and causing releases to the surrounding soils, groundwater, and surface waters. Permafrost, or ground that is permanently frozen, is a vital component to the North Slope ecosystem. Raising the temperature of permafrost through operation of E&P waste pits can mobilize contaminants and cause erosion, as well as release bound-up carbon and organic materials through greenhouse gases.
A study conducted by the U.S. Environmental Protection Agency (EPA) of reserve pits and nearby pond areas revealed an increase in concentrations of petroleum hydrocarbons, salts, and other contaminants from samples collected in ponds downgradient of reserve pits. Concentrations of petroleum hydrocarbons, barium, chloride, potassium, chromium, copper, iron, nickel, lead, and selenium have been reported. Moreover, wildlife studies conducted by the Arctic National Wildlife Refuge determined that macro-invertebrates in tundra ponds, an important food source for birds, were becoming depleted.
Several petroleum companies operating on the North Slope began putting their general liability insurers on notice, as more data from studies pointed to potential pollution damages to the environment coming from the reserve pits. At about the same time, the Alaska Department of Environmental Conservation (ADEC) began exploring options and new regulations. Insurance carriers argued that the insured needed to demonstrate that a release of contamination occurred from the reserve pits and that a directive for cleanup was required by the ADEC. Otherwise, the carriers’ position indicated that the removal of the wastes in the reserve pits would be considered a deferred cost-of-doing-business expense that should be borne by the insured directly as part of their ongoing operation and maintenance costs.
Closure Solutions
By the mid-1990s, it became increasingly clear that the ADEC would require a new method of disposal of drilling wastes and that traditional reserve pits posed many potential long-term environmental liabilities.
ADEC instituted a new closure standard – Alaska Administrative Code 18, Chapter 60, Section 440 (18 AAC 60) – that required reserve pits to be capped. The closure process involved excavation of the reserve pits below the drilling waste/tundra interface, collection of closure and surface water samples, and return of the reserve pit landscape to original pre-drill conditions.
A settlement agreement was reached between ARCO and the National Resources Defense Council (NRDC) which directed ARCO to use an alternative disposal method, known as the “grind-and-inject” (G&I) method to dispose of fluids underground at a new G&I plant facility.
Alternative Cleanup Solutions
G&I alternative disposal methods were derived from down-hole disposal methods used in the 1940s that were first used to inject water produced from oil and gas drilling into depleted wells. However, the down-hole method did not involve injecting solids. ARCO then borrowed several mining techniques to grind and pulverize suspended rock materials in the mud recirculation system to successfully demonstrate this method would work. The mud passed through shaker screens, desanders, and centrifuges at the surface to remove finer particles, so the slurry could be pumped into the formation without plugging the fine pores and permeable channels in the rock formation.
As the G&I method became the industry standard on the North Slope, it soon became practicable to excavate and haul the wastes from the reserve pits for disposal at the G&I plant, where it was made into slurry and injected into the subsurface via several injection wells.
Conclusion
To date, more than 2.5 million cubic yards of reserve pit material and over six hundred reserve pits have been closed in Alaska. The G&I process has helped eliminate reserve pits that once dotted the North Slope landscape – improving aesthetics, as well as removing potential sources of long-tail environmental liability. In addition, the permafrost, surface water quality, and wildlife habitats have been restored.
HETI…Here to Help
HETI staff continue to monitor E&P activities at drilling and petroleum operations in various states and stay informed of new regulations in the oil industry when dealing with E&P wastes. HETI’s extensive engineering and environmental experience enable us to assist our clients in understanding the risks and changing regulatory environment of E&P activities and technology.
References:
“Drilling fluids and the Arctic Tundra of Alaska: Assessing contamination of wetlands habitat and the toxicity to aquatic invertebrates and fish”; Woodward, D., E Snyder-Conn, R. Riley, and T. Garland; US Environmental Protection Agency EPA/600/J-88/246
“Oil Drilling in Alaska”; FEE Foundation for Economic Education; September 1, 1993; Sarah Anderson
18 Alaska Admin. Code 60.440 – Closure of inactive reserve pits; October 26, 2021
“30 Strong: The drilling waste dilemma”; Petroleum News; Volume 12, No. 41
“Site-Wide Project Work Plan-Part I; Part 2: Current Conditions Report Prudhoe Bay Facility, Alaska”; Oasis Environmental; January 28, 2008
“Effects of Prudhoe Bay Reserve Pit Fluids on Water Quality and Macroinvertebrates of Arctic Tundra Ponds in Alaska”; Yukon Flats National Wildlife Refuge and Fairbanks Fish and Wildlife Enhancement Office; September 1987
“Oil Development Damages Air, Water, and Wildlife”; the Arctic National Wildlife Refuge
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