Oil and gas fields in Utah do not just produce oil and gas. Pores in the reservoir rocks that contain oil and gas also contain water. This water has resided in the rocks for thousands and perhaps millions of years. Over time, the water naturally dissolves minerals in the surrounding rock, adding chemical constituents such as chlorides or bicarbonate to the water, which is produced along with the oil and gas. The hydrocarbon production generates saline (briny) non-potable water that requires disposal.
Disposal of Produced Water
The environmentally sound disposal of produced water affects the economics of hydrocarbon resource development. Thus, there is an economic incentive to minimize the amount of water produced and/or generate revenue by treating and reusing produced water, particularly in arid regions of the western U.S. Specific Uinta Basin water issues include water use/reuse for well drilling and completion (e.g., hydraulic fracturing), appropriate sites for disposal/reuse of water, development of systems to manage the produced water streams, and differing challenges for gas versus oil producers.
Injection is the preferred method of disposal over evaporation ponds. Injection of high volumes of produced water near fault zones is known to cause significant earthquakes in Oklahoma and other states. However, no such seismic events have been recorded in Utah from water injection because the aquifers are low pressure and faulting in the areas is limited; most injection sites are remote and away from populated areas.
Large volumes of produced saline water are typically disposed of by several techniques:
- Hydraulic Fracturing3%Recycling produced water to be used for hydraulic fracturing is an effective way to reuse the non-potable water.
- Evaporation Ponds11%The produced water is hauled from the well site to specially designed, lined storage ponds where it evaporates. Approximately 8 percent of the water evaporates from these ponds, allowing continued delivery of new water annually.
- Waterfloods18%Produced water serves half the need for waterflooding projects that help produce more oil or gas from a field.
- Injection60%Produced water can be injected via wells to a sufficient depth in porous rock as to not cause contamination of shallow freshwater aquifers.