A comprehensive environmental analysis (EA) of 23 offshore oil and gas platforms operating on the US Outer Continental Shelf off Southern California found no significant impact from the use of well stimulation treatments (WST) there, the US Bureau of Safety and Environmental Enforcement and the Bureau of Ocean Energy Management jointly reported.
The evaluated treatments included fracturing and nonfracturing treatments, which may be used to enhance production from existing or new wells where formation permeability and falling reservoir pressure are limiting oil recovery, according to the Programmatic Environmental Analysis prepared by Argonne National Laboratories.
Four WSTs were evaluated:
• Diagnostic fracture injection test (DFIT), which is used to estimate key reservoir properties and parameters that are needed to optimize a main fracture job.
• Hydraulic fracturing, which involves injection of fracing fluid at a pressure (typically determined by a DFIT) necessary to induce fractures within the producing formation.
• Acid fracturing, which is similar to hydraulic fracturing except that instead of using a proppant to keep fractures open, an acid solution is used to etch channels in the rock walls of the fractures, thereby creating pathways for oil and gas to flow to the well.
• Matrix acidizing, a nonfracing treatment in which an acid solution injected into a formation where it penetrates pores in the rock to dissolve sediments and muds, opening existing channels to allow formation fluids (oil, gas, and water) to move more freely to the well. Matrix acidizing also removes formation damage around a wellbore, which also aids oil flow into the well, the programmatic EA said.
The two US Department of the Interior agencies conducted the EA under settlement agreements regarding their compliance with the National Environmental Policy Act, Outer Continental Shelf Lands Act, and Coastal Zone Management Act. Pending completion of the EA, BSEE agreed to withhold approvals of future drilling permits and permits to modify WSTs involving hydraulic fracturing and other well stimulation treatments on the OCS off Southern California.
Under the agreements, BSEE agreed to develop a mechanism to increase transparency in the permit approval process, as well as a method to alert the public of newly submitted complete permit applications for hydraulic fracturing or acid well stimulation. The programmatic EA will provide the agency’s Pacific Region with valuable information as it considers future WST applications, it said.
In their Finding of No Significant Impact concerning their proposal to allow WSTs to be used on the OCS off Southern California, the agencies said that potential adverse impact appeared insignificant. “In some cases where impacts are somewhat more pronounced, such as with discharge of produced water, the impacts are minor, short-term and localized,” they added.
BSEE and BOEM also considered:
• The degree to which the proposed action could affect public health and safety.
• Unique characteristics of the geographic area such as proximity to historic or cultural resources, park lands, prime farmlands, wetlands, wild and scenic rivers, or ecologically critical areas.
• The degree to which the effects on the quality of the human environment are likely to be highly controversial.
• Whether possible effects on the human environment are highly uncertain or involve unique or unknown risks.
• Whether allowing use of these WSTs would establish a precedent for using others or represents a decision about a future consideration.
• Whether the action is related to other actions with individually insignificant but cumulatively significant impacts.
• The extent to which districts, sites, highways, structures, or objects listed in or eligible for listing in the National Register of Historic Places may be affected, or significant scientific, cultural, or historical resources may be lost or destroyed.
• The degree to which the action may adversely affect an endangered or threatened species or its habitat that has been determined to be critical under the 1973 Endangered Species Act.
• Whether the action potentially violates federal, state, or local environmental protection laws and requirements.
BSEE and BOEM said they received more than 10,000 comments on the draft assessment during the 30-day public comment period that ended on Mar. 23. After reviewing those comments, the bureaus revised the final programmatic EA’s text where appropriate, including amending the statement of purpose and need, clarifying the descriptions of alternatives, and adding information on greenhouse gases and climate change.
The evaluated offshore resource area environmental impacts included water quality changes from discharges of produced water, and the potential for associated impacts to fish and wildlife, they indicated.
Considering the low expected concentrations of well stimulation treatment chemicals and the protective nature of the EPA’s National Pollutant Discharge Elimination System General Permit and required monitoring of aquatic life, the analysis in the EA affirms that wastewater discharges from proposed well stimulation activities will not have a significant impact on the environment, BSEE and BOEM said.
Accidental releases of well stimulation treatment fluids have a relatively higher potential to have consequence, but the probability of an accident occurring and the reasonably foreseeable size of a resulting release are so small that such accidents would not be expected to cause a significant impact, they added.
Responding to the agencies’ announcement, National Ocean Industries Association Pres. Randall B. Luthi said it confirms what the offshore oil and gas industry already knows—that there are no significant impacts from offshore well stimulation treatments.
“We hope this report quickly ends the moratorium on well stimulation techniques offshore California,” he said. “The sooner operations can resume [there], the better.”
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