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Hydraulic Fracturing

Safely Unlocking the Potential of Shale
Hydraulic fracturing involves pumping a mixture of mostly water and sand, with a small amount of additives (disclosed in FracFocus), into the reservoir under high pressure to create fractures, or cracks, in the target rock formation. This increases the production rate and ultimate recovery of oil and natural gas from a well.

Coupled with advanced horizontal drilling, hydraulic fracturing makes it possible to develop shale plays that were previously uneconomic. These technologies have unlocked oil and gas deposits for Marathon Oil in the South Texas Eagle Ford shale, North Dakota Bakken shale, Oklahoma STACK and SCOOP, and New Mexico Delaware Basin.

We take steps to minimize the impacts by:

  • Ensuring well integrity
  • Conserving fresh water
  • Reducing air emissions from flaring and other sources
  • Managing waste responsibly

Well Integrity

To protect well integrity, Marathon Oil follows industry best practices, internal procedures and applicable laws and regulations for proper well construction. This includes selecting the appropriate materials of construction, testing and monitoring of hydraulic fracturing during production operations.

Pre-Drilling Evaluation

Marathon Oil’s Environmental Management Standard requires each business unit to develop a plan to conduct pre-drill sampling to evaluate the baseline quality of water sources located within a quarter mile of drill sites. Water sources are tested for common, naturally occurring components and other parameters that can be found in hydraulic fracturing fluids or produced water. Groundwater wells are resampled if there are any indications that a casing integrity issue may exist.

To protect groundwater, we use steel casing and cement in the wellbore as physical barriers. Our suppliers’ tubular materials must meet API specifications and our own expectations for manufacturing, as well as the chemistry quality of steel for casing and tubing. If our pre-drilling evaluation indicates potential for hydrogen sulfide, we select tubing that meets the relevant ANSI/NACE sour service standards based on the region. This helps mitigate any material integrity corrosion issues.

Well Construction

During well construction, we apply industry best practices and comply with state rules for drilling and completions. These include pumping cement back to surface to ensure isolation and pressure testing the casing string on every well. We also perform pressure tests to determine the integrity of casing connections. Any casing left isolated is filled with packer fluid, a mixture of water, corrosion inhibitors and biocide, to mitigate corrosion.

Our onsite supervisors are certified in well control via industry developed, third-party classes. Regular drills and audits are required by the company to maintain preparedness on site.

Before we perform hydraulic fracturing operations, we identify potential fracturing corridors in relation to surrounding wells to detect any wells that need to be shut in or monitored for pressure communication during the operation.

Hydraulic Fracturing Operations

While hydraulic fracturing is under way, Marathon Oil operations control center staff create a dashboard using our telemetry system. The dashboard includes pressure alarms established for each individual monitor well based on our engineers’ criteria. These alarms notify the control center if hydraulic fracturing operations approach the maximum acceptable pressure or in the loss of pressure that could indicate a casing integrity issue. Our control centers operate around the clock to provide status updates of current operations and notify Marathon Oil staff if action is required.


During production, our operations personnel monitor casing via telemetry. Additional production safeguards include packer isolation and fluid, casing chemical treatments with corrosion inhibitor, and casing integrity testing such as caliper logs and pressure testing. Known production casing integrity repairs are documented in our central well history repository for knowledge management.


To protect surface and groundwater resources and natural habitat, we have procedures that help us manage and dispose of our produced fluid waste in accordance with all federal, state and local regulations. Oilfield produced fluids are stored in tanks, which have secondary containment to mitigate the risk of spills to the environment. We utilize electronic and physical means for monitoring recovered and stored fluids.

See the Materials Management section for waste handling utilizing third parties. Marathon Oil uses SCADA (supervisory control and data acquisition) systems to monitor and operate company-owned disposal facilities. These facilities are located in the Eagle Ford and Bakken assets. Injection pressure and rate is continually monitored and regular casing integrity verification is performed in accordance with state and/or federal regulations or if there are indicators a more frequent check is advisable.

Marathon Oil supports state-level disclosure of fracturing fluid components. We worked with other operators and trade organizations to implement FracFocus, a voluntary online chemical registry for hydraulically fractured wells. We have logged all our wells drilled and hydraulically fractured in the U.S. in FracFocus, a total of approximately 3,500 wells through December 2020. Our contracts routinely require our service companies to disclose their fracturing components to FracFocus, but we can’t contractually require a service company to disclose constituents that are protected by trade secret laws.

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