Hydraulic Fracturing


Technological developments and drilling productivity in oil and gas exploration and production are propelling U.S. production. The combination of advanced geosciences, reservoir modeling, hydraulic fracturing and horizontal drilling have been instrumental in increasing the efficient production of oil and gas reservoirs both in mature fields and in areas not previously produced. Hydraulic fracturing is one of many techniques Occidental uses to maximize production in certain fields. Hydraulic fracturing is effective in stimulating the flow of hydrocarbons embedded in tight rock formations. These formations contain oil and gas in small pore spaces, and the creation of hairline fractures through the application of pressurized fluids, allows hydrocarbons to flow more readily to the well.

Well Integrity and Testing

All wells are required by federal and state regulatory agencies to design casing and cementing plans to protect groundwater. Before drilling any well, Occidental conducts extensive geologic research to investigate the depth and lateral extent of any fresh groundwater regime to ensure its protection. We apply applicable American Petroleum Institute (API) specifications and comply with all required regulations. Agencies then review and approve all plans and casing designs.

Occidental selects well completion or stimulation techniques, including for hydraulic fracturing, based on the characteristics of the reservoir rock. Occidental's first priority is to maintain asset integrity at both surface facilities and wells. We employ rigorous, industry-proven specifications to test the casings of both vertical and horizontal oil and gas wells. The testing of well integrity and safety involve multiple phases throughout the lifecycle of the well.

Well integrity and groundwater protection is provided with multiple layers of steel, cemented in place, which isolate the well from surrounding water-bearing zones.  Design variables include length, thickness, tensile strength and composition of the casing for a given reservoir and rock formation. The cementation of the casing and proper sealing of annular spaces creates a hydraulic barrier to both vertical and horizontal fluid migration, thus protecting water resources.  Two or more layers of casing are required in order to provide redundancy and protect water resources. Well casing design parameters are summarized below:

  • Surface casing reaches beyond fresh groundwater zones and are fully cemented —this isolates and creates a physical barrier between the materials in the well and any strata of freshwater zones, preventing a threat to freshwater bodies.

  • Inside the surface casing, a second casing is installed and cement is added between the casings. All cementing work is monitored. The volume of cement pumped and temperature are controlled and monitored to ensure the cement barrier is in-place to prevent any fluids migration.

  • At the production casing or the well completion stage, during which fracturing may be performed, Occidental installs production casing or strings (also known as a third casing) in the production zone.

Occidental verifies wellbore integrity by observing the cementing of the casing and through periodic pressure testing in strict accordance to industry specifications and state regulations. Tests include measurement of fluid volume, temperature surveys, cement bond logs, and casing evaluations. Finally, we develop a Risk Register – a comprehensive risk assessment of all major activities (drilling, well completion, hydraulic fracturing, etc.) for each and every basin project.  This process identifies and logs all environmental and site issues, and the mitigations designed to address them.

Hydraulic Fracturing Fluids

Hydraulic fracturing is carefully designed and implemented by specialized service companies with oversight by Occidental engineers to use only the amounts of water and additives necessary to stimulate the flow of oil and gas from the hydrocarbon-bearing zone into the oil and gas well. Hydraulic fracturing fluids comprise water, a proppant such as sand, and other chemical ingredients representing a very small percentage of the fluid's composition. Service companies have developed expertise in formulating hydraulic fracturing fluids with specific properties based on the subsurface geology in the oil and gas reservoir. As with all activities for which we retain contractors, Occidental carefully selects companies that have strong health, safety and environmental performance to conduct hydraulic fracturing in our operations.

Occidental is committed to conducting hydraulic fracturing in a manner that does not impact the environment or the communities in which we operate. It is Occidental's practice to avoid diesel fuels, including any of the following chemicals: benzene, toluene, xylene and ethylbenzene (collectively BTEX), in hydraulic fracturing treatments.* Throughout its operations, Occidental is increasing the rate of recycling and reuse of water, which decreases our freshwater withdrawals, but also the need for transportation and disposal of water.

Occidental is committed to public disclosure about its hydraulic fracturing operations. In 2011, Occidental was an early participant in FracFocus ®, a website created by the Ground Water Protection Council and the Interstate Oil and Gas Compact Commission to provide for well-specific voluntary disclosure of hydraulic fracturing operations, including the chemical ingredients used in fracturing fluids. In addition to providing a national registry, the website provides factual information about hydraulic fracturing and groundwater protection. While Occidental and its service companies may exclude certain fluid ingredients protected under terms of confidentiality, Occidental strives to reduce claims of confidentiality for hydraulic fracturing fluid ingredients. Occidental also maintains on-site Safety Data Sheets (SDS) for all of the chemicals and fracturing fluid additives it uses. Several states also use FracFocus® for regulatory disclosures. As a leading producer of oil and gas in the United States, Occidental remains at the forefront in disclosing hydraulic fracturing, including in jurisdictions where such disclosure is voluntary. Please refer to FracFocus.org if you would like to access the chemical registry or for more information about how hydraulic fracturing works, groundwater protection, chemical use and related regulations.

* In certain hydraulic fracturing fluid ingredients, BTEX components may be present in trace amounts.  In such cases, the BTEX components will be disclosed in accordance with FracFocus procedures.FracFocus may exclude chemicals protected by claims of protected / confidential information.

Hydraulic Fracturing Related Produced Water

The volumes and sources of water required by Occidental vary considerably by local basin, even from well to well. In all operations, Occidental strives to minimize the use of potable water sources and maximize the re-use of produced (waste) water. Occidental's water use per job in the Permian Basin averages 500,000 gallons. Occidental's commitment to using produced water from oil and gas reservoirs and other non-potable sources wherever feasible reduces our demand for freshwater. Produced (or flowback) water, along with varying volumes of drilling muds and fracturing fluids can be collected and reused in a closed loop system. Depending on the volume and chemical properties of the produced water, Occidental and its service companies employ a range of mitigation techniques to manage the potential environmental impacts of drilling materials and flowback fluids. Occidental works collaboratively with its service companies to improve drilling and production techniques to enhance the efficiency of water usage and to minimize the amount of chemicals required for hydraulic fracturing.  Several techniques include:

  • Re-use of drilling fluids to the maximum extent; Occidental avoids sending any wastewater to disposal

  • Drilling using closed loop systems in areas with high freshwater tables

  • Within our U.S. drilling operations, Oxy stores drilling muds, other (oily) residuals and flowback water in closed containment systems or tanks for on-site storage and eventual disposal.

Hydraulic Fracturing Technology and Communities of Practice

Hydraulic fracturing technology is a core activity that directly drives well productivity for both new and existing wells. Occidental aims to continuously improve its productivity and efficiency testing and using new hydraulic fracturing technologies. A real-time monitoring system was established to monitor fracturing operations in the Permian Basin. The system provides an understanding of fracturing concepts and an opportunity to improve design and completion processes while also contributing to the education of engineers assigned to the field.

"As our technical capabilities continue to grow, it will be more important than ever that we communicate and share learnings across the organization." - Harris Swartz, Vice President Worldwide Drilling and Completions

In an effort to improve communicating lessons learned and best practices, and to collaborate with other functions, Occidental established a Completions Performance Community of Practice (CoP). The CoP is a true multi-disciplined collaboration between employees based in Houston and those in the field offices. This new CoP is an example of Occidental exploring new technologies and industry best practices to empower its people, maximize the value of assets, and to establish a culture of innovation.