ExxonMobil works to manage our water use and to limit adverse impacts to water resources and consumers from our withdrawals and discharges, taking into consideration factors such as quality and availability.
Using the latest version of the oil and gas industry association for environmental and social issues (IPIECA) global water tool, we identified that almost 35 percent of our major operating sites are located in areas with the potential for water scarcity. We pursue opportunities to reduce our water use and develop site-specific management strategies such as the deployment of water conservation technologies, the use of alternative freshwater sources, recycling of municipal and industrial wastewater, substitution with lower-quality water sources and harvesting of rainwater.
Water management is an important aspect of hydraulic fracturing operations. Water use by basin differs due to geologic and reservoir characteristics and optimization of drilling and completion designs. For example, a Williston Basin well in North Dakota requires 6 million gallons for hydraulic fracturing, whereas a Permian Basin well in western Texas requires 15 million gallons of water.
ExxonMobil seeks to continuously improve the development and implementation of water management strategies. Part of this effort involves improving our understanding of not only the quantity of our water consumption, but also when and where this consumption occurs.
Performance and initiatives
In 2016, the net freshwater consumption at our operations was 290 million cubic meters, a decrease of more than 3 percent from the 2015 consumption of 300 million cubic meters and a more than 9 percent decline since 2007.
When the Banyu Urip, Indonesia, operations required increased injection water volumes to maintain adequate reservoir pressure, we developed a large reservoir to capture and store excess water available in the wet season that would have otherwise not been used. Using the reservoir helped mitigate potential effects of our water usage on the local population during the drier months when water resources are scarcer.
Produced water, which results from upstream oil and gas operations, is typically managed onshore by injection into deep underground reservoirs. For offshore production facilities, produced water is managed by re-injection into an associated reservoir or by treatment and discharge into the marine environment in accordance with applicable regulatory requirements.
For our Upstream projects, our Water Management Standard outlines minimum expected environmental performance and mitigation measures. This Standard establishes the planning and design basis for reducing impacts to surface waters, ground waters, estuarine and marine waters as well as to the associated habitats and users, from a use or consumption viewpoint as well as with regard to discharge quality.
Performance and initiatives
Up Close: Advancing the use of engineered wetlands to treat industrial wastewater
Over the past five years, ExxonMobil Research Qatar (EMRQ) has conducted extensive research to understand the feasibility of utilizing engineered wetlands to treat industrial wastewater for beneficial reuse in arid environments. Water quality characterization, influent and effluent water management and system maintenance are just a few of the important factors that need to be considered when designing such a system. In 2016, EMRQ commissioned a microbiology laboratory to study the functions and structure of microbial communities in wetlands to optimize wetland water treatment systems. EMRQ then completed a design for an experimental wetland to study the treatment of gas field-produced water to better understand the feasibility of using such systems for large-scale applications.
The topic of induced seismicity continues to generate attention. In some instances, due to unique geologic conditions, oil and gas operations may trigger seismic activity. Such operations may include reservoir depletion, wastewater disposal injection and, in rare situations, hydraulic fracturing.
We support risk management and mitigation approaches to seismicity that take into consideration the relative risks associated with the specific context and geography of the proposed operation. Mitigation methods include assessing factors such as fluid volume, formation character, tectonic setting, operating experience and local construction standards. At XTO Energy, a subsidiary of ExxonMobil, we follow a disciplined injection well siting protocol prior to siting a disposal well using available data — including federal, state or internal seismic information — to conduct a risk assessment.
Performance and initiatives
ExxonMobil Upstream Research Company continues to advance the science of induced seismicity, risk assessment and mitigation. Our multi-disciplinary team integrates subsurface engineering, geophysics, geology, structural engineering and data analytics to understand the types, sources and potential hazards of seismicity. Such advances enable us to integrate reservoir, geomechanics and probabilistic models resulting in an improved risk assessment of potential fault slippage due to saltwater disposal operations. In order to improve the risk management of induced seismicity, we share our knowledge and advanced approaches with academic and government researchers and regulatory agencies.
ExxonMobil and Stanford University jointly developed a freely available software modeling tool assessing the potential risk of induced seismicity from industry saltwater disposal wells. Using data such as underground stress levels and reservoir parameters, the tool evaluates the potential for fault slip near disposal well locations. The tool is being used by regulatory agencies and energy companies to reduce the risk of induced earthquakes.
The issue of oil and gas operations and seismicity is a matter of public interest. No matter the cause — natural or human activity induced — local communities have concerns about seismic activity in their area. For example, in response to communities in The Netherlands, Nederlandse Aardolie Maatschappij, a joint venture field operating company in which ExxonMobil participates, developed a risk assessment framework using the rigorous standards set by the earthquake engineering community for tectonic earthquakes. This resulting risk assessment has been reviewed by external experts and supporting documents were made publicly available. The framework is regularly evaluated and updated in response to new data and scientific studies to ensure that it is based on the latest, most advanced research. Our approach to transparent risk management helps provide the government with a scientific basis for balancing the concerns of the community with the energy needs of The Netherlands and neighboring countries.