Oil & Natural Gas Projects
Exploration and Production Technologies
Modeling of Water-Soluble Organic Content in Produced Water
This project was funded through DOE's Natural Gas and Oil Technology Partnership
Program. The program establishes alliances that combine the resources and experience
of the nation's petroleum industry with the capabilities of the national laboratories
to expedite research, development, and demonstration of advanced technologies
for improved natural gas and oil recovery.
The objective of this project is to develop a model that will allow the prediction
of the production of water-soluble organics as a function of measurable parameters,
such as crude composition, formation characteristics, and produced-water composition.
Oak Ridge National Laboratory (ORNL)
Oak Ridge, TN
The project has provided a computational tool based on analysis and modeling
of oil/brine samples, to be used to predict the water-soluble organic content
in brines associated with deep-well oil production. ORNL has summarized and
published results of the Petroleum Environmental Research Foundation collaboration
that led to the study of water solubles in produced water.
The computational model could be used prior to production from new facilities
to assist in the development of a more selective and focused approach to produced
water cleanup, leading to cost savings and reduced environmental impact.
Large amounts of brine are often associated with oil and gas production. Because
these produced waters are in contact with oil at high pressures, they can become
contaminated with water-soluble organic compounds. The discharge of produced
water in the Gulf of Mexico is regulated by NPDES (National Pollutant Discharge
Elimination System) permits, which specify that total oil and grease in the
water be below a daily maximum of 42 ppm. Analysis of the produced water for
total petroleum hydrocarbons by Environmental Protection Agency methods 413.1
or 1664, however, does not distinguish between carboxylic acids/other polar
compounds and more environmentally harmful hydrocarbons. Hence, remediation
of a billion barrels of produced water per annum in the United States is based
on aqueous organic concentrations that exceed the actual content of oil and
grease. The goal of the project is to provide a computational tool, based on
analysis and modeling of oil/brine samples, to predict the water-soluble organic
content in brines associated with deep-well oil production. Such a model could
be used prior to production from new facilities to assist in the development
of a more selective and focused approach to produced water clean-up, lending
to cost savings and reduced environmental impact.
The type and amount of organics that are soluble in produced water is not well
understood, leading to inefficiencies in produced water clean-up prior to its
discharge into the ocean. Industry participants and ORNL embarked on a study
of organic solubility in produced water, including characterization of the organic
component in produced water and modeling of its solubility. The characterization
of the produced water is complete and shows that the water-soluble component
is primarily polar with a discernible trend in increased solubility with increasing
To model aqueous-hydrocarbon systems, ORNL successfully used a simple liquid-liquid
equilibrium model to fit the pH-dependence data that were generated in a crude-oil/simulated
brine system. The model incorporates the acidity of the polar components. Results
of calculations agree with the trend seen in the experimental results, where
methylene-chloride extractable range material (particularly C10-C20) becomes
more soluble as the pH increases beyond 7. This is because of increased deprotonation
in the basic aqueous phase.
The advantage of a thermodynamic equilibrium model is that changing conditions,
such as temperature dependence and salinity, can be incorporated into the expressions
for the activity coefficients. Volatile components and the dependence of solubility
on pressure can be introduced with an additional gaseous phase, represented
by an equation of state.
Current Status (October 2005)
The project is in its final year.
Project Start: March 28, 2002
Project End: December 21, 2005
Anticipated DOE Contribution: $500,000
Performer Contribution: $50,000 (9 % of total)
NETL - Jesse Garcia (firstname.lastname@example.org or 918-699-2036)
ORNL - Joanna McFarlane (email@example.com or 865-574-4941)