Oil & Natural Gas Projects
Exploration and Production Technologies
Wettability and Prediction of Oil Recovery from Reservoirs Developed with
Modern Drilling and Completion Fluids
The objectives of this project are to:
- Improve understanding of the wettability alteration of mixed-wet rocks that
results from contact with the components of synthetic oil-based mud (SBM) formulated
to meet the needs of arctic drilling.
- Investigate cleaning methods to reverse the wettability alteration of mixed-wet
cores caused by contact with these SBM components.
- Develop new approaches to restoration of wetting that will permit the use
of cores drilled with SBM formulations for valid studies of reservoir properties.
New Mexico Institute of Mining and Technology
University of Wyoming
In the course of this project, performers have studied the effects of SBM
surfactants on wetting in mixed-wet cores, identified a previously unrecognized
mechanism for wetting alteration due to asphaltene destabilization that can
occur when crude oil mixes with synthetic base oils, and developed a cleaning
procedure for use with contaminated cores.
In the Arctic, severe surface conditions combined with a fragile ecosystem
make advance planning of production facilities especially critical while limiting
the choices of fluids that can be used for drilling. SBMs muds now can be
formulated with low viscosities so that they can be used in arctic conditions,
but all oil-based muds adversely affect the wetting state of recovered cores.
Using outcrop rock and selected stock tank crude oils researchers have been
able to assess the affects of synthetic base oils and surface active additives
on wetting and to design a cleaning system that adequately reverses the effects
of oil-based drilling mud contamination, allowing wettability assessment of
the limited samples that would be available from an arctic drilling project
Wettability controls the rate and extent of fluid flow when two or more phases
are flowing in a reservoir. Correct assessment of reservoir wetting is an
important part of planning production facilities and strategies. However,
the uncontaminated core and oil that are required to perform wettability assessments
correctly are not available, especially when wells are drilled with oil-based
fluids. Nevertheless, traditional and synthetic oil-based drilling fluids
are increasingly chosen, necessitating improved methods of identifying contamination,
assessing its effects, and, if possible, cleaning samples for further study.
In this project, researchers have addressed the issues associated with the
various components of SBM of the sort most likely to be selected for arctic
Project researchers have:
- Developed interfacial tension, contact angle, and atomic force microscopy
(AFM) methods for studying complex interactions among crude oils, SBM base oils,
SBM surfactants, and mineral surfaces.
- Investigated effects of crude oils, SBM base oils, and SBM surfactants on
wetting of mixed-wet sandstone cores.
- Demonstrated that SBM base oils can destabilize asphaltenes and alter wetting
by surface precipitation.
- Developed a cleaning procedure that adequately removes contaminants from cores
acquired during drilling/coring projects that use SBM drilling fluids, allowing
wettability testing of contaminated samples.
Two main approaches to wettability testing were combined in this work: surface
tests of mineral wetting and core wettability tests of the rate of imbibition.
Parallel tests of similarly treated surfaces and cores can help to differentiate
between effects that are correctly ascribed to wettability alteration and
effects that may have other explanations. The project performers also chose
to examine the effects of some individual SBM components in order to demonstrate
the effects of surface active additives, such as emulsifiers, as well as the
effects of synthetic base oils that are not themselves surface-active but
affect wetting by changing the stability of asphaltenes.
Mixed wetting-with corners and smallest pores remaining water-wet and larger
pores that are exposed to oil becoming less water-wet or more oil-wet-is widely
regarded as a likely wetting scenario in oil reservoirs. The project performers
have focused attention on the effects of SBM components on the wetting of
surfaces after exposure to various crude oils and on the wetting of mixed-wet
cores. Initial experiments were designed to select a range of crude oils for
subsequent SBM tests. In most cases, treatments with emulsifiers made cores
less water-wet. Cores could also be made less water-wet by displacement of
asphaltic crude oils by paraffinic or olefinic synthetic base oils.
Finally, the researchers have designed and tested a cleaning regimen for removal
of SBM-related wetting damage that should allow the use of SBM-contaminated
cores in reservoir wettability tests.
Current Status (July 2006)
This project has been completed.
Project Start: October 1, 2001
Project End: September 30, 2005
Anticipated DOE Contribution: $850,000
Performer Contribution: $420,000 (33% of Total)
NETL - Rhonda Jacobs (email@example.com or 918-699-2037)
New Mexico - Jill Buckley (firstname.lastname@example.org, or 505-835-5405)
Final Report [PDF-1.36MB]
Seven semi-annual reports to DOE.
Bryant, E., Bowman, R.S., and Buckley, J.S., Wetting Alteration of Mica Surfaces
with Polyethoxylated Amine Surfactants, presented at the 8th International
Reservoir Wettability Symposium, May 16-18, 2004, Houston, TX (accepted for
publication in J. Pet. Sci. Eng., 2005).
Buckley, J.S., and Fan, T., Crude Oil/Brine Interfacial Tensions, paper SCA
2005-P017, presented at the 2005 SCA Symposium, Toronto, Canada, August 21-25.
Creek, J.L., Gonzalez, D., Wang, J.X., Muhammad, M., Chapman, W., Hirasaki,
G.J., and Buckley, J.S., Effect of Synthetic Oil-Based Drilling Fluid Contamination
on Asphaltene Stability, presented at the 6th International Conf. on Petroleum
Phase Behavior and Fouling, Amsterdam, Netherlands, June 19-23, 2005 (submitted
to J. Disp. Sci. Tech.).
Skalli, L., Buckley, J.S., Zhang, Y., and Morrow, N.R., Surface and Core
Wetting Effects of Surfactants in Oil-Based Drilling Fluids, presented at
the 8th International Reservoir Wettability Symposium, May 16-18, 2004, Houston,
TX (accepted for publication in J. Pet. Sci. Eng., 2005).
Tong, Z. and Morrow, N.R., Variations in Wetting Behavior of Mixed-Wet Cores
Resulting from Probe Oil Solvency and Exposure to Synthetic Oil-Based Mud
Emulsifiers, presented at the 8th International Reservoir Wettability Symposium,
May 16-18, 2004, Houston, TX (accepted for publication in J. Pet. Sci. Eng.,
Zhang, Y., Wang, J.X., Morrow, N.R., and Buckley, J.S.: "Effect of Synthetic
Drilling Fluid Base Oils on Asphaltene Stability and Wetting in Sandstone
Cores," presented at the 5th International Conference on Petroleum Phase
Behaviour and Fouling, Banff, Alberta, Canada, June 13-17, 2004 (accepted
for publication in Energy&Fuels, 2005)
AFM image of a mica surface after exposure to an SBM emulsifier. The surfactant
rearranges but cannot be removed by scraping (as shown in the center).