The goal of the project was to build on the previous development of resistivity logging tools to develop cross-well imaging hardware and software, to calibrate and field-test the transmitter and receiver systems, and to use the cross-well imaging tool for monitoring carbon dioxide injection. Three development phases and 13 specific tasks were written into the contract. The results included a complete reservoir simulation and field management analysis, based on work with the cross-well imaging system. The main objective was to develop a cross-well electromagnetic system (EM) to provide a formation resistivity distribution between steel-cased wells and apply it in the Permian Basin.

Program
The project was selected under the Broad-Based Announcement DE-PS-22-40759, issued in December 1999. The goal of this solicitation was to slow or even halt the decline in production from U.S. oilfields by developing more-effective and lower-cost oilfield production and environmental compliance technologies. A major area of interest was advanced imaging technologies.

Electromagnetics Instruments, Inc. (EMI)
El Cerrito, CA

Lawrence Livermore National Laboratory (LLNL)
Livermore, CA

Cross-well EM imaging technology, based on earlier radar imaging technology, will help interpret the reservoir rock and fluid flow through the reservoir between wells. The necessary resolution to accurately map fluid properties has been missing from conventional seismic analysis.

Cross-well EM imaging is designed to give accurate an measurement of oil saturations in the areas between wells. Previous logging technologies could only generate oil saturation data close to the wellbore. EM logging can provide the operator with an actual image of fluid migration and show where specific areas of undeveloped reservoir remain.

The cumulative efforts of four previous projects, conducted by LLNL from 1984 to 1999, resulted in the design, construction, and bench-testing of EM logging tools that can measure resistivity from behind steel casing. The original work was completed under project FEW 6038 during 1984-1993.

The second project-FEW 6039, 1989-1991-established the precision level of instrumentation necessary in the field environment to image the reservoir.

FEW 6040 (1990-1992) established a laboratory facility to measure the resistivity of porous media saturated with water and/or petroleum, or steam. The research conducted at LLNL resulted in creation of the company EMI by the principal investigator.

The fourth project-DE-FG03-96ER82159, 1996-1999, conducted by EMI-was intended to design and construct a prototype inductive logging device to measure formation resistivity from within a steel-cased borehole. The steel casing induction logger tool was intended for reservoir characterization and process monitoring in an oilfield. The Cross-well Electromagnetic Imaging Tool was developed during 1991- 2000 and tested in a five-well pattern test in Richmond, CA, prior to commercial field tests.

The first field applications of the EM tool were:

• A crosswell survey conducted at Kern River oilfield in California in 1998. The project mapped residual oil saturation and determine the factors that controlled steam and oil flow in the heavy oil reservoir. Identification of the steam path allowed redesign of the steamflood to produce unswept areas.
• Cross-well EM imaging applied at Lost Hills field in California in 1997-98. This effort imaged waterflood performance in the Belridge diatomite. Chevron Corp. used two fiberglass-cased wells to observe the results of water injection in this fractured reservoir. Imaging resistivity changes over time demonstrated that cross-well data could be used to map migration of the water and provided a means for understanding reservoir dynamics and optimizing oil recovery. A prototype tested EM between steel-cased wells at Chevron's Lost Hills field in California early in the project.

Project Results
The cross-well imaging system progressed from laboratory model/bench scale to full-field deployment. The sensitivity of the transmitters and receivers was improved, and the unit is now capable of imaging resistivity through steel-cased wells. The cross-well tool proved successful in monitoring a CO2 flood and was used to plan and manage water and CO2 injection strategies.

Benefits
Cross-well EM imaging proved to be 10 times more effective than the previous logging techniques used for CO2 monitoring in Vacuum oilfield in New Mexico. Information obtained from EM surveys allows field operators to optimize injection and production operations and thus produce more oil in a cost-effective manner.

Progress made in the technology of imaging through fiberglass and steel casing will significantly increase the application of the technique in regions where uncased wells cannot be used. New advances in single wellbore imaging holds great potential for use offshore, where the expense of idling wells for logging procedures will be mitigated by a reduction in the number of wells necessary to complete the EM survey.

(November 2005)
The project is complete. Following the successful demonstration of the EM tool's effectiveness, especially single borehole imaging, imaging through steel casing, and CO2 monitoring, EMI was purchased by Schlumberger, a major oilfield service company, in 2003. Schlumberger is backing the continued development and implementation of the cross-well EM tool with a capital investment of $15 million, indicating the company's confidence that cross-well EM logging tools have a future place in the petroleum industry. new captions:

$767,821

$382,809 (33% of total)

Other Government Organizations Involved: Lawrence Livermore National Laboratory

NETL - Paul West (paul.west@netl.doe.gov or 918-699-2035)
Electromagnetics, Inc. - Michael Wilt (mwilt@eminc.com or 519-232-7997)