Develop and test an advanced system incorporating both seismic sensors and tiltmeters in one tool. Instrumentation will be developed and tested to improve viewing distance and accuracy.

Pinnacle Technologies, Inc., Houston, Texas 77090
Sandia National Laboratories (see FEW04-012298), Albuquerque, New Mexico 87185

The industry has made significant progress in hydraulic fracturing, with much support by the DOE, but this continues to be an area ripe for progress. Stimulation of unconventional formations is a particular challenge. The complex fracture geometries that result from stimulating wells in unconventional formations make it difficult to optimize individual treatments to ensure pay zone coverage, adequate fracture length and sufficient conductivity. Field development strategy and determination of the most efficient well spacing and pattern can also be very difficult in these reservoirs and is largely affected by the hydraulic fracture geometry. By increasing the field of application and accuracy of fracture mapping, this project will play a key role in improving development economics.

This project addresses limitations in hydraulic fracture mapping technology and provides industry with an improved system to measure created fracture geometry. The improvements will lead to wider and more effective application of hydraulic fracture mapping. Microseismic and tiltmeter hydraulic fracture mapping are proving to be very useful technologies allowing producers to optimize individual fracture treatments and field development. Development of a combined microseismic receiver-tiltmeter system eliminating the need for two observation wells will help reduce costs and simplify field operations.

The DOE has funded various projects in the development of microseismic technology. The industry has grown to an estimated $50 million per year and the larger service companies are now offering this technology. Pinnacle estimates the 90 percent of their microseismic business is for unconventional gas reservoirs; gas shales, tight gas sands and coal-bed methane. All are significant resources for future gas production.

Results
The concept of a single microseismic tool combining geophones and tiltmeters has been proven. A joint-inversion routine was developed for analysis of data from the combined array. New techniques for analyzing source data from microseismic events were successfully developed. The combination of these two sensors will allow the use of a single observation well, reducing field operating costs for this procedure. The combined package of geophones and tiltmeters has undergone long term testing.

Benefits 
Many unconventional reservoirs require fracture stimulation. Mapping this stimulation provides knowledge of internal reservoir structure and performance of the frac job, both important parameters in further development of the reservoir, design of the hydraulic stimulations to be applied, and control of costs. This new tool will be able to operate in a single observation well with a greater range of operations allowing its use in fields with larger well spacing.

Summary
The project is complete. The concept of a single microseismic tool combining geophones and tiltmeters has been proven successful. The design that was adopted, the stacking of the receivers, also resulted in an improved signal-to-noise ratio. A joint-inversion routine was developed for analysis of data from a combined array.

Because tilt-meter and microseismic data sets are extremely diverse (the “tilts” of the rock are aerial mechanical responses while microseismic events are points of released energy), the computer code architecture needed to extract the desired parameters to process this data had to be modified. As part of this project the Marquardt-Levenburg code, which was in FORTRAN, was converted to C++.

Also as part of this project, new techniques to analyze source data from microseismic events were successfully developed. Characterization of source data is critical in establishing the bearing between source and tool and, probably even more important, the orientation of the stress axis. This orientation will change depending on the regional tectonic environment and whether or not it is in extension or compression.

An accelerometer sensor package was built and tested. Although accelerometers have certain advantages over geophones and this package shows promise, a considerable amount of noise is present in the acquired data. Further is work is necessary to reduce this noise.

The combined package of geophones and tiltmeters underwent successful long term testing in the San Andreas Fault Observatory Well at Depth (SAFOD), both in the pilot well and in the observatory well. The observatory well presented a harsher, more corrosive, environment to the tools because of its greater depth, providing a test for the cable interconnections between tool segments.

(July 2007)
This project has been completed.

$612,222

$320,500

NETL - Gary Covatch (gary.covatch@netl.doe.gov or 304-285-4589)
Pinnacle Technologies - Larry Griffin (larry.griffin@pinntech.com or 281-876-2323)

Final Report [PDF-2.87MB]

Pertinent Publications:
Warpinski, N.R., Griffin, L.G., Davis, E.J., and T. Grant, 2006, Improving Hydraulic Frac Diagnostics by Joint Inversion of Downhole Microseismic and Tiltmeter Data, SPE 102690

Warpinski, N., 2006, Hydraulic Fracture Mapping with Hybrid Microseismic/Tiltmeter Arrays, GasTIPS, vol. 12, no. 3, p. 17- 10.