AutoLab Series :: New England Research, Inc.

Development and Constraint of Physical Models for Geothermal Reservoirs

The development of effective exploitation strategies requires scientifically sound characterization of geothermal reservoirs. Surface geophysical data are potentially the most powerful and cost effective means of exploration and characterization, providing images of the subsurface structures prior to extensive drilling.

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AutoLab Series

The AutoLab systems provide integrated measurement, analysis, and reporting of ultrasonic velocities, permeability, resistivity, pore volume compressibility, and deformation at fluid pore pressures to15,000 psi (100 MPa), confining pressures to 30,000 psi (200 MPa), and temperatures to 250°F (121°C). All units are supplied with a custom software system which is capable of acquiring data and controlling experiments on the AutoLab 1000, 1500, and 2000.

For each type of measurement, dedicated coreholders, electronic modules to support the data acquisition and AutoLab software to control the measurement sequence and process the data have been coordinated to form an integrated, turnkey unit.

PS² Ultrasonic Transducer
These coreholders measure one compressional and two orthogonally polarized shear waves and waveforms at confining pressures, pore pressures, and temperatures appropriate for each system. Each transducer operates at a center frequency of 500 to 700 kHz.
Permeability
A new measurement technique to measure fluid permeability at in situ conditions has been developed at NER. The method involves the control of a complex transient in pore pressure at the upstream side of the sample while monitoring the pore pressure response at the downstream end. Permeability is computed by fitting the response to analytical solutions. The standard configuration is suitable for permeabilities between 5 millidarcys and 0.5 Darcy. The significant advantages to this technique is its short duration (10 seconds), small pore pressure perturbation (50 psi), and complete automation for acquisition and processing.
Complex Electrical Impedance (Formation Factor)
Resistivity is measured as a function of frequency, stress, and temperature for both two and true four electrode techniques. NER's ZMeter impedance analysis is used to perform true four electrode measurements at frequencies between 0.02 Hz and 100 kHz. Two electrode measurements, especially at high frequencies, employ an HP Impedance Analyzer.
Dual Permeability/Resistivity Coreholder
NER has developed a single coreholder and supporting software that allows for measurement of both permeability and complex resistivity at any stage of an experiment. In addition to the time savings, this combination produces more consistent data, a critical feature in cases where specimens are experiencing permanent deformation.
Dual Velocity/Resistivity Coreholder
For some rocks, it is possible to measure velocity and resistivity simultaneously. Standard PS2 velocity transducers can be modified for two electrode resistivity measurements. The frequency range for resistivity is decreased when using this combination. AutoLab software fully supports this measurement combination.

AutoLab 500 [download pdf brochure] This is a compact and economical system for accurate measurement of compressional and shear wave velocities, formation factor (electrical resistivity), and bulk modulus as a function of effective pressure. The confining pressure (to 10,000 psi) and pore pressure (to 7,500 psi) are manually controlled with hand pumps and intensifiers.
AutoLab 1000 [download pdf brochure] A high-throughput system which has the capability of routine measurements of compressional and shear wave velocities, permeability, formation factor (electrical resistivity), pore volume compressibility, and bulk modulus as a function of effective pressure. The AutoLab 1000 has computer controlled servo hydraulic intensifiers for confining pressure (to 15,000 psi) and pore pressure (to 10,000 psi). Specimens can be tested at temperatures to 250° F.
AutoLab 1500 [download pdf brochure] This is a small footprint triaxial system used to measure compressional and shear wave velocities, permeability, formation factor, pore volume compressibility, and deformation as a function of state of stress at temperatures to 125°C, confining pressures to 10,000 psi and pore pressures to 7,500 psi. Each of the stress axes (loading axis, confining pressure, and pore pressure) is a computer controlled servo-hydraulic intensifier. To facilitate fluid exchange, two pore pressure intensifiers are standard. The maximum specimen size for the AutoLab 1500 is 1.5 inch diameter cylindrical specimens.
AutoLab 2000 [download pdf brochure] This high-end triaxial system provides all of the capabilities described in the other AutoLab systems. The main difference is higher overburden pressures, pore pressures, differential stresses, and larger specimen sizes. The AutoLab 2000 can be designed and fabricated to handle specimens up to 4.00 inches in diameter and a much broader range of experiment types.