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Test system simulates earth for charges fired into rock, improving oil and gas exploration
By Jennifer Palumbo
A client that provides perforation equipment and services for the oil and gas industry required a simulated test system to study the performance of shaped charges fired into rock samples in a down-hole environment. The test system needed to accurately show the effects of different charges on various formations as they would occur under the earth.
Originally the perforation testing was performed on the surface by firing charges into concrete. This method of testing was inaccurate due to the physical differences in concrete and formations, as well as the lack of a high-pressure environment that mimics pressures below the earth's surface.
Test system simulates earth's pressure
In an 80-day period, Optimation designed and built a test system that simulates the confining earth's pressure, the wellbore pressure, and the pore pressure and flow.
This is achieved through the use of a single, high-pressure, variable speed pump and valves. The system chamber currently runs up to 6,000 pounds per square inch (psi), with an expansion capability to run at 30,000 psi. The system is connected to the control room via Ethernet and Internet protocol (IP) cameras, allowing operators to run tests from a remote location.
Computerized control of the system is done through a single-user interface screen. This screen contains the ability to open and close automated valves, set pressure and flow setpoints, and monitor the pressure and flow values from the sensors. A location can be specified to store the data collected, and charts display data over time as it is collected.
This type of research requires a data acquisition system with high resolution and capability of high data rates. The National Instruments cRIO system provides the necessary performance, resolution, and data rates and also allows for custom filter programming to be added in the FPGA section of the hardware. This met the client's needs from a research perspective; the system is easily configurable and modified when a new test is developed.
Two rates of data acquisition
As a shot is fired through the core sample, there are two rates of acquisition - high speed and low speed. The high-speed inputs are acquired at 100 kHz using a digital trigger or a computer start button to begin acquisition and record for the duration of the shot. The high-speed inputs are sampled at a rate of 100,000 samples per second. A trigger signal from the fire command is sent to the hardware controller to prompt the high-speed analog input acquisition.
The low-speed signals are sampled continuously at 100 Hz per channel for voltage or current sampling. Critical process channels requiring high data reliability are connected to an input module that has anti-aliasing filtering, 24-bit resolution and up to 100 samples per second per channel. Digital outputs are used to operate the air solenoids that open and close the automated valves.
The system will generate an alarm condition if certain pressures are exceeded. The software immediately closes all valves and turns off all pumps in the event of an alarm or emergency stop condition. The controller transitions the system to a safe state if there is a disconnection of the interface during a power outage or network failure.
The system data is logged to disk in two different files per run: a high-speed data file (shot data) and a low-speed data file (process data). Data is hardware timed and stored with an initial timestamp. The files used for logging are set by the operator prior to running a test.
Since the earth's crust is varied in its different substances (hard and porous), it is beneficial to exploration companies to know which charges work best on each formation. Development of this simulated test system significantly impacts geologists' ability to pinpoint within the well's regions and maximize efficiency and production. As field experts begin to understand more about the relationship between pressure and perforation using data acquired by the simulation test system, strategies will be refined to improve and revolutionize fracture stimulus and down-hole production methods.
ABOUT THE AUTHOR
Jennifer Palumbo (firstname.lastname@example.org) is a marketing communications specialist at Optimation, a global design, engineering, and fabrication company headquartered in Rochester, N.Y. Optimation is a member of the Control System Integrators Association (CSIA). More information about Optimation is available at www.optimation.us. To learn about CSIA, visit www.controlsys.org.