One of the biggest breakthroughs in natural gas exploration has come through the use of seismic testing — state-of-the-art sound wave technology that helps locate natural gas and oil formations deep within the earth. Chesapeake and other operators in the Barnett Shale conduct seismic surveys to map natural gas reservoirs. This data allows us to more accurately drill wells and improve operational efficiency, which can help increase royalties.
Seismic testing is based on echo technology. Anyone who has ever shouted hello into a canyon to hear his or her voice bounce off the rock walls has experienced a primitive form of this phenomenon. Most expectant parents are familiar with a more sophisticated example of this technology through a sonogram. Just as a sonogram uses sound waves to create detailed images of an unborn baby, seismic testing uses sound waves to create a 3-D image of the earth. By doing so, geoscientists can pinpoint and map where reservoirs of natural gas are located before drilling begins.
Seismic testing is safe and environmentally friendly, and is designed to have minimal impact on the surrounding area. The sound wave vibrations used during testing will not harm a home’s foundation or damage property. In fact once it is complete, property owners usually can’t tell seismic testing has taken place.
How It Works
The earth’s crust is composed of different layers. Each layer, including the shale that holds natural gas, has unique properties that make it interact differently with energy. During seismic testing a vehicle will send sound waves into the earth. The waves bounce back to the surface when they come in contact with a layer with properties that are different than the layer above it, just like the echo in a canyon wall. Geophysicists measure how long it takes these waves to bounce back to the surface using small, sensitive listening devices called geophones. The geophones send the data to a recording truck . Later it is processed into 3-D images that create a map of the earth’s subsurface layers. This map helps geoscientists identify the location of natural gas.
Phases of Seismic Testing
Phase 1 — Obtain Permission and Permits
Before any work begins, permission from the surface and mineral rights owners and the proper permits must be granted before placing geophones, data boxes and small cables aboveground on the property. This equipment is temporary and unobtrusive.
Phase 2 — Determine Data Collection Sites
Geophysicists will visit the selected test site to take a careful look at the area and determine where geophones should be placed. Small flags will be placed on the ground to mark these locations.
Phase 3 — Place Seismic Equipment
Crews will stake geophones into the ground approximately 165 feet apart. Small remote seismic recorders (RSRs) will be placed on the ground close to the curb (where possible) to listen to the signals. Cables the size of household extension cords will connect the geophones to the RSRs. The cables, similar to speaker wire, do not carry a current and never penetrate the ground. These small pieces of equipment remain for approximately three to six weeks.
Phase 4 — Record Data
During the actual test, trucks will drive through the area and occasionally lower a vibrating mechanism to the ground to send a sound wave down into the earth. Geophones detect this low-volume sound as sound waves as they are reflected back to the earth’s surface and the data is recorded to the RSR boxes. Once the data is recorded, it is transmitted to the recorder vehicle. Inside this high-tech command center, computers and diagnostic equipment combine the data for the geophysicist and later convert it into a 3-D subsurface map.
Phase 5 — Removal of Equipment
Once testing is complete all equipment is removed with little, if any, evidence remaining.
Seismic Vibrations
Vibrations from seismic testing are relatively small, generally moving between 0.05 and 0.17 inches per second. The U.S. Bureau of Mines states the safe level of high-frequency ground vibrations is 0.50 inches per second, which is between 3 to 10 times that of seismic testing. Put into perspective, activities such as slamming a door, hammering a nail into a wall or jumping to the floor from a chair cause much higher vibrations than seismic testing. It would be virtually impossible for the sound waves created during a seismic test to cause damage to surrounding buildings or structures and company engineers ensure vibrations remain well below the U.S. Bureau of Mines’ standards.
Seismic Data
It takes skilled analysts and advanced technology to make sense of and interpret the data produced during a seismic test. In a mature shale play such as the Barnett, the data is used as a mapping tool for operations and not as a discovery tool for leasing. Chesapeake already has an established well-development plan. Seismic tests simply allow the company’s drillers to more accurately steer the drillbit through the shale to ensure the well is in the most productive zone. This benefits all mineral rights owners in a unit by assisting to maximize the production of natural gas that will be sold at market.
Similar to a photo release, permission is required from the mineral owner to use the data collected during a seismic test. The required documentation also ensures that mineral owners are notified about seismic testing in the area. In instances where the mineral owner has not granted permission for the use of the data, data representing the mineral acreage will be blacked out and not viewed or used during analysis.
Successful Seismic Exploration in the Metroplex
Chesapeake has successfully completed seismic surveys across much of North Texas, including historic firsts — surveying the Dallas/Fort Worth International Airport and Main Street in the iconic Fort Worth Stockyards.
Chesapeake has conducted safe and unobtrusive seismic tests extensively in residential neighborhoods from Benbrook to Grapevine. In North Richland Hills, for example, a seismic test encapsulating more than 29,000 acres and almost 48,000 rooftops within 46 square miles was seamlessly completed. North Texas residents can be assured each neighborhood will receive the same level of care and uncompromising commitment to safety if a seismic test is scheduled.
If you have any questions regarding Chesapeake’s seismic testing, please call us at 817-502-5000.
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