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Current Issue
Issue No. 31 July/August 2010 |
 Photo Essay: Seismic testing in Louisiana provides new information about Haynesville Shale To see exactly what’s involved in a 3-D seismic project, photographer Jim Domke tagged along with seismic experts from Dawson Geophysical and Chesapeake Energy, who were conducting a $7.5 million proprietary seismic project for Chesapeake in the Haynesville Shale play in northwest Louisiana this summer. The project covered 97.20 square miles, or 62,208 acres and it took 85 days to complete the seismic recording phase.
Seismic testing provides exploration and production companies like Chesapeake Energy with additional data about a geographic area before drilling commences, to help provide better chances for successful wells. The seismic test project generally overlays and extends a little beyond the area on which the company wants to focus.
3-D seismic imaging utilizes seismic field data to generate three dimensional “pictures” of underground formations and geologic features, according to information on the Chesapeake Web site, www.chk.com. 3-D seismic allows geophysicists and geologists the opportunity to study the composition of the earth's crust in a particular area.
This is extremely useful in the exploration of natural gas, as an actual image can be used to estimate the probability of formations existing in a particular area and the characteristics of that potential formation. This technology has raised the success rate of exploration efforts. In fact, the use of 3-D seismic has increased the likelihood of successful reservoir locations by up to 50 percent. By providing data about the location of natural gas reservoirs, 3-D seismic imaging ensures more accurate placement of drillsites and results in more productive wells.
The northwest Louisiana “Stanley 3D” seismic project, located in DeSoto Parish, has had several phases, according to Dawson and Chesapeake officials. They began with permitting required by local, state and federal agencies, as well as with all private entities, such as landowners, located within the project area. The right of way permitting took268.5 days, and required 6,095 total permits. In addition, permits were required from the Louisiana Game and Fish Commission, the Sabine River Authority and the U.S. Army Corps of Engineers. They also conducted an archaeological field survey, recommended by the Louisiana Department of Culture, Recreation and Tourism, to identify and develop an avoidance plan for cultural resources.
The second phase of the survey project involved creating a grid pattern to cover the project with lines, or cables, for transmitting the seismic data gathered in the field back to recording boxes and/or the recording truck, also known as the dog house (like cutting up a layer cake into small equal pieces). One set of lines runs in one direction with data receiver stations, or listening devices known as geophones, equally spaced along each line and the other set of lines runs in another direction, with energy source stations, where shot holes will be drilled, evenly spaced along each line. This completes the grid with each station, also known as receivers or source points, having been surveyed within the project, along with all structures, pipelines, etc. having been identified. This is done for each project, whether it’s a few square miles to several hundred square miles.
In an urban area like the Barnett Shale, vibroseis trucks can often be used to vibrate the ground and create an energy source for a seismic survey. However, due to the sometimes rugged and difficult to access northwest Louisiana terrain, it was determined that the third phase of this particular project, generating the sound waves, would be conducted using small amounts of a special seismic explosive, also called the “acoustic energy source.” A small drilling rig was used to drill a shot hole at each source station, so that the seismic explosive could be placed in the hole to generate energy to create the reflected sound waves for the study. Project officials estimate they will have drilled about 16,000 small shot holes before the project is finished. The sound waves originating from the energy source in the hole are analyzed to determine sub-surface information for future gas drilling projects. Energy source parameters, such as how deep to dig the shot holes, are selected after extensive testing. A ground motion study is also conducted simultaneously with the source testing to determine safe offset distances, as specified by the U.S. Bureau of Mines.
The final phase of the seismic project includes collecting and recording the sound data, then cleaning up after the project.
Chesapeake and Dawson officials asked that the pictures in this photo essay be “dedicated to the hundreds of hard working men and women who go to the field each day to set up and collect the data from these projects.” Photos by Jim Domke.
Caption for photo at top:
After permits are secured and the grid map is set up, this survey crew of five used an Inertial Navigation System (INS) in the dense woods of northwest Louisiana to map receiver and source stations. While three members of the crew cut and flag a trail to stations, the other two mark the station’s position with the INS equipment. Crew members pictured are Adam Manor, Augustin Alvarado, Martin Rodriguez, Gumersindo Mercado and Jose Mercado. Jim Domke photo.
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