By Al Pickett, special contributor
Seismic’s earthshaking technologies enter a new era.
Often compared to the use of ultrasound in medicine, seismic surveys are used by oil and gas explorers to produce detailed images of various rock types and their location beneath the Earth’s surface in an effort to determine the location and size of oil and gas reservoirs.
As technology has advanced, so has the ability of seismic surveys to provide geophysicists and operators with a wide variety of critical information.
“It is exciting for us because the technology continues to develop,” observed Steve Jumper, chairman, president, and chief executive officer of Midland-based Dawson Geophysical, a service company with 1,100 employees providing two-dimensional (2D) and 3D seismic surveys all across the United States. “When I came into the business 30 years ago, we were in the exploration business, shooting 2D lines. It was individual prospect by prospect. Then, with 3D exploration, we offered ‘where-to-drill’ technology.
“As the industry has moved into horizontal drilling in unconventional resource plays, we come later in the cycle. Companies have their position and their drilling plans, and the seismic is later to the table. Our primary focus has become where not to drill. But as we continue to improve on technology, I believe we will move back into added value to help operators begin to understand rock fabric and rock types as well. Seismic can help find the sweet spot to determine what well will be the most productive. This is an exciting opportunity, an exciting frontier, combined with petrophysical and geological information, to learn more about the rock type and not just where to drill.”
The bottom line, according to Jumper, is to help its clients find oil and gas.
“We are in the business of reducing risk, improving success probability, and reducing finding and development costs,” he added. “Our technology continues to improve and add value to the chain.”
Jumper also noted that the need to reduce costs is even more important than ever with the recent decline in crude oil prices.
While 3D seismic surveys provide a much more extensive amount of information, some companies still find shooting 2D seismic lines useful. For example, A. Darryl James, vice president of exploration for Midland-based Tall City Exploration, LLC, said his company shoots 2D seismic surveys along the well track to avoid potential hazards when drilling horizontal Wolfcamp wells.
“We do it to avoid faults and changes or dips in the formation,” he explained. “It keeps you out of trouble.”
One might think that since 2D seismic surveys have been used for years in the Permian Basin, it wouldn’t be necessary to shoot new surveys. But James said older 2D seismic surveys are often not on the same track as the new horizontal wells that Tall City plans to drill.
“We look at old seismic and reprocess it,” he acknowledged. “It gives us a guide for setting our wells, but we shoot our own modern 2D seismic.”
Of course, much more advanced 3D seismic surveys are now available and are being used in the Permian Basin, as well. James describes 2D seismic as looking at a window pane or a slice that provides just a narrow bit of data, while 3D seismic surveys are looking at glass cube, providing a more complete view of the acreage being shot.
3D seismic is expensive, however, so James said most exploration and production companies in the Permian Basin only use it when shooting a large contiguous acreage. He pointed out that Tall City Exploration has a 60,000-acre contiguous block in Borden County in which it plans to conduct a 3D seismic shoot this year.
“With 3D seismic, you see stratigraphy and what is good and what is bad,” he offered. “It helps you place wells in positive locations. We don’t have a geophysicist on staff, but we use an independent geophysicist [to read the processed seismic surveys].”
Evolution of 3D
After the price collapse in 1998, a slow period intervened, but Dawson Geophysical’s business picked up in 2003 and 2004, Jumper said.
“We started shooting 3D surveys in natural gas plays,” he stated. “When we first started in the Barnett Shale [in the Fort Worth Basin in North Texas], especially in Wise County, where they were drilling horizontal and fracturing, we were [still] a six-crew company, and we had a hard time keeping up with the demand. Some people said there wouldn’t be a need for seismic because of horizontal drilling. But we had five of our six crews active in the Barnett. Then we started working in the Fayetteville Shale in Arkansas, the Woodford in northeastern Oklahoma, and the Marcellus in Pennsylvania and West Virginia. By 2008, we were a 16-crew company, and 95 percent of our business was east of Interstate 35 in natural gas unconventional resource plays.”
Dawson Geophysical currently has 10 crews providing 3D seismic surveys in the Permian Basin, the Mississippi Lime in northern Oklahoma, the Bakken Shale in North Dakota, the D-J Basin in Colorado, and the Eagle Ford Shale in South Texas.
“The Permian Basin and the other oil shale plays began to come back to life in 2011,” Jumper continued. “We are doing the same thing we were doing in the natural gas plays, but we are doing it in places that are easier to operate.”
He pointed out that each survey is different. For example, many of its natural gas seismic survey were done in an urban environment or in rugged terrain in West Virginia.
“In the oil seismic surveys, it is in more wide open spaces in most cases where the surveys are bigger and we can use vibrators and increased channel counts,” Jumper remarked. He said Dawson Geophysical’s work begins after the exploration and production company has its acreage position intact.
“The first step is to sit down with the design geophysicist and operational people to identify the company’s interest and objectives,” Jumper explained. “We then design the size of the survey, what type of energy source is needed, the channel count, etc. The intent is to bring value to the chain, to get the highest resolution possible at the most cost-effective method and the shortest cycle time.”
Then Dawson Geophysical, its client, or a third party secures permission from both the surface and mineral stakeholders to conduct the seismic survey. He said the survey could range from 20 square miles to more than 400 square miles. The next step is to determine the locations for each recording channel and each source point.
“How they are spaced is variable,” Jumper maintained. “Nothing is standard. You may have move things around because of highways or railroad tracks or compressor stations located on the acreage. In West Texas, the primary energy source is vibrators, so you don’t need a drilling contract to set dynamite charges.”
Dawson’s crew then shows up and deploys the recording channels and energy sources, which he describes as “shooting the survey.” After the data is collected and put on disk, it is sent to data processing, which Jumper said can be done by the Dawson Geophysical or a third party. It is then sent to a geophysicist to interpret the cube of information that includes depth and spatial information, providing the client with a subsurface geologic model.
He said Dawson Geophysical doesn’t perform the data interpretation and doesn’t maintain a seismic survey library. The survey is the property of the client that hires Dawson to do the work.
One of the new developments in the seismic survey industry in recent years, according to Jumper, is the use of cable-less recorders that are independent autonomous nodes.
“The recording device, geophone, and battery supply are contained in one unit and are GPS-synchronized to each other and the energy source,” he said. Information from each cable-less record is downloaded, with the end result equivalent to the more traditional cable system. Jumper said Dawson Geophysical operates both cable and cable-less systems. He said there has also been significant improvement in actual vibrator energy sources.
“They work in a broader band frequency range with more accuracy,” Jumper explained. “You get a higher resolution with more energy in the ground. We now have 62,000-pound vibrators. Electronics and hydraulics have improved, too, generating a better signal.”
He noted that his company is getting more and more involved in multi-component recording.
“It records additional seismic waves from the traditional primary waves,” Jumper added. “The intent is to allow us to compare rock property and rock types.”
As with the move from 2D to 3D, the multi-component seismic surveys are made possible by increased computing power, giving clients more understanding and interpretation analysis, he said.
Microseismic is another relatively new use of the technology, according to James, that is used in what he calls science wells or observation wells.
“When you fracture each stage, you can see each burst of energy,” he says of the use of microseismic surveys, “to determine how far you are cracking the rock up and down and laterally. You get a feel of where your fracture goes. You may only treat 150 feet, but the fracture might be impacting 350 feet.”
James cited as an example of the importance of the microseismic technology the SSH Unit #23-1H well that Tall City Exploration completed in late 2012 in the Wolfcamp formation north of Big Spring in Howard County.
“When we drilled that well, the closest horizontal well was 68 miles away,” he claimed. “It caused a lot of excitement and spurred a lot of activity.”
The well, which has a 7,800-foot lateral, had initial production of 736 barrels of oil equivalent per day and has now produced more than 140,000 barrels of oil. Tall City Exploration, with its partner Element Operating, has since drilled 30 horizontal wells in that same area of Howard County, according to James.
He said his company has used microseismic on two of the 30 wells it has drilled in Howard County, including that initial horizontal well. “By using microseismic, you can not only see how far you are cracking the rock laterally but also up and down,” James explained. “You want to see if you are reaching into an upper zone, which could be good or bad. It is important if you are using zipper fracs or simultaneous fracs. It is very useful.”
Jumper said microseismic survey can be done with a wireline in the borehole or on the surface level, which is the service that Dawson offers.
“We deploy sensors on the surface around an active wellbore,” he explained. “We are listening 8,000 to 10,000 feet from where the fracturing is taking place.”
Jumper compared the changes in seismic surveys to the high definition television sets found in our homes.
“HD TV is no good with an analog signal,” he offered. “For example, now, you can record or back up your TV program to see something again. There have been changes in analytics and data processing techniques. There is an increased demand for more statistics. Surveys done even as recently as the late 1990s don’t have the statistics and attributes to take advantage of what the software can do.”
Dawson Geophysical received a great deal of publicity when it did a 3D seismic survey at Dallas-Fort Worth Airport in 2006, but Jumper said his company has since worked at a number of additional airports.
“One of the most unusual projects we got involved in was in East Texas where we used four different types of energy sources and three different types of recording devices,” he recalled. “We used hydrophones in the water and cable-less and cable systems in the same area. Another interesting project was in West Virginia, where we had to deploy our equipment by helicopter because of the topography.”
Jumper said Dawson has been involved in surveys covering as large as 600 or 700 square miles and have had other projects requiring 24-hour operation modes. The company is also testing new vibrator technology.
Regardless of the environment or the type of method it uses to conduct the seismic survey, Jumper emphasized that service companies such as Dawson Geophysical are designed to add value to a company’s search for oil or gas.
Al Pickett is a freelance writer in Abilene and author of four books. He also owns the West Central Texas Oil Activity Index, a daily and weekly oil and gas reporting service. For more information, email firstname.lastname@example.org.