New SEG president links economics to decisions about geophysical work

Sept. 4, 2017
Communicating the economic value of seismic data can be challenging, observes career geophysicist Nancy J. House, who has an advantage in this area.

Communicating the economic value of seismic data can be challenging, observes career geophysicist Nancy J. House, who has an advantage in this area. To an undergraduate degree in geology and geophysics from the University of Wyoming and a master's degree in geophysics from the Colorado School of Mines, the incoming president of the Society of Exploration Geophysics added post-graduate work in economics. The extra expertise helps her deliver a message about geophysical work: "Even though it's expensive, it's very valuable."

In a recent interview in which she discussed topics ranging from geophysical roles in the development of unconventional reservoirs, trends in the profession, and women in the industry, House emphasized the link between economics and geophysical services sometimes spurned as luxuries-and what that link means for the future.

"I don't think the sky is going to open up and the money is going to come rolling in," she said. For geophysicists, that increasingly means finding work outside oil and gas in which to apply their skills.

The economics

The 40-year SEG member who consults from Littleton, Colo., described how economics helps her communicate the value of seismic data.

"When I'm trying to convince somebody to license 5 sq miles of seismic data and they're a small company they say, 'Oh, well, if you need 20 sq miles of seismic data to give me the interpretation I need then that's too much money. We can't afford that.'"

House said she might respond, "What if we got just the 5 sq miles instead of 20, and the cost would be $250,000 instead of $1 million for 20 sq miles commonly suggested?" And she'd ask how many wells the company planned to drill. If the answer were, say, 80 wells, she'd point out that the cost would be less than $3,200/well and tell the client, "You would pay that much for a log. Can you afford to not guarantee that each one of your wells is planned and executed as well as it could be with the insight that 3D seismic can give?"

House has worked as a geophysicist with EXCO Resources Inc., Chevron Corp., EnCana Oil & Gas (USA) Inc., Repsol-YPF, Mobil Oil Corp., Phillips Petroleum Co., and Exxon Co. USA. While at EnCana, which she joined in 2003, she applied geophysical methods to what she calls the first unconventional play: Jonah gas field in Wyoming. Development involved hydraulic fracturing driven by economics.

"It was a factory," she said. The challenge was to stay ahead of engineers planning development by acquiring, processing, and interpreting seismic data in time to ensure valuable results. At one point, a manager told House the company had a pad of six wells waiting 8 weeks for completion and asked, "Is there anything you'd like to do?"

She integrated borehole microseismic results with 3D seismic volumes to help manage hydraulic fracturing. In microseismic work, the sonic energy central to seismic methods comes not from impulses induced at the surface and reflected to recording instruments but directly from subsurface events-in this case nearby frac jobs. Three-component geophones in the boreholes recorded longitudinally oriented compressional waves (P-waves) and slower-propagating, laterally oriented shear waves (S-waves).

From arrival times and amplitudes, which indicate signal strength, House calculated P and S-wave velocities-the ratio of which can indicate rock characteristics-determine azimuth, or arrival angle, and determine perforation-shot locations. She integrated that information with the geological model and seismic data and to monitor fracture orientation and densities. This analysis is now common practice for use of microseismic (passive seismic) information.

Beyond rock properties

Refinement of those methods and the use of tools such as 3D vertical seismic profiling with long offsets (distances between shot points and receivers) enables geophysicists to interpret more than fracture information. With sufficient offsets and azimuthal sampling, House said, "You can do prestack inversion and instead of getting lithology you can start to bring out P velocities, shear velocities, and the densities. From those three properties of the rock you can produce 3D seismic volumes that tell you whether a zone has more total organic content or is more rigid and susceptible to fracing. So all of a sudden you can look way ahead and find the sweetest spots in an unconventional play."

Prestack inversion generates several volumes of rock properties from recorded data before stack-a processing step that sums data to improve the signal-to-noise ratio and lower computational requirements. Now, geophysicists use simultaneous prestack inversion, which expands application of the technique with 3D data volumes to other elastic properties of a reservoir and yields more information about lithology and fluid content.

House called prestack simultaneous inversion one of three main applications of geophysics to unconventional resource development. The initial application is describing the basic geometry of a play, employing regional seismic. The second is using seismic data during drilling to predict the landing zone and optimum angle of entry and to predict faults or other hazards to drilling or completions.

Microseismic itself, she added, "has come a long way," now using not only geophones in wellbores but arrays at or near the surface or continuously-recording receiver nodes to monitor frac jobs or locate faults from natural seismic energy in the subsurface.

Big data

An important trend within geophysics, House said, is the use of big-data analytics in seismic interpretation.

"By the time you've inverted some of these high-quality 3D surveys and generated attributes from that inversion along with all the other attributes, it becomes too much for the human brain to handle," she said. An attribute is an element for interpretation derived from seismic data.

In a recent project with "beautiful data" from the Eagle Ford shale in Texas, House progressed through a full prestack simultaneous inversion, generated attributes, and determined the underlying physical processes. When she finished the interpretation she had 97 attributes.

"How do you internalize and sort through all that data?" she asked, saying the problem shows why big-data analytics "is going to be the big one."

Companies have produced neural-net methods for sorting through families of attributes and performing correlations.

"This is just a machine way of sorting all that out so that you can put some rational interpretation to it," House said.

Many early-career geophysicists are migrating to jobs involving data analytics, she noted, adding that some nongeophysicists seem to hope for seismic interpretation that doesn't involve people.

Beyond oil and gas

While that vision might lack practicality, the pressures of a shrinking oil and gas industry force geophysicists to seek untraditional roles. New abundance in oil and gas markets reflects success by professionals whose work expands supply. But by lowering prices of fluid hydrocarbons, it creates hardship for the successful.

"We may need to scale back our expectations in terms of value and focus on the human and environmental benefit of the science," House said.

She cited earthquake prediction as an area in which geophysicists have become increasingly active since the devastating Indian Ocean earthquake and tsunami of 2004. Advance information about when tsunamis would hit specific places, she said, "could have saved thousands and thousands of lives."

Geophysicists with funding from Geoscientists Without Borders (GWB), and SEG Foundation Program, received support for an initial project to predict the tsunami arrivals based on earthquake locations. Through a later grant they translated results into an early-warning system, the "20-20-20 rule" to help coastal residents survive tsunamis by exiting the danger zone without waiting for official communications. House cites a recent presentation by Carolus Prasetyadi, Bridge Over Troubled Water: Tsunami Disaster Prevention in Java, at a special Asia Ocean Geosciences Society session highlighting GWB projects.

"It's possible because there's a delay between the first arrival, which is the compressional wave, and the shear wave, which is the one that really causes the damage. And that delay is a function of how far you are away from the epicenter," House explains.

The rule, with related guidance, now appears in areas susceptible to tsunamis such as the one that struck Java in 2004.

"If you feel the ground shaking for 20 sec or more, you have 20 min or less to reach an elevation 20 m higher than you are now," House said. In other areas, such as California and Taiwan, seismologists at agencies or universities are pioneering early-warning systems based on the delay between first arrivals and the shear-wave arrivals that can allow for a few seconds of warning before destructive shaking starts. "Just being able to issue an instantaneous warning that could give a surgeon about ready to make a cut 30 sec to do something different than planned could be monumental."

She noted that young professionals increasingly become geophysicists intending to do environmental work, believing, "It's a lot more important to be doing something for the sake of humanity than making a lot of money."

SEG, she added, has modified its mission statement to include the social contribution of geophysics.

Women in geophysics

Women might account for as much of 40% of the early-career geophysical workforce but less than 10% overall, according to a survey in which gender had to be inferred, House said. Departure of women from the industry tends to occur at age 30-40.

"I want it to be like Star Trek, where you're totally diverse, and it [gender] doesn't make a difference," said the 2012-13 chair of the SEG Women's Network Committee.

During her own career, "There have been unconscious biases applied at various points." Treating women differently from men "just seems like a very chivalrous thing to do."

For example, a manager might say, "I couldn't send you to a Third World country because you don't have a wife. You don't know how hard it is to get maids and dogs taken care of and kids in school," House said. Her response to such a judgment: "Having drivers to take kids to school and having maids is a huge improvement, so why are you allowed to decide for me what can happen?"

House observes, "Often seemingly thoughtful gestures sometimes limit opportunities, such as in this instance. This is a very subtle, even considerate, form of discrimination known as 'benevolent sexism.'"

Her advice: "Before you make a decision for someone, ask yourself if it is a decision they are qualified to make, depending on the circumstances and their level of comfort with the situation. If it is then let them decide; if you do, it is discriminatory."

House added, "Those kinds of comments have persisted. But that doesn't mean that it's all over the place or not changing." But she thinks the industry needs to make "a concerted effort" to move women into leadership positions.

House, SEG's second female president, would like to see a program of skits to illustrate questions such as, "Is this discrimination, or is this not? Are you being chivalrous, or are you removing opportunities. It's hard to recognize."

On balance, she said, "I'm encouraged, but I don't think that the work is over."

About the Author

Bob Tippee | Editor

Bob Tippee has been chief editor of Oil & Gas Journal since January 1999 and a member of the Journal staff since October 1977. Before joining the magazine, he worked as a reporter at the Tulsa World and served for four years as an officer in the US Air Force. A native of St. Louis, he holds a degree in journalism from the University of Tulsa.