A geoscience company some have billed as “Silicon Valley meets the oil patch” has undertaken a study over the Allegheny National Forest in Pennsylvania.
Airborne geophysical datasets newly acquired by NEOS GeoSolutions were combined with existing seismic, well, and public domain datasets to better understand the potential of the Marcellus resource play in a roughly 2,500 square-mile area of investigation.
Due to the large amounts of natural gas contained within the Marcellus formation, the development of shale has increased rapidly over the last decade; but high spatial variability of both petrophysical and petrochemical properties, along with variations in basement topography and composition, create a challenge in identifying the most prolific, liquids-prone parts of the shale when using only seismic data.
So, in 2013 NEOS GeoSolutions acquired airborne magnetic, electromagnetic, radiometric, gravity and hyperspectral datasets to gain better insight into the region’s geology and, especially, the structure and the composition of the basement that underlies the shale.
“We’re taking a set of holistic measurements from the basement below the reservoir, up through the reservoir interval itself and then on the surface of the earth, and we combine all of these both qualitatively and quantitatively to provide additional insight to what is going on throughout the geologic column,” said Chris Friedemann, chief commercial officer at NEOS GeoSolutions.
From August through October 2013, more than 12,700 line-kilometers of airborne gravity, magnetic, radiometric and passive-source electromagnetic data were acquired.
At the request of one of the program’s underwriters, NEOS undertook a series of analyses to map basement topographic and lithologic variations, which were hypothesized to cause localized areas of high BTU production. By integrating and inverting several of the non-seismic datasets, NEOS identified a high-susceptibility region within the basement, which suggested lateral lithological variations within the basement do, in fact, exist.
NEOS also noted a correlation with Marcellus shale production rates and liquids-content, as had been hypothesized.
Operationally, Friedemann said, acquiring airborne multi-physics data can be beneficial because it is obtained using either fixed-wing aircraft or helicopters, which makes data acquisition over a large area fast and cost-effective. Airborne operations also involve fewer people, minimizing HSE risks.
Once the information was acquired, each measurement was interpreted individually to extract subsurface insights including structure, faulting and rock and fluid property variations.
What Comes Next
The next stage is to combine certain measurements qualitatively and quantitatively to derive more insight.
“For example, we might look at the hyperspectral measurements to identify oil seeps on the surface, and then we may go back to the magnetic analyses to see how those seeps got to the surface and whether or not those seeps might have migrated up faults that we mapped using the magnetic data,” Friedemann said.
NEOS GeoSolutions also analyzes the data sets for subtle patterns and correlations. Using proprietary algorithms and advanced mathematics and data analytics techniques, they are able to identify the geophysical attributes that correspond with the areas on the subsurface where the higher production, more liquids-prone wells would be found, Friedemann said.
Our predictive methodology involves sorting through these datasets to see first, are there attributes that correlate with the known areas of goodness ... and then pattern searching over a very broad area to see whether or not those same correlative attributes exist in underexplored areas of the play. These insights allow our clients to figure out whether and where you might go next to drill the next wave of wells whose attribute suites match the previous best wells in the play,” he said.
The company has used similar approaches for programs in Colorado, Wyoming, southern California and Argentina and is in the process of acquiring data over onshore Lebanon.
Environmental Aspects
The development of the Marcellus shale has increased rapidly because of the large quantities of natural gas in the formation. It hasn’t been without controversy, though, especially in this environmentally-sensitive region.
Production within Appalachia has been going on for nearly 100 years, Courtney Ford, marketing manager for NEOS GeoSolutions noted, so there are many abandoned wellbores.
“Some have been properly abandoned, but many have not been as they often were drilled by small operators or private landowners,” she said.
By using the magnetic data, NEOS GeoSolutions can identify potentially orphaned wellbores, as the iron from the casing strings (assuming they are still in place) cause detectable magnetic anomalies.
NEOS also can use the hyperspectral data to map oil seeps and methane gas plumes on the surface and, in combination with the orphaned wellbore analysis, determine whether any of the potential orphaned wellbores appear to be leaking.
In addition, NEOS uses the airborne electromagnetic data to identify shallow gas pockets in the subsurface, which might represent a geo-hazard when drilling, as well as natural gas incursions into aquifers, which have commonly occurred throughout Appalachia as hydrocarbons naturally migrated toward the surface over the course of geologic time.