A Wyoming-based company is working with Shell International Exploration and Production to adapt a sweet spot sensor technology used in the coalbed methane industry for the past 15 years to identify natural gas and natural gas liquids in shale formations. WellDog Pty Ltd.’s patented downhole Raman spectroscopy technology could reduce hydraulic fracturing in shale operations by 30 to 50 percent, WellDog CEO John Roper told Rigzone.
On Tuesday, the company announced it had been collaborating with Shell over the past year and a half to adapt the technology for use in shale gas formations. The new service will focus on identifying the locations where natural gas and natural gas liquids occur in shale formations, allowing producers to focus development efforts, reduce drilling costs, optimize production, and reduce the number of hydraulic fracturing stages and associated water usage, according to an Oct. 7 press release.
“Our main mission is to use technical subsurface data to help operators be more efficient and more sustainable,” said Roper. WellDog’s downhole technology, which directly measures chemicals at specific depths using lasers and detectors, utilizes Raman spectroscopy, a well-established laboratory chemical analysis technique developed after the discovery of the Raman Effect in 1928. This technique is used to analyze many chemicals and chemical systems because of its ability to give unique Raman signals.
The Raman Effect is when light scatters from a molecule with a slightly changed energy, or color, due to the excitation of the molecule’s chemical bonds. This change is representative of the energy of the excited bond or bonds. Observing the scattered colors of light from a material indicates which molecules comprise that material.
Due to the sensitivity of the chemicals’ molecular structure, Raman spectroscopy has been described as a “fingerprint” technique, with every chemical giving a unique Raman signal, or spectrum. Raman spectroscopy allows for direct quantification of chemicals, and, in contrast to infrafred systems, is not overly sensitive to water. WellDog’s Raman spectrometers are also encased in corrosion-resistant stainless steel housings, allowing them to be used downhole in high reservoir pressure and temperature environments, the company said in a statement. Lots of people are producing shale gas and oil now, and have many tools to figure out where to go, said Roper. “Those tools vary from looking at organic content to thermal maturity.”
However, none of the tools really tell where the gas is. It may tell them about the rock and suggest where the hydrocarbons should be. Roper noted that there’s a growing number of researchers who are pointing out that shale fracking, in 30 to 50 percent of cases, doesn’t result in a productive reservoir. “In their view, this is tied to the variability in gas and oil distribution and underlying reservoir,” said Roper. In its June 2013 report “Technically Recoverable Shale Oil and Shale Gas Resources: An Assessment of 137 Shale Formations in 41 Countries Outside the United States”, the U.S. Energy Information Administration (EIA) cited a Society of Petroleum Engineers paper that reports that up to 50 percent of fracked stages are not productive due to reservoir heterogeneity.
According to that paper, a study including the production logs from 100 horizontal wells showed an enormous discrepancy in production between perforation clusters that is likely due to rock heterogeneity. “Because of shale rock heterogeneity over short distances, neighboring well productivity varies significantly, and well productivity across the formation varies even more,” said EIA in the report. Shale formation productivity also varies by depth. Shale heterogeneity also means that some parts of shale formations can have relatively high productivity wells, or sweet spots, while wells in other areas are less productive.
Because productivity also varies significantly for wells in the same neighborhood, a single well test cannot establish a formation’s productivity or even the productivity within its immediate neighborhood, EIA noted. “This complicates the exploration phase of a shale’s development because a company has to weigh the cost of drilling a sufficient number of wells to determine the local variation in well productivity against the risk that after drilling enough wells, the formation under the company’s leases provides to be unprofitable.” While many techniques and technologies exist to say where oil and gas should and might be, operators tell WellDog that these tools do not provide direct evidence of where hydrocarbons reside.
“It is the production risk that heterogeneity represents that our beta stage service is directed at,” said Roper. WellDog’s technology has been used to find sweet spots in coalbed methane, and to identify risky spots where carbon dioxide and methane exist. Over the past decade, a number of coal bed methane customers asked WellDog to adapt the technology for use in shale, said Roper. The partnership with Shell – whom WellDog has worked with on and off over the past 15 years – will leverage WellDog’s technology and Shell’s geochemical and petrophysical experience in shale gas evaluation.
Shell is now leading beta trials of the technical service being developed from the program, WellDog said in a statement. Roper said that other companies are being invited to participate in these beta trials. Getting the technology into as many beta trials as possible will allow for its limitations to be explored and prepare the technology for commercialization, said Roper. Specifically, the company will perform measurements under a number of different conditions to understand its limitations and to determine how to extend its capabilities, not just in terms of measurement but also to extend hardware capabilities of temperature and depth. Roper said the company would be focusing on these activities during the next couple of quarters.
Initial efforts will focus on wet and dry gas; over the next year, work will be conducted on extending the technology’s use for finding oil. Founded in 1999, the company initially focused on building its sensor technology for attachment to manned submersibles to analyze gas hydrate plumes offshore. In the early 2000s, WellDog began applying its technology to map sweet spots and coals in coalbed methane fields in the Powder River Basin.
The recession in 2008 – which resulted in U.S.-based coalbed methane operators halting workers -– prompted the company to focus on coalbed methane commercial operations overseas in China and Australia. The company has been active in Australia since 2010. WellDog has provided services to operators in all major basins, including the Permian, Eagle Ford, Bakken and the Niobrara. The company also has worked for international operators in Canada, New Zealand and Mozambique.