Subsurface contamination doesn’t leave a mark anyone can photograph. It accumulates underground over years, detectable only through wellbore samples, pressure readings, and reservoir simulations. When SilverBow Resources and El Dorado Gas & Oil went to trial against ETC Field Services in McMullen County in February 2023, AZA Law and co-counsel from Hogan Thompson put more than a dozen expert witnesses on the stand to prove that Energy Transfer’s injection operations had physically invaded two mineral estates and caused $41.8 million in quantifiable damage.

The expert count reflected what subsurface trespass cases demand: a proof chain running from geological modeling through reservoir engineering to economic damages. Each link can’t be handled by the same specialist.

The evidence chain AZA Law built

Todd Mensing, an attorney and AZA Law firm partner who served as lead trial counsel for SilverBow, assembled a team of experts spanning three disciplines. Geologists mapped the physical path of hydrogen sulfide and carbon dioxide through the Wilcox formation after Energy Transfer injected those gases into a disposal well near Tilden. Petroleum engineers documented how the migration disrupted SilverBow’s and El Dorado’s ability to drill. Economists translated the operational interference into a damages figure tied to lost net revenues and well abandonment costs.

Each category of expert carried a specific burden. The geologists had to establish that the injected gases had physically entered the plaintiffs’ mineral estate. The petroleum engineers had to connect that intrusion to specific operational harms: wells that could not be drilled as planned, equipment modifications required to handle corrosive hydrogen sulfide, production timelines that had to be restructured. The economists had to anchor every dollar of the damages claim to one of those documented harms.

Texas courts evaluate scientific expert testimony under Rule of Evidence 702, which applies a six-factor reliability test: whether the theory has been tested, whether it relies on subjective interpretation, whether it has undergone peer review, its potential error rate, its general acceptance in the relevant scientific community, and whether it has non-judicial applications. Reservoir simulation modeling, the tool the trial team’s geologists used to demonstrate plume migration, has been employed in the oil and gas industry for decades and is generally accepted as reliable. That acceptance didn’t guarantee admissibility, but it gave the modeling a foundation strong enough to clear the threshold.

Where the defense broke open

Energy Transfer fielded its own experts, and subsurface models were presented showing that the injected gases had remained within the permitted zone. The trial turned on whose models the jury believed.

AZA Law’s cross-examination targeted the credibility of Energy Transfer’s modeling directly. Mensing told the Texas Lawbook that the first turning point came when his team forced the defense’s experts to admit that their models did not reflect real-world conditions. “The first big crack was when we got their experts to admit that their models do not reflect the real world. And it was that stark,” he said.

The second moment came during partner Cameron Byrd’s cross-examination of a different defense expert. Energy Transfer had argued that SilverBow and El Dorado could simply drill around the contamination plume. Byrd pressed the witness until he conceded that requiring the plaintiffs to change their operations was itself an acknowledgment of interference.

“Cameron Byrd pointed out on cross that that’s admitting interference, because it’s making us do something differently than we have the right to do, which is drill the way we want,” Mensing said. “It was very crystallized in that moment, he pointed out even those measures would cost money.”

From geological data to a jury verdict

After two weeks of testimony and roughly five hours of deliberation, the jury awarded SilverBow $24.5 million and El Dorado $17.3 million. The damages categories tracked the expert testimony precisely: lost net revenues from wells that could not be completed as planned, and costs for plugging and abandoning existing wells that the contamination had rendered unworkable.

The gross negligence claim was rejected by the jury, which would have opened the door to punitive damages. That finding limited the recovery to compensatory damages, but the $41.8 million combined award still placed the case among the National Law Journal’s top 100 verdicts for 2023.

Most commercial disputes involve harm that surfaces in financial statements, contracts, or visible physical damage. Oil and gas trespass through subsurface injection isn’t like that. The harm accumulates invisibly, underground, over years of field operations. Proving it requires trial teams willing to invest in the kind of expert infrastructure the AZA Law firm assembled for the SilverBow case: geologists who can reconstruct a plume’s migration path, engineers who can document operational interference well by well, and economists who can present a damages model that a lay jury can follow from the first dollar to the last.

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