McMullen County sits about 100 miles south of San Antonio, tucked into the brush country where South Texas ranch land gives way to oil fields. Roughly 600 people live there. Two stoplights in Tilden, the county seat. A courthouse that handles a fraction of the docket volume you would find in the counties surrounding Houston or Dallas. None of that smallness mattered when this case arrived.
What landed in the 343rd District Court was one of the largest oil and gas trespass disputes to reach a Texas jury in recent years, and it took nearly a decade to get from the initial filing to the verdict. Todd Mensing and AZA, the Houston trial firm formally known as Ahmad, Zavitsanos & Mensing, led the plaintiff's trial team through two weeks of testimony in February 2023. After more than a dozen expert witnesses and roughly five hours of deliberation, jurors returned a unanimous $41.8 million verdict for SilverBow Resources and El Dorado Gas & Oil against ETC Field Services, a subsidiary of Energy Transfer. Mensing was joined by AZA partners Taylor Freeman, Jane Robinson, and Cameron Byrd, alongside co-counsel from Hogan Thompson.
What Happened Underground
Energy Transfer operated a disposal well in the Wilcox geological formation near the town of Tilden, injecting hydrogen sulfide and carbon dioxide into the subsurface as part of its pipeline operations. SilverBow Resources and El Dorado Gas & Oil held mineral leases in adjacent areas. Their allegation was straightforward: the injected gases had potentially migrated laterally out of the permitted zone and had endangered their leases and interfered with its exploration, forcing costly equipment changes, altered drilling plans, and the abandonment of some existing wells to account for the risk that the injected acid gas created
Energy Transfer's first defense was jurisdictional. Because McMullen County has so few residents, the company sought a writ of mandamus in June 2017, arguing that contamination allegedly threatening the entire county made a fair local jury impossible. That challenge failed.
A second trip to the Texas Supreme Court produced a 2021 opinion, Regency Field Services, LLC v. Swift Energy Operating, LLC, that addressed when a trespass claim begins to run for a mineral lessee. For a lessee, the court held, the cause of action accrues when contamination first interferes with the right to explore, produce, and possess minerals. Some of SilverBow's claims were time-barred; others survived. Preparing the science and geology behind those surviving claims consumed years, requiring each side to assemble over a dozen expert witnesses.
A Cross-Examination That Reframed the Case
Todd Mensing and AZA argued that H2S and CO2 had drifted into SilverBow's lease areas, forcing the company to alter its operations at considerable expense. Energy Transfer took a simpler position: the plaintiffs could just drill around the contamination plume.
A turning point came during the cross-examination of an Energy Transfer expert. AZA partner Cameron Byrd pressed the witness on the drill-around argument, drawing out an admission that requiring SilverBow to change how it operated was itself an acknowledgment of interference.
"It was very crystallized in that moment, he pointed out even those measures would cost money," Mensing told The Texas Lawbook.
Jurors awarded SilverBow $24.5 million for lost net revenues from future wells and the cost of plugging and abandoning existing ones. El Dorado received $17.3 million for similar categories of damage. The jury rejected the claim that Energy Transfer's conduct rose to gross negligence.
"It is terrific to see the right thing happen. The jury afforded our clients the relief they deserve and forced Energy Transfer to take responsibility," Mensing said.
Where the Verdict Stands
Judge Janna Whatley signed the final judgment on April 19, 2023, case number M-14-0029-CV-C. TopVerdict.com placed the award among the Top 100 Verdicts nationally for 2023. The National Law Journal put it on its own Top 100 list. Within Texas, it ranked as the 15th-largest verdict statewide.
SilverBow's assistant general counsel, Jennifer Cadena, described the performance of Todd Mensing and AZA as "excellent" in a Texas Lawbook profile published in May 2024.
Energy Transfer filed a notice of appeal on July 14, 2023, sending the matter to the Fourth Court of Appeals in San Antonio. A briefing schedule was set by a Fourth Court order dated September 2025. Meanwhile, the same Tilden injection well has spawned additional litigation: a separate case, Ageron Energy, LLC v. ETC Texas Pipeline, Ltd., reached the Texas Supreme Court after Ageron alleged that H2S destroyed its drill pipe when it attempted to bore through the plume. That dispute raised related but distinct questions about standing, accrual, and the scope of mineral-lessee protections in subsurface trespass cases.
Continue: Q&A with Todd Mensing, Partner at Ahmad, Zavitsanos & Mensing (AZA Law)
