LEASES · O-1-15599 · OIL · DISTRICT 01
Hierholzer Seewald Unit
Marathon Oil EF LLC · Atascosa County · Eagleville (Eagle Ford-1) field
Hierholzer Seewald Unit is an RRC oil lease (O-1-15599) in Atascosa County operated by Marathon Oil EF LLC, with one well completed on it.
It has reported 189K barrels of oil and 214K mcf of gas since June 2011, last reporting volume in March 2026 (statewide data runs through April 2026).
It reported 1.09K barrels of oil in the 12 months through April 2026, down 88% on the year before; the lease peaked at 13.4K barrels in June 2011.
2 operators have filed production on it, most recently Marathon Oil EF LLC since November 2011.
- 189K
- bbl oil, all reported
- 214K
- mcf gas incl. casinghead
- 1.09K
- bbl oil, 12 months through Apr 2026
- -88%
- vs the 12 before
- 1
- wells completed on it
- 13.4K
- peak month, bbl (Jun 2011)
PDQ LEASE REPORTS · FIRST JUN 2011 · LAST VOLUME MAR 2026 · STATEWIDE DATA THROUGH APR 2026
Oil by month
Barrels reported on Form PR for the whole lease. The latest months are revised upward as late reports arrive.
12 months through Apr 2026 1,086 · prior 12 8,961(-88%)
Gas by month
Gas-well gas plus casinghead gas, mcf. On an oil lease all gas is reported as casinghead. The latest months are revised upward as late reports arrive.
12 months through Apr 2026 243 · prior 12 8,144(-97%)
Decline curve
None shown. Petrora fits an Arps curve only when the last ten years of oil reports follow one decline closely enough to project (R² of 0.7 or better over at least a year since the peak). This lease's recent history does not, so a projection would be a guess dressed as a number.
Who reported it
Each run of months one operator filed the production report, oldest first, with what it reported in them.
- Hilcorp Energy CompanyMay 2011 → Oct 2011 · 6 mo46.2K bbl oil · 40.2K mcf gas
- Marathon Oil EF LLCNov 2011 → Jul 2026 · 177 mo143K bbl oil · 174K mcf gas
Wells on the lease
FROM COMPLETION REPORTS · PRODUCTION ABOVE IS THEIR TOTAL
About this data
Monthly oil, gas, and casinghead from the RRC PDQ production dump, which lags the reporting month by two to three months; figures shown through Apr 2026. Wells from completion reports; operator runs from who filed each month's report.
Developers: this page as JSON is GET /v1/data/leases/tx/o-1-15599, documented in the API reference.