Two stacked Texas plays in the same column — what's the difference, and what does it mean if your lease covers both?
Quick answer
The Austin Chalk and the Eagle Ford Shale are stacked above one another across central and south Texas. The Eagle Ford sits directly below the Austin Chalk; in most counties of overlap, the two zones are separated by 100-300 ft. Many Giddings-trend leases — and most south Texas leases — cover both depths.
For mineral owners whose lease covers both, your interest may receive royalty income from Austin Chalk wells, Eagle Ford wells, or both — depending on what each operator chooses to drill.
Austin Chalk: Upper Cretaceous fractured chalk; production driven by natural fractures supplied by chalk matrix; depths 7,000-12,000 ft TVD across the Giddings trend
Eagle Ford Shale: Upper Cretaceous calcareous shale; production driven by induced fractures from hydraulic stimulation of low-permeability matrix; depths typically 9,000-13,000 ft TVD in central Texas; deeper to the south
Both plays produce oil, condensate, and natural gas — but the mix varies by depth and geography:
Austin Chalk: predominantly oil and condensate in the Giddings trend; gassier in the south
Eagle Ford: three-window play — oil window in the north (Karnes / DeWitt), condensate window in the middle (Live Oak / McMullen), dry-gas window in the south (Webb / Dimmit / La Salle)
Austin Chalk: commercial production since 1960; commercial horizontal since the early 1990s; modern long-lateral era began approximately 2018
Eagle Ford: commercial production began 2008-2009 with Petrohawk's Hawkville field discovery; the play is purely a 21st-century unconventional phenomenon
Austin Chalk: mix of modern long-lateral redevelopers (EOG, Magnolia, Crownquest) and a long tail of legacy short-lateral horizontal and vertical operators going back to the 1960s
Eagle Ford: dominated by large public independents (EOG, ConocoPhillips, Chesapeake, Devon, Marathon, Magnolia, BP) with limited private/stripper operator presence
Many Giddings-trend and south Texas mineral interests are subject to leases that cover BOTH Austin Chalk and Eagle Ford depths. For a current valuation, both zones must be considered:
Currently producing zone — what's actually generating royalty checks today
Other-zone optionality — the value of future drilling in the unproduced zone
Lease terms specific to each zone — some leases have different royalty rates or different held-by-production rules per depth
A valuation that only credits the currently-producing zone undervalues the interest. Request a written offer that explicitly accounts for both Austin Chalk and Eagle Ford economics.
Buckhead Energy buys mineral rights across both Austin Chalk and Eagle Ford depths.
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