“Empty Space Is Not a Mineral”: Surface Ownership of Subsurface Caverns and In‑Kind Salt Royalties in Myers‑Woodward, LLC v. Underground Services Markham, LLC

“Empty Space Is Not a Mineral”: Surface Ownership of Subsurface Caverns and In‑Kind Salt Royalties in Myers‑Woodward, LLC v. Underground Services Markham, LLC

I. Introduction

The Supreme Court of Texas’s decision in Myers‑Woodward, LLC v. Underground Services Markham, LLC and United Brine Pipeline Company, LLC, No. 22‑0878 (Tex. May 16, 2025), is a major contribution to Texas property and oil-and-gas law in two distinct but related areas:

  • Ownership and use of subsurface “pore space” and salt caverns; and
  • Characterization of reserved mineral royalties as in‑kind versus value-based.

The dispute arises from a salt dome in Matagorda County where modern technology has made underground salt caverns highly valuable for hydrocarbons storage. The instruments in issue—a 1947 mineral deed and correction deed, and a 2008 salt deed—were drafted long before salt caverns became a storage commodity, leaving the parties to litigate who owns the newly created cavern space and how royalties on salt production must be calculated.

The Court’s opinion, authored by Chief Justice Blacklock, establishes and reaffirms several key principles:

  • Subsurface space, including voids and caverns, belongs to the surface estate absent an express agreement to the contrary—even when that space lies within a salt formation.
  • Empty space is not itself a “mineral” and is not part of the mineral estate simply because it is created by mineral extraction.
  • The mineral estate’s “dominant” status confers only a limited, implied right to use surface and subsurface space as reasonably necessary to produce the tract’s minerals; it does not authorize off‑lease storage uses.
  • A mid‑20th‑century deed reserving “a royalty of 1/8 of all the oil, gas, or other minerals produced” created an in‑kind royalty in “other minerals” (including salt), not merely a right to 1/8 of market value at the wellhead.
  • The court of appeals decision in Mapco, Inc. v. Carter, to the extent it recognized mineral‑estate ownership of salt-storage caverns, is expressly overruled.

Collectively, these holdings entrench a relatively bright-line rule for pore-space ownership and provide important guidance for royalty interpretation in legacy mineral instruments.

II. Case Background

A. The Property and Chain of Title

  • Tract: 160 acres in Matagorda County, Texas.
  • Current surface owner: Petitioner Myers‑Woodward, LLC (“Myers”).
  • Mineral history:
    • 1947 mineral deed: Myers’s predecessors conveyed the mineral estate—“all of the said oil, gas and other minerals in, on and under said land”—to the predecessor of Respondents, while reserving a royalty interest.
    • 1947 correction deed: Executed three months later to correct an “inadvertent” failure to reserve royalty in “gas or other minerals.” It reserved “a royalty of 1/8 of all the gas or other minerals in, on, or under, or that may be produced from” the land, so that the grantors would receive “a total royalty interest of 1/8 of all the oil, gas, or other minerals (except sulphur) produced.”
    • 2008 salt deed: By this time, Texas Brine Company held the mineral estate. It conveyed to USM “all of [its] right, title and interest, in and to all of the salt and salt formations only” in the property, “subject to” existing royalty obligations.

B. The Dispute

After acquiring the salt rights, USM began solution mining and created substantial underground caverns. Two streams of conflict emerged:

  1. Ownership and use of the salt caverns
    • USM sought a declaration that it owned the subsurface caverns created by its mining and could use them to store hydrocarbons and other substances produced off‑site.
    • Myers contended that the caverns were part of the surface estate, and that USM’s use was limited to the purposes specified in the 1947 deed—“mining, drilling and operating for [salt]” and related operations.
  2. Calculation of salt royalties
    • The 1947 correction deed reserved a 1/8 royalty in “gas or other minerals.”
    • USM argued Myers was entitled to 1/8 of the market value at the wellhead of the salt (about $0.09/ton, producing ~$258,850 in total royalty), backed by fixed-price royalty agreements as “comparable sales.”
    • Myers contended the royalty was in kind, entitling it to 1/8 of the salt produced (or the net proceeds from its actual sale). Myers’s expert, using USM’s actual sales to Formosa Plastics and Occidental Chemical, calculated that 2015–2017 royalties should exceed $1.3 million, and Myers asserted over $2 million for the full production period.

C. Lower-Court Rulings

  • District court
    • Held that USM “is the owner of the subsurface caverns created by its salt mining activities.”
    • But denied that USM could store off‑tract hydrocarbons there, limiting use to the purposes in the 1947 deed—mining, drilling, operating for salt, and associated facilities.
    • Ruled that Myers was entitled to 1/8 royalty “based on the market value of the salt at the point of production,” adopting USM’s market‑value theory and valuation (~$258,850).
  • Court of appeals (Corpus Christi–Edinburg), 699 S.W.3d 1 (Tex. App. 2022)
    • Affirmed the royalty calculation and market‑value approach.
    • Reversed the cavern ownership ruling, holding that, under Texas law and the instruments, the surface owner retains ownership of non‑mineral subsurface components—including voids and caverns.
    • Limited USM’s use of caverns to that reasonably necessary to produce the salt, rejecting any claim to store off‑lease hydrocarbons.
    • Expressly questioned the consistency of Mapco, Inc. v. Carter, 808 S.W.2d 262 (Tex. App.—Beaumont 1991), with modern Texas law.

Both sides petitioned for review. The Supreme Court granted both petitions.

III. Summary of the Supreme Court’s Opinion

A. Subsurface Cavern Ownership and Use

The Court affirms the court of appeals’ core holding on cavern space:

  • Ownership: The surface owner, Myers, owns the subsurface space, including the hollow salt caverns created by USM’s mining operations.
  • Nature of mineral estate: USM owns the salt as a mineral, but not the “salt formation” and not the voids created within it. “Empty space is not a mineral, no matter how economically valuable it becomes.”
  • Use rights: USM, as holder of the dominant mineral estate, may use surface and subsurface (including caverns) only as reasonably necessary to produce salt from the tract. It has no right to use those caverns to store hydrocarbons or other substances produced off‑site.
  • Rule restated and generalized: “The surface owner, and not the mineral lessee, owns the possessory rights to the space under the property's surface,” absent an agreement otherwise—even when that space is within mineral‑bearing formations.
  • Mapco overruled: To the extent Mapco, Inc. v. Carter had recognized mineral‑estate ownership of salt storage caverns, it is expressly overruled as inconsistent with Texas law.

B. Royalty Characterization and Calculation

On the royalty issue, the Court reverses the lower courts:

  • The 1947 correction deed’s reservation of “a royalty of 1/8 of all the gas or other minerals in, on, or under, or that may be produced” is interpreted as an in‑kind royalty, parallel to the in‑kind oil royalty explicitly reserved in the original 1947 deed.
  • Thus, Myers is entitled to a 1/8 interest in the actual minerals produced (here, salt) or, in monetary terms, to 1/8 of the net proceeds from the sale of that production, not merely to 1/8 of an independently determined “market value at the point of production.”
  • The trial proceeded on the mistaken premise that only market value at the wellhead was relevant. That error likely affected evidence, expert testimony, and related rulings (including an implied marketing covenant claim), so the Court remands for a new determination under the proper legal standard.
  • The Court rejects USM’s argument that Myers waived the in‑kind theory by later asking for market‑value relief in a summary-judgment motion after the trial court had already rejected the in‑kind argument.

In final disposition:

  • The court of appeals’ judgment is affirmed as to ownership and use of cavern space.
  • The court of appeals’ judgment is reversed as to the amount of royalty owed.
  • The case is remanded to the district court for further proceedings consistent with the opinion.

IV. Detailed Analysis

A. Precedents and Authorities Shaping the Decision

1. Humble Oil v. West (Texas: Reservoir vs. Minerals)

In Humble Oil & Refining Co. v. West, 508 S.W.2d 812 (Tex. 1974), the Court conceptually distinguished:

  • the mineral estate, and
  • “the matrix of the underlying earth, i.e., the reservoir storage space.”

There, because Humble owned both surface and minerals, the distinction did not resolve any ownership conflict, but it foreshadowed a doctrinal line between:

  • the minerals themselves, and
  • the geological structure and pore space that can hold those minerals or other substances.

Myers‑Woodward seizes on that distinction and extends it decisively to the context of separated estates: the “reservoir storage space” belongs to the surface estate, not the mineral estate, absent a contrary grant.

2. Lightning Oil and Regency: Possessory Rights to Subsurface Space

In Lightning Oil Co. v. Anadarko E&P Onshore, LLC, 520 S.W.3d 39 (Tex. 2017), the Court held that a mineral owner did not have the right to exclude a neighboring operator from drilling through its subsurface to reach minerals in an adjacent estate, so long as no unreasonable interference with mineral development occurred. The Court emphasized:

“The mineral estate generally includes the right to possess the minerals but does not include the right to possess the specific place or space where the minerals are located.”

Later, in Regency Field Services, LLC v. Swift Energy Operating, LLC, 622 S.W.3d 807 (Tex. 2021), the Court crystallized the principle:

“[T]he surface owner, and not the mineral lessee, owns the possessory rights to the space under the property's surface.”

These cases provide the doctrinal backbone for the Myers‑Woodward holding: the mineral estate is conceptualized as a profit‑à‑prendre (a right to exploit and remove minerals) coupled with implied use rights, rather than fee-simple ownership of the rock, voids, and spaces beneath the surface.

3. Dunn‑McCampbell & Emeny: Federal Courts Applying Texas Law

Two federal decisions, applying Texas law and cited approvingly, reinforce this approach:

  • Dunn‑McCampbell Royalty Interest, Inc. v. National Park Service, 630 F.3d 431 (5th Cir. 2011):
    “[T]he holder of a mineral estate has the right to exploit minerals, but does not own the subsurface mass.”
  • Emeny v. United States, 412 F.2d 1319 (Ct. Cl. 1969):
    “[T]he surface of the leased lands and everything in such lands, except the oil and gas deposits covered by the leases, [are] still the property of the respective landowners. This include[s] the geological structures beneath the surface, including any such structure that might be suitable for the underground storage of ‘foreign’ or ‘extraneous’ gas produced elsewhere.”

The Court incorporates these views to affirm that “pore space” and geological structure are part of the surface estate.

4. Treatises: Smith & Weaver, Williams & Meyers, and Kuntz

The Court’s position aligns with leading treatise authority:

  • Smith & Weaver, Texas Law of Oil and Gas: Pore-space storage is more properly a surface right.
  • Williams & Meyers, Oil and Gas Law: The mineral estate confers only limited exploitation rights “including the right to use pore space while leaving the surface estate owner as the corporeal owner of both the space and the rock.” Storage of substances from other lands is not reasonably implied in favor of the mineral estate.
  • Kuntz, The Law of Oil and Gas: The landowner has the right to use land for subsurface storage of gas and other substances, absent regulation to the contrary.

These authorities characterize pore space and geological structures as a component of the surface estate, not part of the severed mineral estate.

5. Mapco v. Carter: Now Overruled Minority View

Mapco, Inc. v. Carter, 808 S.W.2d 262 (Tex. App.—Beaumont 1991), suggested that a mineral estate owner retained a property interest in storage caverns created by salt mining and was entitled to compensation for their use. Though this Court previously reversed Mapco “on other grounds,” it had not squarely confronted its cavern‑ownership rationale until Myers‑Woodward.

Here, the Court expressly disapproves and overrules Mapco to the extent it conflicts with the rule that subsurface storage space belongs to the surface owner. It notes that:

  • Mapco cited little Texas authority for its key holding,
  • it has rarely been cited and is widely viewed as the minority position, and
  • it stands in tension with the later cases of Lightning Oil and Regency Field Services.

6. Coastal Oil v. Garza: Rule of Capture and USM’s “Solid Minerals” Argument

USM attempted to confine the “pore space belongs to surface” rule to migratory minerals like oil and gas. It leaned on Coastal Oil & Gas Corp. v. Garza Energy Trust, 268 S.W.3d 1 (Tex. 2008), where the Court recognized the tension between:

  • ownership-in-place of oil and gas, and
  • the rule of capture (the right to take migrating hydrocarbons as they flow into a well).

Coastal Oil emphasizes that the mineral owner is not entitled “to the molecules actually residing below the surface,” but rather to a fair chance to recover them. USM took from this that:

  • The limitation on “molecule ownership” is unique to migratory hydrocarbons governed by capture principles.
  • By contrast, for solid minerals like salt or coal, the mineral owner should own the actual molecules—and by extension, the physical structures (voids) created when those molecules are removed.

The Court acknowledges the difference between migratory and solid minerals and notes coal‑jurisdiction authority (e.g., Middleton v. Harlan‑Wallins Coal Corp., 66 S.W.2d 30 (Ky. 1933); Lillibridge v. Lackawanna Coal Co., 22 A. 1035 (Pa. 1891)) supporting broader rights for coal owners to use mined-out caverns. But the Court declines to build a separate Texas rule for solid minerals. Instead, it rests on two simpler points:

  1. Textual chain of title: USM’s predecessor received a conveyance of “minerals,” not of “salt formations,” and could not convey more than it owned.
  2. Bright-line administrability: Introducing a special rule for cavern space within mineral formations (salt) and a different rule for caverns within non‑mineral rock would inject needless complexity into property law and transactional practice.

Thus, the Court avoids deciding whether solid minerals are always to be treated like oil and gas for all purposes, but holds that, in any event, USM does not own the cavern space.

7. Coyote Lake Ranch, Acker, and Robinson: Implied Surface-Use Rights and Their Limits

On the scope of USM’s usage rights in the caverns, the Court relies on well‑established implied-right doctrines:

  • Coyote Lake Ranch, LLC v. City of Lubbock, 498 S.W.3d 53 (Tex. 2016):
    “The severed mineral estate has the implied right to use as much of the surface estate as reasonably necessary to produce and remove minerals. The mineral estate is called ‘dominant’ and the surface estate ‘servient,’ not because the mineral estate is in some sense superior, but because it receives the benefit of the implied right of use of the surface estate.”
  • Acker v. Guinn, 464 S.W.2d 348 (Tex. 1971):
    The mineral owner is “entitled to make reasonable use of the surface” (and, by extension, subsurface) for mineral production, but not beyond that purpose.
  • Robinson v. Robbins Petroleum Corp., 501 S.W.2d 865 (Tex. 1973):
    The mineral owner may not “increase the burden on the surface estate for the benefit of additional lands,” and the surface owner is entitled to protection from non‑consensual uses that benefit production on other tracts.

These doctrines allow USM to use cavern space if reasonably necessary for salt production, but not to transform that space into a commercial storage facility for foreign hydrocarbons.

8. Heritage, Nettye Engler, Yzaguirre, BlueStone: Royalty Interpretation and Market Value

On the royalty side, the Court situates its analysis within its broader contract‑interpretation jurisprudence:

  • Heritage Resources, Inc. v. NationsBank, 939 S.W.2d 118 (Tex. 1996):
    “Our task is to ascertain the parties’ intentions as expressed in the [document].”
  • Nettye Engler Energy, LP v. BlueStone Nat. Res. II, LLC, 639 S.W.3d 682 (Tex. 2022):
    “[P]arties are free to make their own bargains, and courts are obligated to enforce agreements as the parties intended.”
  • Yzaguirre v. KCS Res., Inc., 53 S.W.3d 368 (Tex. 2001): Recognizes that “market value” and “proceeds” can diverge, and that market value is typically determined via comparable sales.
  • BlueStone Nat. Res. II, LLC v. Randle, 620 S.W.3d 380 (Tex. 2021): Approves the “workback method,” which estimates wellhead market value by backing out post‑production costs from downstream sales proceeds.

The Court in Myers‑Woodward underscores that it is not announcing a new default rule that any specific phrasing always yields an in‑kind royalty. Instead, the opinion applies the general contract-law method—examining the entire set of instruments, their history, and context—to conclude that, here, the parties intended an in‑kind royalty on gas and other minerals.

B. The Court’s Legal Reasoning

1. Ownership of Salt Caverns: “Empty Space Is Not Salt”

The cavern‑ownership analysis proceeds in two key steps: (1) a textual chain-of-title analysis, and (2) a preference for a simple, consistent rule for subsurface space.

a. Chain of Title and Scope of the Mineral Conveyance

The Court begins with an important caution: labels like “surface estate” and “mineral estate” are useful but not determinative. The actual rights of each estate depend on the language of the conveyances.

  • 1947 deed: conveyed “all of the said oil, gas and other minerals in, on and under said land” to USM’s predecessor.
  • What is a “mineral” here? Salt qualifies; the conveyance includes the salt itself but not necessarily every geological feature of the salt dome.
  • 2008 salt deed: conveyed to USM “[a]ll of [Texas Brine’s] right, title and interest, in and to all of the salt and salt formations only.”

USM argued that the 2008 reference to “salt formations” included the entire geological mass, including voids. The Court calls this out as overreaching:

  • USM’s predecessor never received “salt formations” as such; it received minerals.
  • Under the basic nemo dat principle (“a grantor cannot convey to a grantee a greater or better title than [he] holds”), the 2008 deed could not enlarge USM’s interest beyond what the predecessor owned.
  • Thus, “the most USM could have obtained from its predecessor is ownership of the salt itself—not ownership of a ‘salt formation,’ and not ownership of non-salt substances or spaces adjacent to the salt.”

This leads to the Court’s blunt formulation:

“Put more simply, despite its apparent complexity, much of this case boils down to the elementary observation that empty space is not salt.”

Because the mineral estate includes only the salt, not the spaces where salt used to be, the caverns are part of the surface estate.

b. Bright-Line Rule for Subsurface Space

The Court then reinforces the general rule that emerged from Lightning Oil and Regency Field Services:

“We therefore hold, once again, that ‘the surface owner, and not the mineral lessee, owns the possessory rights to the space under the property's surface,’ absent an agreement otherwise.”

USM’s contrary position would require Texas law to draw a distinction between:

  • subsurface voids within mineral‑bearing formations (e.g., salt domes), which USM says should belong to the mineral estate; and
  • subsurface voids within non‑mineral rock formations, which everyone agrees are surface estate property.

The Court expressly declines to create such a bifurcated regime, citing the value of simplicity and predictability:

  • It is not clear what the practical consequences would be of carving out a separate rule for salt‑encased space.
  • Regardless, creating special sub‑classes of pore space would “invite greater complexity and uncertainty into the law.”

By reaffirming a uniform rule—that subsurface space belongs to the surface owner unless expressly granted—the Court resolves the longstanding tension introduced by Mapco and aligns Texas with the mainstream property-law approach to pore space.

2. Scope of the Mineral Estate’s Implied Right to Use Caverns

Having located cavern ownership in the surface estate, the Court addresses whether USM nonetheless has a right to use that space under the “dominant estate” doctrine.

  • The mineral estate has an implied easement to use as much of the surface and subsurface as is “reasonably necessary to recover its minerals.”
  • This right is functional and limited: it exists for the purpose of developing and producing the minerals from the tract.

Applying that standard:

  • USM may use cavern space “for the production of its salt,” e.g., to conduct solution‑mining operations, handle brine, dispose of waste associated with salt production, etc., so long as such use is reasonably necessary and does not unreasonably burden the surface.
  • USM may not use cavern space to store hydrocarbons or other substances produced off‑site. Such storage:
    • does not aid salt production,
    • likely impedes further mining, and
    • imposes additional burdens on the surface for the benefit of outside lands, which Robinson prohibits.

Crucially, USM did not even attempt to argue that off‑site storage is “reasonably necessary” to produce salt. Its entire claim was premised on asserted ownership of the formations, not an implied production right. Once the ownership claim fails, there is no remaining legal basis for USM’s proposed storage use.

3. Royalty Interpretation: In‑Kind vs Market-Value Royalty

The royalty dispute hinges on how to characterize the 1947 correction deed’s reservation of:

“a royalty of 1/8 of all the gas or other minerals in, on, or under, or that may be produced from the above described land.”

The parties agreed that the critical issue was whether this language creates:

  • an in‑kind royalty (i.e., a share of actual production, or its sale proceeds), or
  • a value-based royalty (i.e., 1/8 of market value at the wellhead, regardless of actual sales price).
a. Starting Point: The In‑Kind Oil Royalty in the Original Deed

The original May 1947 mineral deed reserved:

“a perpetual one-eighth (1/8th) royalty on all the oil that may be produced and saved from [the property], the same to be delivered at the wells or to the credit of Grantors . . . into pipe line to which the wells may be connected.”

Both parties accept that this language—especially “to be delivered at the wells”—unambiguously creates an in‑kind oil royalty. They also agree that explicit “delivery” language is a hallmark of in‑kind royalties.

b. The Correction Deed: Adding Gas and “Other Minerals”

The August 1947 correction deed explains its own purpose:

  • The parties had “inadvertent[ly]” failed to reserve any royalty in gas or other minerals in the original deed.
  • They now “amended” the deed so that, “in addition to the royalties on oil and sulphur therein reserved,” the grantors would receive “a royalty of 1/8 of all the gas or other minerals” from the land.
  • It concludes by stating the parties’ overarching intent:
    “it being intended that [the grantors] shall receive a total royalty interest of 1/8 of all the oil, gas, or other minerals (except sulphur) produced from said land.”

USM’s argument was essentially formalistic: because the correction deed did not repeat the “delivered at the wells” language for gas and other minerals, those royalties must be value-based. The Supreme Court finds this unpersuasive for two reasons:

  1. Textual symmetry: The correction deed describes the royalty on oil, gas, and other minerals together as a “total royalty interest of 1/8 of all” production, without distinction. If the absence of “delivery” language meant gas and other minerals were value-based, it would also imply that the correction deed either misdescribes or alters the in‑kind nature of the oil royalty—something the Court finds unlikely given the deed’s stated purpose.
  2. Stated intent of the parties: The correction deed states it was intended simply to add gas and other minerals to the preexisting royalty structure, not to create a wholly different royalty regime for those substances.

The Court thus concludes that:

  • “Myers’s understanding of its royalty—as an in-kind royalty—is not inconsistent with a natural reading of the deed’s language.”
  • The more plausible reading of the instruments, taken together, is that the parties meant to create identical 1/8 in‑kind royalties for oil, gas, and other minerals.

Importantly, the Court does not announce a categorical rule that any reserving language of “1/8 of all the oil, gas, and other minerals produced” is always in‑kind. Instead, it explicitly limits its holding to the reading of this 1947 deed pair, in which:

  • the original deed already contained an in‑kind oil royalty with delivery language, and
  • the correction deed self‑identified as a technical fix to include gas and other minerals in the same 1/8‑of‑production royalty.

The Court also notes, without deciding, the oddity that:

  • USM’s market‑value approach would yield about $258,850 in total royalties, whereas
  • Myers’s net‑proceeds approach (based on actual Formosa and Occidental sales) would yield in excess of $2,000,000—a more than seven‑fold difference.

Given salt’s relative price stability during the relevant period, the Court implicitly questions how such a gulf could exist between market value and actual sale price. It acknowledges, consistent with Yzaguirre, that such divergence is possible, but flags that when such large differences appear, courts should be especially careful in construing contract language and in choosing between market‑value and proceeds measures.

d. No Waiver by Myers

Finally, the Court rejects USM’s waiver argument. After the trial court had already denied Myers’s in‑kind interpretation, Myers later moved for summary judgment seeking “1/8 of the market value at the point of production,” which USM characterized as an abandonment of the in‑kind theory.

The Supreme Court disagrees, aligning with In re Estate of Phillips, 700 S.W.3d 428 (Tex. 2024):

  • A party does not waive an argument simply by advancing a fallback position after the trial court has definitively rejected the primary theory.
  • Myers properly preserved its in‑kind argument at the trial level; the judgment is adverse to Myers on that issue; and the argument is squarely before the appellate courts.

C. Impact on Future Cases and Areas of Law

1. Pore Space and Subsurface Storage: A Clear Texas Rule

Myers‑Woodward cements a clear rule in Texas:

  • Ownership: The surface estate owns subsurface pore space and voids under the land—including caverns within salt or other mineral formations—unless a conveyance expressly provides otherwise.
  • Mineral estate role: The mineral owner’s rights in subsurface space are limited to:
    • possession of the minerals themselves; and
    • a nonpossessory, implied easement to use as much surface and subsurface as is reasonably necessary to produce those minerals from the tract.

Practically, this has immediate relevance for:

  • Hydrocarbon storage in salt caverns and depleted reservoirs;
  • CO2 sequestration projects, where large pore‑space volumes are needed for permanent storage;
  • Produced‑water injection and other subsurface disposal operations; and
  • Brine/salt cavern projects used for commercial storage of third‑party commodities.

In all such contexts, unless instruments say otherwise, the default contracting counterparty for storage and pore‑space rights is the surface owner, not the mineral owner—although mineral owners and lessees will still be central in negotiating how such operations coexist with mineral development.

2. Drafting and Transactional Practice

The opinion provides strong incentives for careful drafting:

  • Pore-space clauses: Parties who want the mineral estate to own or control pore space (or caverns) must say so expressly. Reliance on generic “oil, gas, and other minerals” grants will not suffice.
  • Salt and other solid minerals: For salt domes, sulfur mines, coal seams, and similar resources, deed drafters should specify whether the grant includes:
    • the mineral in place only,
    • the entire formation (rock matrix and voids), or
    • storage rights (including use for off‑tract substances).
  • Royalty clauses: Where parties desire a value-based royalty, they should draft unambiguous language (e.g., “royalty shall be paid in cash in an amount equal to 1/8 of the market value at the wellhead”) rather than relying on shorthand “1/8 of all production” language.

3. Litigation Over Legacy Instruments

For older deeds and leases:

  • Pore space: Surface owners are now in a stronger position to claim ownership and control of subsurface structures, even if those structures were created by a mineral operator’s efforts.
  • Royalties: Royalty owners will likely rely on Myers‑Woodward to argue that broadly phrased “1/8 of all the oil, gas, and other minerals produced” reservations—especially where coupled with delivery or physical-production language—are in‑kind, or at least “proceeds”‑based.
    • Operators will attempt to distinguish this case based on its specific correction‑deed context and explicit reference to delivery in the original deed.

4. Alignment with National Trends

The decision aligns Texas with the emerging national consensus and scholarly commentary that:

  • surface owners own subsurface pore space;
  • mineral owners hold limited exploitation rights; and
  • storage of “foreign” substances (e.g., off‑tract hydrocarbons, CO2) is a surface‑estate use absent explicit grant.

This uniformity will facilitate cross‑jurisdictional investment in large‑scale storage projects by clarifying predictable default rules in Texas.

V. Complex Concepts Simplified

Surface Estate
The bundle of rights retained by a landowner when the mineral estate is severed. It includes:
  • the land’s surface,
  • the non‑mineral subsurface (rock, soil, and voids), and
  • the airspace above the land,
subject to any easements (including the mineral estate’s implied use right).
Mineral Estate
A separate estate that includes:
  • ownership of the specified minerals in place (e.g., oil, gas, salt), and
  • a right to enter the land and use as much of the surface and subsurface as reasonably necessary to explore for, produce, and remove those minerals.
It does not include ownership of the surrounding rock matrix or pore space unless explicitly granted.
Dominant Estate
The mineral estate is called “dominant” because it carries an implied easement to use the surface (and subsurface) to produce minerals. The surface estate is “servient” in that respect, but still owns all property interests not expressly conveyed.
Pore Space / Cavern Space
The voids, hollows, or microscopic spaces within rock formations that can hold fluids or gases. In this case, pore space includes both:
  • the naturally occurring porosity and permeability of rock, and
  • the large artificial caverns created by removing salt.
Texas law now clearly treats pore space as part of the surface estate absent a contrary agreement.
In‑Kind Royalty
A royalty interest that entitles the holder to:
  • a share of actual production (e.g., 1/8 of the oil or salt at the wellhead), or
  • the proceeds from the sale of that share of production (after appropriate costs are deducted, depending on the contract).
Language referencing delivery of physical minerals to the royalty owner (e.g., “to be delivered at the wells”) is classic in‑kind language.
Value-Based Royalty (Market Value Royalty)
A royalty that entitles the holder to a percentage of the market value of production at a specified location (often “at the wellhead”), regardless of the actual price obtained by the operator. Market value is usually proven through comparable sales or the workback method.
Market Value at the Wellhead & Workback Method
“Market value at the wellhead” is the price a willing buyer would pay a willing seller for the product at the wellhead, absent compulsion. When actual sales occur downstream (e.g., at a plant), the workback method estimates wellhead value by:
  1. starting with the downstream sales price, then
  2. subtracting reasonable post‑production costs (transport, processing, etc.) from the wellhead to the point of sale.
Rule of Capture
A doctrine primarily applicable to oil and gas, under which a landowner or lessee who drills a well and produces hydrocarbons owns them even if they migrated from beneath neighboring lands. It complicates the notion of owning specific “molecules” under a tract and thus influences how courts conceptualize mineral ownership.
Implied Covenant to Market
In many leases, courts imply a duty on the operator to market production reasonably and obtain the best price reasonably available under prevailing conditions. Although not decided in detail here, the trial court’s error about the nature of the royalty potentially affected Myers’s implied covenant claim, contributing to the need for remand.
Correction Deed
An instrument executed after an earlier deed, intended to correct mistakes or omissions in the original conveyance. Courts read correction deeds together with original deeds to determine the overall intent of the transaction.
Waiver in Appellate Practice
A party may waive an argument by failing to raise it in the trial court or by expressly abandoning it. However, merely advancing alternative or fallback theories after the trial court has rejected a primary argument does not constitute waiver of that primary argument on appeal.

VI. Conclusion: Key Takeaways and Broader Significance

Myers‑Woodward, LLC v. Underground Services Markham, LLC is a landmark in Texas property and energy law, with two especially important contributions.

  1. Subsurface Caverns and Pore Space
    • The Court squarely holds that subsurface space belongs to the surface owner absent a contrary agreement, even when that space lies within a salt formation or other mineral‑bearing geological structure.
    • The mineral estate does not own the rock or voids; it owns the minerals and an implied right to use surface and subsurface space as reasonably necessary for on‑tract production.
    • Mapco’s contrary suggestion that mineral owners own salt-storage caverns is expressly rejected.
    • This ruling provides a clear and administrable framework for underground storage, injection, and sequestration projects in Texas and aligns the state with mainstream doctrinal and scholarly views.
  2. Royalty Characterization in Legacy Instruments
    • By carefully reading the original 1947 deed and its correction deed together, the Court concludes that a reservation of “a royalty of 1/8 of all the gas or other minerals” is an in‑kind royalty where the deeds show the parties intended a unified 1/8‑of‑production royalty for oil, gas, and other minerals.
    • This reinforces a contextual, text‑driven approach to royalty interpretation: courts will not impose default “market-value” or “proceeds” characterizations when the instruments themselves point in a different direction.
    • Operators and royalty owners alike are reminded that older deed language can have large financial consequences when courts apply it according to the parties’ expressed intent.

Overall, the Court’s opinion is notable for its adherence to textualism, its insistence on maintaining simple and predictable default rules where possible (“empty space is not a mineral”), and its sensitivity to the practical stakes in contemporary subsurface use and royalty disputes. Going forward, Myers‑Woodward will be a central authority in any Texas case involving pore-space ownership, salt-cavern storage, or the construction of legacy royalty clauses.

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