Mineral Rights law pertains to the acquisition and ownership rights in oil and gas both under the soil before discovery and after its capture. Drilling companies do not always exclusively own the land they seek to drill on. In many agreements, the companies own the mineral rights while another party owns the other rights to the property itself. Mineral rights lessees have a right of reasonable access to leased land to explore, develop, and transport minerals. The drilling company in this situation owns what is known as the mineral estate. In an "unless-delay rental" lease, a lessee agrees to pay delay rentals so long as the lessee is not drilling on the property. An "unless" oil and gas lease terminates automatically if the lessee fails to drill within the specified time or pay the delay rentals as called for in the lease. To trigger the clause in the oil and gas release to show that the lessee no longer has to make delay rental payments, the lessee must commence drilling. To commence drilling a well under the habendum clause means that substantial preparations for such drilling has been undertaken, as long as such measures have been commenced in good faith and with due diligence. The habendum clause sets out these terms as well as, most significantly, identifying the parties to the transaction and their interests in the conveyed real property.

Private title to all land in Texas emanates from a grant by the sovereign of the soil (successively, Spain, Mexico, the Republic of Texas, and the State of Texas). Under the laws of Spain and Mexico, mines and their metals or minerals did not pass by the ordinary grant of the land without express words of designation. In one of the earliest acts of the Congress of the Republic of Texas, this rule was adopted, and it was continued in force after Texas had become a state. A grantee of land before 1866 therefore had no interest in the minerals in the land unless that interest was expressly granted. By a provision of the state Constitution of 1866, which was carried over in substantially the same language into the Constitutions of 1869 and 1876, the state released to the owner of the soil all mines and mineral substances therein. This constitutional provision had retrospective effect; the landowner was given complete ownership of the minerals in all lands that passed from the sovereign before the effective date of the Constitution of 1876. A similar relinquishment to the landowner of the sovereign's retained interest in minerals was made in the revision of the Texas Civil Statutes in 1895, though it has not been litigated in the courts. Since 1876, it has been assumed that a grantee of land from the sovereign has received all minerals unless they are expressly reserved. Since 1895 substantial acreage of the public domain has been conveyed by the sovereign with a retention of rights to the minerals. Under the Relinquishment Act of 1919, as subsequently amended, the surface owner is made the agent of the state for the leasing of such lands, and both the surface owner and the state receive a fractional interest in the proceeds of the leasing and production of minerals. A considerable portion of the land of the state has been allocated to various educational institutions, some of which has not been sold but merely leased for mineral development.

To the extent that a landowner also owns the minerals in his tract, he may legally sever such minerals from the surface estates. The owner of the minerals may produce them himself. The usual practice, however, is for a lease to be executed by the mineral owner to an operator who undertakes to develop the minerals. Although several lease forms are in use, their provisions are generally uniform; the significance of the variant provisions is not to be minimized, however. Typically, under a lease the operator assumes all expenses of operations to develop the mineral resources in return for a conveyance of 7/8 interest in them; the landowner or lessor retains 1/8 interest free and clear of all costs. This interest of the mineral owner or lessor is what is correctly known as royalty, although the term is sometimes more loosely used to describe an undivided interest in minerals arising out of an instrument other than a mineral lease.

Legally, oil and gas are minerals. About 2/3 of the 254 counties in Texas produce oil. About 54,000,000 acres of land in the state were under oil and gas lease in 1947. Since the mid-1950s oil and gas royalties have increased. The basic royalty on oil and gas was increased from 1/8 to 1/6 by the public school and other state land boards in 1955 and by the Board for Lease of University Lands in 1960 on gas and in 1961 on oil. The practice of overriding royalties being utilized as a portion of leasing and development promotion fees in the oil and gas industry, in amounts ranging from 1/32 to 1/4, has increasingly become a common practice. By 1995 royalties for state-run lands of the Permanent School Fund had a minimum standard of 6.25 percent of the gross value. Royalties in Texas, however, are usually negotiable and depend on a number of factors, including type of mineral and deposit.