The issue is whether proceeds from bundled minerals leases must be proportionately reduced if one or more of the leases expire because production ceased. This case calls for interpreting a 1953 assignment of a production payment – an oil payment, as it's also called – from four minerals leases. McDaniel, the successor to the production payment, sued for contract breach and conversion after Apache Deepwater reduced the payment because two leases expired when production ceased. Apache argues that the production payment, like an overriding royalty interest, should be diminished when a lease ends and that Texas law does not require a proportionate-reduction clause. McDaniel contends the assignment specifies one fractional interest applied to all production from the designated surveys and, in the absence of a reduction clause, expresses the parties' intent to allocate risk. The trial court ruled for Apache, but the court of appeals reversed.