Texas counties are about to send out the 2020 property valuations for producing minerals and wells. Valuations are based on average prices in 2019, production volumes, decline curves and estimated well life on January 1, 2020. Generally the taxes due have been around 3% of annual income. This will certainly not be the case where prices have fallen so precipitously and many wells are being shut-in or having the production choked back.
The state of Texas General Land Office (GLO) is allowing wells under State leases to be shut-in through December due to the low prices. This includes RAL leases for mineral classified lands. So it is possible that mineral owners will receive income only through May or June and then no income for the rest of the year. This means that mineral owners need to put aside the current income now to pay property taxes at the end of the year. And that tax could be 15%+ of the total income for the year for wells shut-in now.
Valuations can only be protested for a short time in the spring. Consider contacting your state representative, state senator and Governor Abbott about property tax relief this year.