Loss of oil royalties from state lands as well as a decrease in sales tax and other tax revenues will lead to a state budget shortfall. State unemployment will spike, and retail and real estate revenues will take a hit. Not necessarily good for the Texas economy.
Your description of OPEC is accurate, but an interesting historical note is that OPEC was modeled after the Texas Railroad Commission, which limited Texas oil production to support oil prices for much of the early and mid 20th century.