Depends on circumstances. The Gulf (of Mexico) oil fields remain of course, but I'd think the Soviets would target the major wells. A lot depends on how dispersed individual wells are of course; if they are all grouped within a kilometer of each other a big strike can take out the pumps in one shot; even a small warhead is too much to waste on some individual pump somewhere miles away from any others. Surely the refining and other processing centers have been taken out. Will they go for offshore rigs? Maybe attack subs are tasked with either seizing them or blowing them up as opportunity permits.
Will the Soviets have trashed Mexican and Venezuelan wells and industry the same degree, to deny surviving Yankees the resources to recover? What about Trinidad?
In all cases, the oil is at any rate in the ground. It is not gone whereas the demand for it has been reduced, in the short run to zero (people want it all right but there is no means to get it) and when someone gets around to reestablishing pumping and refinery operations again, perhaps having to build the infrastructure from scratch, by sheer necessity many people surviving who wish they could get some petroleum products have adapted in the meantime to doing without, and either have adapted their engines to some other feedstock, cannibalized the engines for parts useful in other applications, or their engines have suffered from neglect. So the real effective market is a fraction of the number of survivors who wish they could be in it. Known, proven fields will be suitable for a long time to come...provided we recall that some fields that have been heavily pumped were in operation pre-exchange because of measures taken to pressurize them to squeeze out the last dregs--those fields are effectively exhausted in the new context, unless either strategic reasons force someone to try to exploit them anyway or until someday far in the future when the better fields have been brought low and it becomes cost effective to work the more labor-intensive ones again.
So in the abstract--people should concentrate on using oil, not biodiesel. Except that the people who most want the oil might not have easy, close access to an oil field, and the ones they can reach are all bombed out, lousy with fallout on the surface where they have to perform new drilling and pump assembly and pipeline and tank operations, the refineries are gone and need to be rebuilt somewhere. The whole infrastructure is shot to hell, quite deliberately.
If the Soviets did not have a missile to spare for Tallahassee, I suppose the amount of targeting they can afford just to kill resources American survivors might want overseas is limited and they will stick to decapitating the most vulnerable chokepoints. Meaning Mexican and Venezuelan crude might be going begging for a market--enter Graham's envoy, or eventually President Regan's, with some cutters and destroyers along with a couple hidden attack subs, escorting decent sized tankers--who knows, maybe even a first class giant supertanker and offering a mix of New Dollars and immediate barter--the New Dollars are mainly good for saving up and buying stuff from the USA in the future when the nation is producing for export again. But are they getting any better offers? And how valuable is what the Yankees have to barter immediately to them? In this case, oil imports and new refinery production--possibly from new refineries ginned up by the engineering students at the universities--might start flowing before the prewar reserves that survived in the region are depleted.
But on the other hand, suppose there are no petroleum refineries left to speak of, and making a serviceable one is not a summer project for half trained undergrads and grad students but something that needs tools to make the tools, and it will be 5 years or more before globally traded petroleum is a thing again? Suppose it takes longer than that to drill on the Texas fields again, and the offshore operations fail for lack of repair parts and are just a drop in the bucket?
If the people of Florida and the Gulf region generally are starving for lack of basic staple crops, then yes it might be impossible to devote anything to biodiesel. But--Florida is humid and Florida is sunny, it is land that grows biomass pretty lushly. So is the southern tier of Alabama and Georgia. Meanwhile, land that is perfectly good for growing plants as such might be bad for growing food for human consumption! A lot of good cropland has been contaminated with fallout and the food chain just concentrates it. As the years pass the radiation levels will drop and between natural processes and human guided ones, radioisotopes and merely chemical contamination from the daughter products will be lowered...though a major portion of what is dangerous in fallout is plutonium, from unfissioned weapons core material, and a little bit of that goes a long way. Half-life is on the order of either 10,000 or 100,000 years I forget which--either way, vast swathes of otherwise perfectly good looking land must be avoided, because of plutonium contamination. The animals of the ecosystem will perforce take their chances, and it will be a race between natural processes somehow sequestering the Pu away, the natural exponential decay into something else, and the flora and fauna adapting to have selective advantage in such an environment, developing plutonium tolerance. On the scale of human lifetimes and even civilizations none of this progress will be visible I think--for thousands of years to come, unless we figure out ways to actively scrub out the plutonium, the majority of good land on Earth can produce food that can be eaten only by those prepared to accept the consequences of cumulative plutonium contamination. From around the periphery it might be possible to pick and choose products that can be eaten for 4 or 5 years cumulatively and only take 10-20 years off life expectation. Deeper in, just breathing the air might cost years of life expectancy.
But there would be relatively little harm done if the biomass grown there could be refined into biodiesel, and this or its chemical precursors filtered somehow chemically to get the incidence of plutonium down. If such biodiesel fuel is abundant enough in terms of the number of human workers who work on it and need to be fed by others, it might be possible to filter the exhaust so as to trap the Pu that remains and prevent use of the engines from contaminating the corridors the vehicles operate on. PU contaminated jet fuel might be OK for flights that avoid going over the good land that is left. It could be good for ships at sea, and someday transport that uses the heavy contaminated zones as corridors for obnoxious modes of transport---SSTs for instance--might indifferently use it.
The point being, the land no longer can be used to raise food anyway. But it can provide fuel. The question becomes, does it make sense to devote the necessary human labor to grow and harvest suitable biodiesel or other biomass projects for fuel use.
My intuition is that a certain level of biodiesel cultivation is going to make sense in the Gulf region for about 5-10 years until the global or anyway hemispheric petroleum business gets restarted. Once the minimum necessary levels of mining and refining are restored to fully satisfy military and vital productive process needs, surplus petroleum products will go on sale and as people re-adapt to the opportunity to simply purchase mined petroleum products again that market will spiral upward while the bottom falls out biodiesel, and the fields are abandoned.
Another valid objection is that obviously, even if workers can be shielded from taking in any ambient radio-nuclei, work in these zones will be both difficult and dangerous. They will be quite hot, unless they work mainly at night, even then probably pretty hot if they wear protection suitable for keeping the bad atoms out. They must live, when not fully suited up, in small, confined clean volumes and only considerable labor and material (imported from outside the hot zones, or in some lucky cases cleansing local materials such as concrete might prove suitable enough) can build these protected volumes. Their food must be imported, their drinking water either trucked in too or fanatically scrubbed. Who will do such work?
Two categories come to mind.
1) volunteers who are very well rewarded. Since Graham is reasonably liberal but no socialist, I suppose they would simply be offered large paychecks in New Dollars, and undergo hardship the way oil rig workers and miners and so forth do, for high pay.
2) Conscripts. Specifically, Florida (and the neighboring states' and Federal) prisoners. Generally speaking the hard part of running a prison or work camp is keeping the inmates from heading for the hills and taking their chances in the wilderness. Well, if they run, they die. They would be plonked down in the midst of a radioactive hellscape. Graham was rather famous, or infamous depending on what side you were on OTL for a high execution rate as governor--I am not sure if this carries over into a harsh attitude toward convicts in general or just a special hardness toward those who crossed the line into capital offenses. But we've already seen them rounded up and shot. A lot of people remain behind bars left over from before the Exchange. It seems reasonable to offer many of them the opportunity to earn their freedom before their sentences would run out on extra hard work. Perhaps if they were also paid, not in cash but in New Dollar denominated bonds or something like that, on a decent pay scale, the combination of intense stick--"if you run, God have mercy on your soul and you will have quite a low priority for what terminal radiation sickness treatment we can manage to offer" versus carrot--"We will instruct courts and urge private hiring practices to be lenient about pre-Exchange criminal records for those who serve out the labor camp programs with OK compliance and diligence, and shorten the sentence, and pay you in cash-worthy savings you can spend when you get out, with bonuses for outstanding performance and you also get a reasonable priority for resources you need to be decently comfortable off the job and safe on it" might add up to few escape attempts, decent productivity, and high levels of production of material for processing.
I might also add that with much of the population dead and the rest under rationing, with usage of available fuels organized toward the most cost-effective options--say, bus services that operate only when the bus is full up, not on a fixed schedule, and only for those with suitable travel permits, trucks loaded at the waterway docks to the limit to haul goods with mass efficiency, the land is not being used for anything else and so methods that use land area prodigally and conserve on labor and resources are appropriate.
I mentioned biodiesel on the assumption that petroleum will be hard to come by in Florida and immediate surrounds, but land, sunlight and rain are abundant--especially since we can use land that is otherwise quite dangerous for human beings simply to inhabit, let alone live off of.
Being doctrinaire based on textbook arguments developed in one situation will not work well when the situation is radically different. The balance of economic resources is drastically changed in the post-Exchange world; many outcomes that would seem wacky or be just plain impossible in our world are favored in the new circumstances. Exactly what they are depends on very detailed analysis. Where can Florida get the oil they'd need to sustain minimal and rationed forms of the basics of 1980s standards of living? If it need not all be oil the outcomes may be quite a lot better than if only petroleum mined from the ground could possibly do. The rationality of using some other resource might be temporary, but if it helps get over a tough hump, better we at least consider it than reject it out of hand because some wiseacre proved to someone's satisfaction in a book that it can't help the global situation of OTL.
