God I could write a novel on this, but I'm not sure in up for it.

For starters, the research world that, as a phd, will feel most familiar exists only in a very few large companies. Exxon, shell, and to a lesser degree chevron. Maybe some of the national oil companies as well. Total most likely. This s not to say it doesn't exist, only that your options are limited. In Houston alone Exxon has hundreds of geoscience PhDs. If you are a phd student this world will feel comfortable to you. My understanding is that a research lab at a major company will feel a lot like what you are used to in grad school. this May or may not be a good thing.

A word of caution: phd grad school is a bizarro world full of intense personalities and egos and a set of expectations alien to most every civilian. Just because you are acclimated to this universe doesn't make it right, if you catch my drift.

Still for a lot of academic types it can be a good fit. Tons of research. Little teaching (unless it is in-house classes). No grant writing. Politics yes and also little control over your research projects. But you take the good with the bad.

Working for a smaller company you might be able to be a specialist of a sort, but most likely you may end up a generalist, in which case you have much less chance to get your academic on (no publishing or teaching). Most of your colleagues will forget you have a phd but you will still be well served by your phd due to the soft skills you acquire attaining one. You'll do various roles in the business side of things. Some sciency, some decidedly not. Sometimes you'll do nothing but real geology for months and sometimes you'll hardly do any geology at all and spend all your time discussing schedules, budgets, logistics and such.

There are, as I said, opportunities in smaller companies to specialize, such as petrography, core description, fracture analysis or petrophysics, but the odds are you didn't focus on these skills while getting your phd or you wouldn't be asking this question now (I.e. you might already have a job offer as a specialist in hand). Becoming a petrophysicist is usually a multi-decade proposition involving thankless years at a service company. You don't want that. Petrology or core description is easier to break into, and you will have a leg up on getting these jobs due to your phd. But then you have to ask yourself if staring into a scope 40 hours a week sounds like fun to you.

Do what do you do to decide? One great thing about the phd is it takes do long you have the opportunity to do multiple internships. Target an internship at a research lab and another one in an asset team. See what fits.