Unfortunately, there are not many oil and gas companies which hire fresh graduates and train them as petrophysicists.
My suggestion is to join a service company, such as a well logging company (Schlumberger, Baker Hughes, Halliburton) or a mud logging company as a field engineer. You can get trained in data acquisition and interpretation with them. After gaining some experience, you can apply to an oil and gas company for a position in petrophysics.