Despite the increasing international commitment to improve security in the Gulf of Guinea, no, regional military forces are not routinely providing any direct protective presence on or near oil platforms, as far as I can tell.
However, in many cases there may be armed private security forces. Quoting from a 2016 article:
Although bordering on unauthorised or even illegal practices at times, private security contractors have become a critical stand-in security provider, while states, regional and international actors step up their commitments to bring about more maritime-security governance in the Gulf of Guinea.
The rise of maritime private security in the Gulf region during recent years has been described as "exponential". Even so, armed private security is present on some oil platforms, but not necessarily all. According to a consultant interviewed in 2013, it depends on the specific level of risk facing a given project and location. Among other international laws, the use of private security on oil platforms is governed by the ISPS code, an international standard for vessel and port security.
