Abstract: An apparatus for production testing. According to one aspect, the apparatus is modular and suitable for transport and assembly in the field. The apparatus comprises a platform and one or more pressure vessels. The platform includes a mounting bracket for the pressure vessel and the mounting bracket includes a guide mechanism. The guide mechanism allows the pressure vessel to be lowered into the mounting bracket and coupled to the platform for example using a load sling on a helicopter. According to another aspect, the pressure vessels comprise spherical containers and the spherical containers are configured to be heliportable to a field site.