System and method for deploying and using at least one control module for in-riser and open water operations

A multi-module electrohydraulic control system for use in a subsea well operation, comprising:

• a controllable subsea tool disposed along a well string;
• and
• a modular control system coupled into the well string to provide control inputs to the controllable subsea tool, the modular control system comprising:
• a first control module selectively connectable into the modular control system to control the controllable subsea tool;
• and
• a second control module selectively connectable into the modular control system to provide supplemental control for an additional subsea tool, each of the first control module and the second control module comprising a mandrel, accumulators, flow control valves for hydraulic actuation and chemical injection fluid, and a sensor system, each of the first control module and the second control module being sized to fit through a rotary table of a rig during deployment to a subsea location.