Intelligent multiplex system for subsurface wells

Abstract

A subsea well installation is equipped with means for performing required control functions as directed by electrical command signals transmitted over a primary cable from a remote surface location. The subsea installation includes a logic system which effects desired normal or emergency control functions according to self-contained programs or in accordance with instructions received from the surface. Multiplexing means at both locations substantially reduce cable dependency and reduce the number of electrical conductors required in the cable. Cable dependency and signal traffic are further reduced by the provision of self-contained means in the subsea logic system which verify that correct instructions have been received without need for retransmitting the received instructions to the surface. When the primary cable is damaged or communications are otherwise interrupted, a special subsea logic is initiated to control operation of the well installation and a submerged buoy is automatically released. An auxiliary cable is carried by the buoy to the water surface to permit power and communications to be re-established with the underwater installation. The buoy may also carry a storage battery or the subsea logic system, or both, so that the buoy may be released to carry these components to the surface as required for repair or periodic maintenance. Communications and power connections between the underwater installation and the cable are established through waterproofed, inductive coupling means which permits the cables to be quickly and easily connected and disconnected from the well installation without diver assistance.