Automatic pump chamber control adjustment

Abstract

A method and system for lifting drilling mud from subsea to a drilling vessel, which uses a pump having a body with a chamber, and a bladder in the chamber. The bladder attaches to the body and defines water and mud sides in the chamber. A mud inlet valve allows mud into the mud side of the chamber; which moves the bladder into the water side and urges water in the water side from the chamber and through a water exit valve. Pressurized water enters the chamber through a water inlet valve, which in turn pushes the bladder and mud from the chamber through a mud exit valve. The bladder separates the mud and water as it reciprocates in the chamber. The travel of the bladder in the chamber is controlled to prevent damage from contact with the chamber.

What is claimed is: 
     
         1 . A mud lift pump for lifting drilling mud from a subsea wellbore comprising:
 a housing;   a water space in the housing;   a mud space in the housing that is in pressure communication with the water space;   a bladder mounted in the housing having a side in contact with the water space and an opposing side in contact with the mud space, and that defines a barrier between the water and mud space; and   a controller for limiting a travel of the bladder within the chamber.   
     
     
         2 . The mud lift pump of  claim 1 , further comprising:
 a water inlet having an entrance in selective communication with a source of pressurized water, and an exit in communication with the water space;   a water discharge having an entrance in communication with the water space, and an exit in selective communication with a water effluent line;   a mud inlet having an entrance in selective communication with drilling mud from a subsea well an exit in communication with the mud space; and   a mud discharge having an entrance in communication with the mud space, and an exit in selective communication with a lift line that connects to a drilling vessel.   
     
     
         3 . A method of pumping mud from a subsea wellbore comprising:
 providing a pump comprising, a housing, a water space in the housing, a mud space in the housing that is in pressure communication with the water space, and a bladder mounted in the housing having a side in contact with the water space and an opposing side in contact with the mud space, and that defines a flow barrier between the water and mud space; and   controlling movement of the bladder within the chamber, so that the bladder avoids contact with the housing.