Subsea completion annulus pressure compensation system

A method for self-regulating pressure within an annulus of a subterranean wellbore, the method comprising:

• positioning an accumulator proximate to a subsea wellhead at an entry point of a subterranean wellbore, wherein the accumulator is in an environment surrounded by a regulating fluid, and wherein the accumulator comprises:
• an annulus fluid chamber that contains an annulus fluid;
• a regulating fluid chamber that contains the regulating fluid;
• an inlet that provides fluidic communication of the regulating fluid between the regulating fluid chamber and the environment in which the accumulator is positioned, wherein the inlet allows a regulating fluid pressure of the regulating fluid within the regulating fluid chamber to be substantially similar to a hydrostatic pressure of the regulating fluid in the environment surrounding the accumulator;
• and
• a physical fluidic barrier movably disposed between the annulus fluid chamber and the regulating fluid chamber;
• and
• installing piping between the annulus fluid chamber of the accumulator and the annulus of the subterranean wellbore,
• wherein the physical fluidic barrier moves to increase a first size of the annulus fluid chamber and decrease a second size of the regulating fluid chamber when an annulus fluid pressure of the annulus fluid within the annulus fluid chamber exceeds the second regulating fluid pressure of the regulating fluid within the regulating fluid chamber by a first threshold value, wherein the physical fluidic barrier moves to decrease the first size of the annulus fluid chamber and increase the second size of the regulating fluid chamber when the regulating fluid pressure of the regulating fluid within the regulating fluid chamber exceeds the annulus fluid pressure of the annulus fluid within the annulus fluid chamber by a second threshold value, wherein increasing the first size of the annulus fluid chamber reduces pressure in the annulus of the subsea wellbore by allowing the annulus fluid to flow from the annulus to the annulus fluid chamber of the accumulator through the piping, and wherein decreasing the first size of the annulus fluid chamber increases pressure in the annulus of the subsea wellbore by allowing the annulus fluid to flow from the annulus fluid chamber of the accumulator to the annulus through the piping.

A system for subsea wellbore operations, the system comprising:

• a wellbore drilled into a subterranean formation, wherein the wellbore has positioned therein a casing string, a tubing string disposed within the casing string, and an annulus fluid disposed between the tubing string and the casing string;
• a subsea wellhead mounted at the entry point of the wellbore;
• an accumulator positioned in an environment surrounded by a regulating fluid, wherein the accumulator comprises:
• an annulus fluid chamber that contains the annulus fluid having a first pressure at a first time;
• a regulating fluid chamber that contains the regulating fluid having a second pressure at the first time;
• an inlet that provides fluidic communication of the regulating fluid between the regulating fluid chamber and the environment in which the accumulator is positioned, wherein the inlet allows the second pressure of the regulating fluid within the regulating fluid chamber to be substantially similar to a hydrostatic pressure of the regulating fluid in the environment external to the accumulator during the first time and during subsequent times;
• and
• a physical fluidic barrier movably disposed between the annulus fluid chamber and the regulating fluid chamber;
• and
• piping having a first end and a second end, wherein the first end penetrates an aperture in the subsea wellhead and terminates in the annulus of the subsea wellbore, and wherein the second end terminates in the annulus fluid chamber of the accumulator,
• wherein the physical fluidic barrier moves to increase a first size of the annulus fluid chamber and decrease a second size of the regulating fluid chamber at a second time when the first pressure exceeds the second pressure by a first threshold value, wherein the physical fluidic barrier moves to decrease the first size of the annulus fluid chamber and increase the second size of the regulating fluid chamber at the second time when the second pressure exceeds the first pressure by a second threshold value, wherein increasing the first size of the annulus fluid chamber at the second time reduces pressure in the annulus of the subsea wellbore by allowing annulus fluid to flow from the annulus to the annulus fluid chamber through the piping, and wherein decreasing the first size of the annulus fluid chamber at the second time increases pressure in the annulus of the subsea wellbore by allowing annulus fluid to flow from the annulus fluid chamber to the annulus through the piping.