Large volume subsea chemical storage and metering system

A method of providing chemicals to a sea floor installation, comprising:

• providing a storage tank in a subsea environment, the storage tank comprising:
• an outer container;
• at least two inner containers disposed within the outer container, the at least two inner containers comprising:
• a first inner container containing seawater;
• and
• a second inner container containing at least one chemical;
• wherein the at least two inner containers are flexible;
• and
• wherein the at least two inner containers are pressure balanced;
• wherein the volume of the outer container remains fixed, and the volumes of the at least two inner containers are variable;
• injecting the at least one chemical at a subsea point of consumption through an outflow valve in the second inner container;
• wherein as the volume of the at least one chemical in the second inner container decreases, seawater from the subsea environment flows through an inflow valve in the first inner container to increase the volume of seawater in the first inner container.

A liquid storage tank, comprising:

• an outer container, wherein the outer container is rigid;
• at least two inner containers disposed within the outer container, the at least two inner containers comprising:
• a first inner container containing seawater;
• and
• a second inner container containing at least one stored liquid;
• wherein the at least two inner containers are flexible;
• at least one sensor disposed in the annular space between the outer container and the at least two inner containers;
• wherein the at least two inner containers are pressure balanced;
• and
• wherein the volume of the outer container remains fixed, and the volumes of the at least two inner containers are variable.

A method of providing chemicals to a sea floor installation, comprising:

• providing a storage tank in a subsea environment, the storage tank comprising:
• an outer container;
• at least two inner containers disposed within the outer container, the at least two inner containers comprising:
• a first inner container containing seawater;
• and
• a second inner container containing at least one chemical;
• wherein the at least two inner containers are flexible;
• and
• wherein the at least two inner containers are pressure balanced;
• wherein the volume of the outer container remains fixed, and the volumes of the at least two inner containers are variable;
• lowering the storage tank to the sea floor, wherein the storage tank further comprises fixed and variable buoyancy chambers disposed along at least one wall of the outer container, each variable buoyancy chamber comprising at least one water inlet, and wherein the lowering comprises:
• flowing water into the at least one water inlet.