Patent ID: 8455402

Claim:
A method of producing a fluid from a wellbore comprising providing a variable density fluid in a subterranean formation, where the variable density fluid comprises: a base fluid selected from the group consisting of a drilling fluid, a sealant and a produced fluid, and a plurality of elements that change their volume/weight ratio in response to a condition selected from the group consisting of pressure, temperature, and chemical composition of the base fluid, where the elements each comprise a non-deformable body and at least one cellular, compliant component, each cellular, compliant component comprising at least one gas-filled void, and where the elements have an average expanded state size and an average contracted state size, and where the volume ratio of the average expanded state size to the average contracted state size is at least about 2.5, and conducting a wellbore operation selected from the group consisting of constructing a wellbore with the variable density fluid, producing the variable density fluid from the wellbore, sealing at least a portion of the wellbore and combinations thereof.