Method for reducing the permeability of subterranean formations

A method for reducing the permeability of a subterranean formation penetrated by a wellbore comprising:

• dispersing discrete solid structures of polyester polymers into a wellbore fluid containing water, said polymer being substantially insoluble in water and degradable in the presence of water at the formation temperature to oligomers which are at least partially soluble in a formation fluid and
• placing said wellbore fluid containing said structures dispersed therein into said wellbore.

A method for reducing the permeability of a subterranean formation penetrated by a wellbore comprising:

• dispersing discrete solid structures of polyester polymers into a wellbore fluid containing oil, xylene or toluene, said polymer being substantially insoluble in said wellbore fluid and degradable in the presence of water at the formation temperature to oligomers which are at least partially soluble in a formation fluid and
• placing said wellbore fluid containing said structures dispersed therein into said wellbore.

A method for reducing the permeability of a subterranean formation penetrated by a wellbore comprising:

• dispersing into a wellbore fluid discrete solid structures comprising a polymer having the repeating unit:
• ##STR3## wherein R is H, C.sub.1 to C.sub.4 alkyl and n is sufficiently large to form a solid polymer, said polymer being substantially insoluble in said wellbore fluid and degradable in the presence of water at the formation temperature to oligomers which are at least partially soluble in a formation fluid and
• placing said fluid containing said structures dispersed therein into said wellbore.

A method for reducing the permeability of a subterranean formation penetrated by a wellbore comprising:

• dispersing discrete solid structures comprising a polyester polymer into a wellbore fluid, said polymer being substantially insoluble in said wellbore fluid and degradable in the presence of water at an elevated temperature to oligomers which are at least partially soluble in a formation fluid,
• placing said wellbore fluid containing said structures dispersed therein into said wellbore, and
• placing a hot fluid into said wellbore to raise the temperature of said formation to said elevated temperature.