A composition and method are given for self-destructive fluid loss additives and filter cakes in wellbores and subterranean formations. The fluid loss additives and filter cakes are formed from a mixture of particulate solid acid-precursors, such as a polylactic acid or a polyglycolic acid, and particulate solid acid-reactive materials, such as magnesium oxide or calcium carbonate. In the presence of water, the solid acid-precursors hydrolyze and dissolve, generating acids that then dissolve the solid acid-reactive materials. The composition is used in oilfield treatments such as drilling, completion and stimulation where it disappears when it is no longer needed without the use of mechanical means or injection of additional fluids.

Degradable material assisted diversion (DMAD) methods for well treatment, DMAD treatment fluids, and removable plugs for DMAD in downhole operations. A slurry of solid degradable material is injected into the well, a plug of the degradable material is formed, a downhole operation is performed around the plug diverter, and the plug is then degraded for removal. Degradation triggers can be temperature or chemical reactants, with optional accelerators or retarders to provide the desired timing for plug removal. In multilayer formation DMAD fracturing, the plug isolates a completed fracture while additional layers are sequentially fractured and plugged, and then the plugs are removed for flowback from the fractured layers. In DMAD fluids, an aqueous slurry can have a solids phase including a degradable material and a fluid phase including a viscoelastic surfactant. The solids phase can be a mixture of fibers and a particulate material.

A method is given for treating a subterranean formation penetrated by a wellbore with a viscosified fluid. The fluid contains a solid hydrolysable polyacid that upon dissolution and hydrolysis releases an acid that is a breaker for the viscosifying system. Suitable solid hydrolysable polyacids include polylactic acid and polyglycolic acid. The fluid also contains a pH control agent, present in an amount sufficient to neutralize any acid present in the solid hydrolysable polyacid before the injection and to neutralize any acid generated by the solid hydrolysable polyacid during the injection, so that the acid breaker is not available to break the fluid during the injection. In one embodiment the viscosifier is a viscoelastic surfactant fluid system and the solid hydrolysable polyacid is of a size selected to be a fluid loss additive, for example in fracturing or gravel packing. In another embodiment, the solid hydrolysable polyacid is used in particles sufficiently small that they enter the pores of the formation. In either case, the viscosifier is broken after the solid releases more acid than can be neutralized by the pH control agent.

Of the many methods provided, in one embodiment, a method is provided that comprises: providing an acid-generating fluid that comprises an acid-generating compound, a base fluid, and a salt; placing the acid-generating fluid in a well bore penetrating a subterranean formation; allowing the salt to affect the hydrolysis of the acid-generating compound; and allowing the acid-generating compound to produce an acid that then acidizes at least a portion of the formation or damage contained therein.

Methods of isolating particular zones within a subterranean formation utilizing self-degrading cement compositions are provided. An example of a method of the present invention is a method that includes: providing a self-degrading cement composition that includes a degradable material, an acid source, a base source, and a water source; placing the self-degrading cement composition in a zone within a subterranean formation; and allowing the self-degrading cement composition to set to form a solid mass that is capable of isolating the zone from a well bore penetrating the zone or from another zone.