Soluble deverting agents

Abstract

Methods and compositions for stimulating single and multiple intervals in subterranean wells by diverting well treatment fluids into a particular direction or into multiple intervals using water soluble coated diverting agents are described. The water soluble coating of the diverting material is preferably a collagen, poly(alkylene) oxide, poly(lactic acid), polyvinylacetate, polyvinylalcohol, polyvinylacetate / polyvinylalcohol polymer or a mixture thereof applied as a coating on any number of proppants. The method allows for the diverting of the flow of fluids in a downhole formation during a well treatment, such as during a fracturing process. Following completion of a treatment such as a hydraulic stimulation, the soluble diverting agent can be dissolved and removed by the water component of the well production.

Description

[0001] The present application claims priority benefit to U.S. provisional application Ser. No. 60 / 646,231 filed Jan. 21, 2005, the entire contents of which are incorporated by reference herein.FIELD OF THE INVENTION [0002] The present invention provides methods and compositions for treating subterranean wells and, more specifically, provides methods and compositions for stimulating multiple intervals in subterranean wells. In particular, this invention provides methods and compositions for diverting well treatment fluids into multiple intervals by introducing propping materials coated with a water soluble polymer e.g. collagen, polyvinyl acetate / polyvinyl alcohol, polyalkyl oxides, poly(lactic acid), periodic chart elements of group I or II (alkali metal or alkaline earth metal) silicate polymer, or combinations thereof with materials that are slowly water soluble for use in redirecting the flow of stimulation fluids from a tubing string into the subterranean environment. DESCRIPTI...

AI Technical Summary

Benefits of technology

[0017] The present invention provides water soluble polymer coated proppants as diverting agents and methods of using such diverting agents for treating a subterranean formation. The diverting agent together with a carrier liquid is introduced into a subterranean formation. The liquid carrier flows into fractures and / or intervals within the subterranean formation. The fractures or intervals present varying degrees of permeability. In accordance with the methods of the present invention, the liquid carrier with diverting agent will flow to the most permeable interval first. The temperature of the formation will cause the water soluble polymer coating of the diverting agent to soften and swell, thereby plugging the fracture.

Problems solved by technology

Some intervals may possess relatively low injectivity, or ability to accept injected fluids, due to relatively low permeability, high in-situ stress, and / or formation damage.

If the created fracture breaks into this zone, the well can be ruined due to excess water and a cut off of the petroleum components of the productive interval.

Above the created fracture zone a gas cap may exist which would cause harm to the production of the well because of gas bypassing the liquid petroleum components of the well.

However, conventional diversion techniques may be costly and / or may achieve only limited success.

In this regard, mechanical diversion techniques are typically complicated and costly.

Furthermore, mechanical diversion methods are typically limited to cased hole environments and depend upon adequate cement and tool isolation for achieving diversion.

The efficient and simultaneous treatment of multiple sets of perforations over an extended vertical section has thus been a problem in well stimulation for numerous years.

However, the wax beads have limited melting points, from about 138° F. to about 192° F., making them useless if the formation temperature exceeds their melting point.

Naphthalene particles are readily soluble in oil, but melt at about 180° F., thereby limiting their use to applications in lower-temperature formations.

Furthermore, sodium chloride cannot be used with hydrofluoric acid to treat subterranean wells due to the formation of insoluble precipitates which can problematically block the wellbore.

However, the diverting action of such diversion agents is often difficult to predict and monitor, and may not be successful in diverting treatment fluid into all desired intervals.

These problems may be further aggravated in open hole completions, especially in highly deviated completions having large areas of a formation open to the wellbore.

The presence of natural fractures may also make diversion more difficult.

In light of all these advances and new techniques, the diverting action of diverting agents is often difficult to predict and monitor, and may not be successful in diverting treatment fluid into all the desired intervals, thereby failing to allow maximum benefit from the fracture procedure.

The presence of natural fractures within the subterranean formation can also serve to make diversion more challenging.

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