Compositions and methods for filter cake removal

Abstract

The present disclosure provides compositions for removing filter cake from a subterranean borehole and methods for degrading filter cake and filter cake removal. The composition contains an encapsulated peroxygen (e.g., acrylic resin coated ammonium persulfate), a surfactant (e.g., nonionic surfactant), and optionally an unencapsulated peroxygen. The method (e.g., a one-step method) involves contacting the filter cake with the composition, and allowing the composition to remain in contact with the filter cake for a period of time sufficient to degrade the filter cake. The reaction of the composition with the filter cake results in acidic conditions, thereby eliminating any need for follow up acid treatments. The composition is stable enough to effectively remove filter cake at temperatures up to 250° F. or greater. Through filter cake removal, the method provides for increased flow, production, and/or recovery of oil and gas hydrocarbons from a subterranean formation.

What is claimed is: 
     
         1 . A composition for removing filter cake from a subterranean borehole, said composition comprising: (a) an encapsulated persulfate; and (b) a nonionic surfactant, wherein the encapsulated persulfate is present in an amount from about 0.01 to about 20 weight percent, and the nonionic surfactant is present in an amount from about 0.01 to about 50 weight percent, based on the total weight of said composition, when said composition is introduced into the borehole; or said composition comprising: (a) an encapsulated persulfate; (b) a nonionic surfactant; and (c) an unencapsulated persulfate, wherein the encapsulated persulfate is present in an amount from about 0.01 to about 20 weight percent, the nonionic surfactant is present in an amount from about 0.01 to about 50 weight percent, and the unencapsulated persulfate is present in an amount from about 0.01 to about 20 weight percent, based on the total weight of said composition, when said composition is introduced into the borehole. 
     
     
         2 . The composition of  claim 1 , further comprising a variable density brine. 
     
     
         3 . The composition of  claim 1 , wherein at least one component of the composition is mixed with fresh water, brine water, formation water with potassium chloride or other salts added, or combinations thereof, prior to introduction into the subterranean borehole. 
     
     
         4 . The composition of  claim 1 , wherein the encapsulated persulfate is selected from the group consisting of encapsulated sodium persulfate, encapsulated potassium persulfate, encapsulated ammonium persulfate, and combinations thereof. 
     
     
         5 . The composition of  claim 1 , wherein the encapsulated persulfate is cured acrylic resin encapsulated persulfate. 
     
     
         6 . The composition of  claim 1 , wherein the encapsulated persulfate is coated ammonium persulfate. 
     
     
         7 . The composition of  claim 1 , wherein the encapsulated persulfate provides a controlled time release of the persulfate. 
     
     
         8 . The composition of  claim 1 , wherein the persulfate from the encapsulated persulfate decomposes from a direct reduction reaction, a surface catalyzed reaction, and/or a free radical decomposition reaction. 
     
     
         9 . The composition of  claim 1 , wherein:
 the nonionic surfactant is selected from the group consisting of an ethoxylated plant oil based surfactant, a fatty alcohol ethoxylate, a fatty acid ethoxylate, a fatty acid amide ethoxylate, a fatty acid ester, a fatty acid methyl ester ethoxylate, an alkyl polyglucoside, a polyalcohol ethoxylate, a sorbitan ester, a soy alkyltrimethyl ammonium chloride, an ethoxylated coco fatty acid, an ethoxylated coco fatty ester, an ethoxylated cocoamide, an ethoxylated castor oil, and combinations thereof; or   the nonionic surfactant is selected from the group consisting of a fatty alcohol ethoxylate, a fatty acid ethoxylate, a fatty acid ester, a fatty acid methyl ester ethoxylate, an alkyl polyglucoside, a polyalcohol ethoxylate, a soy alkyltrimethyl ammonium chloride, a monococoate, and combinations thereof; or   the nonionic surfactant is selected from the group consisting of an ethoxylated coco fatty acid, an ethoxylated coco fatty ester, an ethoxylated cocoamide, an ethoxylated castor oil, a monococoate, and combinations thereof; or   the nonionic surfactant comprises a sorbitan ester selected from the group consisting of sorbitan monooleate having a Hydrophile-Lipophile Balance (HLB) range from about 2.8 to about 8.8; sorbitan monolaurate having a Hydrophile-Lipophile Balance (HLB) range from about 4.6 to about 12.6; sorbitan monopalmitate having a Hydrophile-Lipophile Balance (HLB) range from about 2.5 to about 10.5; and sorbitan monostearate having a Hydrophile-Lipophile Balance (HLB) range from about 2.7 to about 8.7; or   the nonionic surfactant comprises an ethoxylated sorbitan ester selected from the group consisting of a polyethylene glycol (PEG) sorbitan monooleate having a range of about 2 to about 40 PEG groups, and having a Hydrophile-Lipophile Balance (HLB) range from about 10 to about 20; a polyethylene glycol (PEG) sorbitan monolaurate having a range of about 2 to about 40 PEG groups, and having a Hydrophile-Lipophile Balance (HLB) range from about 10 to about 20; a polyethylene glycol (PEG) sorbitan monopalmitate having a range of about 2 to about 40 PEG groups, and having a Hydrophile-Lipophile Balance (HLB) range from about 10 to about 20; and a polyethylene glycol (PEG) sorbitan monostearate having a range of about 2 to about 40 PEG groups, and having a Hydrophile-Lipophile Balance (HLB) range from about 10 to about 20.   
     
     
         10 . The composition of  claim 9 , wherein the ethoxylated coco fatty acid is a polyethylene glycol (PEG) coco fatty acid having a range of about 5 to about 40 PEG groups, and a Hydrophile-Lipophile Balance (HLB) range from about 10 to about 19; the ethoxylated castor oil is a polyethylene glycol (PEG) castor oil having a range of about 2.5 to about 40 PEG groups, and a Hydrophile-Lipophile Balance (HLB) range from about 2.1 to about 16; the ethoxylated cocoamide is a polyethylene glycol (PEG) cocamide having a range of about 2 to about 20 PEG groups, and a Hydrophile-Lipophile Balance (HLB) range from about 2 to about 19. 
     
     
         11 . The composition of  claim 1 , further comprising a chelate, wherein the chelate is selected from the group consisting of a mono-, di-, tri- or tetra-sodium ethylenediaminetetraacetic acid (EDTA), a mono-, di-, tri- or tetra-potassium ethylenediaminetetraacetic acid (EDTA), sodium ethylenediamine-N,N′-disuccinic acid (EDDS), and combinations thereof. 
     
     
         12 . The composition of  claim 1 , further comprising a cosolvent, wherein the cosolvent is selected from the group consisting of a terpene, methyl soyate, ethyl lactate, methyl lactate, ethyl acetate, and combinations thereof 
     
     
         13 . The composition of  claim 1 , which is applied to the subterranean borehole as, or in combination with, a drilling fluid, treatment fluid, stimulation fluid, fracturing fluid, a fluid used in an enhanced oil recovery technique, or a combination thereof