Fluids and techniques for hydrocarbon well completion

Abstract

The Invention relates to novel fluids and techniques to optimize/enhance the production of hydrocarbon from subterranean formations (e.g., “completion fluids”), in particular, fluids and techniques are disclosed and claimed which remove wellbore damage and near-wellbore damage in the form of coating formed from drilling and production-related operations (“filtercake”); the techniques can be applied either by themselves or in conjunction with other completion operations, such as gravel packing; preferred embodiments are chelating agent and enzyme systems in a viscoelastic surfactant (VES) matrix.

We claim:  
     
         1 . A well completion fluid for breaking filtercake having substantial calcite and starch content, said fluid comprising a chelating agent and an enzyme, wherein said chelating agent is present in a quantity effective to promote the dissolution of calcium carbonate and said enzyme is suitable for dissolving starch.  
     
     
         2 . The well completion fluid of  claim 1  wherein said enzyme is selected from the group consisting of α-amylase and β-amylase.  
     
     
         3 . The well completion fluid of  claim 2 , wherein said enzyme is α-amylase and is present in said fluid at a concentration of between 0.05 and 1.5%.  
     
     
         4 . The well completion fluid of  claim 1  further comprising a salt.  
     
     
         5 . The well completion fluid of  claim 1 , wherein said salt is selected from the group consisting of KC 1  and NH 4 Cl  
     
     
         6 . The well completion fluid of  claim 4 , wherein said salt is present in said fluid at a concentration of between 3 and 5%.  
     
     
         7 . The well completion fluid of  claim 1 , wherein said chelating agent is selected from the selected from the group consisting of 1-hydroxyethylidene-1,1-diphosphonic acid-1 (HEDP), aminotri(methylene phosphonic acid (ATMP), diethylenetriaminepentamethylenephosphonic acid (DTPMP), ethylenedieminetetraacetic acid (EDTA), cyclohexanediaminetetraacetic acid (CDTA), diethylenediaminepentaacetic acid (DTPA), and nitrilotriacetic acid (NTA).  
     
     
         8 . The well completion fluid of  claim 7  wherein said chelating agent is EDTA and is present in said fluid at a concentration between 5 and 28%.  
     
     
         9 . The well completion fluid of  claim 3  wherein said enzyme is α-amylase and is present in said fluid at a concentration of about 0.5%.