Fluids for use in oilfield development comprising deacetylated xanthan gum and at least one compound increasing the ionic strength of the medium

Abstract

The invention concerns guar-free fluids capable of being used in oil mining and containing deacetylated xanthan gum in the form of a polypentamer, combined with at least one compound increasing the medium ionic strength. The invention also concerns the use, as filtrate reducer with improved properties, of deacetylated xanthan gum in the form of a polypentamer, combined with a compound increasing the medium ionic strength and a standard filtrate reducer.

1 - 21 . (Canceled).  
     
     
         22 . A process for controlling fluid loss, at a temperature between 100 and 140° C., of a guar-free drilling fluid comprising a xanthan gum having a percentage of acetyl groups in the range 0 to 3%, said xanthan gum being in the form of a polypentamer, said process comprising the step of adding to said fluid at least one compound which increases the ionic strength of the fluid, and at least one fluid loss control agent.  
     
     
         23 . A process according to  claim 22 , wherein the drilling fluid comprises 0.01% to 2% of the xanthan gum.  
     
     
         24 . A process according to  claim 22 , wherein the range is 0 to 2%.  
     
     
         25 . A process according to  claim 22 , wherein the fluid loss control agent is selected from the group consisting of cellulose compounds, polyacrylamides, high molecular weight polyacrylates, succinoglycanes, native starch, native starch derivatives, and charcoal.  
     
     
         26 . A process according to  claim 22 , wherein the compound increasing the ionic strength of the fluid is a salt of mineral or organic acid.  
     
     
         27 . A process according to  claim 26 , wherein the salt is an alkali metal halide, alkaline-earth metal halide, a sulphate, carbonate, bicarbonate, silicate, phosphate, an alkali metal formate, alkaline-earth metal formate, alkali metal acetate, or an alkaline-earth metal acetate.  
     
     
         28 . A process according to  claim 27 , wherein the compound increasing the ionic strength of the fluid is an alkali or alkaline-earth metal chloride.  
     
     
         29 . A process according to  claim 27 , wherein the compound increasing the ionic strength of the fluid is a sodium silicate.  
     
     
         30 . A process according to  claim 22 , wherein the compound increasing the ionic strength of the fluid is present in said fluid in an amount of 5000 to 110000 parts per million.  
     
     
         31 . A process according to  claim 22 , wherein said fluid further comprises a thinner or dispersing agent in a quantity of 0 to 1% with respect to the total fluid weight.  
     
     
         32 . A process according to  claim 31 , wherein the thinner or dispersing agent is selected from the group consisting of polyphosphates, tannins, lignosulphonates, lignin derivatives, peats, lignites, polyacrylates and polynaphthalene sulphonates.  
     
     
         33 . A process according to  claim 22 , wherein said fluid further comprises an oxygen scavenger in an amount of 0 to 0.25% with respect to the total fluid weight.  
     
     
         34 . A process according to  claim 22 , wherein said fluid further comprises a weighting compound selected from the group consisting of alkaline-earth metal sulphates, carbonates, silicates, alkaline-earth metal bromides, zinc bromides, and iron oxides.  
     
     
         35 . A process according to  claim 31 , wherein said fluid further comprises at least one mineral colloid selected from the group consisting of attapulgite, barite and bentonite.  
     
     
         36 . A process according to  claim 22 , the drilling fluid further comprises water.  
     
     
         37 . In a process for controlling fluid loss in a guar free drilling fluid comprising a fluid loss control agent, wherein the improvement comprises the step of: 
 a) combining the fluid control agent with a xanthan gum having a percentage of acetyl groups in the range 0 to 3%, said xanthan gum being in the form of a polypentamer, and at least one compound which increases the ionic strength of the fluid, and    b) operating at temperatures between 100 and 140° C.    
     
     
         38 . A process for controlling fluid loss of a guar-free drilling fluid, comprising the steps of: 
 1) having in the fluid as a fluid loss control agent a xanthan gum having a percentage of acetyl groups in the range 0 to 3%, said xanthan gum being in the form of a polypentamer, at least one compound which increases the ionic strength of the fluid, and optionally at least one further fluid loss control agent, and    2) operating at a temperature of between 100 and 140° C.    
     
     
         39 . A process for stabilising the rheological properties of a fluid used in oil production, at temperatures between 100 and 140° C., comprising the step of having in the fluid a xanthan gum having a percentage of acetyl groups in the range 0 to 3%, said xanthan gum being in the form of a polypentamer, and at least one compound which increases the ionic strength of the fluid.  
     
     
         40 . A process according to  claim 39 , wherein the fluid used in oil extraction is a fluid used in well development operations, drilling operations, work-over operations, completion operations or oil field production.