Methods for testing stimulation fluids

Abstract

A method of testing the performance of a stimulation fluid by placing a sample of the stimulation fluid or a precursor thereof into the body of a downhole tool, positioning the tool in juxtaposition with a rock face at a downhole location, forming a sealing contact between the rock face and the tool; and injecting the sample into the rock face while monitoring pressure and/or flow rates during the injection of the sample into and/or production of formation fluid from the rock face to derive a measure of the effectiveness of the stimulation fluid in creating openings in the rock face.

What is claimed is: 
     
         1 . A method of testing the performance of a stimulation fluid, comprising the steps of
 placing a sample of said stimulation fluid or a precursor thereof into the body of a downhole tool;   positioning said tool in juxtaposition with a rock face at a downhole location;   forming a sealing contact between said rock face and the tool; and   injecting said sample into said rock face while monitoring pressure during the injection of the sample to derive a measure of the effectiveness of said stimulation fluid in creating openings in said rock face.   
     
     
         2 . A method in accordance with  claim 1 , wherein prior to the injection a hole is drilled into the rock face through which the sample is injected. 
     
     
         3 . A method in accordance with  claim 2 , wherein the rock face is completed as open hole. 
     
     
         4 . A method in accordance with  claim 1 , wherein the pressure is monitored essentially continuous to derive an injection profile. 
     
     
         5 . A method in accordance with  claim 1 , wherein flow rates and pressures are monitored during injection into and/or production of fluids from the rock face. 
     
     
         6 . A method in accordance with  claim 5 , wherein IPR curves are determined to evaluate the effectiveness of the stimulation fluid. 
     
     
         7 . A method in accordance with  claim 5 , wherein time evolution of the skin effect is determined to evaluate the effectiveness of the stimulation fluid. 
     
     
         8 . A method in accordance with  claim 5 , wherein a Provost-Economides type of test is used to evaluate the effectiveness of the stimulation fluid. 
     
     
         9 . A method in accordance with  claim 5 , wherein the flow rate from an etched hole at a given production pressure differential is used to determine a geometric parameter representative of the size of said etched hole. 
     
     
         10 . A method in accordance with  claim 1 , further comprising the step of reversing the flow to produce fluid from the formation after the injection and analyzing components of reversed flow. 
     
     
         11 . A method in accordance with  claim 10 , wherein the reversed flow is monitored for the presence of the stimulation fluid or reaction products of the stimulation fluid. 
     
     
         12 . A method in accordance with  claim 10 , wherein the reversed flow is monitored for a transition point indicating the onset production of formation fluid from the formation. 
     
     
         13 . A method in accordance with  claim 1 , wherein the injection pressure is selected to be above the rock fracture pressure. 
     
     
         14 . A method in accordance with  claim 1 , wherein multiple positions facing a identical or similar rock type are identified and the tool is positioned successively at said positions to allow the injection of several samples. 
     
     
         15 . A method in accordance with  claim 1 , wherein multiple downhole locations each facing a identical or similar rock type are identified and the tool is positioned successively at said locations to allow the injection of several samples during a single downhole tool trip.