Wettability and fluid displacement in a well

Abstract

An inverter fluid that intermixes with a non-aqueous (e.g., oil) external/aqueous internal fluid to cause external/internal inversion is designed. This includes testing a selected inverter fluid with a test fluid having a composition nominally equivalent to the composition of the non-aqueous external/aqueous internal fluid. A quantity of the designed inverter fluid is made and placed in the annulus of a well, such as an oil or gas well, to remove the non-aqueous external/aqueous internal fluid on at least a portion of one or more surfaces of the annulus. This can include pumping the inverter fluid along with a stream of cement. The inverter fluid displaces at least part of the non-aqueous external/aqueous internal fluid in the annular region and inverts the coating of non-aqueous external/aqueous internal fluid sufficient to remove the coating ahead of the cement. Determining a suitable inverter fluid comprises: measuring a parameter related to electrical conductivity of an initial mixture including (1) a test fluid having a composition nominally equivalent to the non-aqueous external/aqueous internal fluid and (2) part of a selected inverter fluid; and adding a further part of the selected inverter fluid to the initial mixture until the measured parameter indicates the external/internal phases of the test fluid have inverted.

What is claimed is:  
     
       1. A method of water-wetting an annulus in a well, wherein at least a portion of one or more surfaces of the annulus has an oleaginous external/aqueous internal fluid on it, comprising: 
       designing an inverter fluid that intermixes with the oleaginous external/aqueous internal fluid to cause the oleaginous external/aqueous internal fluid to invert, including testing a selected inverter fluid with a test fluid having a composition nominally equivalent to the composition of the oleaginous external/aqueous internal fluid;  
       making a quantity of the designed inverter fluid to be placed in the annulus of the well; and  
       placing the quantity of inverter fluid in the well for inverting the oleaginous external/aqueous internal fluid on at least a portion of one or more surfaces of the annulus.  
     
     
       2. A method as defined in claim  1 , wherein the testing and the making are performed at the well. 
     
     
       3. A method as defined in claim  1 , wherein the testing includes: 
       measuring a parameter related to the electrical conductivity of an initial mixture comprising the test fluid and part of the selected inverter fluid; and  
       adding a further part of the selected inverter fluid to the initial mixture until the measured parameter indicates the test fluid has inverted from an oleaginous external/aqueous internal state to an aqueous external/oleaginous internal state.  
     
     
       4. A method of cementing a well in which a tubular string is disposed with an annular region adjacent the outer surface of the tubular string, at least part of the annular region having an oleaginous external/aqueous internal fluid, the method comprising: 
       designing an inverter fluid that intermixes with the oleaginous external/aqueous internal fluid to remove at least a coating of the oleaginous external/aqueous internal fluid on the outer surface of the tubular string, including testing a selected inverter fluid with a test fluid having a composition nominally equivalent to the composition of the oleaginous external/aqueous internal fluid;  
       making a quantity of the designed inverter fluid to be placed in the annulus of the well; and  
       pumping the quantity of inverter fluid in the well along with a stream of cement, wherein the quantity of inverter fluid leads the stream of cement such that the pumped inverter fluid displaces at least part of the oleaginous external/aqueous internal fluid in the annular region and inverts the coating of oleaginous external/aqueous internal fluid sufficient to remove the coating ahead of the cement, at least part of which pumped inverter fluid is subsequently displaced by the pumped stream of cement.  
     
     
       5. A method as defined in claim  4 , wherein the testing and the making are performed at the well. 
     
     
       6. A method as defined in claim  4 , wherein the testing includes: 
       measuring a parameter related to the electrical conductivity of an initial mixture comprising the test fluid and part of a selected inverter fluid; and  
       adding a further part of the selected inverter fluid to the initial mixture until the measured parameter indicates the test fluid has inverted from an oleaginous external/aqueous internal state to an aqueous external/oleaginous internal state.  
     
     
       7. A method of determining an inverter fluid to use for inverting a composition of an oleaginous external/aqueous internal fluid in a well, the method comprising: 
       measuring a parameter related to the electrical conductivity of an initial mixture including (1) a test fluid having a composition nominally equivalent to the oleaginous external/aqueous internal fluid and (2) part of a selected inverter fluid; and  
       adding a further part of the selected inverter fluid to the initial mixture until the measured parameter indicates the test fluid has inverted from an oleaginous external/aqueous internal state to an aqueous external/oleaginous internal state.  
     
     
       8. A method as defined in claim  7 , further comprising determining a concentration of an inverter fluid ingredient used in the added further part relative to the total of selected inverter fluid in the initial mixture and added further part of the selected inverter fluid. 
     
     
       9. A method as defined in claim  7 , further comprising determining the total volume of the selected inverter fluid in the initial mixture and the added further part of the selected inverter fluid and determining the ratio of the determined total volume to the volume of test fluid in the initial mixture. 
     
     
       10. A method as defined in claim  7 , wherein: 
       the method further comprises making the initial mixture, including mixing the test fluid and a spacer fluid as the selected inverter fluid; and  
       adding a further part of the selected inverter fluid includes titrating a selected surfactant in the initial mixture.  
     
     
       11. A method as defined in claim  7 , wherein: 
       the method further comprises making the initial mixture, including mixing the test fluid, and a spacer fluid/surfactant composition as the selected inverter fluid, in a selected ratio; and  
       adding a further part of the selected inverter fluid includes titrating additional spacer fluid/surfactant composition in the initial mixture.  
     
     
       12. A method as defined in claim  7 , further comprising: 
       heating the test fluid and the inverter fluid to a temperature corresponding to a temperature in the well in which the determined inverter fluid is to be used; and  
       heating and stirring the initial mixture during the measuring and adding steps.  
     
     
       13. A method as defined in claim  12 , further comprising determining a concentration of an inverter fluid ingredient used in the added further part relative to the total of selected inverter fluid in the initial mixture and added further part of the selected inverter fluid. 
     
     
       14. A method as defined in claim  12 , further comprising determining the total volume of the selected inverter fluid in the initial mixture and the added further part of the selected inverter fluid and determining the ratio of the determined total volume to the volume of test fluid in the initial mixture. 
     
     
       15. A method as defined in claim  12 , wherein: 
       the method further comprises making the initial mixture, including mixing the test fluid and a spacer fluid as the selected inverter fluid; and  
       adding a further part of the selected inverter fluid includes titrating a selected surfactant in the initial mixture.  
     
     
       16. A method as defined in claim  12 , wherein: 
       the method further comprises making the initial mixture, including mixing the test fluid, and a spacer fluid/surfactant composition as the selected inverter fluid, in a selected ratio; and  
       adding a further part of the selected inverter fluid includes titrating additional spacer fluid/surfactant composition in the initial mixture.