Completions index analysis

Abstract

A method for determining a hydrocarbon-bearing reservoir quality prior to a hydraulic fracture treatment based on completions index is disclosed. The method comprises a step performing a test determining a hydraulic pressure at which a hydrocarbon-bearing reservoir will begin to fracture by pumping a fluid in a wellbore, wherein the wellbore extends from a surface to the reservoir and the wellbore has one or more perforations in communication with reservoir; a step generating a pressure transient in the wellbore, the pressure transient travels from the surface to the reservoir through the perforations and reflects back the surface after contacting the reservoir; a step measuring response of the pressure transient at sufficiently high sampling frequency; a step determining fracture hydraulic parameters of the perforations and the reservoir using the measured response; and optimizing a stimulation treatment to the reservoir based on the determined fracture hydraulic parameters.

What is claimed is: 
     
       1. A method for determining a hydrocarbon-bearing reservoir quality comprising:
 performing a test determining a hydraulic pressure at which a hydrocarbon-bearing reservoir will begin to fracture by pumping a fluid in a wellbore, wherein the wellbore extends from a surface to the reservoir and the wellbore has one or more perforations in communication with the reservoir; 
 generating a pressure transient in the wellbore, the pressure transient traveling from the surface to the reservoir through the perforations and reflecting back to the surface after contacting the reservoir; 
 measuring the response of the pressure transient at a sampling frequency, wherein the measured response includes pressure measurement over a period of time; and 
 determining a hydraulic parameter of the perforations, wherein the step of determining a hydraulic parameter of the perforations includes transforming the measured response to produce a transformed response, wherein the step of transforming includes providing a window having a time duration that is shorter than the period of time in the measured response, applying the window to the measured response to encompass a portion of the measured response, and determining maximum and minimum pressure in the measured response encompassed by the window, and; 
 calculating rate of decay of the transformed response. 
 
     
     
       2. The method of  claim 1 , wherein the step of transforming the measured response further comprises calculating the difference between the maximum pressure and the minimum pressure. 
     
     
       3. The method of  claim 2 , wherein the difference is produced as part of the transformed response. 
     
     
       4. The method of  claim 1 , wherein the time duration of the window is 1 second. 
     
     
       5. The method of  claim 1 , the step of transforming the measured response further comprises sliding the window over the measured response at an increment of time to transform the entire measured response. 
     
     
       6. The method of  claim 5 , wherein the step of transforming the measured response further comprises determining maximum and minimum pressure in the portion encompassed by the window for each increment of time. 
     
     
       7. The method of  claim 6 , wherein the step of transforming the measured response further comprises calculating the difference between the maximum pressure and the minimum pressure in the portion encompassed by the window for each increment of time. 
     
     
       8. The method of  claim 7 , wherein the differences are produced as part of the transformed response. 
     
     
       9. The method of  claim 5 , wherein the increment of time is 0.01 second. 
     
     
       10. The method of  claim 1 , wherein the step of calculating rate of decay of the transformed response comprises finding peaks of the transformed response and fitting an exponential decay to the peaks. 
     
     
       11. The method of  claim 1 , wherein the method further comprises calculating a reflection half-life from the rate of decay. 
     
     
       12. The method of  claim 11 , wherein the method further comprises correlating the reflection half-life to a modeled hydraulic resistance. 
     
     
       13. The method of  claim 12 , wherein the modeled hydraulic resistance is obtained from adjusting an element of an electrical model representing the wellbore over a range of values. 
     
     
       14. The method of  claim 13 , wherein the element is a resistor. 
     
     
       15. The method of  claim 1 , wherein the measured response provides pressure information over a period of time and the transformed response provides pressure information different from the pressure information provided by the measured response over the same period of time. 
     
     
       16. The method of  claim 15 , wherein the pressure information provided by the transformed response includes a plurality of peaks and the rate of decay is calculated based on the peaks. 
     
     
       17. The method of  claim 1 , wherein the hydraulic parameter is flow resistance. 
     
     
       18. The method of  claim 1 , wherein the sampling frequency is more than 2 Hz. 
     
     
       19. The method of  claim 1 , the step of transforming the measured response further comprises applying the window to the measured response at an increment of time to encompass a next portion of the measured response. 
     
     
       20. The method of  claim 19 , wherein the step of transforming the measured response further comprises determining maximum and minimum pressure in the next portion of the measured response encompassed by the window.