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 hydraulic parameters of a hydraulic system before performing a fracturing operation comprising:
 generating a pressure transient in the hydraulic system having a wellbore before performing a fracturing operation, wherein the wellbore extends from a surface on which an injection well head is installed to a reservoir that is untreated by the fracturing operation and includes one or more perforations in communication with the untreated reservoir, and the pressure transient travels from the surface to the untreated reservoir through the wellbore and the perforations of the wellbore, and back to the surface after contacting the untreated reservoir; 
 measuring the response of the pressure transient at a sampling frequency; 
 determining hydraulic resistance of the perforations of the wellbore and hydraulic capacitance of the untreated reservoir using the measured response, wherein the determining step includes:
 generating an electrical model including a resistive element and a capacitive element for the hydraulic system and executing the electrical model to produce simulated pressure transient response of the hydraulic system, wherein the step of executing the electrical model includes inputting a voltage to the electrical model that represents a pressure transient; and 
 comparing the simulated pressure transient response with the measured response and adjusting the resistive element and the capacitive element of the electrical model until the simulated pressure transient response matches or closely matches the measured response; and 
 saving the simulated pressure transient response and values of the adjusted resistive element and capacitive element in a database. 
 
 
     
     
       2. The method according to  claim 1 , wherein the step of determining hydraulic resistance of the perforations of the wellbore comprises determining a flow resistance of the perforations of the wellbore. 
     
     
       3. The method according to  claim 2 , wherein the step of determining a flow resistance of the perforations of the wellbore includes determining the rate the measured response decays and the number of bounces the measured response contains. 
     
     
       4. The method according to  claim 1 , further comprises generating additional pressure transients to determine closure of fractures in the untreated reservoir and reduction in completions index versus time. 
     
     
       5. The method according to  claim 1 , wherein the step of generating a pressure transient generates a pressure transient by reducing or stopping the pump rate of a pressure pumping equipment. 
     
     
       6. The method according to  claim 1 , wherein the step of generating a pressure transient generates a pressure transient by rapidly opening and closing a valve or by employing a pressure oscillator or a mechanical shutter. 
     
     
       7. The method according to  claim 1 , wherein the determined hydraulic capacitance of the untreated reservoir is related to a surface area inside the untreated reservoir. 
     
     
       8. The method according to  claim 1 , further comprising determining whether there is a hole in a casing of the wellbore. 
     
     
       9. The method according to  claim 1 , wherein the sampling frequency is more than 2 Hz. 
     
     
       10. The method according to  claim 1 , further comprising measuring response of a pressure transient generated in a different section of the hydraulic system at a sampling frequency and comparing the measured response of the different section with the simulated pressure transient response and values of the adjusted resistive element and capacitive element saved in the database. 
     
     
       11. The method according to  claim 1 , wherein the step of generating an electrical model including a resistive element and a capacitive element for the hydraulic system includes lumping the resistive element and the capacitive element into an impedance that represents an electrical or mechanical property of the wellbore. 
     
     
       12. The method according to  claim 1 , wherein the pressure transient is generated within the first 30 seconds of a test of determining a hydraulic pressure at which the untreated reservoir will begin to fracture. 
     
     
       13. A method for determining hydraulic parameters of a hydraulic system before performing a fracturing operation comprising:
 generating a pressure transient in the hydraulic system having a wellbore before performing a fracturing operation, wherein the wellbore extends from a surface on which an injection well head is installed to a reservoir that is untreated by the fracturing operation and includes one or more perforations in communication with the untreated reservoir, and the pressure transient travels from the surface to the untreated reservoir through the wellbore and the perforations of the wellbore, and back to the surface after contacting the untreated reservoir; 
 measuring the response of the pressure transient at a sampling frequency; 
 determining hydraulic resistance of the perforations of the wellbore and hydraulic capacitance of the untreated reservoir using the measured response, wherein the determining step includes:
 numerically optimizing a neural network by extracting variables from the measured response and providing the extracted variables as inputs to the neural network; 
 generating an electrical model including a resistive element and a capacitive element for the hydraulic system and executing the electrical model to produce simulated pressure transient response of the hydraulic system; 
 determining corresponding variables from the simulated pressure transient response; and 
 comparing the corresponding variables from the simulated pressure transient response with the variables from the measured response and determining hydraulic capacitance of the untreated reservoir based on the comparison. 
 
 
     
     
       14. The method according to  claim 13 , wherein the variables include a variable representing a depth of a drilling stage, rate of decay, slope ratio of the initial reflection to the incident reflection, or initial pressure drop in a test of determining a hydraulic pressure at which the untreated reservoir will begin to fracture. 
     
     
       15. The method according to  claim 13 , wherein the step of determining hydraulic resistance of the perforations of the wellbore comprises determining a flow resistance of the perforations of the wellbore. 
     
     
       16. The method according to  claim 15 , wherein the step of determining a flow resistance of the perforations of the wellbore includes determining the rate the measured response decays and the number of bounces the measured response contains. 
     
     
       17. The method according to  claim 13 , wherein the pressure transient is generated within the first 30 seconds of a test of determining a hydraulic pressure at which the untreated reservoir will begin to fracture. 
     
     
       18. The method according to  claim 13 , further comprising measuring response of a pressure transient generated in a different section of the hydraulic system at a sampling frequency and comparing the measured response of the different section with the simulated pressure transient response and values of the adjusted resistive element and capacitive element saved in the database. 
     
     
       19. The method according to  claim 13 , wherein the step of generating a pressure transient generates a pressure transient by reducing or stopping the pump rate of a pressure pumping equipment. 
     
     
       20. The method according to  claim 13 , further comprises generating additional pressure transients to determine closure of fractures in the untreated reservoir and reduction in completions index versus time.