The embodiments described herein relate to a system and method of applying periodic energy pulses to a portion of a wellbore, fracture(s), and/or near wellbore to interrogate and/or stimulate at least a portion of the wellbore, fracture(s), and/or near wellbore.
Hydraulic fracturing of a wellbore has been used for more than 60 years to increase the flow capacity of hydrocarbons from a wellbore. Hydraulic fracturing pumps fluids into the wellbore at high pressures and pumping rates so that the rock formation of the wellbore fails and forms a fracture to increase the hydrocarbon production from the formation. Proppant may be used to hold open the fracture after the fracturing pressure is released. While hydraulic fracturing may be used to increase hydrocarbon production by creating fractures within a wellbore, the condition of the fracture may not be known. An analysis of the fracture may be beneficial to determine the optimal pressure required to change a property of a fracture and potentially increase hydrocarbon production from the fracture.
It may be beneficial to develop systems and methods that could be used to improve the performance of typical hydraulic fracturing techniques. It may also be beneficial to develop system and methods that may be used to analyze the wellbore and fracture properties before, during, and after hydraulic fracturing.
The present disclosure is directed to a system and method for using pressure pulses that overcomes some of the problems and disadvantages discussed above.
One embodiment of a wellbore system comprises a work string and a downhole device connected to a portion of the work string, the downhole device configured to deliver periodic energy pulses to a portion of a wellbore. The system may include at least one sensor configured to measure energy pulses in the portion of the wellbore, wherein the at least one sensor is configured to determine at least one property of the wellbore based on the energy pulses detected by the at least one sensor. The at least one sensor may be connected to the downhole device. The periodic energy pulses may comprise seismic waves and the at least one sensor may comprise a geophone. The periodic energy pulses may comprise pressure waves and the at least one sensor may comprise a pressure sensor.
The portion of the wellbore may comprise at least one fracture in the formation. The system may include a first isolation element and a second isolation element such that a fracture is positioned between the isolation elements. The isolation elements may be packing elements. The system may include a first packing element, wherein the first packing element is positioned below the at least one fracture and the downhole device is positioned adjacent the at least one fracture. The system may include a second packing element, wherein the second packing element is positioned above the downhole device. The work string may be coiled tubing. The downhole device may be a vibratory tool and the periodic energy pulses may be oscillating pressure waves. The vibratory tool may be a fluid hammer tool that creates the oscillating pressure waves based on the Coandă effect. The frequency and/or amplitude of the oscillating pressure waves may be varied during operation of the fluid hammer tool.
The downhole device may be an acoustic device and the periodic energy pulses may be acoustic waves. The system may include proppant positioned within the at least one fracture and the proppant may be configured to release energy when actuated by the periodic energy pulses. The proppant may be explosive proppant or flagration proppant. The proppant may be various proppant disclosed in U.S. provisional patent application No. 62/040,441 entitled Hydraulic Fracturing Applications Employing Microenergetic Particles by D. V. Gupta and Randal F. LaFollette filed on Aug. 22, 2014, which is incorporated by referenced herein. The at least one sensor may be configured to measure energy pulses in the portion of the wellbore from the periodic energy pulses. The at least one sensor may be connected to the downhole device. The at least one sensor may be configured to determine at least one property of the at least one fracture based on energy pulses detected by the at least one sensor. The at least one property may be a width of the fracture, a length of the fracture, a shape of the fracture, and/or a propped length of the fracture.
One embodiment is a method of supplying energy pulses to a portion of a wellbore comprising positing a downhole device adjacent a portion of a wellbore and delivering periodic energy pulses from the downhole device to the portion of the wellbore. The method may include determining one or more properties of the wellbore based on energy pulses reflected from the wellbore. The portion of the wellbore may include at least one fracture. The method may include determining one or more properties of the at least one fracture. The property may be a length of the fracture, a width of the fracture, a propped length of the fracture, a propped width of the fracture, and/or a shape of the fracture.
The method may include modifying a frequency of the periodic energy pulses in real-time. The method may include modifying a magnitude of the periodic energy pulses in real-time. The method may include reevaluating in real-time the one or more properties of the wellbore on the modified reflected energy pulses. The method may include modifying in real-time a flow rate of a fluid flowing through the downhole device to modify the frequency and magnitude of the periodic energy pulses. The method may include modifying in real-time a signal to the downhole device to modify the frequency and magnitude of the periodic energy pulses in real-time. The method may include changing a property of the fracture with the periodic energy pulses. The periodic energy pulses may enlarge a width and/or a length of the fracture. The periodic energy pulses may inhibit growth of the fracture. The periodic energy pulses may increase the conductivity of the fracture. The method may include cleaning up the at least one fracture with the periodic energy pulses. Cleaning up the at least one fracture may include enhancing transport of proppant into the at least one fracture or breaking down a layer of a formation adjacent to the at least one fracture having a low-permeability.
One embodiment is a wellbore system comprising a work string, at least one downhole device connected to a portion of the work string, the downhole device configured to deliver periodic energy pulses to a portion of the wellbore, and at least one sensor configured to determine at least one property of the wellbore based on detected energy pulses. The downhole device is configured to selectively modify a magnitude and a frequency of the periodic energy pulses. The periodic energy pulses may be pressure waves, acoustic waves, and/or seismic waves.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the invention as defined by the appended claims.
The downhole device 20 is connected to a work string 10 that is used to position the downhole device 20 at a desired location within the wellbore. The work string 10 may be various types work strings or combinations of various types of works strings such as wireline, coiled tubing, or jointed tubing as would be appreciated by one of ordinary skill in the art having the benefit of this disclosure. The downhole device 20 may be positioned adjacent to a portion of a wellbore that is desired to be stimulated by the periodic energy pulses and/or interrogated by the periodic energy pulses. The downhole device 20 may be positioned within a wellbore adjacent to a fracture 2 such that the periodic energy pulses 21 may be delivered to the fracture 2 and the formation surrounding the fracture 2. Reflective energy pulses 22 will be reflected by the wellbore and be returned to the downhole device 20. Sensors 50 may record and/or analyze the reflective energy pulses 22 to determine in real-time various characteristics of the fracture and/or wellbore as will be discussed herein. The sensors 50 could be used to determine properties of wellbore components based on the energy pulses within the wellbore. The sensors 50 may be connected to the downhole device 20 and/or may be positioned at the surface or at various locations within the wellbore. The sensors 50 may be battery powered sensors positioned within the wellbore. The sensors 50 positioned within the wellbore may record the measurements from the energy pulses in memory and/or may transmit the measurements to the surface via various mechanisms such as an e-line within or along the work string 10. The sensors 50 positioned within the wellbore could transmit measurements to the surface via other mechanisms such as via TELECOIL™ offered commercially by Baker Hughes of Houston, Tex.
The downhole device 50 may be positioned between two isolation elements to focus the periodic energy pulses 21 and reflective energy pulses 22. For example, the downhole device 50 may be positioned between the packing element 40 and 60 that may be actuated within the casing 1 of the wellbore to focus the periodic energy pulses 21 and reflective energy pulses 22 within a desired portion of the wellbore. The packing elements 40 and 60 may be connected to the downhole device 20 and/or the work string 10 via a packer tool 30 used to actuate the packing element 40 between an actuated and non-actuated state. A single packing element 40 may be used below the downhole device 20. Likewise, the downhole device 20 may be used to generate periodic energy pulses 21 within the wellbore without an upper packing element 60 or a lower packing element 40.
The periodic energy pulses 21 may be used to interrogate a fracture 2 to determine various properties of the fracture 2, such as width of the fracture, length of the fracture, propped length of the fracture, propped width of the fracture, conductivity of the fracture, compliance of the fracture, and/or shape of the fracture. The periodic energy pulses 21 may be used to stimulate or inhibit growth in a fracture 2 in a wellbore.
The magnitude and/or frequency of the periodic energy pulses 21 from the downhole device 20 may be varied during the interrogation and/or stimulation.
The downhole device 20 may be vibratory device that generates periodic energy pulses 20 with the wellbore. For example, the vibratory device may be a fluid hammer tool such as the EasyReach Extended-Reach Tool™ offered commercially by Baker Hughes of Houston, Tex. The vibratory device may be a fluid hammer tool that oscillates creating periodic pulses based on the Coandă effect. U.S. Pat. No. 8,727,404 entitled Fluidic Impulse Generator, which is incorporated by reference in its entirety herein, discloses a vibratory downhole device that may be applicable to produce the desired periodic energy pulses.
It may be beneficial to use a downhole device 20 to provide a periodic energy pulse 21 to a fracture 2 of a wellbore during the hydraulic fracturing of the fracture 2. The same downhole device 20 may be used to interrogate the wellbore and/or stimulate the wellbore. It may be important that such a downhole device 20 be able to produce consistent energy pulses over a long period of time.
A computer model, based on the Method of Characteristics, was developed for the EasyReach™ tool by the inventors to assess the fracture capability as a pressure pulse resonator. The mathematical model assumes that the wellbore and the fracture are tubes for which the wave speed is known. The wave propagation speed in coiled tubing is provided for by the following equation with ρ for the fluid density, w for the wall thickness of the coiled tubing, d is the outside diameter of the coiled tubing, E for Young's modulus of the coiled tubing material, and K for the fluid bulk modulus.
The wave speed downstream of the downhole device 20 can be interpolated from a given frequency and complex velocity table, depending on the wellbore and/or fracture properties. At any given time, the tool frequency may be used to calculate the wave speed in the wellbore and fracture. During simulation the frequency of periodic energy pulses from the EasyReach™ tool starts at 7 Hz and vary between 5 Hz and 9 Hz. The frequency for other downhole devices 20 may vary with respect to the frequencies of the EasyReach™ tool.
By delivering periodic energy pulses 21 to a portion of a wellbore and fracture 2, the properties of the wellbore and/or fracture 2 may be determined by mathematically modeling the system as a resonant system based on wave data within the wellbore. The wave data within the wellbore may be provided by sensors 50 connected to the downhole device, sensors 50 positioned within the wellbore, and/or sensors 50 at the surface. In addition to interrogating the wellbore and fracture 2, the periodic energy pulses 21 may be used to effect changes in a fracture as discussed herein.
Although this invention has been described in terms of certain preferred embodiments, other embodiments that are apparent to those of ordinary skill in the art, including embodiments that do not provide all of the features and advantages set forth herein, are also within the scope of this invention. Accordingly, the scope of the present invention is defined only by reference to the appended claims and equivalents thereof.
The present application claim the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 62/040,508, filed Aug. 22, 2014, entitled “System and Method for Using Pressure Pulses for Fracture Stimulation Performance Enhancement and Evaluation,” the disclosure of which is incorporated by reference herein in its entirety.
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