Tunable down-hole stimulation system

摘要

Tunable down-hole stimulation systems feature closed-loop control of pumps and tunable down-hole stimulators. Stimulators generate and hydraulically transmit broad vibration spectra tuned for resonance excitation and fracturing of geologic materials adjacent to the wellbore. Feedback data for controlling stimulation includes backscatter vibration originating in stimulated geologic material and detected at the stimulator(s). For initial fracturing with relatively large particle sizes, the power spectral density (PSD) of each stimulator output is down-shifted toward the lower resonant frequencies of large particles. As fracturing proceeds to smaller (proppant-sized) fragments having higher resonant frequencies, backscatter vibration guides progressive up-shifting of stimulator PSD to higher vibration frequencies. Stimulator power requirements are minimized by concentrating vibration energy efficiently in frequency bands to which geologic materials are most sensitive at every stage of stimulation. Geologic fragmentation efficiency is thus optimized, with inherent potential for plain-water fracs completed with self-generated proppant.

主权项

1. A method for tuning a down-hole stimulation system, the method comprising
providing at least one frac pump maintaining a fluid environment in a wellbore, said fluid environment contacting geologic material adjacent to said wellbore; providing a tunable down-hole stimulator in said wellbore, said stimulator comprising a vibration generator responsive to a periodic control signal by transmitting to said geologic material, via said fluid environment, a vibration burst simultaneously comprising a plurality of vibration frequencies; and providing a programmable controller, said programmable controller transmitting each said periodic control signal to said tunable down-hole stimulator; wherein said vibration generator comprises an electromagnetic driver, a movable hammer, and a fluid interface, said movable hammer being responsive to said electromagnetic driver for periodically striking said fluid interface, and rebounding therefrom during an adjustable rebound cycle time, to transmit one said vibration burst to said geologic material via said fluid environment; wherein said electromagnetic driver is responsive to each said periodic control signal; wherein each said vibration burst has an adjustable power spectral density, each said adjustable power spectral density being responsive to one said adjustable rebound cycle time; wherein each said vibration burst excites induced geologic resonance vibration in said geologic material; wherein said fluid interface comprises at least one accelerometer for detecting each said vibration burst and detecting time-shifted backscatter vibration energy from said induced geologic resonance vibration, said at least one accelerometer transmitting an accelerometer signal derived from detected vibration; wherein each said adjustable rebound cycle time is responsive to one said accelerometer signal for tuning said down-hole stimulation system; and wherein shortening one said adjustable rebound cycle time up-shifts one said adjustable power spectral density.