Characterizing oil, gasor geothermal wells, including fractures thereof

Abstract

An excitation event in an oil, gas or geothermal well creates a responsive signal having lower and higher frequency components, which higher frequency component provides information about one or more characteristics of the well. Examples of such characteristics pertaining to a subterranean fracture include: breakdown pressure at fracture initiation, time it takes proppant to reach and to screenout the tip of the fracture, fracture geometry and fracture growth, fracture closure pressure, relative fluid flow through respective perforations, and horsepower requirements to perform a fracture treatment. One excitation event includes creating an excitation signal having a maximum amplitude change occurring within a time t , which is less than a period t of the higher frequency component. Wavelet processing may be used to separate or distinguish the higher frequency waveform from the lower frequency waveform. The information can be used to control a process (for example, a fracturing process) applied to the respective well or one or more other wells. In another aspect, an unidentified signature waveform is compared to identified signature waveforms in a neural network computer database to create an identity for the unidentified signature waveform relative to an identified signature waveform in the database. A system to determine a characteristic of an oil, gas or geothermal well is also disclosed.