Abstract: A system including a sonic source deployed in a first borehole and a fiber optic distributed sensor deployed in a second borehole, both boreholes extending from an earth surface into a formation. The optical fiber is configured to react along its length to incident sonic waves generated by the sonic source and propagating through the first borehole, through the formation, and through the second borehole. The system further includes an optical source to launch optical pulses into the fiber optic distributed sensor while the sonic waves are incident on the fiber optic distributed sensor. The system also includes a data acquisition system coupled to the fiber optic distributed sensor to detect temporal variations in coherent Rayleigh noise (CRN) generated in the fiber optic distributed sensor in response to the optical pulses and the incident sonic waves; and a computer system configured to receive data from the data acquisition system.

Abstract: The disclosure provides a borehole tool for seismic data collection. The tool comprises a cable to be positioned within a borehole and at least one sensor for measuring seismic signals mounted on the cable. The sensors provide measurements of particle motion (velocity or acceleration) perpendicular to an axis of the borehole. The disclosure also provides methods of seismic surveying, which involves positioning the tool in the borehole, firing a seismic source generating a seismic wave and measuring particle motion associated with the passing seismic wave perpendicular to an axis of the borehole using the at least one sensor for measuring particle motion.

Abstract: Method for determining geometric characteristics of a hydraulic fracture includes performing a baseline seismic survey for a geological formation. A velocity model is created by combining results of the baseline seismic survey and additional geoscientific information, and seismic properties of the geologic formation are evaluated. At least one strong flat lithological reflector disposed below a planned fracture is identified. A numerical model of elastic wave propagation in the geologic formation with a fracture with given properties is created. Hydraulic fracturing is performed and after fracturing when the fracture is maintained open and pressurized seismic surveys are performed. The fracture's dimensions and shape are determined by comparing the first and the second reflected and refracted seismic signals and solving an inverse problem with the use of the numerical model.

Abstract: Neutrally-buoyant tools for seismic data collection are provided that may range from several hundred meters to several kilometers in length and have integrated sensors which move along with the borehole fluid in response to a passing seismic wave. The disclosure also provides methods of deploying neutrally-buoyant tools, which includes using a tractor, adding a weight or both to the tool in order to overcome the difficulty of lowering a neutrally buoyant tool into a borehole, and optionally occasionally clamping the tool to the borehole to alleviate tension in the tool. This disclosure also provides methods of acquiring seismic data, which involves positioning a neutrally-buoyant tool in a borehole such that the tool is able to move relatively freely along with the borehole fluid in response to a seismic wave passing through the fluid, firing a seismic source, and using the sensors to collect seismic data generated thereby.

Abstract: The disclosure provides neutrally-buoyant tools for seismic data collection. The tools may range from several hundred meters to several kilometers in length and have integrated sensors which move along with the borehole fluid in response to a passing seismic wave. The disclosure also provides methods of deploying neutrally-buoyant tools, which includes using a tractor, adding a weight or both to the tool in order to overcome the difficulty of lowering a neutrally buoyant tool into a borehole, and optionally occasionally clamping the tool to the borehole to alleviate tension in the tool. This disclosure also provides methods of acquiring seismic data, which involves positioning a neutrally-buoyant tool in a borehole such that the tool is able to move relatively freely along with the borehole fluid in response to a seismic wave passing through the fluid, firing a seismic source, and using the sensors to collect seismic data generated thereby.

Abstract: A method for determining properties of a formation is described herein. The method includes disposing a well-logging tool in a borehole. The well-logging tool includes a device for varying temperature of the formation and two acoustic logging probes located symmetrically along the well-logging tool length relative to the device for varying temperature of the formation. During the logging tool movement in the borehole, continuous varying of the formation temperature, continuous acoustic logging, and continuous measurement of formation temperature are performed. Dependencies of the measured velocity and attenuation of the Stoneley waves as functions of the measured temperature of the formation are obtained. Based on the obtained dependencies, properties of the formation are determined.

Abstract: Method for determining geometric characteristics of a hydraulic fracture comprises performing a baseline seismic survey for a geological formation. A velocity model is created by combining results of the baseline seismic survey and additional geoscientific information, and seismic properties of the geologic formation are evaluated. At least one strong flat lithological reflector disposed below a planned fracture is identified. A numerical model of elastic wave propagation in the geologic formation with a fracture with given properties is created. Hydraulic fracturing is performed and after fracturing when the fracture is maintained open and pressurized seismic surveys are performed. The fracture's dimensions and shape are determined by comparing the first and the second reflected and refracted seismic signals and solving an inverse problem with the use of the numerical model.

Abstract: The method for a productive formation properties determination comprises positioning a complex well-logging tool in a borehole, the well-logging tool consists of the device for the formation temperature impact and two similar logging probes located symmetrically along the well-logging tool relative to the device for the formation temperature impact. During the logging tool movement in the borehole continuous formation temperature impact and formation temperature measurement are performed. Based on the obtained dependencies of the formation parameters in question as a function of temperature the productive formation properties are determined.

Abstract: The invention relates to the methods for determining the permeability of a geological formation saturated with a liquid and provides for a method, a system and a logging tool for estimating permeability. The method comprises exciting a formation with acoustic energy pulses propagating into the formation, measuring the acoustic response signals produced by the acoustic exciting and the electromagnetic signals produced by said acoustic energy pulses within the formation and separating components from said measured acoustic response signals and said measured electromagnetic signals representing Stoneley waves propagating through the formation. The acoustic response signals and electromagnetic signals representing Stoneley waves propagating through the formation are synthesized. The separated acoustic response signal and electromagnetic signal components and the synthesized Stoneley wave signals are compared.

Abstract: Method to monitor reservoir fracture development and its geometry may find its application at oil and gas fields as well as in coal mining industry. The method provides injection of conductive fracturing fluid into the wellbore under pressure enabling to create a fracture in the formation and penetrate into it. At the stage corresponding to the end of the fracturing fluid charging a series of voltage pulses is applied to the fracturing fluid. In the well parameters of the electromagnetic field and/or acoustic signals resulting from applying the voltage pulses to the fracturing fluid are measured, and the fracture tip coordinates are determined.

Abstract: A method for estimating a permeability of a formation surrouning a borehole comprises applying transient well-test conditions to the borehole. A portion of the formation is excited with an acoustic signal. The acoustic response corresponding to the acoustic exciting is measured with an acoustic receiver located within the borehole. The permeability of the formation is estimated using the acoustic response.

Abstract: The invention concerns a method for determining the position, in a formation (1) containing at least one electrolytic liquid, of an interface (6) in relation to a bore hole (2). One stimulates at a first instant the interface (6) with an excitation signal, one detects at a second instant (t2) a response signal converted by electro-osmosis or electrokinetic coupling effect and, if appropriate, the exication signal after reflection at a third instant (t3). With the three instants and the propagation velocity of the signals, one calculates the distance between the interface (6) and the bore hole (2).

Abstract: A method for characterizing a formation. The method comprises exciting the formation with an acoustic wave propagating into the formation. A seismo-electromagnetic signal produced by the acoustic wave within the formation is measured. The method further comprises exciting the formation with an electromagnetic exciting field. An electromagneto-seismic signal produced by the electromagnetic exciting field within the formation is measured. The measured seismo-electromagnetic signal and the measured electromagnetic-seismic signal are analyzed to evaluate characterizing parameters of the formation.

Abstract: An apparatus for determining fluid-pressure diffusivity in a borehole (12) in a formation (10) includes an electrode (16) and a strain measuring device (18),(20) (or a particle velocity measuring device (18),(20) or a particle acceleration measuring device (18),(20)) disposed a fixed distance from the electrode (16). The electrode (16) injects an electrical current into a point on a wall of the borehole (12). The strain measuring device (18),(20) measures strain (or the particle velocity measuring device (18),(20) measuresd particle velocity or the particle acceleration measuring device (18),(20) measures particle acceleration) at the fixed distance from the point of injection of the electrical current over time. The fluid-pressure diffusivity is determined based on the measured strain (or measured particle velocity or measured particle acceleration) over time.

Abstract: A porous geological formation contains electrolytic fluid. During the geophysical prospecting of the formation, a region of interest of the formation where the electrolytic fluid is found is stimulated with an excitation signal. The excitation signal corresponds to an energy of a first type. The excitation signal is converted in the region of interest into a response signal. The response signal corresponds to an energy of a second type. The response signal is detected. An electric polarisation is applied to the region of interest so as to strengthen the response signal relative to what it would be in the absence of polarisation. The electric polarisation comes about by means of a continuous or quasi-continuous polarising electric field. The polarising electric field is modulated in frequency with a frequency which is low relatively to the excitation frequency.

Abstract: An apparatus for determining fluid-pressure diffusivity in a borehole (12) in a formation (10) includes an electrode (16) and a strain measuring device (18),(20) (or a particle velocity measuring device (18),(20) or a particle acceleration measuring device (18),(20)) disposed a fixed distance from the electrode (16). The electrode (16) injects an electrical current into a point on a wall of the borehole (12). The strain measuring device (18),(20) measures strain (or the particle velocity measuring device (18),(20) measuresd particle velocity or the particle acceleration measuring device (18),(20) measures particle acceleration) at the fixed distance from the point of injection of the electrical current over time. The fluid-pressure diffusivity is determined based on the measured strain (or measured particle velocity or measured particle acceleration) over time.

Abstract: The invention concerns a method for determining the position, in a formation (1) containing at least one electrolytic liquid, of an interface (6) in relation to a bore hole (2). One stimulates at a first instant the interface (6) with an excitation signal, one detects at a second instant (t2) a response signal converted by electro-osmosis or electrokinetic coupling effect and, if appropriate, the exication signal after reflection at a third instant (t3). With the three instants and the propagation velocity of the signals, one calculates the distance between the interface (6) and the bore hole (2).

Abstract: It is a process of geophysical prospecting of a porous geological formation (1) containing at least one electrolytic fluid, comprising the following steps: stimulation of a region of interest (90) of the formation where the electrolytic fluid is found with an excitation signal corresponding to an energy of a first type, in such a way that the excitation signal is converted in the region of interest into a response signal corresponding to an energy of a second type, detection of a response signal, application of an electric polarisation to the region of interest (90) so as to strengthen the response signal relative to what it would be in the absence of polarisation.

Abstract: A method of monitoring a fluid front movement is provided. The method includes: determining at least two techniques for monitoring the fluid front movement; determining a configuration of monitoring sensors, corresponding to the at least two monitoring techniques, from a joint sensitivity study of the at least two techniques; acquiring data with the monitoring sensors; and monitoring the fluid front by joint inverting the data.

Abstract: A method of monitoring a fluid front movement is provided. The method includes: determining at least two techniques for monitoring the fluid front movement; determining a configuration of monitoring sensors, corresponding to the at least two monitoring techniques, from a joint sensitivity study of the at least two techniques; acquiring data with the monitoring sensors; and monitoring the fluid front by joint inverting the data.