Abstract: Methods and apparatus to control a formation testing operation based on a mudcake leakage are disclosed. A disclosed example method for use with a downhole tool disposed in a wellbore comprises measuring a property of a mudcake layer at a first location in a wellbore, determining a value representative of an estimated leakage through the mudcake layer based on the property, and determining, based on the value, whether to continue a formation testing operation.

Abstract: The invention is a method of constructing a three-dimensional fracture density log of a porous formation traversed by fractures and a borehole. A number N of intersections between the fractures and the borehole is measured over a section of the borehole of length L located at a depth d, from observations of the wall of this section. A conditional probability law of the three-dimensional fracture density is then estimated, knowing the number N of intersections. The value of the three-dimensional fracture density at depth d is determined by calculating the mean of this conditional probability law. Finally, the three-dimensional fracture density log is constructed by repeating the previous stages for different depths. A three-dimensional fracture density uncertainty log can also be associated by calculating quantiles of the conditional probability law.

Abstract: A method and reservoirs are described that provide for controlling gas pressure within a porosity storage reservoir. In embodiments, gas is injected into the porosity storage reservoir while water is being extracted from the reservoir to provide greater efficiency in extracting the water from the reservoir. The gas may be injected at a predetermined target pressure or at a variable pressure. In other embodiments, a vacuum is applied to the reservoir while water is being injected into the reservoir to provide greater efficiency when introducing water into the reservoir.

Abstract: A method, system and computer program product for determining permeability of an earth formation of a reservoir are disclosed. A method may include: providing formation testing data of the earth formation; defining layering of the earth formation; determining a geological model for each layer; modeling pressure transient in the earth formation by representing pressure transient within a layer using an analytical solution and representing pressure transient between two layers using a numerical solution, the analytical solution selected based on at least one of the respective geological model and data regarding a drilled well of the reservoir, and a parameter of the analytical solution and a parameter of the numerical solution being determined based on the formation testing data; and determining the permeability of the earth formation based on the pressure transient model.

Abstract: Earth formations are characterized by using an array of electrodes which can measure streaming potentials in the formation, and by interpreting the data obtained by the electrodes. The electrodes are placed on a wireline tool, a LWD tool, or in a fixed manner about a completed wellbore. The measured streaming potentials are generated by drilling with an overbearing pressure, slitting the mudcake in a borehole, acid injection, or any of various other manners which causes fluid movement. The data obtained is interpreted to locate fractures, measure formation permeability, estimate formation pressure, monitor drilling fluid loss, detect abnormal pressure, etc. Particularly, a streaming potential voltage transient having a double peak profile signifies the presence of a formation fracture.

Abstract: The present invention provides method for detecting the possible presence of surfaces layers of diagenetic origin by establishing divergence between well signatures such as logs, particularly for use in predominantly carbonate reservoirs.

Abstract: A borehole logging system for the measure and the telemetry of properties and conditions of a well borehole environs. The system is embodied to measure fluids within the borehole, to measure high resolution images of the wall of the borehole, to transfer of data to and from equipment operating within the borehole environment, and to determine the status of equipment operating within the borehole. The embodiments are based upon emission, measurement and processing of electromagnetic radiation in the near infrared (NIR) region of the radiation spectrum.

Abstract: In one method, the permeabilities are obtained by correcting the geometric factor derived from combining the FRA analysis and buildup analysis. In a second method, the permeabilities are obtained by combining the spherical permeability estimated from buildup analysis and the geometric skin factor obtained from history matching the probe-pressure data. In other methods, horizontal and vertical permeabilities are determined by analysis of pressure drawdown made with a single probe of circular aperture in a deviated borehole at two different walls of the borehole.

Abstract: In one method, the permeabilities are obtained by correcting the geometric factor derived from combining the FRA analysis and buildup analysis.

Abstract: A nuclear imaging probe 1 for measuring the density of a subsurface formation GF in a limited zone surrounding a well-bore hole WBH. The probe comprises: a pad 2 having a face arranged so as to be positioned in contact with a well-bore wall WBW, at least one radioactive source 4 arranged within the pad for transmitting incident photons PI towards the well-bore wall, and at least one sensor 5 spaced away from the radioactive source and isolated from the radioactive source by a shield 6 arranged into the pad for receiving photons scattered PS by the limited zone.

Abstract: A borehole tool including an interferometer, a light source, a chamber containing a sliding weight having a first optical prism, a second optical prism located within the chamber, a tilt measuring device, and a timing device operatively associated with the interferometer. The light source, the interferometer, and the first and second optical prisms are configured to cause light emitted by the light source to form a first beam and a second beam that interfere with each other. The interferometer measures distances traveled by the sliding weight in the upward and downward direction by counting the fringes caused by the interference between the first beam and the second beam. The tilt measuring device measures the angle of the chamber relative to vertical. The influence of friction on the sliding weight's motion is eliminated by comparing the distances traveled by it in its upward and downward path over an equal time interval.

Abstract: The present invention provides a method and apparatus for using an acoustic logging tool conveyed in a borehole in an earth formation for determining a characteristic of the formation. The method comprises using a first acoustic source for generating an acoustic signal in the earth formation at a first frequency. A second acoustic source spaced apart from the first source is used for generating an acoustic signal in the earth formation at a second frequency different from the first frequency. An acoustic receiver is used for receiving a third acoustic signal indicative of said characteristic. The third acoustic signal has a frequency substantially equal to a difference between the first frequency and the second frequency. The third acoustic signal is produced by a nonlinear interaction between the first signal and the second signal in a portion of said earth formation.

Abstract: In one method, the permeabilities are obtained by correcting the geometric factor derived from combining the FRA analysis and buildup analysis. In a second method, the permeabilities are obtained by combining the spherical permeability estimated from buildup analysis and the geometric skin factor obtained from history matching the probe-pressure data. In another method, horizontal and vertical permeabilities are determined by analysis of pressure drawdown made with a single probe of circular aperture in a substantially horizontal borehole at two different walls of the borehole.

Abstract: In one method, the permeabilities are obtained by correcting the geometric factor derived from combining the FRA analysis and buildup analysis. In a second method, the permeabilities are obtained by combining the spherical permeability estimated from buildup analysis and the geometric skin factor obtained from history matching the probe-pressure data. In other methods, horizontal and vertical permeabilities are determined by analysis of pressure drawdown made with a single probe of circular aperture in a deviated borehole at two different walls of the borehole.

Abstract: A drill string comprises a first drill string member having a male end; and a second drill string member having a female end configured to be joined to the male end of the first drill string member, the male end having a threaded portion including generally square threads, the male end having a non-threaded extension portion coaxial with the threaded portion, and the male end further having a bearing surface, the female end having a female threaded portion having corresponding female threads, the female end having a non-threaded extension portion coaxial with the female threaded portion, and the female end having a bearing surface. Installation methods, including methods of installing instrumented probes are also provided.

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 specification discloses a downhole tool that determines hydraulic permeability of a downhole formation taking into account one or both of the dip angle of the borehole relative to the formation, and damage to the borehole wall and invasion of borehole fluid—collectively referred to as skin.

Abstract: A method is disclosed for predicting attenuation in real time while drilling using a portable continuous wave technology (CWT) tool to obtain amplitude spectra as a function of frequency for the cuttings at the rig site. Attenuation is predicted, and plotted as a function of frequency to monitor hydrocarbon content changes, fluid front moves, and pressure mapping or plotting attenuation as a function of depth to calibrate high resolution seismic data and interpret amplitudes for formation permeability determination.

Abstract: A method is disclosed for determining viscosity and density of fluid from formations surrounding an earth borehole, including the following steps: (a) suspending a formation testing device in the borehole; (b) drawing formation fluid into the device; (c) causing the fluid to flow in a flow line under a first set of conditions; (d) causing the fluid to flow in the flow line under a second set of conditions; (e) measuring a first fluid pressure differential in the flow line during fluid flow under the first set of conditions, and measuring a second pressure differential in the flow line during fluid flow under the second set of conditions; and (f) determining density and viscosity of the fluid as a function of the first and second measured pressure differentials.

Abstract: A method for determining formation pressure at a depth region of formations surrounding a borehole, including: keeping track of the time since cessation of drilling at the depth region; deriving formation permeability at the depth region; causing wellbore pressure to vary periodically in time and determining, at the depth region, the periodic and non-periodic component of pressure measured in the formations; determining, using the time, the periodic component and the permeability, the formation pressure diffusivity and transmissibility and an estimate of the size of the pressure build-up zone around the wellbore at the depth region; determining, using the time, the formation pressure diffusivity and transmissibility, and the non-periodic component, the leak-off rate of the mudcake at the depth region; determining, using the leak-off rate, the pressure gradient at the depth region; and extrapolating, using the pressure gradient and the size of the build-up zone, to determine the formation pressure.

Abstract: A method and apparatus for of determining a formation parameter of interest. The method includes placing a tool into communication with the formation to test the formation, determining a first formation characteristic during a first test portion, initiating a second test portion, the second test portion having test parameters determined at least in part by the determinations made during the first test portion, determining a second formation characteristic during the second test portion, and determining the formation parameter from one of the first formation characteristic and the second formation characteristic. The apparatus includes a draw down unit and a control system for closed loop control of the draw down unit. A microprocessor in the control system processes signals from a sensor in the draw down unit to determine formation characteristics and to determine test parameters for subsequent test portions.

Abstract: A method for collecting data regarding a matric potential of a media includes providing a tensiometer having a stainless steel tensiometer casing, the stainless steel tensiometer casing comprising a tip portion which includes a wetted porous stainless steel membrane through which a matric potential of a media is sensed; driving the tensiometer into the media using an insertion tube comprising a plurality of probe casing which are selectively coupled to form the insertion tube as the tensiometer is progressively driven deeper into the media, wherein the wetted porous stainless steel membrane is in contact with the media; and sensing the matric potential the media exerts on the wetted porous stainless steel membrane by a pressure sensor in fluid hydraulic connection with the porous stainless steel membrane. A tensiometer includes a stainless steel casing.

Abstract: A compression cell for rock or soil core samples applies and restores lithostatic or overburden pressure to core samples extracted from wells drilled deep into the earth. A method of applying lithostatic pressure to a core sample is disclosed along with the apparatus which effects the application. The cell construction that maintains the litho static pressure and the process of utilizing the cell and sample under essentially deep earth ambient conditions are set forth.

Abstract: Disclosed is a new method for providing accurate real time predictions of pore pressure and fracture gradient, at the rig site by determining the wave velocity from drill cuttings by a portable continuous wave technology (CWT) tool that measures drill cuttings at high resonant frequency and then using the velocity obtained in combination with the novel method of the present invention to arrive at accurate predictions for pore pressure and fracture gradient. The new technique offers real time pore pressure prediction at the rig site with small error margin that is not otherwise available using seismic, VSP, or check shot velocities in exploration.

Abstract: The present invention provides a tool assembly for use in field applications to monitor at least one condition in a well or other hole. The tool assembly may include a computing unit for directing operation of the tool assembly and may be sized to be operable in a hole having a diameter of 1 inch, and in some cases even smaller. In one aspect, the tool assembly is designed to significantly conserve power. Sensor readings may be taken at different schedules to conserve power when frequent readings are not required. Also, internal electronics of the tool assembly can be operated at a low voltage. In one aspect, the tool assembly is assemblable by simple rotatable engagement of the components, with electrical interconnections being made automatically by the rotatable engagement without keying of components. In another aspect, the tool assembly is networkable with other like tool assemblies and monitorable from a central location.

Abstract: We disclose density measurement methods that are accurate over an extended range of standoff distances. One method embodiment includes: a) obtaining a standoff distance, a near detector count rate, and a far detector count rate; b) determining a formation density measurement using near and far detector count rates when the standoff distance is less than a predetermined value; and c) determining the formation density measurement using just the far detector count rate and the standoff distance measurement when the standoff distance is greater than the predetermined value. The method may further include calculating a calibration parameter when the standoff distance is less than the predetermined value. The calibration parameter serves to calibrate a standoff-based correction to the far detector count rate, enabling accurate formation density measurements at large standoff distances. The measurements are made with a rotating logging tool, causing the standoff distance to cycle between large and small values.

Abstract: A method of measuring resistivity values in relation to the azimuthal displacement of a measurement sensor displayed on a measurement-while-drilling device in a wellbore environment is disclosed. The present invention also provides an instantaneous reading of resistivity values. A resistivity sensor measures a volume having a circular cross-section, and whose center is the geometric center of the tool. Averaging removes measurement errors, such as those due to tool motion. Information on the formation resistivity is obtained as a function of the location of the center of the tool. A method of acoustic standoff determines offset of the drill tool and distances to walls. The operator gains knowledge of bedding layer formation and dip from azimuthal dependence of standoff and resistivity values.

Abstract: A method of monitoring pore pressure, comprises the steps of: (a) providing downhole in a well a sealable container, (b) sealing in the container a sample of fluid at a baseline pressure and a sample of a formation having an initial pore pressure, (c) measuring the change in pressure of the fluid sample, the pressure of the fluid sample and the pore pressure of the formation sample sealed in the container tending to equalize over time, and (d) estimating the initial pore pressure relative to the baseline pressure from the measured change in fluid sample pressure.

Abstract: A method for predicting the secondary porosity system (SPS) porosity, and thereby permeability, of a coal bed involves determining an initial condition in the coal bed, including an initial SPS pressure and an initial sorbed gas composition, determining a pressure strain effect due to increasing the SPS pressure to a value greater than the initial SPS pressure, and determining a sorption strain effect due to changes in the sorbed gas composition resulting from decreasing the methane content and increasing the content of a stronger adsorbing fluid (SAG) relative to the initial sorbed gas composition. Preferably, the method uses data from test injections of water and/or a weaker adsorbing fluid (WAG) and a SAG. The data is used in the inventors' model to compute a SPS porosity and an absolute permeability at a reference SPS pressure and a reference sorbed gas composition. Preferably, the reference pressure is atmospheric pressure.

Abstract: The present invention is directed to methods and apparatus for using a formation tester to perform a pretest, in a formation having low permeability, by intermittently collecting a portion of fluid at a constant drawdown rate. The drawdown pressure is monitored until a maximum differential pressure is reached between the formation and the tester. Then the piston is stopped until the differential pressure increases to a set value, at which time the piston is restarted. The controlled intermittent operation of the piston continues until a set pretest volume is reached. The modulated drawdown allows for an accurate collection of pressure versus time data that is then used to calculate the formation pressure and permeability. The present invention also finds applicability in logging-while-drilling and measurement-while drilling applications where power conservation is critical.

Abstract: Techniques for using gravity in applications such as drilling and logging. Techniques are present for (1) gravity well logging using gravity sensors arrays; (2) creating density pseudosections using gravity measurements; (3) performing Gravity Measurement While Drilling (GMWD) using single or multiple gravity sensors; and (4) geosteering using GMWD.

Abstract: A drill bit, comprising a bit body, a sensor disposed in the bit body, a single journal removably mounted to the bit body, and a roller cone rotatably mounted to the single journal.

Abstract: Method and device for evaluating, simultaneously and with a single equipment, physical parameters such as the absolute permeability and the porosity of fragments taken from a fragmented artificial or natural porous medium.

Abstract: We disclose density measurement methods that are accurate over an extended range of standoff distances. One method embodiment includes: a) obtaining a standoff distance, a near detector count rate, and a far detector count rate; b) determining a formation density measurement using near and far detector count rates when the standoff distance is less than a predetermined value; and c) determining the formation density measurement using just the far detector count rate and the standoff distance measurement when the standoff distance is greater than the predetermined value. The method may further include calculating a calibration parameter when the standoff distance is less than the predetermined value. The calibration parameter serves to calibrate a standoff-based correction to the far detector count rate, enabling accurate formation density measurements at large standoff distances. The measurements are made with a rotating logging tool, causing the standoff distance to cycle between large and small values.

Abstract: A method for collecting data regarding a matric potential of a media includes providing a tensiometer having a stainless steel tensiometer casing, the stainless steel tensiometer casing comprising a tip portion which includes a wetted porous stainless steel membrane through which a matric potential of a media is sensed; driving the tensiometer into the media using an insertion tube comprising a plurality of probe casing which are selectively coupled to form the insertion tube as the tensiometer is progressively driven deeper into the media, wherein the wetted porous stainless steel membrane is in contact with the media; and sensing the matric potential the media exerts on the wetted porous stainless steel membrane by a pressure sensor in fluid hydraulic connection with the porous stainless steel membrane. A tensiometer includes a stainless steel casing.

Abstract: Formation drilling cuttings are centrifuged and a sediment sample is extracted and heated to burn off surface hydrocarbons. A non-fluorescing diluant is added to the sediment. The sediment is then subjected to UV excitation. Depending upon the permeability of the sediment, the speed at which emitted fluorescence brightens is found to vary. The time and brightness of the emission are measured. The time/brightness relationship is proportional to the permeability of the cuttings and can be used to calculate a relative permeability index for comparison to other know parameters to determine the presence of hydrocarbon and the likelihood of being able to produce the hydrocarbon from a wellbore.

Abstract: A method for predicting the secondary porosity system (SPS) porosity, and thereby permeability; of a coal bed involves determining an initial condition in the coal bed, including an initial SPS pressure and an initial sorbed gas composition, determining a pressure strain effect due to increasing the SPS pressure to a value greater than the initial SPS pressure, and determining a sorption strain effect due to changes in the sorbed gas composition resulting from decreasing the methane content and increasing the content of a stronger adsorbing fluid (SAG) relative to the initial sorbed gas composition. Preferably, the method uses data from test injections of water and/or a weaker adsorbing fluid (WAG) and a SAG. The data is used in the inventors' model to compute a SPS porosity and an absolute permeability at a reference SPS pressure and a reference sorbed gas composition. Preferably, the reference pressure is atmospheric pressure.

Abstract: A method of performing a formation rate analysis from pressure and formation flow rate data. Pressure and flow rate data are measured as fluid is withdrawn from a formation. Variable system volume is accounted for. The pressure and flow rate data are correlated using a multiple linear regression technique. Time derivative terms related to pressure and flow rate are smoothed using a summation technique, thereby providing better correlations than using the time derivatives directly. Formation parameters comprising formation permeability, formation pressure, and fluid compressibility may be determined from the correlation.

Abstract: Apparatus for determining the density of a fluid downhole includes apparatus for measuring compressibility of the fluid and apparatus for determining the speed of sound through the fluid. According to the methods of the invention, density of the fluid is calculated based upon the relationship between density, compressibility, and the speed of sound through the fluid.

Abstract: A method of using nuclear spectroscopy measurements acquired while drilling a subsurface formation including: measuring indicators of a plurality of absolute or relative formation elemental concentrations; processing the measurements to determine a petrophysical parameter associated with the subsurface formation while drilling, and using the petrophysical parameter to determine a drilling parameter. The petrophysical parameter may include, for instance, the permeability of the subsurface formation and the drilling parameter may include, for instance, a change in the orientation of a directional drilling assembly or the point at which to stop drilling. The invention further involves an apparatus adapted to carry out the inventive method.

Abstract: Apparatus for determining the density of a fluid downhole includes apparatus for measuring compressibility of the fluid and apparatus for determining the speed of sound through the fluid. According to the methods of the invention, density of the fluid is calculated based upon the relationship between density, compressibility, and the speed of sound through the fluid.

Abstract: The present invention is directed to methods and apparatus for using a formation tester to perform a pretest, in a formation having low permeability, by intermittently collecting a portion of fluid at a constant drawdown rate. The drawdown pressure is monitored until a maximum differential pressure is reached between the formation and the tester. Then the piston is stopped until the differential pressure increases to a set value, at which time the piston is restarted. The controlled intermittent operation of the piston continues until a set pretest volume is reached. The modulated drawdown allows for an accurate collection of pressure versus time data that is then used to calculate the formation pressure and permeability. The present invention also finds applicability in logging-while-drilling and measurement-while drilling applications where power conservation is critical.

Abstract: A method for determining the characteristics of a subterranean formation penetrated by an existing or drilled well is disclosed. The method uses a mathematical model to estimate formation parameters as fluid exits the formation through a hole and into the wellbore or tool. The model may be adapted to wells having a perforation extending from the wellbore into the formation by mathematically adjusting the perforation to the hole of the mathematical model. The formation properties may be estimated by mathematically eliminating the perforation and replacing it with an enlarged hole radius to simulate the mathematical model.

Abstract: A constant-head soil permeameter for determining hydraulic conductivity of earthen materials is inserted into a borehole at the desired test depth. A calibrated reservoir, disposed on the ground surface, is attached thereto with a suitable length of hose. Water is added to the calibrated reservoir and allowed to flow freely into the borehole until an equilibrium level is reached in the borehole and inside the soil permeameter. The water flowing to the permeameter is throttled by buoyant float pressure that is greatly increased by a lever-and-link valve control assembly which provides considerable mechanical advantage, thereby allowing better constant head control and much greater depths of testing than previously attained by known permeameters. A filtered vent system, backflow check valve, and seals restrict entry of soil particles and debris, thereby minimizing cleaning and maintenance of the invention.

Abstract: The specification discloses a downhole tool that determines hydraulic permeability of a downhole formation taking into account one or both of the dip angle of the borehole relative to the formation, and damage to the borehole wall and invasion of borehole fluid—collectively referred to as skin.

Abstract: A method of monitoring pore pressure, comprises the steps of:

Abstract: System of evaluating physical parameters such as the absolute permeability of porous rocks of a zone of an underground reservoir, from fragments taken from this zone, such as rock cuttings carried along by the drilling mud. Rock fragments (F) are immersed in a viscous fluid contained in a vessel (1). Pumping means (2, 3) first inject into vessel (1) a fluid under a pressure that increases with time, up to a determined pressure threshold, so as to compress the gas trapped in the pores of the rock. This injection stage is followed by a relaxation stage with injection stop. The pressure variation measured by detectors (7, 8) during these two successive stages is recorded by a computer (9). The evolution of the pressure during the injection process being modelled from initial values selected for the physical parameters of the fragments, the computer adjusts them iteratively so as to best get the modelled pressure curve to coincide with the pressure curve really measured. Application: petrophysical measurement.

Abstract: A method and apparatus for determining properties of rocks surrounding a borehole in which electrokinetic signals are generated in the rocks is disclosed. For example, the signals may be generated by the vibration induced by the drilling of the borehole or by a seismic source emitting continuous pressure waves. The electrokinetic signals generated are detected and the signal amplified and processed to measure the porous rock properties.

Abstract: A constant-head soil permeameter for determining hydraulic conductivity of earthen materials is inserted into a borehole at the desired test depth. A calibrated reservoir, disposed on the ground surface, is attached thereto with a suitable length of hose. Water is added to the calibrated reservoir and allowed to flow freely into the borehole until an equilibrium level is reached in the borehole and inside the soil permeameter. The water flowing to the permeameter is throttled by buoyant float pressure that is greatly increased by a lever-and-link valve control assembly which provides considerable mechanical advantage, thereby allowing better constant head control and much greater depths of testing than previously attained by known permeameters. A filtered vent system, backflow check valve, and seals restrict entry of soil particles and debris, thereby minimizing cleaning and maintenance of the invention.

Abstract: The present invention provides a method that is useful in determining the permeability of rock within a subterranean formation surrounding a borehole. The method involves the establishment of a compressional wave in the borehole rock of interest and the subsequent detection of a slow compressional wave that is directly related to the permeability of the rock. The slow compressional wave typically has a velocity of approximately 900 m/s. In contrast, the compressional waves used to make borehole measurements in the past have, velocities of approximately 2000-3000 m/s.