Abstract: The present invention relates generally to an apparatus and method for measuring nuclear magnetic resonance properties of an earth formation traversed by a borehole by generating gradient-echoes. The measurement can be made while drilling or using a wireline tool. The apparatus applies a static magnetic field, B.sub.a, in a volume of the formation which polarizes the nuclei of hydrogenous connate fluids within the formation. The apparatus applies a second magnetic field, B.sub.b, in a volume of the formation. The magnetic fields B.sub.a and B.sub.b are substantially orthogonal in the volume of the formation. A change in the polarity of the magnetic field, B.sub.b, reverses the direction of precession of the nuclei thereby generating a train of gradient-echoes. Each gradient-echo signal is transformed into the frequency domain and the signal frequency is mapped to a radial position in the volume of the formation in order to generate an image of the formation.

Abstract: A method of seismic exploration while drilling from within a borehole containing fluid, with a source and receivers positioned in the borehole is provided, comprising detecting small amplitude signals from waves within the fluid. The method is used to identify signals from waves within the fluid known as tube waves that result from compressional waves converted at the bottom of the borehole. The invention also includes seismic detection apparatus comprising ring hydrophones or similar pressure sensors. The apparatus is preferably attached to a coiled tubing with the drill bit actuated by a separate actuator as source.

Abstract: An actively controlled rotary steerable drilling system for directional drilling of wells, the system having a rotary drive component rotatable within a tubular sliding tool collar that incorporates elastic anti-rotation members to maintain a coupled relation with the borehole wall during drilling. An offsetting mandrel is supported within the tool collar by a knuckle joint for pivotal movement and for rotation relative to the tool collar and has a lower end extending from the tool collar and supporting a drill bit. To achieve controlled steering of the rotating drill bit, orientation of the tool collar is sensed and the offsetting mandrel is maintained geostationary and selectively axially inclined relative to the tool collar by orienting it about the knuckle joint.

Abstract: A method of stabilizing a water-in-oil emulsion, comprising the steps of:a) preparing a composition comprising oil, water, and a silane having bonds that hydrolyse and condense to form a cross-linked polymer, thereby creating a dispsersed aqueous phase in a continuous oil phase;b) allowing the silane to hydrolyse;c) allowing the hydrolysed silane to condense to form a crosslinked polymer at an interface between the oil and the aqueous phase, thereby encapsulating the dispersed aqueous phase.

Abstract: The shape of a sample is determined with a scanning electron microscope ("SEM") by using electron emission from a surface to measure its slope. A surface of a sample is placed in the SEM's electron beam for several known angles, and respective measurements of the electron emission are obtained. A relationship between surface angle and electron emission is derived for the sample from the measurements. Then, as the electron beam is scanned along the surface to measure electron emission, this derived relationship is used to obtain the slope at each scanning point.

Abstract: A tool for initiating a downhole function in a subsurface well, such as a cased well. The tool has memory adapted to store a well-specific reference pattern of one or more downhole well characteristics as a function of position along the well, one or more sensors responsive to the downhole well characteristics, and a clocked processor. The processor is adapted to receive well characteristic signals from the sensors, determine, from the signals and the reference pattern in memory, the position of the tool along the well, and automatically initiate a downhole function at a preprogrammed position along the well while the tool is moved at a substantially constant rate along the well. The tool may be configured in a string of tools for performing multiple downhole functions. In some embodiments the reference pattern is the known spacing of discrete downhole features, such as casing collars. In some other embodiments the reference pattern is a log of a geophysical parameter, such as a natural gamma log.

Abstract: The present invention provides a cementing composition for an oil or analogous well, essentially constituted by a solid fraction suspended in a liquid medium. The solid fraction is constituted by a coarse fraction with a packing volume fraction .PHI..sub.1 which, according to the invention, is maximised, and a fines fraction x with a packing volume fraction .PHI..sub.2 which is less than or equal to the volume fraction x.sub.0 such that ##EQU1## The invention also provides a method of maximising the value of .PHI..sub.1. The invention can minimise fluid loss whatever the materials selected for a cementing composition.

Abstract: A workstation computer system, and its associated method and program storage device, stores a novel software package known as "Variance Cube". The computer system is responsive to a plurality of seismic signals propagating through a cubic volume of an earth formation for generating a cube, representing said cubic volume of earth, where the cube includes a plurality of seismic data samples and where each seismic data sample has a corresponding "variance value" assigned thereto. The computer system also generates one or more maps, such as a time slice map, representing one or more slices through the cube. Each map displays and is used to determine certain geologic features which exist along the corresponding slice through the cube, each map including a plurality of the variance values representing the geologic features, each such variance value being defined as the degree to which an amplitude of each seismic data sample in the cube at a particular reflection time "t" varies about an average amplitude.

Abstract: To take a sample of liquid and/or gaseous hydrocarbon at the surface or down an oil well, use is made of a flexible bag suspended by a tube from a top region of a wall of a closed receptacle. The bag and the tube are made of a flexible material that is leakproof and inert relative to the sample to be taken, such as a cross-linked polymer. The volume of sample admitted into the bag is controlled so as to avoid stretching the wall of the bag.

Abstract: A method and apparatus for determining gas corrected porosity using nuclear magnetic resonance (NMR) and density measurements is disclosed. The total porosity (TCMR) or an earth formation is determined using an NMR tool. A log output is generated that indicates the density of the formation. The density porosity of the formation is determined from the log output. The difference between the TCMR-density porosity log accurately indicates the presence of gas. A gas corrected porosity, .phi., and gas saturation, S.sub.g, are determined based upon the density porosity and TCMR.

Abstract: A safety system for use with an apparatus lowered into a well includes a power supply and a controller that monitors at least a predefined condition of the apparatus. A switch blocks power from the apparatus until the predefined condition is present. A test system includes a test device that generates a signal having a predetermined characteristic (a certain frequency, for example). A controller detects the signal and enables performance of a test operation when the signal of the predetermined frequency is present.

Abstract: A wellbore service fluid comprising polymers having cross-linking groups capable of forming chemical bonds with other polymers without additional monomeric cross-linking agents is described, and related methods, particularly applicable to water control operations.

Abstract: A pressure and temperature transducer includes an elongate housing formed from double rotation cut crystal quartz, an elongate plate-like resonator formed from double rotation cut crystal quartz capable of vibrating under an applied electric field located within the housing, the resonator being formed in unitary construction with the housing. The long edges of the resonator are connected to the interior walls of the housing, and short edges of the resonator are free and extend across the interior of the housing in a substantially continuous curve. Electrodes are located on opposite faces of the resonator for applying an electric field which causes the resonator to vibrate. End caps, formed from double rotation cut crystal quartz, are provided at each end of the housing. A borehole tool includes a tool body which can be positioned in a borehole, a probe for sampling fluid in the borehole; and a pressure and/or temperature transducer, connected to the probe for making measurements on the fluid.

Abstract: A method of locating in situ hydrocarbons in underground formations comprises illuminating the borehole wall with light such as visible, infrared or ultraviolet light or combinations of these, from a source in a tool such as a wireline logging tool or an LWD tool, detecting any fluorescent radiation with a detector in the tool and analyzing the florescent radiation to determine the presence of hydrocarbon in the formation. The tool is moved through the borehole while irradiating the formation and detecting fluorescence. The borehole wall is illuminated and fluorescence detected through a window in the tool which is pressed against the borehole wall with sufficient force to displace any mudcake. The window is made of a wear resistant material such sapphire or diamond and is conveniently secured in a wear resistant housing which might be made of tungsten carbide or the like.

Abstract: Technique and apparatus are disclosed for identifying characteristics of hydrocarbons, such as distinguishing light and heavy formation oil, in formations surrounding an earth borehole. The technique and apparatus can also be used for determining residual oil saturation, permeability, and bound water volume. An embodiment of the method of the invention includes the following steps: providing a nuclear magnetic resonance logging device that is moveable through the borehole; providing, from the logging device, a polarizing magnetic field and cycles of a magnetic pulse sequence, and receiving magnetic resonance spin echoes from the formations; processing the received spin echoes to produce a T.sub.2 distribution; computing a magnetic resonance porosity from the T.sub.2 distribution; deriving a measure of total porosity of the formations; and comparing the magnetic resonance porosity with the total porosity.

Abstract: A high speed, NMR, porosity measuring technique and instrument, is described. The instrument is configured with a long prepolarization region of up to approximately six feet disposed ahead of a short detection region of about six inches. The prepolarization region comprises permanent magnets. The detection region comprises homogeneous magnets and rf antenna. This tool design makes possible the acquisition of NMR porosity measurements at 1800 ft./hr., or more, with wait times between successive detection measurements of approximately one second.

Abstract: A permeability estimator is constructed from the lambda parameter, .LAMBDA., which is the size of dynamically connected pores. For simple pore geometries at high permeabilities, .LAMBDA. should theoretically be proportional to the pore volume-to-surface area ratio. Further, at high permeabilities, the permeability is proportional to .LAMBDA..sup.2 /F where F is the formation factor. Core data are used to establish the proportionality constant. At permeabilities less than about 100 md, the estimated permeability is seen to overestimate the actual permeability by a factor related to the estimate. Thus, a corrected second estimate can be readily made and is shown to match measured permeabilities on a diverse set of sands and shaly sands with a correlation coefficient of 0.89 for log k. The estimate can also be made using NMR relaxation time data with a correlation coefficient of 0.92 for the same data set.

Abstract: The Invention relates to novel fluids and techniques to optimize/enhance the production of hydrocarbon from subterranean formations (e.g., "completion fluids"), in particular, fluids and techniques are disclosed and claimed which remove wellbore damage and near-wellbore damage in the form of coating formed from drilling and production-related operations ("filtercake"); the techniques can be applied either by themselves or in conjunction with other completion operations, such as gravel packing; preferred embodiments are chelating agent and enzyme systems in a viscoelastic surfactant (VES) matrix.

Abstract: A system for use in a subterranean well includes a production tubing and a valve. The production tubing has a port to receive well fluid from a formation. The valve is mounted to the production tubing and includes a sealed housing, a motor, a valve cover, an actuator drive and a sensor. The motor is located inside the housing, and the actuator drive is actuated by the motor to move the valve cover over the port to selectively control the communication of the well fluid between the formation and the passageway of the tubing. The sealed housing may permit the well fluid to accumulate inside the housing over time. The sensor is located inside the housing and provides an indication of the amount of well fluid that has accumulated inside the housing. This information may be useful for such exemplary purposes as predicting when the valve will fail and for evaluating the condition of the valve.

Abstract: A technique is provided for determining a nuclear magnetic resonance characteristic of formations surrounding an earth borehole, including the following steps: providing a logging device that is moveable through the borehole; providing, on the logging device, first and second coils having respective axes that are generally orthogonal; producing, at the logging device, a prepolarizing signal; applying pulse sequence signals to the first and second coils, the pulse sequence signals implementing repeated refocusing of spins in the formations by both adiabatic and non-adiabatic reorienting of the spins to form spin echoes; and detecting, at the logging device, the spin echoes from the formations, the spin echoes being indicative of the nuclear magnetic resonance characteristic of the formations.