Abstract: Logging-while-drilling apparatus and methodologies for measuring streaming potential in an earth formation are provided. The apparatus and methodologies can be utilized to find information relevant to the drilling operations. In particular, since the streaming potential measurement relates directly to fluid flow, the streaming potential measurements can be used to track flow of fluids in the formation. In turn, this information may be used to find information relevant to the drilling operations, such as under-balanced drilling conditions, abnormal formation pressures, open fractures, the permeability of the formation, and formation pressure.

Abstract: A single probe system is utilized to quickly obtain uncontaminated formation fluid samples. The single probe includes an outer guard tube and an inner sampling tube which is slightly recessed relative to the outer tube such that the pressure at the front face of the probe is substantially uniform. Each tube is coupled to its own pump which controls the flow rate of the fluid moving through that tube. Knowing the size of the sampling tube relative to the size of the outer probe tube, and optionally based on relative viscosities of formation fluids and filtrates, the pumps are caused to generate a particular flow rate ratio through the tubes such that an appropriate pressure is maintained at the front face of the probe and such that the fluid flowing through the sampling tube is substantially uncontaminated.

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: Permeability determinations are made from NMR measurements of a logging tool. The NMR measurements are used to find an observed critical spin—spin relaxation time which is used in conjunction with an in situ determination of surface relaxivity of a rock in order to generate permeability determinations.

Abstract: Methods, apparatus, and systems for obtaining information regarding a formation, a casing, or fluid within the casing are provided which utilize an interrogator and one or more sensing devices attached to a casing in a wellbore. The interrogator is located within and may be movable inside the wellbore. The sensing device is positioned and fixed in an opening in the casing. The sensing device includes a housing and a sensor with associated electronic circuitry. The interrogator and sensing device include a magnetic coupling therebetween that is operable when the interrogator and sensing device are positioned in close proximity to one another. Preferably, the magnetic coupling is realized by at least one solenoid winding for the interrogator and at least one solenoid winding for the sensing device, which provide a loosely-coupled transformer interface therebetween. The interrogator and sensing device communicate in a wireless manner over the magnetic coupling therebetween.

Abstract: Methods and apparatus for rapidly measuring pressure in earth formations are disclosed. According to a first embodiment of the apparatus, a probe is provided with a movable piston having a sensor built into the piston. According to a second embodiment of the apparatus, the pressure sensor is mounted adjacent to or within the piston cylinder and a fluid pathway is provided from the sensor to the interior of the cylinder. Methods of operating the first and second embodiments include delivering the probe to a desired location in a borehole, setting the probe against the formation, and withdrawing the piston to draw down fluid for pressure sensing. A third embodiment of the probe is similar to the second but is provided with a spring loaded metal protector surrounding the cylinder and an annular rubber facing. The third embodiment is preferably used in a semi-continuous pressure measuring tool or an LWD tool having a piston controlled bowspring and a piston controlled articulated member carrying the probe.

Abstract: Several optical probes useful in downhole applications are provided. A first probe has a tip in the form of a cubical corner with the diagonal of the cubical corner aligned with the axis of the probe. A second probe has a tip formed in a 45° cone. In these designs, light will bounce respectively three times or twice, but still retain the same orientation. To facilitate drainage, the very tip of the probe may be rounded. Both designs also provide a probe with a large numerical aperture and both are useful for detecting reflectance and the holdup of a multiphase fluid. A third probe uses (hemi)spherical or paraboloid probe tip. The third probe tip has a small numerical aperture and is useful for detecting fluorescence and oil velocity. In all three embodiments, the base behind the probe tip may be tapered to facilitate fluid drainage.

Abstract: A method for characterizing formation fluid using flowline viscosity and density data in an oil-based mud environment includes: making an initial estimate of the density and viscosity of the individual components of the sampled fluid; measuring the volume fractions, density, and viscosity of the total mixture of formation fluid; computing the density and viscosity of the total mixture using the estimate and the measured volume fractions; comparing the computed values with the measured values; and updating the estimate based on the comparison until convergence. The process is repeated as additional data are acquired until the converged computed values differ only by an acceptable amount.

Abstract: Methods and related apparatus for generating dispersion curves and conducting shear slowness logging are set forth. The methods include backpropagating detected dispersive waveforms in the Fourier domain while accounting for dispersion in an anisotropic and inhomogeneous formation, and stacking the processed waveforms. The stacking may occur in the frequency or time domains. The semblance of the stacked and windowed waveforms is compared against the detected waveforms. In accounting for dispersion during backpropagation, a plurality of parameters which describe dispersion curves are varied over ranges in order to optimize semblance. At each depth of interest, it is then possible to obtain a dispersion curve of greatest semblance. Where both an x-dipole and y-dipole are used to generate the waves, a dispersion curve of greatest semblance for each may be generated. In addition, from the dispersion curves, formation shear slowness(es) may be plotted as a function of formation depth and orientation.

Abstract: A method of managing oil fields include installing oil field sensors, coupling them to a local CPU having memory, programming the CPU for data collection and data analysis, and coupling local oil field CPUs to a web server. Human experts are granted access to oil field data in real time via the Internet. The local CPUs provide different levels of data to the web server. The web server provides the option to view raw data, partially analyzed data, or fully analyzed data. The local CPUs are programmed with parameters for analyzing the data and automatically determining the presence of anomalies. Upon detecting the occurrence of an anomaly, the local CPUs are programmed to notify one or more human experts by email, pager, telephone, etc. If no human expert responds to the notification within a programmed period of time, the local CPU automatically takes a programmed corrective action.

Abstract: Tools for investigating an earth formation in the presence of either oil-base or water-base mud include a circuit which induces current into the formation in a focused manner, and a sensor electrode which is isolated from the circuit, at least partially surrounded by the circuit, and located in the area in which the current is focused. The current inducing circuit may be an oppositely polarized double-dipole circuit to which voltage is applied with the two dipoles sharing a common radiating element over which a focused area is formed. Insulators separate the outer electrodes of the double-dipole circuit from the common radiating element. Alternatively, the current inducing circuit is a coil arranged in a partial toroidal configuration in an insulated area that at least partially surrounds the focused area and which separates the focused area from return electrodes.

Abstract: A multiple mode pre-loadable fiber optic pressure and temperature sensor includes a generally cylindrical structure having at least one compression element, a fiber optic having a Bragg grating in contact with one side of the compression element, a diaphragm in contact with the other side of the compression element, and a fluid port in fluid communication with the diaphragm. According to preferred aspects of the, a groove is provided in at least one compression element for receiving the fiber optic. The sensor is pre-loaded by straining the diaphragm over the adjacent compression element when the cover is attached. The compression element in contact with the diaphragm preferably has a contoured surface contacting the diaphragm and the diaphragm is stretched to match that contour. By varying the contour of the compression element and the thickness of the diaphragm, the dynamic range of the sensor can be changed. The preferred diaphragm has a variable thickness and is made as an integral part of the structure.

Abstract: Apparatus and methods for measuring oil flow velocity in a well are provided which utilize fluorescence quenching. A marker which quenches the natural fluorescence of crude oil is chosen and injected into the oil flow at a first location. At a second location, the oil flow is subjected to light at a wavelength which will cause oil to naturally fluoresce. The fluorescence signal is detected at the second location by a sensing probe. The time that it takes for the quenching marker to move from the first location to the second location is measured by sensing a decrease in fluorescence due to the quencher. Fluid velocity is determined by dividing the distance between the marker-ejection point and the optical probe position by the time it took the marker to move that distance.

Abstract: An oilfield data analysis system is based on a four-tier software model which includes a “shared earth model” and a federation of “directory services”. The first tier is a universal graphical user interface (GUI) which can operate on any inexpensive computer as well as on an expensive workstation, i.e. a “web browser”. The second tier is an application server which is coupled to users via the worldwide web and serves geoscientific software applications. The third tier is a geometric modelling system where geometric data is stored and processed. The third tier embodies the “shared earth model”. The fourth tier is a database management system where non-geometric data is stored. According to the invention, there can be (and preferably are) multiple instances of each tier. Communication of data between different tiers is accomplished via XML data exchange.

Abstract: A method of predicting values of formation parameters (e.g., compressional velocity, density, pore pressure, and fracture pressure) as a function of depth includes generating an initial prediction of a profile of the formation parameters and uncertainties associated therewith using information available regarding the formation, obtaining information related to the formation parameters during drilling, and updating the uncertainties as a function of the first prediction and the information obtained in a recursive fashion. Known equations are used for finding initial values, and uncertainties associated therewith are quantified by using probability density functions (PDFs). A Bayesian approach is utilized where “prior PDFs” describe uncertainty prior to obtaining additional information, and “posterior PDFs” account for the additional information acquired. As additional information is acquired while drilling, the posterior PDFs are redefined.

Abstract: Methods for optimization of oil well production with deference to reservoir and financial uncertainty include the application of portfolio management theory to associate levels of risk with Net Present Values (NPV) of the amount of oil expected to be extracted from the reservoir. Using the methods of the invention, production parameters such as pumping rates can be chosen to maximize NPV without exceeding a given level of risk, or, for a given level of risk, the minimum guaranteed NPV can be predicted to a 90% probability. An iterative process of generating efficient frontiers for objective functions such as NPV is provided.

Abstract: A downhole optical apparatus includes an LED source, reflectance and fluorescence detectors, a plurality of fibers, a dichroic mirror (DM), a beam splitter/coupler, a probe, a short-pass filter (SP), a dichroic long-pass filter (LP), and a lens. Source light filtered by the SP is fed to the DM which deflects light of desired wavelengths only. The deflected light is focused by the lens onto a fiber and is ultimately injected into an oil flow by the probe. Light reflected by oil or fluorescing therefrom is received by the probe, and split by the splitter. A small portion is received by the reflectance detector. A large portion is received by the lens and directed to the DM which deflects reflected light and passes light at longer fluorescing wavelengths. Passed light is further filtered by the DM and LP to eliminate remnants of the reflected light, and provided to the fluorescence detector.

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: Methods for downhole waveform tracking and sonic labeling employ “tracking algorithms” and Bayesian analysis to classify STC waveforms. More particularly, according to the tracking part of the invention, a probability model is built to distinguish true “arrivals” (e.g. compressional, shear, etc.) from “false alarms” (e.g. noise) before the arrivals are classified. The probability model maps the “continuity” of tracks (slowness/time over depth) and is used to determine whether sequences of measurements are sufficiently “continuous” to be classified as tracks. The probability model is used to evaluate the likelihood of the data in various possible classifications (hypotheses). Prior and posterior probabilities are constructed for each track using the tracking algorithm. The posterior probabilities are computed sequentially and recursively, updating the probabilities after each measurement frame at depth k is acquired.

Abstract: An apparatus for arresting scalp bleeding includes skull cap having a plurality of inflatable bladders and a pump for inflating the bladders. The methods of the invention include attaching the skull cap to the bleeding victim and inflating the bladders with air using the pump. The inflated bladders exert pressure on the bleeding scalp and result in a hemostasis. According to the presently preferred embodiments, the skull cap has three or four independently inflatable bladders and the pump is a hand pump of the type used to inflate a blood pressure cuff. The pump is preferably provided with a pressure gauge and the bladders are each inflated to about 80 mm Hg.