Abstract: A method for downhole fluid analysis is disclosed. The method includes positioning a downhole fluid sampling tool at first and second locations; extracting and compositionally analyzing samples of reservoir fluid while positioned at the first and second locations; comparing analysis results; and repositioning the tool to a third location depending on the results of the comparison. The compositional analysis can be performed using downhole gas chromatography and mass spectrometry systems and preferably can identify subtle non-homogeneities such as biomarkers. The fluid extraction can be performed using a focuses dual-flowline type sampling probe.

Abstract: A disclosed subsurface electromagnetic field monitoring system includes at least one fiberoptic cable to optically communicate measurements from an array of electromagnetic field sensors in a borehole.

Abstract: A method for predicting at least one property of a geological formation may include generating mapping function values relating a plurality of reference elemental compositions to corresponding reference properties thereof based upon at least one non-linear mapping function. The method may further include determining a sample elemental composition of at least one sample associated with the geological formation and performing, using a processor, an interpolation to map the sample elemental composition to at least one sample property based upon the mapping function values and the at least one non-linear function.

Abstract: An apparatus and method for performing nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) on samples in metallic holders and vessels or in proximity to metallic objects is disclosed.

Abstract: Pulse sequences are applied to a fluid in an earth formation in a static magnetic field and NMR spin echo signals are obtained. The signals are processed to give a distribution of relaxation time at each of the plurality of depths. A quasi-DNA is obtained by autoscaling and a nonlinear mapping of T2 component logs and non-NMR logs. Similarities between the quasi-DNA of the two types of logs are used to estimate formation lithology and fluids.

Abstract: A downhole sampling tool is operated to obtain formation fluid from a subterranean formation, which then flows through a flowline of the downhole sampling tool. Real-time density and optical density sensors of the downhole sampling tool are co-located proximate the flowline. Contamination of the formation fluid in the flowline is then determined based, at least in part, on the real-time density and optical density measurements obtained utilizing the co-located sensors.

Abstract: Disclosed are systems and methods for monitoring a drilling fluid for the formation of gas hydrates. One system includes a borehole containing a drilling fluid being circulated therethrough, a first optical computing device arranged in the borehole and having at least one integrated computational element configured to optically interact with the drilling fluid and detect one or more gas hydrates present therein, and at least one detector arranged to receive optically interacted light generated from optical interaction between the at least one integrated computational element and the drilling fluid, the at least one detector being configured to generate a first output signal corresponding to a characteristic of the one or more gas hydrates.

Abstract: An improved system for sensing includes a first signal source for producing an excitation signal for exciting a specimen having a nuclear quadrupole resonance, a signal sampling device for sampling a response signal received from the specimen to produce a plurality of samples, a data storage device for storing a plurality of data corresponding to said plurality of samples; and a processor for time coherently processing the plurality of data to sense the nuclear quadrupole resonance of said specimen. An optional second signal source for producing a probe signal directed at the specimen can also be used, where the response signal corresponds to the probe signal having reflected off the specimen.

Abstract: Determining a value indicative of gas saturation of a formation. At least some of the illustrative embodiments are methods including: obtaining an inelastic count rate and a capture count rate of a gamma detector for a particular borehole depth; removing at least a portion of the chlorine response from the capture count rate, thereby creating a modified capture count rate; calculating a ratio of an inelastic count rate to the modified capture count rate for the particular borehole depth; determining a value indicative of gas saturation based on the ratio; and producing a plot of the value indicative of gas saturation as a function of borehole depth for a formation that the borehole at least partially penetrates.

Abstract: Systems and methods which provide modeling or simulation of gamma ray (GR) tool response using a hybrid analytical and numerical technique are shown. Embodiments employ a GR tool simulation technique which provides gamma ray information simulated as a function of only the gamma particles which reach the detector without scattering. Embodiments utilize a discretization function to determine the gamma particles which would reach a point detector from each unit volume source of an investigation domain without scattering. Embodiments further utilize the foregoing discretization function with respect to a plurality of point detectors, wherein the particular number and configuration of point detectors are selected to relatively accurately simulate the results of a particular GR detector configuration, such as line detector or volume detector configurations.

Abstract: A technique that is usable with a well includes providing a model so predict measurements that are received by receivers due to transmissions by sources based on estimated positions of the receivers relative to the sources. The estimated positions each have at least two dimensions. At least some of the receivers and the sources are located in the well. On a computer, the estimated positions are automatically refined based on a comparison of the predicted measurements and actual measurements that are obtained by the receivers.

Abstract: A method for indicating the presence of free gas charged sands, and/or hydrates over free gas, and/or hydrates not over free gas, the method using well log data and a rock physics model. Velocity and density of background clays and sands are extracted from the well log data. The extracted velocities and densities are used to build a rock physics model. An AVO response is generated that is representative of free gas-charged sands. An AVO response is generated that is representative of hydrates over free gas-charged sands. An AVO response is generated that is representative of hydrates devoid of free gas. The generated AVO responses are used to construct an AVO crossplot diagram that is further used to distinguish deposits of free gas charged sands from hydrates over free gas, from hydrates not over free gas.

Abstract: A method of interpreting petrophysical measurement data include arranging measurements of at least one physical property of formations into a matrix representing the measurements and selecting a range of number of unobserved factors or latent variables for factor analysis. Factor analysis is performed on the measurement matrix and comprises performing factorization of measurements matrix into a number of factors and performing rotation of the factorization results. Whether the factor loadings for each factor have achieved a “simple structure” is determined and either each of the selected number of factors is associated with a physical parameter of the formations, or one is added to the number of factors and factor analysis and rotation are repeated until factor loadings of all factors have achieved “simple structure” such that the each of the number of factors is associated with a physical property of the formations.

Abstract: A microphonics noise cancellation system and method for improving the energy resolution for mechanically cooled high-purity Germanium (HPGe) detector systems. A classical adaptive noise canceling digital processing system using an adaptive predictor is used in an MCA to attenuate the microphonics noise source making the system more deployable.

Abstract: The present disclosure relates to borehole logging methods and apparatuses for estimating formation properties using nuclear radiation, particularly an apparatus and method for estimating bulk density of a formation. The method may include using gamma ray count rate information to model bulk density. The method may include using time-dependent ratios with a pulsed radiation source. The method may also include dividing gamma ray information by time and/or by energy window. The apparatus includes a processor and storage subsystem with a program that, when executed, implements the method.

Abstract: A method for gain control of a radiation detector includes measuring standard gamma ray spectra for known concentrations of selected radioactive materials found in earth formations. A standards matrix is calculated from the standard gamma ray spectra. A singular value decomposition is computed from a matrix related to measurements of gamma ray spectra, of formations and the standards matrix. A radiation, detector gain is computed from a minimum ratio of null space with respect to data value space of a subsurface formation measurement related matrix and the standards matrix. Gain of the radiation detector is adjusted based on the computed radiation detector gain.

Abstract: The Larmor frequency for an in situ nuclear magnetic resonance (NMR) tool is determined and used to acquire NMR data. An NMR tool is provided and placed in situ, for example, in a wellbore. An initial estimate of the Larmor frequency for the in situ NMR tool is made and NMR data are acquired using the in situ NMR tool. A spectral analysis is performed on the NMR data, or optionally, the NMR data are digitized and a discrete Fourier transform (DFT) is performed on the digitized NMR data. The modal frequency of the spectral analysis or DFT is determined, and the Larmor frequency for the in situ NMR tool is determined using the modal frequency. The NMR tool is modified to transmit at the determined Larmor frequency and then used to acquire further NMR data.

Abstract: A method for simulating a response of a neutron well logging instrument includes in a computer, defining a function of neutron migration length with respect to expected radiation detector counting rate. The function is defined for selected values of formation porosity. The function is related to neutron slowing down length and neutron diffusion length. The function is weighted for formation density. An expected radiation detector counting rate is calculated in the computer using the defined function based on an initial estimation of formation porosity and density.

Abstract: Systems and methods for analyzing an unknown geological sample are disclosed. The system may include at least two analytical subsystems, and each of the at least two analytical subsystems provides different information about the geological sample. The data sets from various analytic subsystems are combined for further analysis, and the system includes a chemometric calibration model that relates geological attributes from analytical data previously obtained from at least two analytical techniques. A prediction engine applies the chemometric calibration model to the combined analytical information from the geological sample to predict specific geological attributes in the unknown geological sample.

Abstract: A method for predicting a pressure window for drilling a borehole in a formation includes: obtaining a pore pressure related data value of the formation using a data acquisition tool; predicting pore pressure uncertainty from the pore pressure related data value of the formation using a processor; estimating uncertainty of a pressure window for drilling fluid using the predicted pore pressure uncertainty using a processor; and applying the estimated uncertainty to the pressure window to provide a modified pressure window using a processor.

Abstract: Methods and related systems are described for estimating fluid or rock properties from NMR measurements. A modified pulse sequence is provided that can directly provide moments of relaxation-time or diffusion distributions. This pulse sequence can be adapted to the desired moment of relaxation-time or diffusion coefficient. The data from this pulse sequence provides direct estimates of fluid properties such as average chain length and viscosity of a hydrocarbon. In comparison to the uniformly-spaced pulse sequence, these pulse sequences are faster and have a lower error bar in computing the fluid properties.

Abstract: Processing gamma count rate decay curves using neural networks. At least some of the illustrative embodiments are methods comprising obtaining a gamma count rate decay curve one each for a plurality of gamma detectors of a nuclear logging tool (the gamma count rate decay curves recorded at a particular borehole depth), applying the gamma count rate decay curves to input nodes of a neural network, predicting by the neural network a geophysical parameter of the formation surrounding the borehole, repeating the obtaining, applying and predicting for a plurality of borehole depths, and producing a plot of the geophysical parameter of the formation as a function of borehole depth.

Abstract: Methods and apparatus suitable for quickly and accurately measuring 13C levels and supporting data in an aqueous fluid reservoir. Interpreting the resulting data to indicate key factors regarding a reservoir and completion methods, including reservoir constraint, gas producibility, and completion success. A sensor and to a sensing method that evaluates the level of hydrologic constraint in aquifers occurring in unconventional reservoirs, such as shales and coals is disclosed. Specifically, Raman spectroscopy is disclosed as a sensor and a sensing method that measures the level of naturally-occurring 13C in an aqueous reservoir and compares the level of 13C to the levels typical for highly constrained and highly unconstrained reservoirs. The disclosed sensor and sensing method also monitors the level of naturally-occurring 13C in a reservoir. Also disclosed is a method of using ?13CDic to evaluate geographic areas of coal bed reservoir water having biologic methanogenic activity.

Abstract: A downhole tool and method for determining a parameter of a formation as a function of radial distance from the borehole into the formation. The tool comprising a nuclear source for irradiating the formation and a plurality of sensors each independently measuring a density of the formation at a different radial depth into the formation. A processor combines the density measurements for determining the parameter of the formation as a function of radial distance.

Abstract: A method of calibrating a measurement device includes: compiling historical calibration data for the measurement device, the historical calibration data including values corresponding to outputs of the measurement device over a first operating duration in environmental conditions associated with an operating environment; projecting the historical calibration data over a subsequent operating duration to generate predictive calibration data; disposing the measurement device in the operating environment and generating measurement signals during the first operating duration and the subsequent operating duration; and generating measurement values from measurement signals generated during the subsequent operating duration based on the predictive calibration data.

Abstract: A computer system and computer implemented method for automatically identifying a hydrocarbon (such as kerogen, gas, oil) rich zone in a well bore includes obtaining well log data comprising neutron data, density data, radioactivity data, and resistivity data representative of physical characteristics of a formation surrounding the well bore and computing an apparent neutron porosity and an apparent density porosity based on the neutron data and density data. A normalized neutron-density separation is computed based on the computed apparent neutron porosity and the computed apparent density porosity and a baseline of the formation is determined for each data type. Using the computed normalized neutron-density separation, the radioactivity data, the resistivity data, and the determined baselines, the presence or absence of a hydrocarbon rich zone is determined. A quality index may further be derived from the data.

Abstract: Disclosed is a model-independent method for accurate prediction of formation and borehole properties from neutron capture cross section measurements. A mapping function is constructed which maps the input measurements to the properties of interest. The mapping function is a linear combination of Gauss radial basis functions. The expansion coefficients and widths of the Gaussian functions are determined uniquely using a database populated with representative samples. For a sample not included in the original database, the desired properties can be estimated from the mapping function using the measurements made on the unknown sample.

Abstract: Method for evaluating cement integrity in a cased well environment using a logging tool that has a neutron source and one or more neutron or gamma ray detectors. Neutron porosity logs are obtained from the well before (42) and after (41) casing. This log data along with well dimensions and material composition parameters are the input quantities to a multi-parameter database (43) that is constructed by computer modeling or laboratory experiments to relate volume fraction for fluid filled channels in the cement sheath to the input quantities. The channel volume fraction (45) corresponding to the input quantities is identified or interpolated (44) from the multi-parameter database.

Abstract: The computer readable medium causes a gas processor with gas processor data storage to implement computer instructions to receive device data in various device protocols simultaneously information from rig based sensors and gas analysis devices, calibrate the devices and graphically present the data using both time events and depth events. The computer readable medium can scale the data and form the geological-hydrocarbon executive dashboard for transmission to various client devices to present real time streaming data, real time calibration information, real time alarms while enabling users to add and remove detection devices and sensors, including rig servers and remote servers, online without shutting down the operation of the computer readable medium.

Abstract: A method for determining volumetric data for fluid within a geological formation is provided. The method includes collecting first and second dataset snapshots of the geological formation based upon measurements from the borehole at respective different first and second times and generating a differential dataset based upon the first and second dataset snapshots. Multiple points are determined within the differential dataset, including a first point representing a first displaced fluid, a second point representing a second displaced fluid, and an injected fluid point that corresponds to properties of the injected fluid. A further third point is determined based on at least one other property of the displaced fluid, and a volumetric composition of the displaced fluids is determined based upon the differential dataset, the first point, and second point, and third point.

Abstract: The invention is related to the development of volatile oil deposits and may be used to determine current gas saturation in a near-wellbore zone in a volatile oil formation. The method for the current gas saturation determination in the near-wellbore zone requires the measurement of the formation rock parameters and formation fluid parameters before the gas accumulation start in the near-wellbore zone and creation of the numerical model of the neutron logging signal change during the production period for the measured formation and formation fluid parameters and expected gas saturation value. During the production period when the well productivity decreases, neutron logging is performed and then the measured signals are matched with the model calculations and based on the provision of the best match of the measured and simulated neutron logging signals gas saturation is determined.

Abstract: The invention is related to the development of gas condensate deposits and may be used to determine current condensate saturation in the near-wellbore zone in the formation. The method for the current condensate saturation determination in the near-wellbore zone requires the measurement of the formation rock parameters and formation fluid parameters before the start of gas-condensate production and creation of the numerical model of the neutron logging signal change during the production period for the measured formation rock parameters and formation fluid parameters and expected condensate saturation value. During the production period when the well productivity decreases, neutron logging is performed and then the measured signals are matched with the model calculations and based on the provision of the best match of the measured and simulated neutron logging signals condensate saturation is determined.

Abstract: An apparatus for estimating a property includes a hollow core tube and an input light guide disposed at least partially within hollow core tube. The apparatus also includes a second gap disposed within the hollow core tube and separated from the input light guide by an air gap width. The second gap is formed of a first solid material and has a second gap width. The apparatus also includes a third gap disposed at least partially within the hollow core tube and being further from the input light guide than the second gap. The third gap is formed of a second solid material and has a third gap width.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: Methods and related systems are described for estimating fluid or rock properties from NMR measurements. A modified pulse sequence is provided that can directly provide moments of relaxation-time or diffusion distributions. This pulse sequence can be adapted to the desired moment of relaxation-time or diffusion coefficient. The data from this pulse sequence provides direct estimates of fluid properties such as average chain length and viscosity of a hydrocarbon. In comparison to the uniformly-spaced pulse sequence, these pulse sequences are faster and have a lower error bar in computing the fluid properties.

Abstract: Formation density measurements in the presence of invasion of drilling fluids. At least some of the illustrative embodiments are methods including: irradiating a formation with gammas from a source of gammas, wherein drilling fluid has invaded the formation, and wherein Pe of the drilling fluid that has invaded the formation is greater than Pe of the formation; determining a first value indicative of a parameter of the formation; determining a second value indicative of a parameter of the formation; determining a third value, the third value determined based on gammas in an energy range different than used in determining the first value; and calculating, using the first, second, and third values, information such as a standoff, a formation porosity, a formation density prior to invasion by the drilling fluid, and radial depth of invasion of the drilling fluid into the formation.

Abstract: A method of constructing a well log of a quantitative property representative of a porous formation, from sample measurements and log data, is disclosed. A quantitative property (mineralogical proportions) of samples selected from among a set of samples is measured and each sample is grouped into homogeneous classes regarding the log data. The average value of the quantitative property is then determined in each class. A well log representing the probability of assigning a sample to each class as a function of depth is constructed. Finally, the well log representing the quantitative property as a function of depth is constructed from the log representing the assignment probability and from the average values.

Abstract: A methodology improves sampling and characterization of heterogeneous, unconventional hydrocarbon-bearing regions. The methodology is designed to integrate consistently across measurements and scales. Additionally, the methodology involves characterizing various scales, such as regional-scale heterogeneity, wellbore-scale heterogeneity, core-scale heterogeneity, sample-scale, and pore-scale heterogeneity. The results are integrated across the multiple scales based on results obtained from the characterization of the scales. The methodology further comprises determining data propagation across the multiple scales in a hydrocarbon-bearing region.

Abstract: To analyze content of a subterranean structure, electric field measurements at plural source-receiver azimuths in a predefined range are received. Total magnetic field measurements are also received at plural source-receiver azimuths in the predefined range. The electric field measurements and the total magnetic field measurements are provided to an analysis module to enable determination of electrical resistivity anisotropy of the subterranean structure.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A method and a device for filtering diagnostic messages obtained from a plurality of elements of a system, each of these elements comprising diagnostic means capable of detecting a failure and of transmitting a message comprising at least one failure indication. The state of at least certain elements of the said plurality of elements is represented by a model of state. After at least one failure message has been received, this message is filtered according to the failure indication that it contains and according to the model of state. In response to the filtering step, the model of state is updated according to the failure indication or the message is rejected. The filtering step is advantageously based on a propositional logic mechanism.

Abstract: A downhole imaging system performs imaging in a borehole penetrating a formation. The system includes a source configured to emit gamma radiation toward an area of the borehole. The system also includes a first plurality of detectors configured to detect backscattered radiation originating from the source. Based on a distance between the source and each of the first plurality of detectors, detection by the first plurality of detectors provides a density image of the area of the borehole.

Abstract: Percolation theory is applied to establish a connection between magnetization decay of nuclear magnetic resonance (NMR) measurements and residual carbon dioxide saturation (Scr). As a result, estimations of Scr are obtained through use of an NMR tool in a formation and appropriate processing. Data may be displayed as a log.

Abstract: A method for determining compositional data for fluids within a geological formation having a borehole therein may include collecting first and second dataset snapshots of the geological formation based upon measurements from the borehole at respective different first and second times, and with the borehole subject to fluid injection between the first and second times to displace fluids in the geological formation adjacent the borehole. The method may further include generating a differential dataset based upon the first and second dataset snapshots, normalizing the differential dataset to generate a normalized differential dataset, determining vertices defining a geometric shape and corresponding to respective different displaced fluid signatures based upon the normalized differential dataset, and determining displaced compositional data with respect to the different displaced fluid signatures based upon a position of a datapoint from the normalized differential dataset on the geometric shape.

Abstract: A method for determining mobile water saturation in a reservoir having a borehole extending through the reservoir is disclosed. The method involves obtaining a first borehole data log while the reservoir is subjected to first fluid conditions, and causing a mobile water displacement in the reservoir by changing the fluid conditions in the borehole to cause the reservoir to be subjected to second fluid conditions, the second fluid conditions differing from the first fluid conditions. The method further involves obtaining a second borehole data log under the second fluid conditions, and estimating the mobile water displacement using the first and second data logs, the estimated mobile water displacement providing an estimate of the mobile water saturation in the reservoir.

Abstract: A method for estimating a property of an earth formation includes: conveying a carrier through a borehole penetrating the earth formation; performing nuclear magnetic resonance (NMR) measurements on a sensitive volume in the formation using an NMR tool disposed at the carrier to provide a distribution of relaxation times; identifying peaks in the distribution of relaxation times; selecting at least one peak based on a characteristic of the at least one peak; and estimating the property using a relaxation time associated with the at least one peak.

Abstract: Apparatus for wellbore logging and method of use are provided for measurement of the annular materials interposed between the logging tool and formation and the apparent formation bulk density in open-hole, cased-hole or other conduit. The logging tool can be centralized in the borehole. Non-collimated gamma radiation is emitted into the surrounding media and the amount of radiation which returns to the tool is measured by multiple omni-directional detectors spaced a pre-set distances from the source to provide multiple radial depths of investigation. The annular thickness and density of materials interposed between the logging tool and the formation may be determined from the detector responses and be used to derive the apparent formation bulk density.

Abstract: Inverting nuclear log data for a geological formation surrounding a borehole involves acquiring nuclear log data for a borehole portion using a moveable nuclear logging tool and acquiring additional log data for the borehole portion using another logging device with superior resolution. Boundaries between adjacent zones are identified that exhibit an attribute of the geological formation to a detectably contrasting degree. From pre-acquired data describing one or more characteristics of the nuclear logging tool, a modelled log of the attributes is generated over the borehole portion, and a zone response is calculated from the pre-acquired data for each zone by using the boundaries to define an initial measure of the depth of each zone and ascribing a value of the attribute in dependence on the depth of each zone.

Abstract: Systems, methods, and devices for quantatively identifying gas zones irrespective of porosity or lithology using nuclear downhole tools are provided. In particular, because some formation materials such as shales can confound some conventional measurements, a gas detection measurement may be obtained that can be used to qualitatively identify gas zones. The as detection measurement may be based at least partly on a relationship between inelastic gamma rays, neutron capture gamma rays, and experimental or modeled formation data, such that the gas detection measurement qualitatively indicates a gas zone when a gas zone is present in a formation irrespective of a lithology or a porosity of the formation.