Abstract: Data acquired using a pulsed nuclear source are susceptible to two sources of error. One error is due to large statistical noise towards the end of an acquisition window. Another source of error is the contamination of the early portion of the data by borehole and other effects. The beginning of the processing window is adjusted based on the signal level at the end of the processing window for the preceding pulsing of the source. The end of the processing window is derived from statistical considerations.

Abstract: Apparatus and methods for measuring radiation in a borehole environment using a YAlO3:Ce (YAP) scintillation crystal. Borehole instruments are disclosed which employ a gamma ray detector comprising a YAP scintillator coupled to a light sensing means such as a photomultiplier tube. One instrument embodiment combines a YAP scintillation detector and a source of pulsed neutrons. Borehole environs are irradiated with neutrons, and induced gamma radiation is measured using a YAP scintillation detector. Response of the detector is used to determine characteristics of the borehole environs. Mechanical and physical properties of YAP are utilized to obtain improved measurements. The relatively short light decay constant of YAP minimized pulse pile-up in the detector when measurements require that the detector be operated during a neutron pulse.

Abstract: In the field of wellbore data logging it is known to use isotopic neutron sources in a neutron capture logging technique. However, continuous isotopic sources are unpopular for regulatory and safety reasons. Attempts to employ neutron generator tubes to generate neutron bursts for use in the neutron capture technique have encountered various difficulties in areas connected with signal identification and processing. The disclosure relates to a method of data logging in which a low burst rate neutron generator tube is pulsed at comparatively low rates to generate neutron bursts that are captured in atomic nuclei in a proximal formation. The gamma radiation arising from the neutron capture is detected over a gating intervals defined by temporally distinct points. The gamma detector output is integrated over the gating interval to provide a measure of the decay rate that is independent of the pulse rate. Consequently the signal processing problems do not arise.

Abstract: For the purpose of reducing artifacts caused by a scan plane tilted with respect to a rotation plane when a multi-row detector is employed, a j-th detector row which an X-ray passing through a pixel point g(x, y) enters is selected based on the distance ?z from a scan center plane to an image reconstruction plane in a z-axis direction and the position (x, y) of the pixel point g in the image reconstruction plane, and data of the j-th detector row is used to determine the pixel value of the pixel point g, where the scan center plane at a certain view angle is defined as an x-y plane, and a direction normal to the x-y plane, i.e., a detector row direction, is defined as the z-axis direction.

Abstract: Methods of analyzing formation fluids in an oilfield environment are near-infrared absorption spectroscopy. Indications of near-infrared absorptions are analyzed to determine the concentration of compounds in a formation fluid sample.

Abstract: A method of reconstructing tomography images comprising: acquiring data on individual radiation events; distributing a weight of the individual radiation events along a line of flight associated with the event determined from the acquired data; and iteratively reconstructing the image based on the individually reprojected data.

Abstract: The invention comprises an apparatus and method for simple fluorescence spectrometry in a downhole environment using a UV light source and UV fluorescence to determine a parameter of interest for a sample downhole. The UV light source illuminates the fluid, which in turn fluoresces light. The fluoresced light is transmitted back towards the UV light source and through the pathway towards an optical spectrum analyzer. API gravity is determined by correlation the wavelength of peak fluorescence and brightness of fluorescent emission of the sample. Asphaltene precipitation pressure is determined by monitoring the blue green content ratio for a sample under going depressurization.

Abstract: An oil sample is subjected to nuclear electromagnetic irradiation downhole, and the electron and/or mass density of the oil sample is determined by measuring the attenuation of the irradiation and relating the attenuation to the electron density. If the irradiation is high energy gamma ray irradiation, the attenuation is considered to be a function of Compton scattering only, which in turn is related to the electron density of the sample. If X-rays are utilized, attenuation is preferably measured in two energy windows. Using the two different attenuation values found in the different windows, the attenuation due to Compton scattering can be found and related to the electron and/or mass density of the sample. In addition, attenuation due to photoelectric absorption may also be determined and related to the presence of one or more heavy elements in the oil (e.g., sulfur) and/or sanding.

Abstract: The invention provides a method for determining phase transition pressure of downhole retrograde condensate. An OBM-contamination value is produced from a time-series of fluorescence values produced by measuring fluorescence emitted from a single-phase flow of OBM-contaminated formation fluid in a downhole cell during a cycle of time. The pressure of fluid in the cell is set at a transition boundary by incrementing drawdown pressure and monitoring the presence or absence of a phase transition. An apparent phase transition pressure value associated with the cycle of time is produced by setting apparent phase transition pressure value equal to cell pressure. This process is repeated for several cycles of time to produce a number of pairs of OBM-contamination value and apparent phase transition pressure value as OBM-contamination decreases over time.

Abstract: An apparatus and method are provided for varying an operating parameter for a nuclear gamma ray tool for evaluating the integrity of gravel packing. The gamma ray outpat intensity and area of investigation are altered by changing a source housing geometry and the material from which the source housing is made. An actuator is provided to slide a variable electron density sleeve over the source and to vary the area of investigation by changing the distance between the source and a detector.

Abstract: The invention relates to refractometry and attenuated reflectance spectrometry in a wellbore environment. Specifically, it pertains to a robust apparatus and method for measuring refractive index of fluids along a continuum (rather than in steps), and for measuring attenuated reflectance spectra, and for interpreting the measurements made with this apparatus to determine a variety of formation fluid parameters. The present invention provides a method and apparatus to distinguish between gas and liquid based on the much lower index of refraction of gas. It can also be used to monitor fluid sample clean up over time. The refractive index of a wellbore fluid is determined from the fraction, R, of light reflected off the interface between a transparent window that has a known refractive index and this fluid. Preferably, the refractive index is measured at some wavelength of light for which the fluid is not highly attenuating but is optimally attenuating.

Abstract: A method and apparatus detects dew precipitation and determines dew precipitation onset pressure in a sample of formation fluid located downhole in an oilfield reservoir. In a preferred embodiment, the method includes (a) isolating a sample of formation fluid downhole; (b) illuminating the sample downhole with fluorescence excitation light; (c) measuring at least one characteristic of fluorescence short from the sample; (d) reducing pressure on the sample; (e) repeating steps (b) to (d); (f) detecting dew precipitation when a change is detected in a parameter that is a function of the at least one characteristic of fluorescence emission; and (g) setting dew precipitation onset pressure equal to pressure on the sample when the change in the parameter is detected. The parameter preferably is a function of fluorescence intensity and fluorescence red shift, and the change is an increase in fluorescence intensity and detection of fluorescence red shift.

Abstract: A method of monitoring gas in a downhole environment is discussed which provides downhole a mid-infrared light emitting diode, operates the diode to transmit respective infrared signals on a first optical path extending from the diode through a downhole gas sample and a second optical path extending from the diode through a reference gas sample, detects the transmitted infrared signals, and determines the concentration of a component of the downhole gas sample from the detected signals.

Abstract: Method and apparatus for providing real-time data indicative of the isotopic composition of formation fluids during drilling. The method includes the steps of: (a) providing a reference fluid having a known isotopic composition in a reference cell; (b) capturing a sample of formation; (c) providing at least one laser beam; (e) passing a beam through the reference fluid, measuring the reference-measurement beam before and after it passes through the reference fluid; (f) and passing a beam through the sample, measuring the beam before and after it passes through the sample, and calculating a first isotope concentration from those measurements. The measurements can provide information relating to the carbon isotopic composition of individual compounds in hydrocarbon gas mixtures, with the individual compounds including methane, ethane, propane, iso- or normal butane, or iso- or normal pentane.

Abstract: A borehole logging system for determining bulk density, porosity and formation gas/liquid fluid saturation of formation penetrated by a borehole. Measures of fast neutron radiation and inelastic scatter gamma radiation, induced by a pulsed neutron source, are combined with an iterative numerical solution of a two-group diffusion model to obtain the formation parameters of interest. Double-valued ambiguities in prior art measurements are removed by using the iterative solution of the inverted two-group diffusion model. The system requires two gamma ray detectors at different axial spacings from the source, and a single neutron detector axially spaced between the two gamma ray detectors. The system can be embodied as a wireline system or as a logging-while-drilling system.

Abstract: Techniques for calibrating well-logging sensors comprising emitting a first signal into a first calibration substance disposed proximate to the sensor, measuring a first sensor response from the first signal, emitting a second signal into a second calibration substance disposed proximate to the sensor, measuring a second sensor response from the second signal, and determining a sensor response function from the first sensor response and the second sensor response. One embodiment includes providing a well-logging sensor having a known response function, determining an expected range of a quality check response of the sensor using a quality-check substance with known properties, emitting a quality check signal into the quality-check substance, measuring the quality check response from the quality check signal, and comparing the expected range with the quality check response.

Abstract: Methods and systems for enabling estimations of porosity that are less sensitive to standoff and borehole size effects, and less reliant on corrective techniques for such effects. In one embodiment, a method is provided for estimating porosity of a formation using a downhole neutron tool. The method includes obtaining a near count rate in water, obtaining a far count rate in water, obtaining a near count rate in the formation and a corresponding far count rate in the formation, subtracting the near count rate in water from the near count rate in the formation to form an adjusted near count rate, subtracting the far count rate in water from the far count rate in the formation to form an adjusted far count rate, and estimating a formation porosity value as a function of the adjusted near count rate and the adjusted far count rate.

Abstract: Method and apparatus for providing real-time data indicative of the isotopic composition of formation fluids during drilling. The method includes the steps of: (a) providing a reference fluid having a known isotopic composition in a reference cell; (b) capturing a sample of formation; (c) providing at least one laser beam; (e) passing a beam through the reference fluid, measuring the reference-measurement beam before and after it passes through the reference fluid; (f) and passing a beam through the sample, measuring the beam before and after it passes through the sample, and calculating a first isotope concentration from those measurements. The measurements can provide information relating to the carbon isotopic composition of individual compounds in hydrocarbon gas mixtures, with the individual compounds including methane, ethane, propane, iso- or normal butane, or iso- or normal pentane.

Abstract: A portion of at least one fiber is moved into an exterior annulus of a well between a tubular structure in the well and the wall of the borehole of the well such that the portion is placed to conduct a signal responsive to at least one parameter in the exterior annulus. One particular implementation uses fiber optic cable with a cementing process whereby flowing cementing fluid pulls the portion of the cable into the exterior annulus.

Abstract: A well logging tool has a neutron source for irradiating formation surrounding a borehole. Two detectors are mounted in a spaced-apart vertical relationship within the tool pressure-resistant housing. Each detector detects capture gamma radiation across the entire gamma ray energy spectrum, windows are set in this spectrum to separate two distinct energy ranges, thereby generating a total of four independent sets of signals, two for each detector. One set of signals is indicative of the hydrogen content and insensitive to the chlorine content of the irradiated formation. The second set of signals is indicative of the hydrogen plus the chlorine content of the irradiated formation. By comparing the sets of signals in two proportional energy ranges, the logging tool allows to generate a log that helps determine the presence or absence of hydrocarbon or salt water in the formation.

Abstract: An indicator mixture that allows pH measurement over a broader range of pH or to a higher accuracy than available using conventional spectroscopic techniques. In particular, the mixture of the present invention is comprised of two or more reagents such that when combined, the reagent mixture is capable of either detecting: (1) a pH range broader or more accurate than that the reagents individually, or (2) pH more accurately than the reagents individually. Also disclosed are methods of making and using the mixture.

Abstract: The present invention relates to an in-vessel or down-hole optical imaging sensor or system for operating in structures which may contain media with different spectral transmission characteristics. The imaging sensor of the present invention selectively emits and/or detects two or more independently controllable wavelengths or wavebands. The imaging sensor comprises illuminating means for emitting radiation of a specified wavelength or waveband through a medium to a target, detector means for detecting the radiation deflected by said target and amplifier means for providing non-linear amplification of the detector means output. The sensor of the present invention may also comprise a sensor window and optical means for directing the radiation through an area of the sensor window in a first direction and optical means for receiving the radiation reflected from the target through the same area of the sensor window in a second direction.

Abstract: The present invention describes a unique method and apparatus for applying near-infrared spectroscopy to estimate weight percent of methane in crude oil from which one can then infer gas-oil ratio (GOR) of crude oils downhole in real time while collecting a fluid sample. The correlation equations provided by this invention use two wavelengths, one centered at 1670 and the other centered at 1682 nm. Both wavelengths are primarily sensitive to the methane peak absorption. To significantly improve the fit, non-spectroscopic parameters, such as temperature or pressure, can be included in the correlation equation. Also, this invention can be used to monitor sample cleanup by monitoring the increase in GOR associated with cleanup as a fluid being pumped from the formation transitions from mostly gas-free filtrate to mostly gas-containing crude oil.

Abstract: Method and apparatus for providing real-time data indicative of the isotopic composition of formation fluids during drilling. The method includes the steps of: (a) providing a reference fluid having a known isotopic composition in a reference cell; (b) capturing a sample of formation; (c) providing at least one laser beam; (e) passing a beam through the reference fluid, measuring the reference-measurement beam before and after it passes through the reference fluid; (f) and passing a beam through the sample, measuring the beam before and after it passes through the sample, and calculating a first isotope concentration from those measurements. The measurements can provide information relating to the carbon isotopic composition of individual compounds in hydrocarbon gas mixtures, with the individual compounds including methane, ethane, propane, iso- or normal butane, or iso- or normal pentane.

Abstract: A method of determining GOR comprising subjecting a fluid to spectroscopic analysis at a first wavelength sensitive to gas and a second wavelength sensitive to oil, determining a response matrix for the contribution of gas at the first and second wavelengths and the contribution of oil at the first and second wavelengths, determining a signal response vector and the two wavelengths, calculating a mass fraction vector from the response matrix and the signal response vector and using the mass fraction vector to determine GOR.

Abstract: A method for analyzing formation fluid in earth formation surrounding a borehole includes storing analytical reagent in a reagent container in a fluids analyzer in a formation tester and moving the formation tester, including the reagent, downhole. Reagent from the reagent container is injected into formation fluid in the flow-line to make a mixture of formation fluid and reagent. The mixture is moved through a spectral analyzer cell in the fluids analyzer to produce a time-series of optical density measurements at a plurality of wavelengths. A characteristic of formation fluid is determined by spectral analysis of the time-series of optical density measurements.

Abstract: Methods of analyzing formation fluids in an oilfield environment are near-infrared absorption spectroscopy. Indications of near-infrared absorptions are analyzed to determine the concentration of compounds in a formation fluid sample.

Abstract: Process for simulation of the response of a detector of radiation emitted by radioactive objects and process for inspection of nuclear fuel elements using this simulation. The objects (16) contain radioelements or mixes of radioelements. Radioactive emission spectra representative of the radioelements or mixes of radioelements are memorized, detection characteristics of the detector (D) and operating characteristics of the received radiation are determined, the radioelements or mixes of radioelements are chosen and the determined characteristics are processed so as to individually reproduce emitted radiation for selected radioelements or mixes of radioelements. Application to the inspection of nuclear fuel rods.

Abstract: A method is disclosed for measuring neutron interaction properties of an earth formation. The method includes irradiating the formation with bursts of high energy neutrons. The bursts have a duration selected to enable detection of short duration burst related phenomena. After at least one of the bursts, short duration burst related phenomena are measured. After a selected number of the bursts, long duration neutron burst-related phenomena are detected. In some embodiments, the short duration burst related phenomena include at least one of inelastic gamma ray related phenomena, neutron slowing down related phenomena and short capture cross section related phenomena.

Abstract: Fiber optic cable is daisy-chained between a plurality of wells. Rather than terminating a piece of fiber optic cable down each well, the fiber optic cable is disposed down, then back up a plurality of wells at once. Using the fiber optic cable, a parameter of interest is measured in each of the wells. The parameter may be temperature which can be sensed by sending optical signals down the fiber optic cable, then measuring the backscattered signals. In one implementation, steam injected into one or more wells is adjusted based upon the parameter readings.

Abstract: The invention comprises an apparatus and method for simple fluorescence spectrometry in a down hole environment. The apparatus and method utilization of two UV light bulbs and an optically clear UV coupler and a fluid containment system. The optically clear UV coupler and fluid containment system are made of sapphire. The apparatus is attached in a manner that enables light transmitted from a light source on the far side of the fluid containment system to pass through a pathway in a plate holding the UV bulbs. UV light illuminates the fluid, which in turn fluoresces light. The fluoresced light is transmitted back towards the UV bulb mount and through the pathway towards an optical spectrum analyzer.

Abstract: A measuring system for in-situ measurements down a well (1) by a spectrometer (4) is provided. The spectrometer (4) includes a radiation source (5) and a detector (6). A probe (15) optically connected to the spectrometer (4) and includes an optical pathway (7) for transmission of a radiation from the radiation source (5) and at least a second optical pathway for transmission of a characteristic radiation from a sample to the detector (6). A positioner is provided to position the probe (15) near a side surface (11) of the borehole (3) and to optically couple the optical pathways (7) to the side surface (11), wherein the probe (15) is traversable up and down the well (1) by way of a guide operatively connected to the probe (15) and to a fixed location at the wellhead. By use of the apparatus and method a concentration of methane or other substance of interest is obtained, and thereby, a potential production of a coal bed methane formation is obtained.

Abstract: A method and apparatus detects dew precipitation and determines dew precipitation onset pressure in a sample of formation fluid located downhole in an oilfield reservoir. In a preferred embodiment, the method includes (a) isolating a sample of formation fluid downhole; (b) illuminating the sample downhole with fluorescence excitation light; (c) measuring at least one characteristic of fluorescence short from the sample; (d) reducing pressure on the sample; (e) repeating steps (b) to (d); (f) detecting dew precipitation when a change is detected in a parameter that is a function of the at least one characteristic of fluorescence emission; and (g) setting dew precipitation onset pressure equal to pressure on the sample when the change in the parameter is detected. The parameter preferably is a function of fluorescence intensity and fluorescence red shift, and the change is an increase in fluorescence intensity and detection of fluorescence red shift.

Abstract: A method is disclosed for operating a well logging tool having a controllable radiation source operatively coupled to a power source. The method includes monitoring at least one condition in a wellbore, and operatively disconnecting the power source from the radiation source when the at least one condition changes. Also disclosed is a downhole measurement assembly, which includes a radiation source, a power source, and at least one interlock operatively connected between the power source and the radiation source, where the at least one interlock is adapted to selectively arm and disarm the radiation source.

Abstract: A logging while drilling and wire line system for analyzing the concentration of carbon dioxide or another substance, in a sample down hole in a bore hole. A chamber is filled with a sample that may be fluid, or condensate and gas. The interior chamber volume is selectably expandable for decompression of the sample. The sample may alternately be decompressed by allowing a sample at formation pressure to enter the chamber at a lower pressure, thereby decompressing the sample. A sensor measures the absorbance, transmittance or attenuated total reflectance of the infrared light. Mid and near infrared light is utilized to identify carbon dioxide, water and a plurality of hydrocarbons. A wiper cleans the transmitter and sensor between readings to reduce measurement error caused by fluid sample contamination.

Abstract: Method and apparatus for providing real-time data indicative of the isotopic composition of formation fluids during drilling. The method includes the steps of: (a) providing a reference fluid having a known isotopic composition in a reference cell; (b) capturing a sample of formation; (c) providing at least one laser beam; (e) passing a beam through the reference fluid, measuring the reference-measurement beam before and after it passes through the reference fluid; (f) and passing a beam through the sample, measuring the beam before and after it passes through the sample, and calculating a first isotope concentration from those measurements. The measurements can provide information relating to the carbon isotopic composition of individual compounds in hydrocarbon gas mixtures, with the individual compounds including methane, ethane, propane, iso- or normal butane, or iso- or normal pentane.

Abstract: A nuclear logging-while-drilling measuring systems, and the correction of the formation property measurements for adverse effects of instrument standoff from the borehole wall, is disclosed. Detector responses for one or more downhole detectors are sampled and recorded over a time segment. The response samples are then sorted by magnitude, and a running integral of the sorted samples as a function of time is performed over the time segment. Linear segments are then fitted to the running integral, wherein each straight line segment is a function of one or more formation properties, and also a function of the standoff distance of the detector from the borehole wall. Segments are then combined to obtain a measure of one or more formation properties of interest such as formation density, where the adverse effects of borehole standoff are minimized. Standoff magnitude is also obtained and can be used to correct other logs, such as a neutron porosity log, for adverse effects of tool standoff and borehole size.

Abstract: An oil sample is subjected to nuclear electromagnetic irradiation downhole, and the electron and/or mass density of the oil sample is determined by measuring the attenuation of the irradiation and relating the attenuation to the electron density. If the irradiation is high energy gamma ray irradiation, the attenuation is considered to be a function of Compton scattering only, which in turn is related to the electron density of the sample. If X-rays are utilized, attenuation is preferably measured in two energy windows. Using the two different attenuation values found in the different windows, the attenuation due to Compton scattering can be found and related to the electron and/or mass density of the sample.

Abstract: A rigid redundant light source for obtaining down hole near infrared data in a NIR data acquisition instrument is provided having a plurality of lamps positioned in close proximity and symmetrically about a common optical axis. A lens system for capturing and collimating the light is provided. The structure is arranged and dimensioned so that a single collimating lens can be used for a plurality of light sources. A switch and sensor is provided for turning on an alternate light source when a first light source burns out. A filter is rotated 90 degrees with respect to the light sources to minimized off axis error when switching between light sources.

Abstract: A method of determining GOR comprising subjecting a fluid to spectroscopic analysis at a first wavelength sensitive to gas and a second wavelength sensitive to oil, determining a response matrix for the contribution of gas at the first and second wavelengths and the contribution of oil at the first and second wavelengths, determining a signal response vector and the two wavelengths, calculating a mass fraction vector from the response matrix and the signal response vector and using the mass fraction vector to determine GOR.

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: The optical density of an oil sample at a plurality of wavelengths over a plurality of different (typically decreasing) pressures is monitored and used to find the size of agglomerated asphaltene particles which are precipitating from the oil sample. The optical density information used in finding the particle size is preferably optical density information relating to the scattering of light due to the asphaltene particles only. Thus, baseline optical density information of the oil sample at a high pressure is subtracted from optical density information obtained at test pressures at each wavelength of interest. Asphaltene particles of a radius of one micron and smaller were found to be powdery, while asphaltene particles of a radius of three microns and larger were found to include paving resins. The precipitation of asphaltenes is reversible by increasing the pressure under certain circumstances.

Abstract: A method of determining GOR comprising subjecting a fluid to spectroscopic analysis at a first wavelength sensitive to gas and a second wavelength sensitive to oil, determining a response matrix for the contribution of gas at the first and second wavelengths and the contribution of oil at the first and second wavelengths, determining a signal response vector and the two wavelengths, calculating a mass fraction vector from the response matrix and the signal response vector and using the mass fraction vector to determine GOR.

Abstract: The present invention relates to an imaging sensor, particularly for use in oil-filled passages such as wells or pipelines, or for passages containing other similar viscous fluids. There is provided a downhole imaging system which operates in a wavelength region outside the visible band, preferably in the infrared region, to permit penetration of the surrounding fluid medium, e.g., oil. Positioning the optical part of the imaging sensor in a chamber whose walls are transparent to the radiation reduces the path length of the radiation in the oil. The chamber is filled with a material highly transmissive of the radiation.

Abstract: Methods of detecting carbon dioxide in downhole environments are provided. Near-infrared light is transmitted through a gas downhole. Indications of near-infrared absorptions are detected from the gas and used to determine the presence of carbon dioxide.

Abstract: A multiple cell radiation detector includes a central cell having a first cylindrical wall providing a stopping power less than an upper threshold; an anode wire suspended along a cylindrical axis of the central cell; a second cell having a second cylindrical wall providing a stopping power greater than a lower threshold, the second cylindrical wall being mounted coaxially outside of the first cylindrical wall; a first end cap forming a gas-tight seal at first ends of the first and second cylindrical walls; a second end cap forming a gas-tight seal at second ends of the first and second cylindrical walls; and a first group of anode wires suspended between the first and second cylindrical walls.

Abstract: Systems for measuring the gas-oil ratio of fluid being produced in a wellbore are provided and generally include an uphole light source which produces a high amplitude near infrared signal at selected wavelengths, an uphole spectrometer, a processor coupled to the spectrometer for making GOR determinations, a plurality of optical cells in contact with wellbore fluid and located along various locations of the wellbore, and a fiber optic system which couples the uphole light source to the “input side” of each of the optical cells, and which couples the “output side” of each of the optical cells to the spectrometer. The light source preferably produces high amplitude NIR light at or around 1.72 microns (an oil peak), 1.67 microns (a methane peak), 1.6 microns (a baseline), and 1.58 microns (a carbon dioxide peak). Various sources are disclosed including tunable sources, diode arrays, and broad band sources.

Abstract: Methods of detecting carbon dioxide in downhole environments are provided. Near-infrared light is transmitted through a gas downhole. Indications of near-infrared absorptions are detected from the gas and used to determine the presence of carbon dioxide.

Abstract: A formation fluid analysis tool has an optical probe that is inserted into the formation. The optical probe carries an internal reflectance crystal and is inserted into the formation so as to get past the mud cake, the flushed zone and the invaded zone and thus be in contact with virgin formation fluid. An acousto-optical tunable filter (AOTF) transmits a single wavelength of light from a broad band light source, the wavelength being controlled by a microwave signal from a processor. This monochromatic light is carried by an optic fiber to the internal reflectance crystal where it undergoes total reflection at the crystal faces in contact with the formation fluid. An evanescent wave propagates into the fluid with a depth of penetration related to the absorption of the light in the fluid. The reflected light carries information about this absorption which is determined by the chemical composition of the fluid. A return fiber conveys the reflected light back to a spectrometer.

Abstract: A logging while drilling and wire line system for analyzing the concentration of carbon dioxide or another substance, in a sample down hole in a bore hole. A chamber is filled with a sample that may be fluid, or condensate and gas. The interior chamber volume is selectably expandable for decompression of the sample. The sample may alternately be decompressed by allowing a sample at formation pressure to enter the chamber at a lower pressure, thereby decompressing the sample. A sensor measures the absorbance, transmittance or attenuated total reflectance of the infrared light. Mid and near infrared light is utilized to identify carbon dioxide, water and a plurality of hydrocarbons. A wiper cleans the transmitter and sensor between readings to reduce measurement error caused by fluid sample contamination.