Abstract: The embodiments herein relate to formation testers having reactive filter materials for detecting analytes in subterranean formation operations. The formation include a body having an outlet, a probe extendable from the body and having a sealing pad and a probe snorkel tube, a flow line within the body, wherein the flow line has an entry end connectable to the probe snorkel tube and an exit end connectable to the outlet in the body, a sample chamber fluidically connectable to the flow line downstream of the entry end of the flow line, and a reactive filter material in the flow line. The reactive filter material sorbs an analyte in a wellbore fluid.

Abstract: Described herein are embodiments of a control system that automatically (1) determines whether a gas extraction system is in a state in which landfill gas is being released into the atmosphere, and (2) automatically controls landfill gas flow to mitigate, prevent and/or stop the release of landfill gas. The control system may control a valve to control flow of landfill gas through well piping of the gas extraction system. The pressure of landfill gas in the well piping at a location upstream of the valve may indicate whether there is a risk of landfill gas being released into the atmosphere. The control system may adjust a position of the valve in response to determining that the pressure at the location upstream of the valve indicates that there is a risk of landfill gas being released into the atmosphere.

Abstract: A tunnel boring device for laying a pipeline in the ground using a boring tool, having; a feed line for supplying a boring fluid to the boring tool; a section, arranged at the rear of the boring tool, for receiving the ground cuttings, wherein the region of the boring tool and the section are filled with boring fluid, with a pressure that corresponds to the pressure in the ground; at least a jet pump for removing the boring fluid mixed with the cuttings; at least one conveying line for removing the boring fluid mixed with cuttings, this line being connected to the delivery side of the pump connected to the section via a suction line. The jet pump is connected to a drive line via which a driving fluid is supplied to the jet pump; the pump is arranged outside then section; and the suction line contains a shutoff valve.

Abstract: A matrix production logging tool for measuring the temperature of produced fluids in a wellbore is described. Accurate production allocation to the pathways between the oil/gas well and the reservoir provides required data for the economic optimization of the techniques and procedures used to complete future wells and optimize the existing well. The low maintenance tool provides precise uphole, downhole and inflow temperature measurements of produced fluids within the wellbore. These are obtained at a plurality of locations along the oil/gas well as the tool is withdrawn, thus providing a matrix of temperature measures along the length of the well. From the temperature traces, inflow as well as up and downhole temperature, can be determined, and mass contribution at each inlet determined. With this method, a production profile along the entire well can be determined as used in further well optimization efforts.

Abstract: Apparatuses, methods and uses thereof, for sampling fluids and volatile components in such fluids, from a high pressure pipe, are provided. The apparatus can include dual floating pistons moveably disposed in two cylinders. The lower portion of the first cylinder can be fluidly connected to the upper portion of the second cylinder. In operation, fluids can enter the upper portion of the first cylinder, controlled by flow limiting means. Once the first cylinder is filled with sample, the pressure on the sample can equalize to the pressure set in the lower portion of the second cylinder. The sample can be exposed to gas to liberate the volatile components of the sample into a vapor phase. The sample, or vapor phase, can then be discharged from the first cylinder to an analyzing device. The apparatus, method and use of the present disclosure can reduce the risk of plugging of the system.

Abstract: The present invention discloses an oil-gas separation cylinder, an oil-gas separation device and an oil chromatography. The oil-gas separation cylinder comprises an oil-gas separation cylinder body of which axe extends in direction of up and down, a separating block which separates the oil-gas separation cylinder body into an upper cavity and a lower cavity, an oil-gas separation cylinder piston movably installed in the lower cavity, an oil inlet passage and an oil outlet passage, and an oil-gas separation cylinder vent arranged at upper end of the upper cavity, wherein both of the oil inlet passage and the oil outlet passage are communicated with the upper cavity, wherein the separating block is provided with a guiding hole and a spaying hole used to communicate the upper cavity to the lower cavity, or the separating block is provided with a spaying hole guiding oil used to communicate the upper cavity to the lower cavity.

Abstract: A process gas analyzer and method for analyzing a process gas carried in a plant section, wherein light from a light source is passed through the process gas and detected via a detector, evaluated in an evaluation unit to produce an analysis result with respect to the absorption in the process gas, where chambers or purging pipes, present between the light source and the plant section and also between the detector and the plant section, are flushed with a purge gas to analyze the process gas, and where the volume flow rate of the purge gas is periodically modulated and the effect of the purge gas on the analysis result is determined based on changes in the detected absorption caused by the modulation and removed from the analysis result to enable a high degree of compensation for measurement errors caused by the purging.

Abstract: Apparatus and method for collecting and preserving in representative condition a fluid sample from a reservoir which comprises: positioning a sample container including a sampler in the vicinity of a subterranean zone to be sampled, and wherein the step of collecting and preserving the sample comprises allowing or causing the sample to first flow into the sample receptacle, wherein the movement of the sample into the sample receptacle is restricted by the movement of a sampling piston, and wherein the movement of the sampling piston is further controlled by the rotation of an electrical motor connected to the sample piston by mechanical linkage such that the rotation of the electric motor in either direction translates to lateral movement of the sample piston, the lateral movement of the sample piston in turn allowing sample to enter the sample receptacle, and wherein once an adequate volume of sample has been collected, reversing the direction of the electrical motor will serve to cause the sample piston to

Abstract: Processing a reservoir fluid sample includes separating the reservoir fluid sample into a vapor phase stream and a liquid phase stream, assessing a composition of the vapor phase stream, sampling a property of the liquid phase steam, and assessing a volume of a components of the liquid phase stream based at least in part on the sampled property of the liquid phase stream. A system for processing a reservoir fluid sample includes a volumetric receptacle adapted to accept the reservoir fluid sample, a phase separator configured to receive the reservoir fluid sample from the volumetric receptacle and to separate the reservoir fluid sample into a vapor phase stream and a liquid phase stream, a gas chromatograph arranged to receive the vapor phase stream from the phase separator, and a liquid flow meter configured to detect an interface including at least one component of the liquid phase stream.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate a pump to obtain a formation fluid sample from a formation adjacent to a wellbore disposed within a reservoir, to detect a phase behavior associated with the fluid sample, and to adjust the volumetric pumping rate of the pump while repeating the operating and the detecting to maintain the pumping rate at a maintained rate, above which the phase behavior changes from a substantially single phase fluid flow to a substantially multi-phase flow. Additional apparatus, systems, and methods are disclosed.

Abstract: A method for determining water saturation in a subsurface formation include determining an invasion depth in the formation from a plurality of measurements made within a wellbore drilled through the formation. The measurements have different lateral depths of investigation into the formation. Carbon and oxygen in the formation are measured at substantially a same longitudinal position as at a position of the determining the invasion depth. The measured carbon and oxygen and the invasion depth are used to determine the water saturation in a substantially uninvaded part of the formation.

Abstract: Methods and apparatus for determining a viscosity of oil in a mixture are disclosed herein. An example method includes determining water fractions of a mixture flowing into a downhole tool and determining viscosities of the mixture. The mixture includes water and oil. The example method also includes determining a viscosity of the oil based on the water fractions and the viscosities.

Abstract: In some embodiments, apparatus and systems, as well as methods, may operate to draw a formation fluid sample into a sampling port included in a down hole tool, to vaporize some part of the fluid sample to substantially fill an injection port with a gas phase, to differentiate gas components in the gas phase to provide differentiated gas components along a concentration gradient, to detect the differentiated gas components, and to determine a fingerprint of the differentiated gas components. Other apparatus, systems, and methods are disclosed.

Abstract: Described herein are variable-volume reservoir (e.g., syringe pump) based processes and systems usable to characterize samples of reservoir fluids, without having to first transport the fluids to the surface. Variable-volume reservoirs are used, for example, for one or more of storing reactants, controlling mixing ratios and storing used chemicals. The processes and systems can be used in various modes, such as continuous mixing mode, flow injection analysis, and titrations. A fluid interrogator, such as a spectrometer, can be used to detect a change in a physical property of the mixture, which is indicative of an analyte within the mixture. In at least some embodiments, a concentration of the analyte solution can be determined from the detected physical property.

Abstract: A gas analyzer system that can detect atmospheric air gasses in drilling mud is used to calculate an actual lag time in a well. The calculated lag time and a theoretical lag time may be compared to estimate a caving percentage in an open hole section of the well.

Abstract: The accuracy of a measurement of the composition of a multiphase sample containing crude oil and water is improved by pouring the sample into a bottle shaped container (1), which is dimensioned such that the oil-water interface (4) is located in an upper portion (3), which forms a bottleneck that has a smaller cross section than a lower portion (2) of the container (1), which lower portion (2) has a substantially frusto-conical shaped intermediate section (8) contiguous with the upper portion (3) that allows accurate water cut measurement even if the oil-water interface is located within the intermediate section (8).

Abstract: A fluid sampling system (220) includes an inline fluid extraction body (210). The inline fluid extraction body comprises an inlet (202), a first outlet (206) and a second outlet (208). A pump (214) directs a portion of a fluid flowing through the inlet into the second outlet. A flow restrictor (222) is fluidically coupled to the second outlet and regulates pressure of fluid flow through the second outlet. An extraction system (230) is fluidically coupled to the second outlet and extracts a gas sample from the fluid sample. The gas sample may then be analyzed by an analyzer.

Abstract: A method for monitoring production from a methane hydrate reservoir includes obtaining a plurality of temperature measurements in a wellbore connected with the methane hydrate reservoir; and deriving a parameter relating to conversion of methane hydrate to carbon dioxide (CO2) hydrate by injection of liquid CO2, wherein the deriving uses a modeling program and the plurality of temperature measurements, wherein the modeling program uses at least one parameter relating to a thermodynamic properties that are substantially different between methane and CO2. The at least one parameter relating to thermodynamic properties may include Joule-Thomson coefficients of methane and CO2. The parameter relating to the conversion of methane hydrate to CO2 hydrate may include a ratio of methane and CO2 in a mixed fluid.

Abstract: Apparatus and systems, as well as methods, may operate to draw a formation fluid sample into a sampling port included in a down hole tool or tool body, to vaporize some part of the fluid sample to substantially fill an injection port with a gas phase, to differentiate gas components in the gas phase to provide differentiated gas components along a concentration gradient in a receiving section, to detect the differentiated gas components with a detector, and to determine a fingerprint of the differentiated gas components. A reaction section and a vacuum section may be used for waste consumption and/or absorption.

Abstract: Apparatus and systems, as well as methods, may operate to draw a formation fluid sample into a sampling port included in a down hole tool or tool body, to vaporize some part of the fluid sample to substantially fill an injection port with a gas phase, to differentiate gas components in the gas phase to provide differentiated gas components along a concentration gradient in a receiving section, to detect the differentiated gas components with a detector, and to determine a fingerprint of the differentiated gas components. The receiving section may comprise a diffusion section. A reaction section and a vacuum section may be used for waste consumption and/or absorption.

Abstract: A portable monitor used to measure landfill gas and landfill well parameters. The portable monitor includes a control unit and a measuring unit that can communication wirelessly with one another. The control unit and/or measuring unit can includes a heating arrangement to increase the temperature of one or more components in the control unit and/or measuring unit in cold environments.

Abstract: A portable monitor used to measure landfill gas and landfill well parameters. The portable monitor includes a control unit and a measuring unit that can communication wirelessly with one another. The control unit and/or measuring unit can includes a heating arrangement to increase the temperature of one or more components in the control unit and/or measuring unit in cold environments.

Abstract: A method for determining water saturation in a subsurface formation include determining an invasion depth in the formation from a plurality of measurements made within a wellbore drilled through the formation. The measurements have different lateral depths of investigation into the formation. Carbon and oxygen in the formation are measured at substantially a same longitudinal position as at a position of the determining the invasion depth. The measured carbon and oxygen and the invasion depth are used to determine the water saturation in a substantially uninvaded part of the formation.

Abstract: Apparatus and methods to monitor contamination levels in a formation fluid are disclosed. An example method involves obtaining first property data indicative of a first fluid property of a formation fluid and second property data indicative of a second fluid property of the formation fluid. A correlation between the first and second property data is generated and third data is fitted to the correlation. A fitting parameter is determined based on the third data indicative of an amount of change of the first property data relative to an amount of change of the second property data.

Abstract: A sensor used to determine the height of one or more fluids in a fluid column and to determine a location of an interface or boundary between a plurality of fluids in a fluid column is disclosed. The sensor includes a plurality of sensing elements comprising a capacitor and other components, such as resistors and inductors. The sensor also includes an oscillator that alters a frequency of an electrical current applied to the sensor, from which the dielectric constant of the fluid in which each sensing element is disposed can be determined. Methods of using such a sensor to determine the relative heights of various fluids in a fluid column are disclosed. In particular, methods of using embodiments of the invention in a well, such as water and petroleum wells, are described.

Abstract: Apparatus and methods to monitor contamination levels in a formation fluid arc disclosed. An example method involves obtaining first property data indicative of a first fluid property of a formation fluid and second property data indicative of a second fluid property of the formation fluid. A correlation between the first and second property data is generated and third data is fitted to the correlation. A fitting parameter is determined based on the third data indicative of an amount of change of the first property data relative to an amount of change of the second property data.

Abstract: The present invention provides a method and apparatus for performing elemental analysis of a formation fluid downhole. The present invention provides elemental analysis of a formation fluid downhole using breakdown spectroscopy. In one aspect of the invention, a method and apparatus are provided for performing laser induced breakdown on a formation fluid sample is provided. In another aspect of the invention a method and apparatus are provided for performing spark induced breakdown spectroscopy. Plasma is induced in a fluid under test downhole. Emissions from the plasma are analyzed to determine the elemental composition of the fluid under test. Emissions include but are not limited to light in the ultraviolet, visible, and near infrared regions of the spectrum. A spectrometer is provided for elemental analysis of a fluid downhole. Elemental analysis yields information about the fluid and the formation from which the fluid originated.

Abstract: The present invention provides a method and apparatus or system for determining an amount of coal tar that can enter, and subsequently be displaced from, a given type of soil for a range of depths of the soil. The method and apparatus also provide verification of the pressure at which coal tar can be displaced from a given type of soil. In particular, the method and apparatus simulate the hydrostatic pressure that a soil sample encounters in the subsurface of the ground. Accordingly, the method and apparatus provide a relationship between the concentration of coal tar in the soil and the pressure required to displace the coal tar from the soil, which allows for an estimation of the amount of coal tar that may be displaced at a particular location or site. Further, the method and apparatus are adaptable for use in the laboratory or the field.

Abstract: A method and apparatus for controlling the production of well treatment fluid is disclosed. The apparatus includes: a sand system, a water system, a pumping system, a blender tub, and a virtual rate control system. The method includes determining an output rate from a sand system; sensing an output rate from a water system; sensing an output rate from a pumping system; sensing the height within a blender tub of a mixture of sand from the sand system and water from the water system; providing a virtual rate control system; and producing a drive signal to the pumping system using the virtual rate control system using a desired rate of well treatment fluid to be delivered to a well, the output rate of the sand system, the output rate of the water system, and the output rate of the pumping system.

Abstract: A method and computer program product of either preventing or minimizing pore pressure increase near the wellbore wall within argillaceous formations through which a borehole has been drilled. By interpreting relevant drilling experience data, the type, extent and time-dependency of wellbore instability mechanisms are determined. The impact of drilling mud designs on the time-dependent wellbore instability and hole enlargement is determined by back-analyzing observed drilling events. At least one field-based criterion relationship between net mud weight reduction percentage ratio and hole enlargement is determined. A maximum allowable percentage ratio(s) of net mud weight reduction and either breakout mud weight or mud weight used for the adopted maximum hole enlargement that the wellbore may experience during drilling is determined. Drilling mud salinity value and salt type to satisfy maximum allowable percentage ratio(s) is then determined.

Abstract: The present invention provides a downhole method and apparatus using molecularly imprinted polymers to analyze a downhole fluid sample or determine the percentage of oil based mud filtrate contamination in a formation fluid sample.

Abstract: A portable monitor used to measure landfill gas and landfill well parameters. The portable monitor includes a control unit and a measuring unit that can communication wirelessly with one another. The control unit and/or measuring unit can includes a heating arrangement to increase the temperature of one or more components in the control unit and/or measuring unit in cold environments.

Abstract: A method for the detection of a fluid leak from a plugged well extending from a surface of the earth to penetrate a subterranean formation which contains fluid by logging a collection chamber positioned in the plugged well.

Abstract: A probe 10,170 is provided that measures the speed of sound and/or vortical disturbances propagating in a single phase fluid flow and/or multiphase mixture to determine parameters, such as mixture quality, particle size, vapor/mass ratio, liquid/vapor ratio, mass flow rate, enthalpy and volumetric flow rate of the flow in a pipe or unconfined space, for example, using acoustic and/or dynamic pressures. The probe includes a spatial array of unsteady pressure sensors 15-18 placed at predetermined axial locations x1-xN disposed axially along a tube 14. For measuring at least one parameter of a saturated vapor/liquid mixture 12, such as steam, flowing in the tube 14. The pressure sensors 15-18 provide acoustic pressure signals P1(t)-PN(t) to a signal processing unit 30 which determines the speed of sound amix propagating through of the saturated vapor/liquid mixture 12 in the tube 14 using acoustic spatial array signal processing techniques.

Abstract: A subterranean environment evaluating apparatus and method, which measure, e.g., the geologic distribution coefficient in a subterranean environments using, e.g., a pit formed by boring. The subterranean environment evaluating apparatus comprises a geologic evaluation sensor, a pump, an analyzer, a PC, a data transmitter, etc., and it is disposed in the pit formed underground by boring. The geologic evaluation sensor is disposed to form a thin layer channel defined by the surface of a rock bed. Groundwater mixed with a tracer is caused to flow through the sensor, and the analyzer measures a change of tracer concentration in the groundwater between before and after contact of the groundwater with the rock bed. The PC determines a breakthrough curve from the change of tracer concentration, thereby calculating the distribution coefficient (Kd) between the rock bed and the groundwater and the effective diffusion coefficient of the rock bed.

Abstract: In a well bore operation in which a particulate is added to a fluid stream, a method of determining the concentration of said particulate in said fluid stream comprising the steps of measuring the rate of flow of the fluid stream, determining the rate of particulate flow in the fluid stream using an acoustic sensor and calculating the concentration of particulate in the fluid stream using results from the measuring and determining steps.

Abstract: A method of measuring a water effect on an underground non-water well includes the steps of assembling a history of water cut (WC) measurements for the well over an extended period of time, determining a water cut rate of change (R) for the well based upon the history of water cut measurements, wherein the water cut rate of change is defined as follows: ? ( WC ) ? ( t ) = R , and identifying whether an anomaly exists based on the determined R.

Abstract: Disclosed is a method of determining the extent of recovery of materials injected into oil wells or subsurface formations. The method includes injection of one or more tracers into an oil well or into a formation. Included in the method are the steps of introducing a material of interest into the oil well or into the subsurface formation associated with the bore of the oil well; introducing a tracer into the oil well or into the subsurface formation associated with the bore of the oil well; recovering from the oil well a production fluid, analyzing the production fluid for a concentration of the chemical tracer present in the production fluid; and calculating the amount of material of interest recovered from the oil well using the concentration of the chemical tracer present in the production fluid as a basis for the calculation.

Abstract: The invention relates to a tool holder serving to receive measurement means (9, 10, 13) for characterizing a multi-phase fluid coming from a deposit (17) through which at least one well (16) passes, and flowing inside said tool holder. According to the invention, the tool holder is provided with an axial cavity (3) and with a first radial opening (4) which opens out in the inside wall of said tool holder and intercepts said axial cavity, said cavity and said opening serving to receive said measurement means. The invention also relates to a device for characterizing a multi-phase fluid coming from a deposit (17) through which at least one well (16) passes, said device comprising: a source unit (9) for emitting gamma rays through said multi-phase fluid, and a detector unit (10) having a scintillator crystal (10a) receiving said gamma rays after they have passed through the fluid.

Abstract: The present invention provides a method and system for controlling mineral scale deposition from a formation fluid. The rate at which scaling is occurring is measured in real time using an attenuated total reflectance probe and a photometer. The results are then used to determine whether to increase, decrease or leave unchanged addition of anti-scaling additives.

Abstract: A method and system of monitoring the movement of at least one front in an inter-well region is comprised of: providing a first well representing the origination of at least one front (such as a saturation front or a salinity front); providing one or more monitoring locations, each equipped with at least one sensor; and monitoring the arrival of at least one front at one or more monitoring locations. The origination well may be any type of permanent or temporary well, but is preferably an injector well. Likewise, the monitoring location(s) may be any type of permanent or temporary well such as an observation well, a production well, an exploratory well, and an appraisal well. Information regarding front arrival times may be used to characterize or appraise the formation. Front arrivals may be monitored as a function of time to develop their respective time evolution and shape.

Abstract: The present invention is a method of calculating non-aqueous phase liquid saturation in a soil sample including the steps of measuring the bulk dielectric constant of the sample, measuring the bulk density of the sample, estimating the bulk porosity of the sample from the measured bulk density and calculating the non-aqueous phase liquid saturation from the measured bulk dielectric constant and the estimated bulk porosity.

Abstract: A system which receives as inputs various measurements of solids and liquids in a clarification system and, from these measurements, determines the various constituents and their fractional makeup within the system. The measurements may be made manually or mechanically, but are preferably made manually. From a quantitative analysis of easily accessible sample points, data is acquired and plugged into a spread sheet program, which numerically and graphically displays the breakdown of the constituents which make up the solids and liquids discharged from a treatment stage or of the entire system.

Abstract: Embodiments of the present invention generally provide methods, apparatus, and systems for determining void fractions of individual phase components of a multiphase mixture. The void fractions may be determined based on measured parameters of the mixture as a whole, such as differential pressure, bulk velocity of the mixture and speed of sound in the mixture. According to some embodiments, the mixture parameters may be measured using non-intrusive fiber optic based sensors. Various other parameters may also be derived from the void fractions, such as individual phase flow rates, liquid holdup and watercut parameters (for oil and gas mixtures).

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

Abstract: Compositions and methods for determining the source of treatment fluids being produced from a production formation having multiple zones by introducing a treatment composition having a tracking material into a zone in the subterranean formation, and detecting the tracking material in treatment composition that flows back from the subterranean formation.

Abstract: In a well bore operation in which a particulate is added to a fluid stream, a method of determining the concentration of said particulate in said fluid stream comprising the steps of measuring the rate of flow of the fluid stream, determining the rate of particulate flow in the fluid stream using an acoustic sensor and calculating the concentration of particulate in the fluid stream using results from the measuring and determining steps.

Abstract: Disclosed is a method of determining the extent of recovery of materials injected into a oil well comprising the steps of: a) preparing a material to be injected into an oil well; b) admixing therewith a chemical tracer compound at a predetermined concentration; c) injecting the admixture into an oil well; d) recovering from the oil well a production fluid; e) analyzing the production fluid for the concentration of the chemical tracer present in the production fluid; and f) calculating the amount of admixture recovered from the oil well using the concentration of the chemical tracer present in the production fluid as a basis for the calculation. Fluorinated benzoic acids are disclosed as a preferred tracer.

Abstract: Method of predicting paraffin deposition risks during hydrocarbon production and/or transport, applicable at an early reservoir characterization and production stage. It comprises forming a database characterizing the hydrocarbons in the formation, including density data acquired by well logging and data obtained by analysis of rock samples taken from the reservoir formation, an analytical representation of the hydrocarbons by a limited number of pseudo-components comprising each certain hydrocarbon classes with a definition of their respective mass fractions and application of data of said base to a thermodynamic model for determining one or more parameters indicative of the crystallization conditions such as, for example, the starting crystallization temperature, the solid fraction that precipitates when the temperatures falls below this starting crystallization temperature, etc. Applications: hydrocarbon production field valuation.

Abstract: A method of identifying the fluid type of subterranean formations according to the correlation between the variation trend of electrical resistivity with depth downhole in a borehole and the variation trend of porosity with depth downhole in the same borehole. The method includes the steps of: a) determining the rate of change with depth of a resistivity parameter (such as deep resistivity) of the formation surrounding the borehole; b) determining the rate of change with depth of a porosity parameter (such as total porosity and/or free fluid porosity measured by a nuclear magnetic resonance technique) of the formation surrounding the borehole; c) determining a comparison of the rate of change with depth of such resistivity parameter and the rate of change with depth of such porosity parameter for a given depth in the borehole; and d) using the comparison to determine the nature of the fluid in the formation surrounding the borehole at that depth downhole or in a given depth window downhole.