Abstract: A method includes receiving first fluid property data from a first location in a hydrocarbon reservoir and receiving second fluid property data from a second location in the hydrocarbon reservoir. The method includes performing a plurality of realizations of models of the hydrocarbon reservoir according to a respective plurality of one or more plausible dynamic processes to generate one or more respective modeled fluid properties. The method includes selecting the one or more plausible dynamic processes based at least in part on a relationship between the first fluid property data, the second fluid property data, and the modeled fluid properties obtained from the realizations to identify potential disequilibrium in the hydrocarbon reservoir.

Abstract: Systems and methods for identifying a likelihood that a reservoir of a geological formation received a secondary charge of hydrocarbons of relatively very different thermal maturity of composition are provided. One method includes positioning a downhole acquisition tool in a wellbore in a geological formation and testing one or more fluid properties of the formation fluid. Data processing circuitry may identify whether a relationship of the one or more fluid properties exceeds a first threshold that indicates likely asphaltene instability. When this is the case, data processing circuitry may be used to model the geological formation using a realization scenario in which multiple charges of hydrocarbons of substantially different thermal maturity or substantially different composition, or both, filled a reservoir of the geological formation over geologic time.

Abstract: A method includes identifying linearly behaving data within obtained data associated with fluid obtained from a subterranean formation. Shrinkage factor is determined based on the linearly behaving data. A function relating GOR data of the obtained fluid with the determined shrinkage factor is determined. A first linear relationship between optical density (OD) data of the obtained fluid and the function is determined. A second linear relationship between density data of the obtained fluid and the function is determined. An oil-based mud (OBM) filtrate contamination property of OBM filtrate within the obtained fluid based on the first linear relationship is determined. A native formation property of native formation fluid within the obtained fluid based on the second linear relationship is determined. A volume fraction of OBM filtrate contamination within the obtained fluid based on the OBM filtrate contamination property and the native formation property is estimated.

Abstract: A downhole tool is operated to pump fluid from a subterranean formation while obtaining fluid property measurements pertaining to the pumped fluid. The downhole tool is in communication with surface equipment located at the wellsite surface. The downhole tool and/or surface equipment is operated to estimate a first linear, exponential, logarithmic, and/or other relationship between compressibility and pressure of the pumped fluid based on the fluid property measurements. The downhole tool and/or surface equipment may also be operated to estimate a second linear, exponential, logarithmic, and/or other relationship between formation volume factor and pressure of the pumped fluid based on the first relationship. The downhole tool and/or surface equipment may also be operated to measure and correct optical density of the pumped fluid based on the first relationship.

Abstract: The present disclosure relates to methods and apparatus for determining a gas-oil ratio based on downhole fluid analysis measurements and calibrated gas-oil ratio parameters. According to certain embodiments, the parameters for calculating the gas-oil ratio may be calibrated using historical data from the reservoir. For example, previously determined gas-oil ratios may be employed to calibrate the parameters to the reservoir. The calibrated parameters may then be employed during sampling operations to determine the gas-oil ratio.

Abstract: A method includes operating a downhole acquisition tool in a wellbore in a geological formation. The wellbore or the geological formation, or both, contains first fluid that includes a native reservoir fluid of the geological formation and a contaminant. The method also includes receiving a portion of the first fluid into the downhole acquisition tool and determining a plurality of properties of the portion of the first fluid using the downhole acquisition tool. The plurality of properties includes a mass fraction of a component of the portion of the first fluid and a density of the portion of the first fluid. The method also includes using the processor to estimate a volume fraction of the contaminant in the portion of the first fluid based at least in part on a composition mass fraction function that depends at least on the mass fraction of the component in the portion of the first fluid and the density of the portion of the first fluid.

Abstract: Disclosed are methods and apparatus pertaining to processing in-situ, real-time data associated with fluid obtained by a downhole sampling tool. The processing includes generating a population of values for ?, where each value of ? is an estimated value of a fluid property for native formation fluid within the obtained fluid. The obtained data is iteratively fit to a predetermined model in linear space. The model relates the fluid property to pumpout volume or time. Each iterative fitting utilizes a different one of the values for ?. A value ?* is identified as the one of the values ? that minimizes model fit error in linear space based on the iterative fitting. Selected values ? that are near ?* are then assessed to determine which one has a minimum integral error of nonlinearity in logarithmic space.

Abstract: A method includes operating a downhole acquisition tool in a wellbore in a geological formation. The wellbore or the geological formation, or both contains a fluid that includes a native reservoir fluid of the geological formation and a contaminant. The method also includes receiving a portion of the fluid into the downhole acquisition tool, measuring a fluid property of the portion of the fluid using the downhole acquisition tool, and using the processor to estimate a fluid property of the native reservoir fluid based on the measured fluid property of the portion of the fluid and a regression model that may predict an asymptote of a growth curve. The asymptote corresponds to the estimated fluid property of the native formation fluid, and the regression model includes a geometric fitting model other than a power-law model.

Abstract: Fluid property modeling that employs a model that characterizes asphaltene concentration gradients is integrated into a reservoir modeling and simulation framework to allow for reservoir compartmentalization (the presence or absence of flow barrier in the reservoir) to be assessed more quickly and easily. Additionally, automated integration of the fluid property modeling into the reservoir modeling and simulation framework allows the compositional gradients produced by the fluid property modeler (particularly asphaltene concentration gradients) to be combined with other data, such as geologic data and other petrophysical data, which allows for more accurate assessment of reservoir compartmentalization.

Abstract: Embodiments of the disclosure can include systems, methods, and devices for determining saturation pressure of an uncontaminated fluid. Downhole saturation pressure measurements and downhole OBM filtrate contamination of a contaminated fluid may be obtained and a relationship may be determined between the saturation pressure measurements and OBM filtrate contamination. The relationship may be extrapolated to zero OBM filtrate contamination to determine the saturation pressure of the uncontaminated fluid. In some embodiments, OBM filtrate contamination may be determined from downhole saturation pressure measurements during pumpout of a fluid.

Abstract: The present disclosure relates to methods and apparatus for determining a viscosity-pressure profile of downhole fluid by measuring the viscosity at several different pressures during a sampling operation. According to certain embodiments, the viscosity may be measured at different times during a sampling operation and used to generate the viscosity-pressure profile. For example, the viscosity may be measured at the beginning of pumping, during filling of a sample chamber, during a pressure-build up period, and while retracting the probe. The measured viscosities may then be employed to determine a profile that represents the change in viscosity that occurs with pressure.

Abstract: Disclosed are methods and apparatus pertaining to processing in-situ, real-time data associated with fluid obtained by a downhole sampling tool. The processing includes generating a population of values for ?, where each value of ? is an estimated value of a fluid property for native formation fluid within the obtained fluid. The obtained data is iteratively fit to a predetermined model in linear space. The model relates the fluid property to pumpout volume or time. Each iterative fitting utilizes a different one of the values for ?. A value ?* is identified as the one of the values for ? that minimizes model fit error in linear space based on the iterative fitting. Selected values for ? that are near ?* are then assessed to determine which one has a minimum integral error of nonlinearity in logarithmic space.

Abstract: A method, apparatus, and program product model address a modeling gap existing between basin and reservoir modeling through the use of a Reservoir Fluid Geodynamics (RFG) model usable for simulations conducted at a relatively fine spatial resolution and over a geological timescale.

Abstract: A method includes identifying linearly behaving data within obtained data associated with fluid obtained from a subterranean formation. Shrinkage factor is determined based on the linearly behaving data. A function relating GOR data of the obtained fluid with the determined shrinkage factor is determined. A first linear relationship between optical density (OD) data of the obtained fluid and the function is determined. A second linear relationship between density data of the obtained fluid and the function is determined. An oil-based mud (OBM) filtrate contamination property of OBM filtrate within the obtained fluid based on the first linear relationship is determined. A native formation property of native formation fluid within the obtained fluid based on the second linear relationship is determined. A volume fraction of OBM filtrate contamination within the obtained fluid based on the OBM filtrate contamination property and the native formation property is estimated.

Abstract: A downhole tool, surface equipment, and/or remote equipment are utilized to obtain data associated with a subterranean hydrocarbon reservoir, fluid contained therein, and/or fluid obtained therefrom. At least one condition indicating that a density inversion exists in the fluid contained in the reservoir is identified from the data. Molecular sizes of fluid components contained within the reservoir are estimated from the data. A model of the density inversion is generated based on the data and molecular sizes. The density inversion model is utilized to estimate the density inversion amount and depth and time elapsed since the density inversion began to form within the reservoir. A model of a gravity-induced current of the density inversion is generated based on the data and the density inversion amount, depth, and elapsed time.

Abstract: Embodiments of the disclosure can include systems, methods, and devices for determining saturation pressure of an uncontaminated fluid. Downhole saturation pressure measurements and downhole OBM filtrate contamination of a contaminated fluid may be obtained and a relationship may be determined between the saturation pressure measurements and OBM filtrate contamination. The relationship may be extrapolated to zero OBM filtrate contamination to determine the saturation pressure of the uncontaminated fluid. In some embodiments, OBM filtrate contamination may be determined from downhole saturation pressure measurements during pumpout of a fluid.

Abstract: A method includes placing a downhole acquisition tool in a wellbore in a geological formation within a hydrocarbon reservoir that contains a reservoir fluid. The method also includes performing downhole fluid analysis using the downhole acquisition tool in the wellbore to determine a measurement associated with the reservoir fluid and using a processor to: estimate a fluid component property by using an equation of state based the measurement and simulate a diffusion process using a diffusive model that takes into account the estimated fluid property. The diffusive model accounts for gravitational diffusion of components in the reservoir fluid. The method also includes using the processor to estimate reservoir fluid geodynamic processes based on the fluid property; compare the estimated reservoir fluid geodynamic processes with the measurement associated with the reservoir fluid; and output reservoir fluid geodynamic processes corresponding to the measurement associated with the reservoir fluid.

Abstract: A downhole tool operable to pump a volume of contaminated fluid from a subterranean formation during an elapsed pumping time while obtaining in-situ, real-time data associated with the contaminated fluid. The contaminated fluid includes native formation fluid and oil-based mud (OBM) filtrate. A shrinkage factor of the contaminated fluid is determined based on the in-situ, real-time data. The contaminated fluid shrinkage factor is fit relative to pumped volume or pumping time to obtain a function relating the shrinkage factor with pumped volume or elapsed pumping time. A shrinkage factor of the native formation fluid is determined based on the function. A shrinkage factor of the OBM filtrate is also determined. OBM filtrate volume percentage is determined based on the shrinkage factor of the native formation fluid and the shrinkage factor of the OBM filtrate.

Abstract: The present disclosure relates to methods and systems for developing an equation of state model for petroleum fluids. In one embodiment, formation fluid from a plurality of depths within a wellbore may be analyzed to determine a change in a gas oil ratio with respect to depth. The change in the gas oil ratio may be employed to determine a ratio of solubility and entropy terms to a gravity term. The resulting ratio can be used to develop the equation of state model.

Abstract: Upper and lower asphaltene weight fractions of fluid proximate ends of an oil column are obtained based on measured OD. Upper and lower maltene partial densities are obtained based on the asphaltene weight fractions. A maltene partial density distribution is obtained utilizing the maltene partial densities and a predetermined diffusion model. An asphaltene partial density distribution is obtained based on the maltene partial density distribution and an estimated mass density gradient. An asphaltene weight percentage is obtained based on the asphaltene partial density distribution and the mass density gradient. The asphaltene weight percentage distribution is converted to an OD distribution utilizing a predetermined correlation. An optimization then reduces differences between the OD distribution and the measured OD data to within a predetermined range to refine a biodegradation time of the predetermined diffusion model. A viscosity distribution may be obtained based on the optimized OD distribution.