摘要:
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. Also, the function includes a ratio of a measured intensity at a first wavelength to a reference intensity, and the reference intensity is a function of a measured intensity at a second wavelength.
摘要:
A method for determining properties of a formation fluid including obtaining data related to an optical density at a methane peak and an optical density at an oil peak for a fluid sample at a plurality of times, calculating an apparent gas-oil-ratio of the sample fluid from the optical density of the fluid sample at the methane peak to the optical density of the fluid sample at the oil peak at each of the plurality of times based on the data, selecting a power function of a sampling parameter for a buildup of the apparent gas-oil-ratio, calculating an exponential constant of the power function based on the data, and determining at least one selected from the group consisting of a contamination free gas-oil-ratio and a percent contamination.
摘要:
Water-based mud filtrate concentration in a downhole fluid sample drawn from the borehole of an oil well is assessed. To measure water-based mud filtrate concentration, a water-based mud having a water-soluble fluorescent dye tracer is pumped into the borehole; sample fluid from a selected downhole location is pumped through a downhole flow line having a window; sample fluid flowing in an excitation region of the downhole flow line is illuminated through the window with fluorescence excitation light; and fluorescence emission from the excitation region is measured to produce a measured value. The measured value represents the fraction of water-based mud filtrate in the sample fluid. A calibration value is determined representing 100% water-based mud filtrate. A method for validating a sample of connate water as having an acceptably low WBM filtrate contamination tests for validation downhole, in real time. Each measured value of the series of measured values is compared with a predetermined fraction of a calibration value. Samples that are validated may be captured and brought to the surface for analysis. A method using the time series data and a predetermined fraction of the calibration value calculates a predicted flushing time to completion.
摘要:
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.
摘要:
Methods of calibrating a fluid analyzer for use in a wellbore are described. An example method of generating calibration data for a fluid analyzer for use in a downhole tool involves lowering a downhole tool including a fluid analyzer to a location in a wellbore, measuring, via the fluid analyzer, a characteristic value of a calibration fluid or a vacuum while the fluid analyzer is at the location, obtaining an expected characteristic value for the calibration fluid or the vacuum at the location, and comparing the measured characteristic value to the expected characteristic value to generate a calibration value for the fluid.
摘要:
A method for determining properties of a formation fluid is provided and includes: obtaining fluid data related to Carbon-Hydrogen molecular bonds in C6+ from a fluid analyzer; and considering the fluid data to calculate mass fractions of hydrocarbon flowing through the fluid analyzer. The method further includes computing gas-oil-ratio of hydrocarbon based on the mass fractions of hydrocarbon. Another method for determining a gas-oil-ratio of a formation fluid includes: obtaining fluid data related to Carbon-Hydrogen molecular bonds in C6+ from a fluid analyzer; considering the fluid data to derive mass fractions of gas and oil; and computing gas-oil-ratio of hydrocarbon based on the derived mass fractions.
摘要:
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. The value of phase transition pressure is determined by extrapolating from a representation of apparent phase transition pressure values versus OBM-contamination values.
摘要:
Methods of calibrating a fluid analyzer for use in a wellbore are described. An example method of generating calibration data for a fluid analyzer for use in a downhole tool involves lowering a downhole tool including a fluid analyzer to a location in a wellbore, measuring, via the fluid analyzer, a characteristic value of a calibration fluid or a vacuum while the fluid analyzer is at the location, obtaining an expected characteristic value for the calibration fluid or the vacuum at the location, and comparing the measured characteristic value to the expected characteristic value to generate a calibration value for the fluid.
摘要:
Methods and apparatus to determine a concentration of nitrogen in a downhole fluid are described. An example apparatus to determine a concentration of nitrogen in a downhole fluid includes a fluid measurement unit to measure a first fluid composition and a density of at least a hydrocarbon and carbon dioxide in a sample of the downhole fluid. Additionally, the example apparatus includes one or more sensors to measure at least a pressure and a temperature of the sample. Further, the example apparatus includes a processing unit to determine a first theoretical density based on at least the first fluid composition, the temperature, and the pressure the sample. Further still, the example apparatus includes an analyzer to determine a first difference between the density of at least the hydrocarbon and the carbon dioxide in the sample and the first theoretical density. The first difference is associated with a concentration of nitrogen in the sample.
摘要:
A gas separation and detection tool for performing in situ analysis of borehole fluid is described. A separation system such as a membrane is employed to separate one or more target gasses from the borehole fluid. The separated gas may be detected by reaction with another material or spectroscopy. When spectroscopy is employed, a test chamber defined by a housing is used to hold the gas undergoing test. Various techniques may be employed to protect the gas separation system from damage due to pressure differential. For example, a separation membrane may be integrated with layers that provide strength and rigidity. The integrated membrane separation may include one or more of a water impermeable layer, gas selective layer, inorganic base layer and metal support layer. The gas selective layer itself can also function as a water impermeable layer. The metal support layer enhances resistance to differential pressure. Alternatively, the chamber may be filled with a liquid or solid material.