Schlumberger Technology Corporation

Robert P Zimmerman

Andrew L Kurkjian

Jonathan Webster Brown

Victor Matthew Bolze

Angus J Melbourne

Timothy L Long

Linward A Moore

Edward Harrigan

A sample module is provided for use in a downhole tool to obtain fluid from a subsurface formation penetrated by a wellbore. The sample module includes a sample chamber carried by the module for collecting a sample of formation fluid obtained from the formation via the downhole tool, and a validation chamber carried by the module for collecting a substantially smaller sample of formation fluid than the sample chamber. The validation chamber is removable from the sample module at the surface without disturbing the sample chamber. A sample chamber is also provided that includes a substantially cylindrical body capable of safely withstanding heating at the surface, following collection of a formation fluid sample via the downhole tool and withdrawal of the sample chamber from the wellbore, to temperatures necessary to promote recombination of the sample components within the chambers. Additionally, the body is equipped so as to be certified for transportation. At least one floating piston is slidably positioned within the body so as to define a fluid collection cavity and a pressurization cavity, whereby the pressurization cavity may be charged to control the pressure of the sample collected in the collection cavity. A second such piston may be provided to create a third cavity wherein a buffer fluid may be utilized during sample collection. Metal-to-metal seals act as the final shut-off seals for the sample collected in the collection cavity of the body. A method related to the use of the sample module and sample chamber described above is also provided.

Formation fluid sampling apparatus and method

A sample module is provided for use in a downhole tool to obtain fluid from a subsurface formation penetrated by a wellbore. The sample module includes a sample chamber carried by the module for collecting a sample of formation fluid obtained from the formation via the downhole tool, and a validation chamber carried by the module for collecting a substantially smaller sample of formation fluid than the sample chamber. The validation chamber is removable from the sample module at the surface without disturbing the sample chamber. A sample chamber is also provided that includes a subtantially cylindrical body capable of safely withstanding heating at the surface, following collection of a formation fluid sample via the downhole tool and withdrawal of the sample chamber from the wellbore, to temperatures necessary to promote recombination of the sample components wihtin the chambers. Additionally, the body is equipped so as to be certified for transportation. At least one floating piston is slidably positioned within the body so as to define a fluid collection cavity and a pressurization cavity, whereby the pressurization cavity may be charged to control the pressure of the sample collected in the collection cavity. A second such piston may be provided to create a third cavity wherein a buffer fluid may be utilized during sample collection. Metal-to-metal seals act as the final shut-off seals for the sample collected in the collection cavity of the body. A method related to the use of the sample module and sample chamber described above is also provided.

A flow-control apparatus enables the taking of representative formation samples at sampling rates less than 10 cc/sec in typical high pressure wells, e.g., to 20,000 psi. Throttle valves are used to control pressure drawdown in the flowline and to continue that pressure control until captured in a sample chamber. Very low flow rates at high pressures are made possible by using a motor-driven, variable orifice, needle valve (throttle valve) and a downhole feedback loop on the piston position. The flow control device uses metered fluid, which is internally contained oil, which overcomes the difficulty of trying to meter 'dirty' (particle laden) well fluids or dual phase gas-liquid fluids. A single probe module (or a dual packer) is coupled with a multi-sample module and the flow control module. This combination can then be used to draw a sample from the formation at a very low flowrate and, hence, a very low pressure differential which keeps the sample pressure above the bubble point (or dew point). In a gas well with condensates or volatile oil, this procedure is extremely important since the sample will contain a realistic fraction of the liquids in the well. If the flowline pressure is dropped below the dew point, the gas expands and fills the sample chamber, leaving the liquids behind and an unrepresentative sample is obtained. The present invention provides the unique ability to obtain a quality sample from low permeability, high pressure formations.

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Friendswoods, TX, United States of America

Robert P Zimmerman