Measurements of rock parameters

Abstract

Methods and apparatus to measure physical parameters such as density and porosity of the rock matrix in a near wellbore area are provided. A borehole tool having a number of transducer elements in a transducer array is placed at an outermost surface of the borehole tool and is capable of emitting focused high frequency ultrasound beams into the rock matrix in the near wellbore area. The transducer array may be placed on the ribs or stabilizers of the borehole tool, and/or on a sleeve with a lower rotational speed, and may include a fronting material with similar acoustic impedance as the rock matrix. A method for measuring physical parameters of the rock matrix in a near wellbore area is also provided where a focused high frequency ultrasound beam is emitted into the rock matrix in the near wellbore area from one or more transducer arrays on a borehole tool.

Description

FIELD OF THE INVENTION[0001]The present invention relates to methods and apparatus to measure physical parameters such as density and porosity of the rock matrix in a near wellbore area as well as the type(s) of fluid present in the near wellbore area.BACKGROUND[0002]In geological exploration and development, formation evaluation indicating the physical properties of a volume of rock next to the borehole is used to determine e.g. whether a potential oil or gas field is commercially viable. Extrapolation of the properties beyond the measurement volume further requires a geological model.[0003]Physical properties of the near wellbore rock are generally evaluated by measurements-while-drilling (MWD), Logging-while-drilling (LWD), by different wireline tools or combinations hereof.[0004]Measurements-while-drilling (MWD) in general covers the collection of directional data enabling well trajectory description in three-dimensional space while extending the wellbore, and also includes pres...

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Benefits of technology

[0030]In a further embodiment the method further comprises emitting series of beams of different focal point positions and/or of different frequencies. By controlling the focal point positions and frequencies, more precise measurements can be obtain...

Problems solved by technology

Further, many wellbores prove to be difficult or even impossible to measure with conventional wireline tools, especially highly deviated wells where hole stability issues may be time critical.

Most wireline measurements are recorded continuously while the sonde is moving, however certain fluid sampling and pressure-measuring tools used for formation sampling require that the sonde be stopped, increasing the risk that the sonde or the cable mi...

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