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Caliper log

Jan 15, 2017

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Science

Saad Raja
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Page 1: Caliper log
Page 2: Caliper log

PRESENTATION ON CALIPER LOG

Department of GeologyUniversity of AJ&K

Muzaffarabad

Page 3: Caliper log

What is well Logging Well log is a continuous record of measurement

made in bore hole respond to variation in some physical properties of rocks through which the bore hole is drilled

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•Caliper tools measure hole size and shape. •The simple mechanical caliper measures a vertical profile of hole diameter. •The more sophisticated geometry tools records two simultaneous calipers and give an accurate borehole shape and orientation.

Caliper Log

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Caliper log

showing hole

Diameter and

some Typical

Responses

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Schematic Caliper tool showing the conversion of a mechanical movement to an electrical signal using a variable resistance

Function of the Tool:•The mechanical caliper measures variations in bore hole diameter with depth.• The measurements are made by two articulated arms pushed against the borehole wall. •The arms are linked to the cursor of a variable resistance. Lateral movements of the arm is translated into the movements of the cursor along the resistance, and hence variation in electrical out put. •The variations in output are translated into diameter variations after a simple calibration.

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•The Caliper Log is a tool for measuring the diameter and shape of a borehole. It uses a tool which has 2, 4, or more extendable arms.

•In the 4 arm (dual caliper) tool, the two opposite pairs work together to give the borehole diameter in two perpendicular directions.

•An example of a 4 arm tool is the Borehole Geometry Tool (BGT).

•This has 4 arms that can be opened to 30 inches (40 inches as a special modification), and give two independent perpendicular caliper readings.

•In the multi-arm tools, up to 30 arms are arranged around the tool allowing the detailed shape of the borehole to be measured.

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Various types of caliper Mechanical Caliper -arm averaging� Ultrasonic Caliper -An Ultrasonic transducer scans �

around the borehole walls, and the reflected travel time is converted to the distance between the sonde and the wall.

Acoustic caliper – calculated from acoustic transit time and velocity

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Mechanical 3-arm averaging caliper

Mechanical 2 arm caliper

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3D image of the ultrasonic caliper. (From Schlumberger)

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Presentation of the Caliper Logs: 1. in ordinary format; 2. in differential format; BS = Bit size

•The caliper log simply is a measure of continuous value of hole diameter with depth. •The curve is traditionally a dashed line. •The horizontal scale may be in inches of diameter or in differential caliper, expressed as increase or decrease in hole diameter about a zero defined by the bit size. •The ordinary caliper log is accompanied by a reference line indicating bit size.

Caliper Log Presentation

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•In a logging context, the greatest application of caliper data is in environmental corrections to other logs that are sensitive to hole size such as Natural gamma ray , Density, Neutron logs.

•Contributory information for lithological assessment.

• Indicator of good permeability and porosity zones (reservoir rock) due to development of mudcake in association with gamma ray log.

•Calculation of mudcake thickness, hmc = (dbit– dh)/2, where h stands for the hole, in inches.

Uses of the Caliper log

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•Selection of consolidated formations for wire line pressure tests, recovery of fluid samples, for packer seating for well testing purposes, and for determining casing setting depths.

•calipers can be used to center logging-tool strings.

•Open hole caliper data are used to estimate the volumes of gravel and cement needed for well-completion planning.