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A device and method for measuring fluid conductivity

A conductivity and fluid technology, applied in the direction of fluid resistance measurement, material resistance, etc., can solve problems affecting measurement accuracy, signal drift, etc., to achieve the effects of ensuring measurement accuracy, eliminating temperature drift, and reducing production costs

Active Publication Date: 2015-12-02
CHINA NAT OFFSHORE OIL CORP +1
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Problems solved by technology

However, the magnetic permeability of the iron core will change nonlinearly with the change of temperature, which will cause signal drift and affect the measurement accuracy; therefore, the coil type fluid conductivity sensor is generally used in room temperature environment, and special measures must be taken in high temperature environment. Solve the contradiction between the sensitivity and temperature stability of the iron core coil

Method used

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  • A device and method for measuring fluid conductivity
  • A device and method for measuring fluid conductivity
  • A device and method for measuring fluid conductivity

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Embodiment

[0095] Generally, the temperature range of the monitoring fluid for cable formation testing is 25°C to 150°C, the selection range of the winding resistance is between 100 and 1K ohms, and the power supply part of the winding transmitting coil is a sinusoidal excitation voltage with an amplitude of 20v and a frequency of 20kHz to 40khz; preferably 20V, 20kHz AC power supply.

[0096]In this embodiment, 25°C to 150°C can be selected as a sampling point with a temperature interval of 25°C, and 6 sample points are selected, assuming that the relationship between the induced voltage generated by the transmitting coil at both ends of the receiving resistor with temperature can be expressed as Relational formula: f(t)=At 3 +Bt 2 +Ct+D; the coefficients A, B, C, and D in the above formula are obtained by inversion of f(t) values ​​measured at six sample temperature points.

[0097] In order to invert more accurately the relationship between the voltage of the transmitting coil at bo...

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Abstract

The invention discloses a fluid conductivity sensor, and a device and a method for measuring fluid conductivity, and relates to the field of wireline logging. The method comprises the following steps: detecting voltage values of the two ends of a receiving resistor at different temperatures when no fluid passes to obtain multiple groups of first voltage values; inverting a relationship between induced voltages generated at the two ends of the receiving resistor by a transmitting coil and temperature variation according to the relationship between the multiple groups of first voltage values and temperature variation; detecting the voltage values of the two ends of the receiving resistor at different temperatures when fluid to be monitored passes to obtain multiple groups of second voltage values; calculating to obtain a relationship between the fluid conductivity and temperature variation according to the relationship between the induced voltages generated at the two ends of the receiving resistor by the transmitting coil and temperature variation and the multiple groups of second voltage values. Due to the design that a winding is connected in parallel with the fluid conductivity sensor and a matched circuit is provided, temperature compensation of the sensor is realized, and measuring accuracy of the coil type fluid conductivity sensor under a high-temperature environment is guaranteed.

Description

technical field [0001] The invention relates to the field of cable logging, in particular to a downhole fluid conductivity sensor and a method for measuring fluid conductivity. Background technique [0002] When the cable formation tester pumps the formation fluid, it needs to monitor the conductivity of the fluid in real time, so as to judge the fluid characteristics and distinguish the formation fluid and the wellbore mud. Therefore, it is necessary to install a fluid conductivity sensor that can work in an underground high temperature environment. [0003] The coil sensor has the characteristics of non-contact and maintenance-free, and is suitable for fluid conductivity detection. These sensors use a pair of mutual induction coils to measure fluid conductivity. In order to improve the sensitivity, a high permeability iron core coil is usually used. Under normal temperature environment, the accuracy and repeatability of this sensor are very good. However, the magnetic ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N27/18G01R27/22
Inventor 刘畅李小邦
Owner CHINA NAT OFFSHORE OIL CORP
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