Non-magnetic Resistivity Measuring Instrument

I. The core requirements and instrument positioning for logging scenarios

The core goal of petroleum logging is to determine the oil content of a reservoir based on the formation resistivity (the resistivity of the oil layer is much higher than that of the water layer). However, during logging while drilling, downhole tools such as non-magnetic drill collars and magnetic stabilizers need to maintain extremely low magnetic permeability (μ ᵣ ≤ 1.05) to avoid interfering with the magnetic field signal of the logging instrument. The non-magnetic resistivity measuring instrument used for logging has a dual positioning:

1. Formation resistivity measurement: As the core sensor of the logging system, the non-magnetic design avoids the interference of the instrument's own magnetic field on the electromagnetic response of the formation, ensuring the accuracy of reservoir parameter measurement.

2. Self inspection of downhole tools: Real time measurement of the electrical resistivity of non-magnetic drill collars and other tools to determine their material uniformity and corrosion degree, and prevent downhole tool failure.

II. Characteristics of specialized logging technology

1. No magnetic structure design.

The probe, housing, and electrodes are all made of non-magnetic alloys (such as Monel alloy and non-magnetic stainless steel), and the circuit has no magnetic core components. The relative magnetic permeability is less than or equal to 1.01, completely eliminating interference with logging magnetic signals.

The electrode is coated with wear-resistant and corrosion-resistant materials, which can withstand the erosion of drilling mud and underground acidic and alkaline environments.

2. Has high temperature and high pressure resistance performance.

The working temperature range can reach -50 ℃~200 ℃, and the pressure resistance level is ≥ 140MPa (suitable for deep and ultra deep well logging), meeting the long-term stable operation of extreme underground conditions.

3. Strong anti-interference ability.

Anti drilling fluid flow interference: The probe adopts a streamlined design to reduce the impact of mud flow on electrode contact; It is built in filtering algorithm to eliminate signal noise caused by conductive particles in the mud.

Anti electromagnetic interference: The shielding layer wraps around the circuit to resist electromagnetic radiation from downhole motors and other logging instruments, ensuring the accuracy of resistivity measurement.

4. Real-time data transmission.

Equipped with mud pulse or electromagnetic wave transmission modules, the measured formation/tool resistivity data is uploaded in real time to the surface control system to achieve real-time analysis and decision-making while drilling.

III. Precautions for use

1. Confirm temperature and pressure resistance parameters: Select the corresponding level of instrument based on the depth and bottom temperature of the target well to avoid using beyond the range;

2. Calibration requirements: Before going down the well, standard non-magnetic test blocks and formation simulation blocks should be used for calibration to ensure that the measurement error is within ± 1%;

3. Maintenance points: Clean the probe electrode after each logging, check for deformation and corrosion of non-magnetic components, and replace worn coatings in a timely manner.