ElectroMagnetic Thickness Tool

Product Overview

The Electro-Magnetic Thickness Tool (EMT) is a cased-hole non-destructive downhole logging instrument based on electromagnetic induction principle. It quantitatively measures wall-thickness, metal loss, corrosion and structural defects of casing and production tubing. As a non-contact inspection device, it requires no fluid coupling medium, and can penetrate wellbore fluid, scale and cement sheath to evaluate multiple concentric tubular strings in one logging run. It is widely deployed for well-integrity surveillance in oil & gas vertical, deviated and horizontal wells.

Working Principle

The tool transmits low-frequency electromagnetic field via transmitting coils, which induces eddy currents within steel casing/tubing wall. The amplitude, phase and decay characteristics of secondary magnetic field generated by eddy currents are closely related to metal wall thickness, conductivity and permeability. Receiving coils capture the response signals, and proprietary inversion algorithms convert raw electromagnetic data into quantitative wall-thickness curves and defect profiles, realizing identification of inner-wall and outer-wall corrosion, pitting and metal loss.

Core Features

◆ Non-contact measurement No mechanical contact with pipe wall, no coupling fluid required. Works stably in gas-filled boreholes, heavy-oil wells and scale-covered tubular surfaces, where ultrasonic tools fail to perform well.

◆ Multi-string evaluation capability Capable of distinguishing and measuring wall thickness for multiple concentric casing/tubing strings, detecting corrosion and damage on outer casings behind cement sheath.

◆ Strong environmental adaptability High-strength pressure-bearing housing and high-temperature electronics support harsh HTHP downhole conditions. Suitable for wireline, slickline and memory logging modes.

◆ Comprehensive defect identification Detects uniform corrosion, pitting erosion, mechanical wear, cracks, perforations and local wall thinning, outputting circumferential thickness distribution along well depth.

◆ Modular & reliable mechanical design Compact tool-string structure, compatible with standard logging tool strings, applicable for highly-deviated and horizontal well logging operations.

Main Measurable Items

◆ Remaining wall thickness of casing & tubing

◆ Metal loss ratio, inner and outer corrosion degree

◆ Pitting, crack, mechanical wear and hole defects

◆ Multi-layer concentric tubular condition evaluation

◆ Collar position and ferromagnetic component locating

Typical Applications

· Long-term well integrity monitoring and casing corrosion surveillance

◆ Pre-workover casing condition assessment & remediation planning

◆ Multi-string completion inspection behind cement

◆ Evaluation for production/injection wells, thermal-recovery heavy-oil wells

◆ Pre-abandonment well condition verification

◆ Risk diagnosis for casing leakage and structural failure

Operating Specifications (General Reference)

◆ Max operating temperature: up to 220 °C

◆ Max operating pressure: up to 100 MPa

◆ Applicable pipe range: 2-3/8 in ~ 20 in tubing/casing

◆ Logging speed: 4-6 m/min

Deployment: wireline / memory / slickline conveyance