Inline Flowmeter Jewel (IFJ / IFJM)

General Description

The Inline Flowmeter Jewel (IFJ / IFJM) is a caged‑spinner production‑logging flowmeter widely deployed in PLT (Production  Logging Tool) strings. It adopts jewelled (sapphire‑based) pivot bearings to support the spinner assembly, which drastically reduces mechanical friction and lowers spinner start‑up threshold, delivering enhanced sensitivity for low‑velocity flow conditions.

Different from expandable full‑bore spinners, this inline tool features a fixed enclosed shroud. Fluid passes through the tool body directly. Spinner rotation is contactlessly captured by Hall‑effect magnetic sensors, generating pulse outputs proportional to spinner revolutions. It can discriminate upward and downward flow directions for cross‑flow identification. The compact inline architecture allows it to be concatenated at any position within the logging tool string, normally run at the bottom of the PLT assembly. It supports both surface‑readout and memory‑mode logging operations.

Working Principle

Downhole fluid impinges on the caged spinner and drives rotation. Jewel bearings minimise pivot friction so the spinner responds to low flow velocities. Integrated magnets rotate with the spinner, triggering the Hall‑effect sensor to produce pulse signals. Each revolution outputs fixed pulses (typically 8‑10 pulses/rev). Surface acquisition systems convert pulse frequency into borehole fluid velocity, and volumetric flow rate is calculated with known borehole/tubing inner diameter.

Key Features

◆Low‑threshold measurement: Jewelled bearing design achieves low spinner threshold, well‑suited for gas‑well and low‑rate well surveillance.

◆Sand‑resistant rugged construction: Protected by solid shroud housing; jewel bearings show better survivability in sand‑producing wells compared with conventional metal‑on‑metal bearings.

◆Full‑deviation capability: Valid measurement performance from vertical wells through highly‑deviated and horizontal wells.

◆Direction‑sensitive output: Distinguishes upward production flow and downward cross‑flow / backflow.

◆Good combinability: Compact OD options (1‑11/16 in, 2‑1/8 in) for tubing, casing, slotted liners and sand‑screen completions; compatible with pressure, temperature, holdup and density sensors in multi‑sensor strings.

Typical Applications

◆Production‑profile logging: Quantify zone‑by‑zone fluid contribution in producers

◆Injection‑profile logging for water‑injector wells

◆Diagnose cross‑flow, packer leaks and channeling behind casing

◆Surveillance for gas wells, sand‑producing wells and horizontal / high‑angle wells

◆Logging inside sand‑screens and slotted liner completions

Representative Technical Specifications