Memory Pulsed-Neutron Decay Tool


Determines water and hydrocarbon saturation in mixed-salinity environments


  • Identifying formation-fluid contact
  • Identifying bypassed pay zones or depleted reservoirs
  • Differentiating low-porosity from gas-filled formations by using bulk inelastic measurements
  • Identifying water production in and behind casing
  • Assessing gravel-pack performance issues

Features and Benefits

  • The 5/8-in. sucker-rod connection enables running the memory pulsed-neutron decay (MPND) tool in combination with other tools, such as the slim Sector Bond® tool, for simultaneous formation and cement evaluation in a single logging run.
  • Lithium ion batteries, augmented with proprietary power-management hardware, enable up to 14 hours of continuous operation.
  • The memory system enables the tool to be conveyed on slickline or wireline, or with coiled tubing, in vertical or horizontal wells for maximum operational flexibility and efficiency with reduced logistical costs.
  • The memory gamma ray casing-collar locator (MGRC-A) provides depth correlation and formation gamma ray. The MGRC-A also functions as a safety sub by combining pressure, programmable temperature, and time delay to prevent inadvertent activation of the neutron generator at the surface.
  • The electronics section controls the pulsing of the neutron generator to create clouds of neutrons at 14 million electron volts (MeV). These high-energy neutrons collide with elements in the borehole and the formation to release gamma radiation for capture and inelastic interactions.
  • The tool delivers depth-based energy spectrum, which can be used to identify lithology and the presence of certain elements in the formation.

Tool Description

The memory pulsed-neutron decay ( MPND) tool acquires and records data that can be used to determine water saturation (Sw) and hydrocarbon saturation (SHC) in mixed-salinity environments. The MPND tool combines conventional capture cross-section measurement (Σ) and porosity with bulk inelastic measurement in a single tool.

When limited space or rig-up height constrains operations, the MPND tool acquires the data needed to inform critical reservoir-management decisions. The memory section enables multiple deployment options for maximum versatility and efficiency.