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Statewide Well Surveys LLC

Electric Log · Gamma-Ray (GR) · Caliper · Sonic Velocity — Variable Density · Deviation

Open Hole Logging Services

Performed after the well is drilled but before casing is installed — the one window when tools can read the formation directly. SWS runs a full suite of open-hole tools to characterize the formations, help identify potential water-bearing zones, and provide the data needed to make informed well-completion decisions.

Cutaway view of an open borehole with a geophysical logging tool being run into the water
Tools & Techniques

The Open Hole Suite

An open-hole survey combines several tools, each reading a different property of the formation. Select one to see what it measures, what it tells you, and when it is used.

Electric Log (E-Log)

The Electric Log measures the natural electrical potential (SP) and electrical resistivity of the formations surrounding the borehole. These measurements help identify changes in formation characteristics and electrical properties with depth.

What it tells you

Formation boundaries and changes in formation resistivity that can help identify potential water-bearing zones.

When to use it

A primary open-hole logging tool used to evaluate subsurface formations, correlate geologic units, and assist with identifying potential aquifer zones and selecting screen intervals.

Gamma-Ray (GR)

The Gamma Ray log measures the natural gamma radiation emitted by the formations surrounding the borehole. It is commonly used to identify changes in lithology, particularly the contrast between clay-rich formations and cleaner sands, gravels, and other formations.

What it tells you

Changes in formation lithology and the location of clay-rich versus cleaner formation intervals.

When to use it

Used for lithologic correlation, identifying formation boundaries, and correlating geologic units between wells. Gamma Ray can also be logged through many types of casing, making it useful for depth correlation in both open and cased holes.

Laterolog 3 (Guard / LL3)

The Laterolog 3, or Guard log, is a focused resistivity tool that forces current straight into the formation. That focusing produces sharp, accurate resistivity readings in thin beds and in boreholes drilled with salty or conductive mud, where a standard electric log struggles.

What it tells you

Focused formation resistivity with improved definition of bed boundaries and formation resistivity contrasts.

When to use it

In thin-bedded formations or salty, conductive drilling fluid, where standard resistivity readings lose resolution.

Caliper Log

The caliper log measures changes in borehole diameter as the tool is pulled up the hole. It maps washouts and cave-ins where soft formations have enlarged the hole, along with tight spots where the hole is undersized.

What it tells you

Borehole diameter and condition — where the borehole is washed out, on-gauge, or tight.

When to use it

Before setting casing or cementing. Caliper data sizes screen and casing and calculates accurate cement volumes.

Sonic Velocity — Variable Density

The Sonic log measures the travel time of an acoustic signal through the formation. The Variable Density Log (VDL) provides a visual display of the received acoustic waveform, allowing changes in formation properties and acoustic response to be evaluated with depth.

What it tells you

Changes in formation acoustic velocity, formation characteristics, and relative formation competency. Sonic data can also be used in evaluating formation porosity when appropriate conditions and interpretation methods are applied.

When to use it

When additional formation characterization, acoustic velocity, competency, or porosity-related information is needed to supplement other open-hole logs.

Temperature & Fluid Resistivity

These logs record the temperature and electrical resistivity of the fluid column in the open borehole from top to bottom. Changes in temperature or fluid resistivity can indicate fluid movement, inflow zones, or changes in borehole-fluid characteristics.

What it tells you

Changes in the fluid column that can help identify potential inflow zones and differences in fluid characteristics with depth.

When to use it

When clients want fluid-column and inflow data in open hole; often run alongside the electric and gamma logs before casing.

Deviation / Verticality Survey

A deviation survey measures how far the borehole has drifted from vertical and in which direction. Water wells are meant to be plumb, but drilling through changing formations causes drift.

What it tells you

The measured path of the borehole — its deviation from vertical and direction with depth.

When to use it

Before pump and casing installation, and on any well with regulatory verticality or straightness requirements.

Related Services

Explore More

Cased Hole Services→ Geophysical Well Logging→ Modern Digital Logging→

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(909) 801-0262 statewidewellsurveys@gmail.com