Link points to Internet Archive / others. Not hosted by InfraLens. Details
IS 14436:1997 is the Indian Standard (BIS) for method of test for laboratory determination of resistivity on rock specimen. This standard specifies the laboratory method for determining the electrical resistivity of saturated cylindrical rock specimens. It details the apparatus, specimen preparation, test procedure, and calculation method required for the test.
Method of test for laboratory determination of resistivity on rock specimen
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Ensuring complete saturation of the rock specimen is critical for accurate and repeatable results, as trapped air will significantly increase measured resistivity.
! Good, uniform contact between the specimen ends and the electrodes is essential to avoid contact resistance errors. A conductive paste or saturated filter paper is often used.
! The resistivity of the saturating fluid must be measured and reported, as it heavily influences the bulk resistivity of the rock specimen.
Suggested Method for Laboratory Determination of the Electrical Resistivity of Rock (1981)ISRM (International Society for Rock Mechanics and Rock Engineering)
HighCurrent
Suggested Method for Laboratory Determination of the Electrical Resistivity of Rock
Defines laboratory procedures for determining rock specimen resistivity, forming a basis for many national standards.
API RP 40 (1998)API (American Petroleum Institute), USA
HighCurrent
Recommended Practice for Core Analysis
Covers electrical property measurements on core samples as part of a comprehensive core analysis workflow for the petroleum industry.
ASTM C1760-20ASTM International, USA
MediumCurrent
Standard Test Method for Bulk Electrical Conductivity of Hardened Concrete
Measures bulk electrical conductivity (inverse of resistivity) on saturated cylindrical specimens, using similar principles but for concrete.
ASTM G57-20ASTM International, USA
LowCurrent
Standard Test Method for Field Measurement of Soil Resistivity Using the Wenner Four-Electrode Method
Focuses on in-situ field measurement of soil resistivity, not laboratory determination on rock core specimens.
Key Differences
≠IS 14436 mandates a two-electrode measurement system, whereas API RP 40 discusses both two-electrode and four-electrode systems, the latter being preferred in special core analysis to eliminate contact resistance errors.
≠API RP 40 places strong emphasis on using saturating brines that chemically and electrically match the rock's native formation water, a critical factor for reservoir evaluation which is less stringent in IS 14436 (mentions tap water or NaCl solution).
≠While IS 14436 specifies a minimum specimen diameter of 47 mm, API RP 40 practices are often adapted for smaller 'plug' samples (e.g., 25.4 mm or 38.1 mm diameter) common in the oil and gas industry.
≠IS 14436 and the ISRM method are generally for geotechnical and civil engineering applications, whereas API RP 40 is explicitly tailored for petrophysical evaluation in hydrocarbon exploration and production.
Key Similarities
≈All standards are based on the fundamental principle of calculating bulk resistivity (ρ) from a measured resistance (R) and the specimen's geometry (ρ = R × A/L).
≈The requirement to fully saturate the rock specimen with a conductive fluid prior to measurement is a common and critical step in IS 14436, ISRM, and API RP 40 procedures.
≈To mitigate electrode polarization and ionic effects at the electrode-rock interface, all relevant standards (IS, ISRM, API) recommend or mandate the use of an alternating current (AC) for the resistance measurement.
≈Both the Indian and international standards (notably ISRM and API) utilize the concept of the Formation Resistivity Factor (F = ρ_rock / ρ_fluid) as a key derived parameter that relates to the rock's pore structure.
Parameter Comparison
Parameter
IS Value
International
Source
Specimen L/D Ratio
2.0 to 2.5
2.0 to 2.5
ISRM (1981)
Minimum Specimen Diameter
≥ 47 mm
≥ 50 mm (ISRM); often smaller (e.g., 25.4 mm) for core plugs (API)
ISRM (1981) / API RP 40
Measurement System
Two-electrode system
Two-electrode or Four-electrode system
API RP 40
Measurement AC Frequency
Preferably 1 kHz
Typically 1 kHz, within a range of 50 Hz to 20 kHz
ISRM (1981)
Saturation Fluid
Tap water or NaCl solution of known concentration
Brine of known resistivity, often simulating formation water
API RP 40
Saturation Procedure
Vacuum saturation for 24 hours
Vacuum saturation until constant weight is achieved
ISRM (1981) / API RP 40
Key Derived Parameter
Resistivity (ρ_r) and Formation Factor (F)
Resistivity (ρ_o) and Formation Factor (F)
API RP 40
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
specimen shapeRight circular cylinder
specimen length to diameter ratio2.0 to 2.5
minimum specimen diameterNX size (approx 54 mm)
saturating fluid resistivity5 to 10 ohm.m (tap water) or specimen pore fluid
test frequencyLow frequency AC to minimize polarization effects
Key Formulas
ρ = R * (A / L) — Electrical resistivity, where R is resistance, A is cross-sectional area, L is length
A right circular cylinder with a length to diameter (L/D) ratio between 2.0 and 2.5. The diameter should not be less than NX size (approx. 54 mm) (Clause 5.1).
Why is the test performed on a saturated specimen?+
To measure the resistivity of the combined rock-fluid system, which is more representative of in-situ conditions below the water table. The pore fluid is the primary conductor in most rocks.
What is the formula used to calculate resistivity?+
ρ = R * (A / L), where ρ is resistivity in ohm-metres, R is the measured resistance, A is the cross-sectional area, and L is the specimen length (Clause 7.1).
Why is low-frequency AC current used instead of DC?+
To minimize electrode polarization and electrolytic effects at the rock-electrode interface, which can cause erroneous voltage readings with a DC source (Clause 4.1).