The rock porosity meter is a device used to measure the percentage of pore volume to total volume (i.e. porosity) in rock samples, and is an important tool for evaluating the oil and gas storage capacity and engineering performance of rocks.
Main measurement principles
Gas permeation method: Based on Boyle's law, porosity is calculated by measuring the pressure changes of nitrogen or helium in rock samples. After injecting gas into the core, record the flow rate and pressure difference of the gas passing through, and calculate the porosity based on the sample volume.
Electrical resistivity measurement method: According to Ohm's law, rock pores hinder current flow, and the higher the porosity, the lower the electrical resistivity. By measuring the resistivity of standard samples, establish a mathematical relationship with porosity, and then calculate the porosity of the test sample.
Archimedes' principle method: Measure the volume change or fluid absorption of rock samples under different conditions, and calculate the porosity by combining density information. This method requires precise control of pressure, temperature, and quality measurement.
Type and Applicable Scenarios
Gas expansion method (helium porosity meter): Using helium as the medium, the porosity is calculated using Boyle's law, with high measurement accuracy and no damage to the sample. Suitable for high-precision scenarios such as scientific research and oil and gas exploration, it can measure total porosity and effective porosity.
Saturation weighing method (liquid immersion method): The porosity is calculated by the mass difference before and after the sample is saturated. The equipment is simple and the cost is low, but the measurement cycle is long and the accuracy may be affected by liquid residue. Suitable for scenarios such as engineering surveys and teaching that do not require high accuracy, it can only measure the total porosity.
Other types: mercury intrusion porosimetry (which can simultaneously measure porosity and pore size distribution), nuclear magnetic resonance (non-destructive, suitable for dynamic monitoring), often used in specialized research scenarios.
Operation and maintenance
Automation level: Fully automated instruments can reduce human error and improve efficiency.
Calibration convenience: supports fast calibration and reduces maintenance costs.
Durability: Choose instruments made of wear-resistant materials and designed to be dust-proof, suitable for outdoor or laboratory environments.