Gas In Situ Determinations

Methane gas in situ determination provides you with an accurate measurement of the volumes of desorbed gas, residual gas and lost gas in a coal seam. SGS staff use the direct method for gas in situ determination. We determine the methane content of the coal by precisely measuring the total volume of gas released from the core samples taken from the seam.

Immediately after drilling, the sample is collected. It is sealed in a specially designed canister, which allows us to measure the volume of gas with high accuracy. It is then shipped to an SGS laboratory with expertise in this type of analysis. Here, the actual release (desorption) of the total volume of gas is determined in three stages:

1. Measurement of desorbed gas
2. Determination of residual gas
3. Estimation of lost gas

For the first few hours of analysis, the volume of desorbed gas released from the sample is regularly measured at short intervals. This data is later used to estimate the lost gas released during retrieval and handling at the surface. The volume of released gas is measured over increasingly longer intervals until the volume decreases to 0.05 ml/g/day for several days.

Once the sample effectively stops releasing gas, SGS staff weigh and prepare the sample for the determination of residual gas. Core samples are crushed and the volume of residual gas measured through water displacement. Finally, the volume of lost gas is calculated graphically. Data for a number of variables including drilling medium, drilling times, times for reaching the surface and time sealed in the canister are applied to reach an accurate volume of lost gas. The actual gas content of the sample is calculated by adding the volumes of desorbed gas, residual gas and lost gas.

Contact us to learn how you can assess the availability of value-added methane in your operation.