Landfill gas production testing and extraction method

A method of controlling an extraction rate of gas from ground at various positions in the ground at which the gas is extracted, the method comprising the steps of:

• determining gas pressure below a surface of the ground at multiple locations with respect to the surface;
• determining a relative permeability of the ground to the gas at each of the locations;
• calculating an adjusted value of the gas pressure at each of the multiple locations based on the relative permeability;
• and
• adjusting the extraction rate at each of the positions in the ground at which the gas is extracted based on relative flow of the gas into and out of the ground as indicated by the adjusted values of the gas pressure.

A method of controlling an extraction rate of gas from underground positions in a landfill comprising trash and a cover layer, the method comprising the steps of:

• determining gas pressure relative to a reference pressure at a predetermined depth in the cover layer at multiple locations with respect to a surface of the landfill;
• determining permeability of the cover layer to the predetermined depth at each of the multiple locations relative to a reference amount;
• dividing each gas pressure by each relative permeability, respectively, to obtain a relative flow;
• obtaining a spatial distribution of the relative flow;
• and
• increasing the extraction rate at positions corresponding to positive flow and decreasing the extraction rate at positions corresponding to negative flow, where positive flow represents gas flow out of the landfill and negative flow represents air flow into the landfill.

A method of extracting gas from various underground positions and determining an additional amount of gas that can be extracted from the underground, the method comprising the steps of:

• extracting the gas;
• determining gas pressure relative to a reference pressure at a predetermined depth underground at multiple locations with respect to a surface of the ground;
• determining permeability of the ground to the predetermined depth at each of the multiple locations relative to a reference amount;
• dividing each gas pressure by each relative permeability, respectively, to obtain a relative flow having areas of negative relative flow and positive relative flow;
• obtaining a spatial distribution of the relative flow;
• and
• determining an amount of additional gas that can be extracted by summing up relative positive flow amounts to obtain a total positive relative flow and multiplying the positive relative flow by a calibration factor, the calibration factor being obtained by determining a total flow rate of air into the ground, summing up the negative relative flow rate to obtain a total negative relative flow, and taking a ratio of the total flow rate of air and the total negative relative flow.