Balancing the amount and composition of gas contained in the pore space of cupriferous rocks

Abstract

From the perspective of economy and safety, balancing gas contained in the pore space of rocks is extremely essential, predominantly to establishments dealing with extraction of mineral resources. One of the main methods of evaluating the amount and composition of gas contained in the pore space of a rock is releasing the gas as a result of comminuting the investigated rock material. In the case of cupriferous rocks, effective comminution is a very difficult task, due to the strength properties of these rocks. The present paper discusses the results of studies into the gas content of cupriferous rocks, obtained by means of an original device named the GPR analyzer. The research was done on 41 samples of dolomites and anhydrites from various areas of two copper mines located in Poland: “Rudna” and “Polkowice-Sieroszowice.” For all samples, on the basis of microscope analyses performed on cuts and polished sections, the open porosity, closed porosity, and total porosity were determined. In the case of the dolomite samples, the total porosity variability fell in the range of 4.75–23.05%, and in the case of the anhydrite samples—in the range of 3.87–16.60%. The maximum gas content of the dolomite samples was 166.67 cm3/kg, and of the anhydrite samples—84.66 cm3/kg. In some of the studied samples, the presence of methane was confirmed. Toxic gases, such as H2S, were not found. The main gas in the pore space of the investigated rocks was nitrogen. Knowing the amount of the released gas and the value of the closed porosity in the investigated samples, the authors were able to estimate the pore pressure of the gas, whose maximum value was 0.583 MPa.