Evolutionary Response Model of Low Maturity Coal Measure Reservoir Space to Temperature-Water Pressure Under Hydrous Pyrolysis.

As an important unconventional oil and gas resource, the exploration and development of coalbed methane has attracted more and more attention. Since coalbed methane mainly exists in adsorbed state, it is important to study the pore space characteristics of coal for the analysis and prediction of coalbed methane content. Thus, in order to explore the evolutional characteristics of reservoir space during the thermal evolution of coal measure source rocks, two series of pyrolysis experiments as well as their corresponding pore structures were conducted. As the temperature and water pressure were the main factors to their organic matter and pores evolution, so temperature (250°C, 300°C, 350°C, 375°C, 400°C, 450°C and 500°C) and water pressure (10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa and 60 MPa) controlled experiments were analyzed. The experimental results show that temperature is positive to the organic matter evolution, and then in further promoted the development of pore structure. Namely, with the increasing thermal maturity, their corresponding pore volume, specific surface area as well as the numbers of macro-pores and micro-pores also gradually increased. But with the increasing water pressure, the pyrolysis productions did not changed obviously as well as their pore structures. It should be the reason of little effect of water pressure on organic matter evolution. Thus, the influence of water pressure on the development of pore structure is not significant compared with the variable temperatures, which has great influence on both liquid and gaseous hydrocarbons. Therefore, this study was helpful to the establishment of the linear equations on temperature and water pressure to the pore structures, which would be in further provide theoretical basis and guidance to the exploration and development of coals. [ABSTRACT FROM AUTHOR]