Sensitivity Analysis of Oil and Gas Production in the In Situ Pyrolysis of Oil Shale

The Maoming basin in south China is rich in oil shale resources, whereas the Youganwo formation is a potential area for large-scale in situ exploration because of its relatively large thickness, high oil content, and good continuity. Based on previous geologic studies on the Maoming basin and the laboratory experimental data, in situ pyrolysis models for shale oil are established using the CMG-STARS software to simulate the in situ heating and reactions. To analyze the major influencing factors, the CMOST module is employed to conduct the sensitivity analysis with accumulated oil and gas production as the target functions. The initial kerogen concentration, formation permeability, activation energy of pyrolysis reaction, frequency factor, heating rate, heating power, heat loss, heat conductivity, heat capacity, and bottom-hole pressure are chosen to be the controlling parameters. A total of 128 cases are calculated for each target function with the fractional factorial sampling method. The sensitivity analysis results demonstrate that the heating power, initial kerogen concentration, and reaction activation energy are the major influencing factors for oil and gas production. The simulation results also reveal that high non-uniformity of the temperature field will cause the light oil to convert to gas and char at the high-temperature zone near the heater well. It is suggested that proper control of formation temperature, such as increasing permeability to promote oil and gas flow and form a more uniform temperature field, will help to prevent oil production loss caused by secondary reactions.