Investigating the thermal effects on hydraulic fracturing propagation and response of numerical models

Ignoring thermal effects in many applications of geomechanics including hydraulic fracturing of deep oil and gas reservoirs and geothermal energy extraction may result in significant errors in output. Production and stimulation of unconventional oil and gas reservoirs is highly dependent on performance of hydraulic fracturing (HF) jobs. These jobs create a network of fractures which are responsible for elevated hydraulic conductivity of the reservoir formation around the wellbore. The fractures increase inflow of hydrocarbons into the wellbore especially in low permeability reservoirs. A sound understanding of HF’s behavior and its relation to the increased production rate, decreases high costs of HF jobs. Thermal effects on HF propagation and mechanism are studied in this paper using the displacement discontinuity method. Firstly, the thermal effects on a thermoelastic model with a thermal source was studied. Models showed that boundaries of the geometrical model should be place farther from what was expected in elastic analyses to avoid boundary effects. The thermal effects were observed far away from the thermal source in the models.Then, thermal effects on a hydraulic fracture was modeled. It was shown that using a cold fluid for HF can decrease the required HF pressure for propagation. The HF width was also increased compared to an elastic model. This is an important parameter in determining hydraulic conductivity of the formation. The lower required pressure for HF propagation reduces the cost of equipment needed for the job, since they are not required to work at very high pressures.