The problem of hydraulic fracture growth in a near wellbore region that has been cooled by injection or circulation of fluid is studied numerically. A transient 2D plane strain thermoelastic model is used to calculate the stress change associated with injection induced cooling. The cooling was calculated for a depth of 4,500 metres assuming water was circulated at 800 L/min to cool a section of the wellbore located in a granite rock mass. The bottom-hole temperature in the well was calculated by applying a well circulation model, which assumes the fluid is injected down a tubing string centered in the well with fluid returning up the annulus. Temperature and stress in the granite reservoir were calculated for circulation times (CTs) of 10 seconds, 5 hours, and 5 days. The resulting thermally modified stresses were then used as field stresses applied to a hydraulic fracturing model that explicitly descretises the wellbore. Injection pressure, fracture width, and fracture growth with time were compared for each cooling period for the three fracture geometry cases. Fracture growth through solid rock occurred in cases 1 while in case 2 the fracture growth occurred along the pre- defined path which contained a number of offsets. Case 3 consisted of a hydraulic fracture growing from the wellbore and intersecting two frictional natural fractures. Results from case 1 produced a bi-winged fracture from two small flaws at the well. The flaws were used to control initiation. We find that the mechanical opening increases as the confining stress decreases as a result of the cooling with time. The fluid pressure in the fracture is also decreased with progressive cooling. When the circulation time is short and little cooling occurs, the pressure increases quickly initially and then decreases gradually as the fracture extends. When the cooling effect is stronger, fracture initiation occurs at a lower pressure and the injection pressure increases as a monotonic function of time. The fracture growth rate is slower for the cooled wellbore case because the fracture opening is greater, increasing the fracture volume and decreasing the rate of growth for constant injection rate simulations. Case 1 provides a base case for planar fracture growth that is compared to the non-planar fractures produced in cases 2 and 3. Case 2 consists of fracture propagation along a predefined path containing offsets. The injection pressure is decreased as cooling increases. Near well pressure losses are reduced especially over the more strongly cooled region near the well. Higher pressures are required to extend the fracture through offsets in the path. The thermoelastic stress change induced by pre-cooling the well has a first order effect on fracture initiation pressure and near wellbore fracture opening. The paper contains results that include fracture growth and interaction with frictional natural fractures where the hydraulic fracture path is modified by the cooling.

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