*4.3. Injecting Temperature*

Steam injection has been most widely used and effective in thermal technology [20]. The steam is injected into the wellbore to decrease the hydrocarbon viscosity. Then, it displaces the hydrocarbon towards the wellbore for production [21]. Instead of the steam injection, hot water injection can be an attractive alternative option. Though hot water injection is less efficient than the steam injection, it is more versatile even in clay-bearing reservoirs, where the steam injection cannot be implemented. The hot water injection is also more suitable for deep reservoirs with high pressure [22]. During the water injection process, controlling injecting temperature has been the primary concern in heavy oil fields.

Figure 9 shows the change in TDR and annulus temperature, the injecting temperature being at 25 ◦C, 50 ◦C, and 75 ◦C lower than the bottom-hole temperature (i.e., 120 ◦C) of this reservoir. The injecting temperature can significantly alter the minimum TDR depth, as shown in Figure 9a. When the injecting temperature increases from 25 ◦C to 75 ◦C, the minimum TDR depth changes from 1000 m to 3000 m. This result is consistent with the

depth where the temperature curves intersect the formation temperature line. Unlike the significant change in minimum TDR depth, the TDR at the bottom-hole change does not show much difference. These observations indicate that injecting temperature control can minimize the thermal disturbance at the bottom hole. If the injecting temperature is around the bottom-hole temperature with a sufficient flow rate, the minimum TDR depth can be near the bottom hole, thereby reducing temperature measurement uncertainty after drilling.

**Figure 9.** The sensitivity analysis of thermal disturbance with varying injection temperatures: (**a**) TDR and (**b**) fluid temperature in the annulus.
