Cold fluid injection

Let us consider fluid flow through fracture network in rock formations. When the fluid temperature is lower than that of rock, the fluid flow removes heat of rock and the rock cools down. The cooling will cause thermal contraction of rock, and as a result fractures are likely to open and to be more permeable. In reality, the test results of fluid injection into rock formations at depths of about 1000 m, show that cold-fluid injection is effective to increase permeability of the rock formations (e.g.. Home et al., 1988, Ariki and Hatakeyama, 1997, Clotworthy, 2000). 

The cold fluid injection will reduce temperature around the injection point, and it will develop a temperature distribution such as schematically shown by a dashed line in the lower part of Figure 6. For simplicity, we approximate here the nonlinear temperature distribution as a step-like distribution shown by a solid line in that figure. 

Fig. 5.4-23 shows a sketch drawing of a BSC (Brogli et al., 1981). The stirred-tank reactor made of glass (a metal version is also available) is surrounded by a jacket through which a heat-transfer fluid flows at a very high rate the jacket is not insulated. The temperature of the circulation loop is regulated by a cascaded controller so that the heat evolution in the reactor is equilibrated by heat transfer through the reactor wall. The temperature in the loop is adjusted by injection of thermostatted hot or cold fluid. 

Cooling of the gases by the injection of a cold fluid (water or oil) which entrains part of the carbon black. 

At the low temperature extreme of hypothermia, body temperature can drop as low as 28.5 °C. The person may appear cold and pale and have an irregular heartbeat. Unconsciousness can occur if the body temperature drops below 26.7 °C. Respiration becomes slow and shallow, and oxygenation of the tissues decreases. Treatment involves providing oxygen and increasing blood volume with glucose and saline fluids. Injecting warm fluids (37.0 °C) into the peritoneal cavity may restore the internal temperature. 

For the requirements of process development and process safety investigation, a bench scale heat flow calorimeter has been developed eind built. Figure 1 outlines its principle. The stirred tank reactor (A) is surrounded by a jacket in which a heat transfer fluid is circulated at a very high rate. A cascaded controller (B) adjusts the temperature of the circulation loop (C) so that heat transfer through the reactor wall equilibrates the heat evolution in the reactor. Injection of thermostated hot or cold fluid is used to adjust the temperature in the loop. 

Figure 6-5 shows a stabilizer with reflux. The well fluid is heated with the bottoms product and injected into the tower, below the top, where the temperature in the tower is equal to the temperature of the feed. This minimizes the amount of flashing. In the tower, the action is the same as in a cold-feed stabilizer or any other distillation tower. As the liquid falls... 

For the purpose of fluid re-injection, either special wells must be drilled or non-productive wells must be used. If an injection well is located within the field of producing wells, there is a risk that relatively cold water from the injection well will flow too rapidly into the aquifer of a producing well, thus deteriorating its performance or even destroying it. In the long run, injection of waste brine into a producing reservoir may have some negative effects. 

Fluid extraction from the reservoir occurs simultaneously with re-injection of cold liquid and air. Atmospheric nitrogen and Ar propagate very fast through the fracture network in the reservoir rocks and arrive at producing regions with negligible thermal interference. This may be used as a simple and cheap method to estimate the three-dimensional permeability tensor. 

Fig. 13.16 Schematic representation of the flow pattern in the advancing front between two parallel cold walls. Black rectangles denote the stretching and orientation of a fluid particle approaching the central region of the front. The curved shape of the front causes fluid particles initially oriented in the y direction to end up on the wall, oriented in the x direction. The velocity profile upstream from the front is in the x direction and is viewed from a coordinate system located on the front. [Reprinted by permission from Z. Tadmor Molecular Orientation in Injection Molding, J. Appl. Polym. Sci., 18, 1753 (1974).]...

Clearly, according to this model the rate of elongation increases with injection rate, with decreasing gap and increasing n. Because the shape of the front is not flat but, as shown in Fig. 13.16, bends backward and becomes tangent to the walls aty = H/2, the fluid elements that were oriented by the fountain flow in the y direction are deposited on the cold wall with an x-direction orientation. 

---