Contrary to popular belief, electrical induction can be an extraordinarily efficient method of heat delivery. Unlike steam and chemical solutions that essentially need to penetrate the entire reservoir, induction heating can drastically alter the reservoir’s pressure gradient just by warming the near-wellbore. Nearly 80% of the available reservoir pressure is expended forcing oil through the area near the casing; viscosity reduction is greatest near the casing, which offsets the unheated pressure gradient. These improved conditions significantly augment oil flow. Since the MxL Induction Heating System is designed to introduce more heat into the production zone than is being removed by produced fluids there is an increase in reservoir temperature. Our inductor designs can achieve higher than 90% efficiency. Because of this, the vast majority of energy put into the system will find its way into the reservoir. MxL systems do not require special completions; we have optimized systems to work with perforated casing, slotted liners, screen inserts and a number of other common completions. Electrical supply is provided via standard ESP cable banded to the tubing and the sensors return their information to the PCU via the ESP cable.

As the oil flows towards the production zone, it is forced to follow a “tortuous path,” as illustrated above. This promotes a “wiping action” between the grains and the incoming fluid, maximizing heat transfer into the reservoir as the average direction of flow is 45 degrees to the radial line toward the casing, while the heat flow is normal to the liquid flow. In long term heating operations, we have observed that heat moves back into the reservoir at fairly predictable rates. Our PEPS software can determine and illustrate how the heat will propagate and eventually stabilize. Additionally, the temperature and pressure sensors in the MxL heaters make them valuable tools for well diagnosis and field testing.

The following videos depict a graphical representation of how the MxL heater affects the production zone of a reservoir. The first graph shows how the temperature of the surrounding reservoir varies while moving radially outward from the casing.

As the MxL tool adds energy to the reservoir, the temperature profile extends out. This graph is animated to show how the temperature profile changes over time. Specific values presented within the animation are meant to model an arbitrary but typical vertical well. Empirical observation has shown that the heat contained within the reservoir tends to persist for a long time. In fact we have seen that when the heater is turned off the incoming fluid will remain above ambient temperature for a long duration. The next video depicts the pressure gradient of the same vertical well and how heating the reservoir will increase production.

In ambient unheated conditions the majority of the pressure drop experienced within the reservoir occurs in the near wellbore area. By applying heat to this area, the viscosity of the produced fluid is decreased. This reduction in viscosity allows for the fluid in the near wellbore area to flow more rapidly, pushing the pressure drop back farther into the reservoir. The MxL heater makes a greater volume of the reservoir experience a pressure drop from ambient, thus a greater volume of fluid is being removed from the reservoir. The final video depicts the temperature profile of a horizontal well.

This graph displays similar information as the first temperature profile video however a horizontal well contains heterogeneous features not typically present within a vertical well. Specifically, the production zone is sandwiched between material of dissimilar thermal conduction and permeability called the overburden and underburden respectively. This creates heterogeneity within the reservoir making a radially symmetrical depiction of the temperature profile inaccurate. In an attempt to accurately display a model of the temperature profile for a horizontal well, isotherms of constant temperature are depicted as expanding rings moving outward from the wellbore. The visual perspective of this graph is as if looking down the length of the horizontal wellbore.
 
 

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