11.3. The method of heat margins.

According to this technology instead of a continuous injection of fluid after its penetration into the reservoir over time there is injected water at the reservoir under the conditions of the reservoir temperature. There is created a heated area (heat margin) in the formation, which moves from the injection well to the producing wells under the influence of cold water injection to the formation.

There are formed three displacement fronts in the reservoir when oil is displaced by the heat margin: 1 - hydrodynamic – the displacement of not heated cold oil by water; 2 - heat front – the displacement of the heated oil of the reduced viscosity by hot water; 3 –the displacement front of hot oil by cold water. Moreover, the 3^-rd displacement front of hot oil by cold water will be behind the previous two. The heat of hot oil will be given to the cold water, that is, the inverse process of heat transfer will be directed to the injection well. The viscosity of the displaced oil will increase, the mobility factor will reduce. The bypassed oil reserves will remain in the formation.

The use of heat margins injection reduces oil recovery compared in comparison with the continuous heat-transfer agent, but it takes considerably less energy to prepare steam or hot water.

To chose the optimum sizeof the heat margins there are developed special techniques, taking into account various geological and physical conditions of the formations bedding, the rate of injection into the formation of the margins of the heat-transfer agent, their parameters and prediction of technological parameters of the development process.

11.4. Combined technologies of enhanced oil recovery of high-viscosity oil deposits.

As it has been already mentioned above, the application of heat-transfer agents injection to the reservoir is associated with high costs of energy, and therefore it increases the cost of output. Professor Kudinov V.I. and his colleagues has developed and embedded the advanced methods of thermal stimulation with the changing of time cycles and with the use of chemicals for enhanced oil recovery in the complex in structure reservoirs in "Udmurtneftegaz" [23,24].

The technology of impulsive - metered thermal stimulation (IMTS) considers cyclic variable injection of heat-transfer agent and cold water in certain proportions to the reservoir. In the formation there is created an effective temperature Т_эф is the top temperature above which oil viscosity decreases significantly (Annex 3). The heating of the formation above this temperature does not increase oil recovery. The advantage of IMTS consists in the limit of the injected to the reservoir heat-transfer agent up to the effective temperature. This technology is applied for fractured-porous reservoirs (Warren – Ruth model). When the cycles of steam-cold water injection are repeated then steam penetrates in the porous blocks and after condensation displaces preheated oil in the fissures.

The modification of the IMTS method is the application of this technology with the pauses before cold water injection. The pauses allow to ensure an additional oil inflow from the blocks to the fissures. This technology resembles the cyclic steam treatment of the producing wells. But the injection is carried out in the injection wells.

V. I. Kudinov offers thermal cyclic reservoir stimulation for the rectangular water flooding systems. In this case, in addition to the central injection well there are used alternating producing wells for the injection of heat-transfer agents that are used interchangeably as producing wells and as injection wells. Thereby the reservoir sweep coefficient by area influence of operational territory increases.