Basis for oil production system by thermal EOR methods

Nevertheless, in case of thermal treatment, certain addidonal condidons may have to be met e.g., in shallow petroleum fields with muldple producing horizons made up of poorly cemented reservoir sands that may have tendency to run, such individual sands should not be unified unless effective measures are first taken to prevent sanding of producing wells. 

Bed thickness determines the degree of utilization of thermal energy that is brought into the oil reservoir or generated within it. On the other hand, with the increase in thickness of a petroliferous bed, the degree of sweep of that bed by the thermal process decreases. 

With steam injection, maximum oil recoveries are obtained from beds not exceeding 25 m in thickness [18]. For in situ combustion, taking into account great mobility of the oxidizer (air), IS m should be the upper limit of bed thickness. From this consideration follows one additional condition beds that are grouped into a single production unit should have a total effective thickness of up to 25 m in the case of steaming treatments, and up to IS m in the case of in situ combustion. 

The degree of heat utilization also depends on the presence of partings in the reservoir stratum. For steaming treatments, it is recommended that the total thickness of the reservoir bed not be more than 2-3 times the effective oil saturated thickness [18], Moreover, the thickness of the individual impermeable interlayers also has an effect on utilization of thermal energy. The interference of heat between successive permeable layers or horizons decreases when they are separated by thick impermeable interlayers. It is also reduced when heat zones shift irregularly along fingers of permeable layers. As a consequence, the overall heat effectiveness of the process suffers [18]. 

Calculations show that these impermeable interlayers separating two adjacent permeable horizons must not exceed 10 m in thickness. If these thicknesses are greater, the adjacent petroliferous layers should not be grouped into a single producing unit. These Hguies are confirmed by results of an analysis run on cores from a development test well drilled in an oil reservoir of the Khorosany field in Azerbaijan. This particular well was drilled in a zone already situated behind the burning front in a bed treated by in situ combustion. 

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