Page 83 - Primer on Enhanced Oil Recovery

74 Primer on Enhanced Oil Recovery

At the pilot site of the Usinskoye field (Russia), for the first time in world prac-
tice, equipment and technology were implemented to work on a deep carbonate res-

ervoir (steam temperature 320 330 C, formation depth at 1400 m).
Modifications of the steam injection method, in particular, the combination of con-
tinuous and cyclic steam injection into reservoirs are used. It was applied at the fields
Kern River, San Adro, Weig Wolf (California, USA). The depth of the deposits is
200 600 m. The thickness of the reservoir is 25 70 m, the viscosity of the oil is
more than 3000 MPa s. Since the 1960s, a combination of continuous and cyclic steam
injection into more than 2500 wells per year has been used at these fields. As a result
of the introduction of recoverable oil reserves reached 35 37% of the geological.
The gravitational drainage technology with steam injection (SAGD) is being intro-
duced in bitumen and super heavy oil fields, especially in Canada and Venezuela.

8.2 In-situ combustion (ISC)

In situ combustion is a process involving in a reservoir oil burning when oxygen
containing gas is injected into the oil containing formation. Oxygen reacts with
hydrocarbons, energy is released and the formation temperature rises. Continues
gas injection allows to create self-sustaining moving burning zone with temperature

200 650 C. The ignition can b provided by the means of electrical discharges or
gas burners. In some cases oil in the formation will ignite itself in oxygen presence
in the formation. In many cases just air pumped into the formation. The other com-
ponent of burning, as the fuel, remains of heavy oil (after upgrading zone passes)
will be used. Burning thermal energy increases formation temperature, this reduces
oil viscosity, partially distills and evaporates oil. Water steam, hot water and gases
misplace the oil towards production wells (Fig. 8.8). ISC is possible only if the
burning process generates enough heat (apart the situation when heat is supplied
continuously from the outside) to sustain itself.
Two main types of ISC are known forward combustion and reverse combus-
tion. In the first case burning zone moves with the direction of the injection gas
(oxidizing media). In the latter case burning front moves in the opposite to the oxi-
dizer direction.
The ISC method was first proposed in the former USSR by Scheiman and
Dubrovai. In 1934 they first applied it at Schirwan oil field in Maikop. The ISC
was later very widely used in the USSR.
From 1960 the method has been widely used in the USA and Venezuela. In 1964
the method was applied at Suplacu de Barcau (Romania) with the recovery efficiency
54%. In the last 20 years the technology is widely used in Canada and India.

8.2.1 Detailed ISC description

The ISC method relies on burning some part of oil in the formation, at the same
time significant part of the oil is pushed towards production wells. In many cases