MOBILITY IN OIL BANK

Mobility in oil bank



Solving an Engineering Problem

Reasons that foam injection is used in an EOR process

Enhanced oil recovery (EOR) refers to the recovery of oil that is left behind after primary and secondary recovery methods are either exhausted or no longer economical. Before proceeding with a discussion of EOR, it is important to have a basic understanding of primary and secondary recovery.

Primary production is the first oil out, the “easy” oil. Once a well has been drilled and completed in a hydrocarbon-bearing zone, the natural pressures at that depth will cause the oil to flow through the rock or sand formation toward the lower pressure wellbore, where it is lifted to the surface. While primary recovery is the least expensive method of extraction, since it uses natural forces to “move” the oil, it typically recovers only 10 to 15 percent of the original oil in place (OOIP).

Foam effectiveness relative to other EOR injectants

Surfactant flooding has the potential to significantly increase recovery over that of conventional waterflooding. The availability of a large number of surfactant structures makes it possible to conduct a systematic study of the relation between surfactant structure and its efficacy for oil recovery. Also, the addition of an alkali such as sodium carbonate makes possible in situ generation of surfactant and significant reduction of surfactant adsorption. In addition to reduction of interfacial tension to ultra-low values, surfactants and alkali can be designed to alter wettability to enhance oil recovery.

An alkaline surfactant process is designed to enhance spontaneous imbibition in fractured, oil-wet, carbonate formations. It is able to recover oil from dolomite core samples from which there was no oil recovery when placed in formation brine.

Mobility control is essential for surfactant EOR. Foam is evaluated to improve the sweep efficiency of surfactant injected into fractured reservoirs.

Answer 1)

According to Hu and Handy, foam can be used in reservoir engineering for control of gas flow in reservoirs. By injection of gas and surfactant-containing water, foam can be generated in a formation, and the mobility of the gas be reduced (Huh, 1989).

The macroscopic effect of a large number of foam films in the pore system is determined by the properties of the individual foam films, the number of foam films, and the properties of the three-dimensional network of open pores where gas can flow. One previous effort to model foam flow was the mechanistic approach, where these entities were accounted for explicity. Another approach was to identify all factors that influence macroscopic foam flow, and parameterize them in an empirical foam mobility function that reproduces experimental foam behaviorThey found that water foam viscosity decreases as the shear rate increases and that it increases as the foam quality is increased. They considered foam flow in porous media to be dependent on foam viscosity and concluded that the gas and liquid phases in the presence of foaming agents can and usually flow simultaneously through the same pore channels in the form of bubbles or ...