Characteristics of Formation Damage and Variations of Reservoir Properties during Steam Injection in Heavy Oil Reservoir

Abstract

Steam stimulation and steam flooding are two kinds of effective processes of enhanced oil recovery for a heavy oil reservoir. But steam can lead to severe and permanent formation damage due to interactions between injected fluids and reservoir rock and liquids. This article presents the laboratory studies undertaken to evaluate the influence of fluid composition, temperature, salinity, pH, dissolution and transformation of minerals, and asphalt deposition on formation damage during steam injection. The degree of damage during steam injection is observed to be dependent on pH and temperature. The technology of casting samples micrographs and scanning electron micrographs is employed to study the variations of reservoir properties after steam injection in each experiment. The mechanisms of formation damage and the characteristics of reservoir property variations are analyzed in heavy oil reservoirs during steam stimulation or steam flooding. The results show that the solubilities of rock and clay increase with increasing temperature and pH. Formation pores are blocked and plugged due to migration and precipitation of new minerals and asphalt deposition away from the steam injection well due to temperature drop and pH reduction in reservoirs. A great deal of asphalt deposition alters formation wettability to increase seepage resistance. Average porosity and average permeability increase near the steam injection well due to the generation of earthworm holes and steam channeling zones under the effect of high pH and elevated temperature. But a large amount of crude oil is left in large and mid-size pores during steam injection in heavy oil reservoirs.

The Role of Asphaltenes in Emulsion Formation for Steam Assisted Gravity Drainage (SAGD) and Expanding Solvent - SAGD (ES-SAGD)

“…For reference, the FTIR spectrums of Ottawa sand and clay have been provided in Figure 7-a and Figure 7-b respectively. Asphaltene and polar oil component deposition in the rock causes dispersion of clays and fines, making them oil-wet and promoting their outflow with the produced oil (Leontaritis et al, 1994;Pang et al, 2010). The presence of clays and significant amount of water in the produced oil are believed to have a combined effect in stabilizing the emulsions.…”

Research on the Mechanism of Decompression and Augmented Injection during Waterflooding Development in Low Permeability Reservoirs

“…In order to enhance the development in low permeability reservoirs, the decompression and augmented injection mechanism is studied. The surfactant could change the wettability of the rock surface, which could reduce the surface and interfacial tension, enhance the emulsifying ability and so on [14][15][16][17]. After the laboratory tests and field application, it is proved that the new surfactant could change the injection water property and rock surface wettability, which could attain the aim of well decompression and augmented injection.…”

The Relation Between (meth)Fluoroacrylate Copolymer Structure and Reservoir Rock Wettability

“…Water blocking and plugging in the porous media caused by extraneous fluid invasion and gas condensation are common in the drilling process, leading to a sharp decline in oil production (Pang et al, 2010). Practice in situ proved that the rock wettability near the borehole is a key factor that determines the position, flow, and distribution of reservoir fluid in porous media and has a great effect on the oil-water relative permeability (Ogunberu and Ayub, 2005;Morrow, 1990;Jiang, 1995).…”