Heavy Oil Recovery From Sandstone Reservoirs in the Mid-Continent Region Using Preformed Particle Gel Enhanced Surfactant
Fractured sandstone reservoirs, like the ones in the Mid-ContinentRegion, contribute in a large extent to the USA production of oil. These fractures in sandstone reservoirs can create significant permeability anisotropy. This will cause any water or surfactant flooding to move preferentially into void space conduits or higher permeability streaks zones, leaving behind considerable amount of oil in the rock matrix. In this paper, we propose combined process of preformed particle gel (PPG) treatment with surfactant flooding. This technique was studied using a series of core flooding experiments. In the first set of experiments, surfactant and PPG will be injected together into fractured Berea sandstone slabs. In another set of experiments, PPG was injected to through the fracture followed by slug of surfactant. Before the experiment, the wettability of the Berea slab was altered to oil-wet using chemically grafting silane molecules treatment to simulate reservoir conditions. To optimize the design several surfactant were screened using phase behavior, IFT, contact angel measurements. Several PPG products were also screened based on gel swelling ratio and strength. The interaction between surfactant and PPG is also presented in this paper. Results showed that PPGs propagated through the mm size fracture and partially plugged it, causing a reduction in fracture permeability. The surfactant solution has been filtrated into the core matrix and possibly reduced the interfacial tension between oil and water. Thus reducing the capillary force and increase the fluid flow in the low permeability matrix. Moreover, oil recoveries were 7-10% of the residual oil saturation bypassed by initial water flooding in the fracture. This coupled method can provide practical and cost-effective solution to small operators in Mid-Continent Region, especially in the Cherokee Basin, where heavy oil production is hindered by the complex Geology and wrongful practice of aggressive water-flooding, which caused the early breakthrough of water. It is our believe that this combined method could be suitable geological features where mm size fractures and channels can be plugged by PPG.
AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014