The Effect of Osmotic Pressure on Improve Oil Recovery from Fractured Shale Formations

Abstract

Shale swelling during drilling is attributed to osmotic pressure, where low-salinity water enters the shale pores to cause swelling. Low-salinity water injected into high-salinity Bakken formation could similarly enter the matrix pores to displace oil by counter-current flow observed in core experiments. As a result, we believe, low-salinity water can potentially enhance oil recovery from oil-wet Bakken formation.In this paper, we report experimental and numerical modeling studies we conducted to evaluate the potential of lowsalinity waterflooding in Bakken. For laboratory experiments, we used horizontal core plugs drilled parallel to the bedding plane.The mathematical included osmotic pressure, gravity and capillary effects. In the mathematical model, the osmotic pressure mass transfer equations were calibrated by matching time-dependent salinities in a published laboratory osmotic pressure experiment. We also modeled oil recovery for a Bakken core using our osmotic pressure mass transport model. The results indicate that osmotic pressure promotes counter-current flow of oil from both the water-wet and oil-wet segments of the core.

Experimental and numerical study on the relationship between water imbibition and salt ion diffusion in fractured shale reservoirs

“…Then, the water enters into the crystal layer to release ions continuously. Because the shale has the characteristics of a non-perfect semipermeable membrane, partial ions can pass through the shale crystal layer and diffuse into water, consequently enhancing the salinity of water (Facharoenphol et al, 2014). In addition, the existence of clay also can increase the pore water salinity in gas shale.…”

Quantitative investigation on the characteristics of ions transport into water in gas shale: Marine and continental shale as comparative study

“…12). Compared with continental shale, much more salt ions precipitated from sea water and can result in higher surface ions density G 0 in marine shale (Abass et al, 2006;Fakcharoenphol et al, 2014). In addition, it is not difficult to find that the ions in shale matrix pores partly come from the sedimentary environment.…”

“…The charged clay interlayers have the characteristics of a semipermeable membrane, which did not restrict water molecule movement, but did restrict ions movement. Moreover, the water molecules pass the semipermeable membrane to enter into the high salinity side, which reduces the difference in salinity and in turn decreases the ions diffusion rate (Fakcharoenphol et al, 2014). In addition, Zolfaghari et al (2014) pointed out that ions diffusion is accompanied by spontaneous imbibition, and the factors that can influence water imbibition can also affect ions diffusion to some extent.…”

“…The increasing overburden weight can continuously compress porous rock during burial, and consequently water is expelled from pores leaving precipitated salts behind (Fakcharoenphol et al, 2014). The interactions of precipitated salts and injected water can cause saline flowback water (Haluszczak et al, 2013).…”

Ion Diffusion Behavior between Fracturing Water and Shale and Its Potential Influence on Production

“…Osmotic pressure is recognized as an important driving force for water imbibition and shale oil production [21]. The abundant content of clay minerals serves as foundation for clay-chemical effects.…”