Water Quality and Well Injectivity: Do Residual Oil-in-Water Emulsions Matter?

Abstract

The present work is a part of a thorough and systematic laboratory study of oil-in-water emulsion flow in porous media that we have undertaken recently to investigate the mechanisms of oil-droplet retention and its consecutive effect on permeability. One of our main objectives was to see how the in-depth propagation of producedwater (PW) residual dilute emulsion could impair the permeability during PW reinjection (PWRI). During this casework, we used granular packs of sharp-edged silicon carbide grains and stable and dilute dodecane-in-water emulsions. The flow experiments were performed under well-controlled conditions, and we studied the effect of most of the relevant parameters, including flow rate, salinity, droplet size, and permeability of the porous medium.A careful monitoring of the salinity and the jamming ratio (JR) allowed us to consider and work separately on the two main mechanisms of droplet capture (i.e., surface capture and straining capture). In a previous paper (Buret et al. 2008), we reported on the effect of salinity and flow rate on emulsion flow through porous media where the pore-size/droplet-size ratio (JR) was very high, ensuring that only droplet capture on pore surface is operative. This paper reports on the effect of salinity and JR on both mechanisms, with the main focus being on the induced permeability impairment.We demonstrated that surface capture could induce significant in-depth permeability losses even at a high JR. The maximum reached permeability loss is very sensitive to salinity and flow rate (shear-thinning effect). This maximum is always lower than a limiting value dictated by the surface-coverage jamming limit of random sequential adsorption (RSA) theory. This limiting value increases while decreasing the JR, according to a simple formula extracted from Poiseuille's law with a mean hydrodynamic thickness of the deposited layer close to the droplet diameter (monolayer deposition). Regarding the straining capture, we determined a critical JR of 7 for this mechanism to occur. Preliminary results using only two JR values and one flow rate are presented. Compared to surface capture, the results show that straining capture induces more severe plugging with a lower rate of propagation. The lower the JR is, the more severe the plugging is and the lower the propagation rate is. However, more investigations are still required, notably using various JRs and flow rates to characterize this important mechanism better.

Flow of Hydrophobically Modified Water-Soluble-Polymer Solutions in Porous Media: New Experimental Insights in the Diluted Regime

“…The cores used were model granular packs composed of sharp-edged silicon carbide (SiC) grains having narrow size distribution and average size of 50 m. Before use, the SiC grains were exposed to chemical and thermal treatment to eliminate impurities such as iron particles or fi nes and to create a thin layer of silica (SiO 2 ) on their surface to make the grains hydrophilic (Buret et al 2010;Medout-Marere et al 2000). Thus, all SiC model porous media used had well-known, homogeneous, and reproducible pore structure and surface properties.…”

The Effect of Mineral Deposition on CO2 Well Injectivity

“…According to Buret et al (2010), injectivity index ␣ can be calculated from pressure differentials. Modifying the parameters for the present CO 2 injectivity investigations leads to the following formula.…”

Development of Injectivity Damage Due to Oily Waste Water in Linear Flow

“…With large and increasing quantity of water produced in oil and gas extraction process, the environmental regulations for water discharge become more and more stringent. Produced water reinjection (PWRI) is now recognized as an important way to address this problem, as it protects environment while improving oil production (Abou-Sayed, et al, 2007;Rousseau, et al, 2008;Buret, et al, 2010). Multi-functional wells such as downhole oil water separation (DOWS) and downhole water loop (DWL) are also used or proposed to control the produced water by injecting it in-situ (Veil and Quinn, 2004;Jin and Wojtanowicz, 2011).…”

“…The oil droplets size distribution in produced water can be divided into several regions as shown in Figure 1, and the soluble oil (do<=5μm) is difficult to remove completely from the water, even treated with the advanced surface facilities (Rhee, et al, 1989;Johnson, et al, 1996). Both experimental and theoretical work has shown that even such tiny soluble oil can cause severe formation damage around injectors by oil droplet capture, especially when there is no oil saturation in the formation at the beginning of injection (McAuliffe, 1973(a); Radke, 1984a, 1986;Rege and Fogler, 1988;Zhang, et al, 1993;Ohen, et al 1996;Bennion, et al, 1998;Civan, 2007;Buret, et al, 2010). Thus it is important to understand and mathematically describe how oil capture and flow blockage develops at and away from the rock face.…”

“…Although, numerous works have been done and many models are available to predict the injectivity decline caused by solid particles, there is a lack of easy to use models to predict the injectivity damage caused by oil contamination in the injection water (Pang and Sharma, 1997;Al-Riyamy and Sharma, 2002;Vaz, et al, 2006;Buret, et al, 2010). Alvarado and Marsden proposed a bulk viscosity model to study the emulsion flow through porous media in 1979, which treats the emulsion as a continuum, single phase fluid, no interaction between oil droplet and pore wall is allowed.…”