Effects of Surfactant Partitioning Coefficient and Interfacial Tension on the Oil Displacement in Low-Tension Polymer Flooding

Complex surfactant formulations have been applied to generate an ultra-low interfacial tension (IFT) (e.g., 10-3 dyne/cm) between the displacing water phase and the displaced oil phase in chemical enhanced oil recovery (CEOR), where the residual oil after waterflooding can be largely recovered as an oil bank. This paper is concerned with a simpler, lower-cost CEOR, in which a sole additive of surface active solvent (SAS) makes low-tension displacement fronts in polymer flooding (e.g., 10-2 dyne/cm) without involving ultra-low IFT microemulsion phase behavior. The main objective of this research is to technically verify such low-tension polymer (LTP) flooding for a secondary-mode oil displacement through a sandpack of 9.5 Darcy. Previous research found that 2-ethylhexanol-7PO-15EO (2-EH-7PO-15EO, or "7-15") as SAS was able to reduce the IFT between polymer solution and the reservoir oil from 15.8 dyne/cm to 0.025 dyne/cm. In this research, the effect of SAS partition coefficient on LTP flooding was studied as an additional factor for SAS optimization. In particular, the comparison between two SAS species, 2-EH-4PO-15EO (4-15) and 2-EH-7PO-25EO (7-25), was important, because they had similar IFT values, but markedly different partition coefficients. The IFT was 0.18 dyne/cm with 4-15 and 0.20 dynes/cm with 7-25; and the partition coefficients were 1.61 with 4-15 and 0.68 with 7-25 at the experimental temperature, 61°C. These two SAS species were compared in secondary-mode LTP flooding with a slug of 0.5 wt% SAS for 0.5 pore-volumes injected (PVI). The oil recovery factor at 1.0 PVI was 65% with 4-15 and 67% with 7-25. At 5.0 PVI, it was 74% with 4-15 and 84% with 7-25. Although these two SAS species gave comparable IFT values, their oil-displacement efficiencies were quite different because 7-25 propagated more efficiently in the sandpack with the smaller partition coefficient. The smaller partition coefficient helped the SAS flow more efficiently in the aqueous phase with less retention in the remaining oil. Optimization of SAS likely requires taking a balance between lowering the partition coefficient and lowering the IFT. The SAS recovery at the effluent was 61% for the 4-15 SAS and 78% for the 7-25 SAS. The propagation of the 4-15 SAS was retarded approximately by 1.0 PVI in comparison to that of the 7-25 SAS. The adsorption of the 4-15 and 7-25 SAS were 0.019 mg/g sandpack and 0.020 mg/g sandpack. With a similar IFT reduction, the SAS with a smaller partition coefficient (i.e., 7-25) resulted in less retention, less retardation, and more oil production for a given amount of injection.

Liver progenitor cell-driven liver regeneration

The liver is a highly regenerative organ, but its regenerative capacity is compromised in severe liver diseases. Hepatocyte-driven liver regeneration that involves the proliferation of preexisting hepatocytes is a primary regeneration mode. On the other hand, liver progenitor cell (LPC)-driven liver regeneration that involves dedifferentiation of biliary epithelial cells or hepatocytes into LPCs, LPC proliferation, and subsequent differentiation of LPCs into hepatocytes is a secondary mode. This secondary mode plays a significant role in liver regeneration when the primary mode does not effectively work, as observed in severe liver injury settings. Thus, promoting LPC-driven liver regeneration may be clinically beneficial to patients with severe liver diseases. In this review, we describe the current understanding of LPC-driven liver regeneration by exploring current knowledge on the activation, origin, and roles of LPCs during regeneration. We also describe animal models used to study LPC-driven liver regeneration, given their potential to further deepen our understanding of the regeneration process. This understanding will eventually contribute to developing strategies to promote LPC-driven liver regeneration in patients with severe liver diseases.

Experimental Investigation of the Effect of Adding Nanoparticles to Polymer Flooding in Water-Wet Micromodels

Recently, the combination of conventional chemical methods for enhanced oil recovery (EOR) and nanotechnology has received lots of attention. This experimental study explores the dynamic changes in the oil configuration due to the addition of nanoparticles (NPs) to biopolymer flooding. The tests were performed in water-wet micromodels using Xanthan Gum and Scleroglucan, and silica-based NPs in a secondary mode. The microfluidic setup was integrated with a microscope to capture the micro-scale fluid configurations. The change in saturation, connectivity, and cluster size distributions of the non-wetting phase was evaluated by means of image analysis. The biopolymer content did not affect the ability of the NPs to reduce the interfacial tension. The experiments showed that the reference nanofluid (NF) flood led to the highest ultimate oil recovery, compared to the Xanthan Gum, Scleroglucan and brine flooding at the same capillary number. In the cases of adding NPs to the biopolymer solutions, NPs-assisted Xanthan flooding achieved the highest ultimate oil recovery. This behavior was also evident at a higher capillary number. The overall finding suggests a more homogenous dispersion of the NPs in the solution and a reduction in the polymer adsorption in the Xanthan Gum/NPs solution, which explains the improvement in the sweep efficiency and recovery factor.

Unlocking the Effects of Fluid Optimization on Remaining Oil Saturation for the Combined Sulfate-Modified Water and Polymer Flooding

Interfacial interactions and wettability alteration remain as the main recovery mechanism when modified water is applied seeking to obtain higher oil recoveries. Fluid-fluid interaction could lead to the development of the called viscoelastic layer at the interface in oil-brine systems. This interfacial layer stabilizes thanks to the slow chemical interaction between oil polar compounds and salts in the brine. This study investigates the role of sulfate presence in injection brine that could possible lead to develop the interfacial viscoelastic layer and hence to contribute to the higher oil recovery. Furthermore, polymer flooding is performed in tertiary mode after brine flood to investigate/unlock the synergies and potential benefits of the hybrid enhanced oil recovery. Brine optimization is performed using the composition of two formation brines and four injection brines. Moreover, interfacial tension measurements and oil drop snap-off volume measurements are performed in parallel with the core flooding experiments to define the role of interfacial viscoelasticity as the recovery mechanism other than wettability alteration. Synthetic seawater spiked with double amount of sulfate depicted potential results of interfacial viscoelastic layer development and hence to contribute the higher oil recovery. Total oil recovery after secondary-mode using sulfate-modified water and tertiary-mode polymer flood was higher than the combination of seawater brine in secondary-mode and polymer flood in tertiary-mode. Nevertheless, experiments helped us concluding that the amount of sulfate added is a critical factor to obtain maximum oil recovery and to avoid pore-plugging problems. We, therefore, demonstrate that executing a detailed fluid optimization leads to promising laboratory results, potentially linked with an improvement in the economics of the field applications.

Optimisation of Smart Water to Enhance Oil Recovery Efficiency in a Part of Oil Field of Upper Assam Basin, India

Researchers have proved the significance of water injection by tuning its composition and salinity into the reservoir during smart water flooding. Once the smart water invades through the pore spaces, it destabilises crude oil-brine-rock (COBR) that leads to change in wettability of the reservoir rocks. During hydrocarbon accumulation and migration, polar organic compounds were being adsorbed on the rock surface making the reservoir oil/mixed wet in nature. Upon invasion of smart water, due to detachment of polar compounds from the rock surfaces, the wettability changes from oil/mixed wet to water wet thus enhances the oil recovery efficiency. The objective of this paper is to find optimum salinity and ionic composition of the synthetic brines at which maximum oil recovery would be observed. Three core flood studies have been conducted in the laboratory to investigate the effect of pH, composition and salinity of the injected brine over oil recovery. Every time, flooding has been conducted at reservoir formation brine salinity i.e at 1400 ppm followed by different salinities. Here, tertiary mode of flooding has been carried out for two core samples while secondary flooding for one. Results showed maximum oil recovery by 40.12% of original oil in place (OOIP) at 1050ppm brine salinity at secondary mode of flooding. So, optimized smart water has been proposed with 03 major salts, KCl, MgCl2 and CaCl2 in secondary mode of flooding that showed maximum oil recovery in terms of original oil in place.

Taxonomy and Pauline Uniqueness

Chapter 1 establishes the two primary theoretical approaches of the book. First, the chapter argues for polythetic classification as a more nuanced and accurate approach to understanding Paul’s divination and wonderworking. This approach moves us away from the notion of Chrsitian uniqueness and toward a historically plausible context for divination and divine power. Second, the chapter argues for thinking in terms of modes of religiosity to better understand Paul as a religious figure. I argue that Paul moves in and out of various modes of religiosity that include practical, mundane understandings of the gods, as well as the theoretical, conceptual, and counterintuitive. He participates in dual modes of religiosity simultaneously, and the seamless overlap broadens his ability to reach his audience. Academic theologians themselves operate usually in the secondary mode of religiosity, which further explains why practices of divination and wonderworking have been disparaged, rejected, or ignored. Addressing the issues of taxonomy and modes of religiosity is critical to the entire project.

Bimodal Temporal Distribution of Herpes Explains Resistant Cases to Oral Antiviral Agents

Herpes Simplex Virus (HSV) is a double-stranded virus that affects the skin and mucous membranes. There has been a long-standing dogma stating that the virus remains dormant and is reactivated from the dorsal root ganglia. However, more recent studies have established that there is a secondary mode of viral reactivation from the epidermis itself. These two distinct reactivation patterns help explain why prophylactic antivirals do not consistently prevent herpes outbreaks.

Impact of Brine Composition and Concentration on Capillary Pressure and Residual Oil Saturation in Limestone Core Samples

Low salinity water flooding (LSF) is a relatively simple and cheap EOR technique in which the salinit y of the injected water is optimized (by desalination and/or modification) to improve oil recovery over conventional waterflooding. Extensive laboratory experiments investigating the effect of LSF are available in the literature. Sulfate-rich as well as diluted brines have shown promising potential to increase oil production in limestone core samples. To quantify the low salinity effect, spontaneous imbibition and/or tertiary waterflooding experiments have been reported. For the first time in literature, this paper presents a comprehensive study of the centrifuge technique to investigate low salinity effect in carbonate samples. The study is divided into three parts. At first, a comprehensive screening was performed on the impact of different connate water and imbibition brine compositions/combinations on the spontaneous imbibition behavior. Second, the subsequent forced imbibition of the samples using the centrifuge method to investigate the impact of brine compositions on residual saturations and capillary pressure. Finally, three unsteady-state (USS) core floodings were conducted in order to examine the potential of the different brines to increase oil recovery in secondary mode (brine injection at connate water saturation) and tertiary mode (exchange of injection brine at mature recovery stage). The experiments were performed using Indiana limestone outcrops. The main conclusions of the study are spontaneous imbibition experiments only showed oil recovery in case the salinity of the imbibing water (IW) is lower than the salinity of the connate water (CW). No oil production was observed when the imbibing water had a higher salinity than the connate water or the salinity of the connate water and imbibing brine were identical. Moreover, the spontaneous imbibition experiments indicated that diluting the salinity of the imbibing water has a larger potential to spontaneously recover oil than the introduction of sulfate-rich sea water. The centrifuge experiments confirmed a connection between the overall salinity and oil recovery. As the salinity of the imbibing brines decreases, the capillary imbibition pressure curves showed an increasing water-wetting tendency and simultaneous reduction of the remaining oil saturation. The lowest remaining oil saturation was obtained for diluted sea water as CW and IW. The core flooding experiments reflected the results of the spontaneous imbibition and centrifuge experiments. Injecting brine at a rate of 0.05 cc/min, sea water and especially diluted sea water resulted in a significant higher oil recovery compared to formation brine. Moreover, when comparing secondary mode experiments, the remaining oil saturation after flooding by diluted sea water, sea water and formation water was 30.6 %, 35.5 % and 37.4 %, respectively. In tertiary injection mode, sea water did not lead to extra oil recovery while diluted sea water led to an additional oil recovery of 5.6 % in one out of two tertiary injection applications.