Production, Properties and Swelling of Composite Agar-Pectic Gel Particles in an Artificial Gastroenteric Environment

The purpose of the present work was to obtain and study the properties of composite calcium-agar-pectic gel particles (CaAPGPs) obtained from aqueous solutions of agar (AA) and apple pectin (AP), from aqueous solutions of agar (AA) and pectin heracleuman (HS) in the presence of Ca2+ ions (0.34 M). The swelling of the obtained composite CaAPGPs in an artificial gastroenteric environment was also investigated. Methods and Results: We used commercial AP AU701 (AP, Herbstreith & Fox KG, Germany), HS isolated from the aerial part of the Sosnovskyi hogweed Heracleum sosnowskyi Manden, and food agar (AA). Spherical composite CaAPGPs were obtained from low-methyl esterified AP with a molecular weight of 406 kDa, pectin HS with a molecular weight >300 kDa, and food agar (AA) in the presence of Ca2+ ions (0.34 M) as a cross-linking agent by the method of ionotropic gelation. It was found that dry CaAPGPs based on AP (Ca-AA-AP) have a diameter of 1.16±0.14-1.23±0.05 mm, which was greater than the diameter of dry CaAPGPs based on HS (Ca-AA-HS) (0.95±0.12-1.16±0.05 mm). The density of dry CaAPGPs based on AP (Ca-AA-AP) with an increase in the concentration of AP in their composition from 1% to 2% increased by 1.7 times – from 0.37±0.07 mg/mm3 to 0.63±0.05 mg/mm3. Dry composite CaAPGPs based on HS (Ca-AA-HS) were denser. With an increase in the HS concentration in their composition from 1% to 2%, the degree of particle density increases by 2.2 – from 0.45±0.03 mg/mm3 to 0.97±0.19 mg/mm3. The swelling and degradation of the obtained dry composite CaAPGPs in an artificial gastroenteric environment were studied. It was found that CaAPGPs formed from 1% AP and 2% AA degraded almost immediately in SIF. Whereas, CaAPGPs formed from 2% AP and 1% or 2% AA completely degraded in SCF after 1 hour of incubation in it. CaAPGPs formed from 1% HS and 2% AA, and particles obtained from 2% HS and 1% AA, remained stable in SIF, and then completely degraded immediately upon entering in SCF. CaAPGPs, consisting of 2% HS and 2% AA, dissolve in SCF after 1 hour of incubation in it.

Successful Field Application of Delayed Water-Swelling, Flexible Gel Particles for In-Depth Waterflood Conformance Improvement in Wide Spacing of Wells with High Temperature and High Salinity

The HD Oilfield, operated by PetroChina, is located in Tarim Basin. It is characterized by high temperature (112 ℃) and high salinity (291000 mg/L), and developed by wide spacing of wells (average 700 m). High vertical and areal heterogeneity lead to early water breakthrough and a poor water sweep efficiency. Effective conformance control is urgently needed, but harsh reservoir conditions, wide well spacing, and discontinuous interlayers pose great challenges for conformance treatments in this field. Because of wide well spacing and discontinuous interlayers, water channeling and crossflow in in-depth part of reservoir could still occur after conformance treatment. To prevent this, in-depth conformance improvement treatments with injecting large volumes of low-cost profile control agents were proposed. To achieve this goal, we designed delayed water-swelling, flexible gel particles that have high deformability and elasticity. Simultaneously, to meet the harsh reservoir conditions, gel particles were designed to have long-term tolerance to high temperature and high salinity. The first treatment was implemented in May 2016, and the total incremental oil by June 2019 was 17347 tons. The treatment validity is more than 36 months, and it keeps being effective. Until now, 9 treatments have been finished. The total incremental oil is 102100 tons until May 2020, and the increment is still going on. The input-output ratio for these 9 treatments is about 8.45, which indicates the treatments were an economic and technical success. In this paper, first we describe the design of gel particles and their properties evaluation by extensive experiments, including water-swelling ability, long-term tolerance to high temperature and high salinity, elasticity, tenacity, injectivity, selectivity, plugging ability, and scouring resistance, etc. Then, we present operation design and control in the field, which is especially important for the success of these treatments. Furthermore, according to production performance as well as the wellhead pressure drop curve, pressure curve of water injection, and water injectivity in injection well, treatment results are discussed in detail to evaluate if the treatment is successful or not. Finally, several important experiences with respect to how to do operation design and field control are summarized. This paper documents a successful case history of in-depth waterflood conformance improvement in wide spacing of wells. These successful field cases together with summarized experience will provide a detailed guide and an updated framework for conformance improvement treatment for operators. In addition, this paper presents an alternative agent, i.e., delayed water-swelling, flexible gel particles, for in-depth waterflood conformance improvement in high temperature and high salinity reservoirs.

Investigation of the mobility of dispersed gels of the Temposcreen polymer-gel system

The article describes the method of optical-electronic observation of the process of sedimentation of gel particles in the polymer-gel system. The analysis of hydrodynamic movement of gel particles in laminar and turbulent modes during the implementation of the Temposcreen technology in oil production is carried out. The effect of hydrodynamic conditions on the mobility of the polymer-gel system in well and reservoir conditions, as well as on the distribution of the dispersal gel phase in the reservoir, is considered. On the basis of the graph theory, the model of fluid flow management in the oil layer by the Temposcreen mobile polymer-gel system is presented.

MWNTs or PEG as Stability Enhancers for DNA–Cationic Surfactant Gel Particles

Cationic surfactants interact with DNA (Deoxyribonucleic acid), forming surfactant-DNA complexes that offer particularly efficient control for encapsulation and release of DNA from DNA gel particles. In the present work, DNA-based particles were prepared using CTAB (Cetyltrimethylammonium bromide) as the cationic surfactant and modified using two different additives: (Multi-Walled Carbon Nanotubes) MWNT or PEG (Poly Ethylene Glycol). The use of both additives to form composites increased the stability of the gel particles. The stability was monitored by the release of DNA and CTAB in different pH solutions. However, not much is known about the influence of pH on DNA–surfactant interaction and the release of DNA and surfactant from gel particles. It was observed that the solubilization of DNA occurs only in very acid media, while that of CTAB does not depend on pH and gets to a plateau after about 8 h. Within 2 h in contact with a pH = 2 solution, about 1% DNA and CTAB was released. Complete destruction for the gel particles was observed in pH = 2 solution after 17 days for PEG and 20 days for MWNT. The composite particles show a considerably enlarged sustained release span compared to the unmodified ones. The dehydration-rehydration studies show that the structure of the composite gel particles, as determined from SAXS (Small-Angle-X-Ray-Scattering) experiments, is similar to that of the unmodified ones. These studies will allow a better knowledge of these particles’ formation and evolution in view of possible applications in drug delivery and release.

Using Plasma Etching to Access the Polymer Density Distribution and Diffusivity of Gel Particles

In this paper we examine the polymer density distribution of gel particles and its effect on solvent diffusivity through the polymer network. In order to access the inner particle regions, external polymer layers were removed by plasma etching, thus reducing them from the outside. Higher polymer densities after erosion showed internal heterogeneity, with the density increasing towards the center of the particles. An exponential decay polymer density model is proposed, and the spatial relaxation length measured. The diffusion of solvent through the particles, before and after the plasma oxidation, revealed a correlation between the diffusion coefficient and the internal density.

Influence of Whey Protein Micro-Gel Particles and Whey Protein Micro-Gel Particles-Xanthan Gum Complexes on the Stability of O/W Emulsions

Appropriate pretreatment of proteins and addition of xanthan gum (XG) has the potential to improve the stability of oil-in-water (O/W) emulsions. However, the factors that regulate the enhancement and the mechanism are still not clear, which restricts the realization of improving the emulsion stability by directional design of its structure. Therefore, the effects of whey protein micro-gel particles (WPMPs) and WPMPs-XG complexes on the stability of O/W emulsion were investigated in this article to provide theoretical support. WPMPs with different structures were prepared by pretreatment (controlled high-speed shear treatment of heat-set WPC gels) at pH 3.5–8.5. The impact of initial WPC structure and XG addition on Turbiscan Indexes, mean droplet size and the peroxide values of O/W emulsions was investigated. The results indicate that WPMPs and XG can respectively inhibit droplet coalescence and gravitational separation to improve the physical stability of WPC-stabilized O/W emulsions. The pretreatment significantly enhanced the oxidative stability of WPC-stabilized O/W emulsions. The addition of XG did not necessarily enhance the oxidative stability of O/W emulsions. Whether the oxidative stability of the O/W emulsion with XG is increased or decreased depends on the interface structure of the protein-XG complex. This study has significant implications for the development of novel structures containing lipid phases that are susceptible to oxidation.