Gel Cake Research Articles

Selective penetration behavior of microgels in superpermeable channels and reservoir matrices

Gel treatment is an effective way to attack excessive water production in many mature oilfields around the world. Selective penetration is desired for successful gel treatments. That is, gel materials should easily penetrate the target zones (i.e., channeling features such as superpermeable channels) without entering/damaging the nontarget zones (i.e., reservoir matrices or oil zones). This study revealed that presence of threshold penetration pressure (ΔPth) was responsible for selective penetration behavior of tested microgels. The concept of ΔPth was utilized to figure out favorable working conditions for effective gel treatments. Microgel dispersions were injected into superpermeable (super-k) sandpacks (mimicking super-k channels in reservoirs, 60–221 darcies), heterogeneous models with super-k channels (79–230 darcies), and sandstone cores (mimicking reservoir matrices, 50–5000 md). The results demonstrated that a minimum differential driving pressure (i.e., threshold penetration pressure, ΔPth) was required to push microgel particles to penetrate channels or matrices. The critical penetration behavior was closely related to the particle/pore size ratio. Low ΔPth at smaller particle/pore ratios was beneficial to allow easy penetration of gel materials into the channeling zones. On the contrary, high ΔPth at larger particle/pore ratios was desirable to prevent gel materials from massively invading and damaging the matrices. Instead, the gel particles accumulated at the inlet surface, and a gel cake was gradually formed. The cake further prevented the invasion of the gels. The cake could be removed by chemical breakers to resume the injectivity/productivity of the matrices. Correlations were developed to describe the relationship between ΔPth and particle/pore ratio. A distinct transition was identified at the particle/pore ratio of about 3. This work could help identify the favorable conditions to achieve successful gel treatments. In an effective conformance treatment, the particle/pore ratio in the channel should be sufficiently low to allow easy penetration of gel materials into the channel (e.g., particle/pore ratio<2 in this study). Meanwhile, the particle/pore ratio in the matrix should be large enough to support a high ΔPth and thus prevent massive gel invasion into the matrix. This study advances the current pore scale studies (a single particle passing through a single channel) to Darcy-scale characterization.

Evaluation and Plugging Performance of Carbon Dioxide-Resistant Particle Gels for Conformance Control

SummaryTraditional polyacrylamide (PAM)-based superabsorbent polymer has been applied to control excess carbon dioxide (CO2) production in CO2-flooding fields. Nevertheless, the application results are mixed because the polyacrylamide-based superabsorbent polymer dehydrates significantly when exposed to supercritical CO2; therefore, we evaluated a novel CO2-resistant gel (CRG) with reliable stability and CO2-responsive properties. Particularly, the CRG swelling ratio (SR) and gel-volume increase after CO2 stimulation if additional water is available. Swollen CRG was placed in high-pressure vessels to examine the weight loss and the property changes before and after exposure to CO2. The breakthrough pressure and CRG-plugging efficiency to CO2 were measured using partially open fractured-sandstone cores. Two water/alternating/gas (WAG) cycles were conducted to test the CRG-plugging performance after CRG injection. The high-pressure vessel-test results show that the CRG is very stable under the supercritical-CO2 condition and no free water is released from the samples. The scanning-electron-microscope (SEM) images confirm that no structural damage was observed in CRG after exposure to CO2. The breakthrough pressure increases with the matrix permeability, which is mainly induced by the internal and external gel cake formed on the rock surface. CRG can reduce the water permeability more than CO2 permeability. CRG-plugging efficiency to CO2 decreases with the increase of WAG cycles. However, in the 0.5-mm fracture model and the 390-md model, CRG-plugging efficiency to water increases with WAG cycles. This phenomenon further indicates that CRG can be stimulated by CO2, which allows CRG to absorb additional water during post-waterflooding. In general, this study reports the concept of the novel CRG and a systematical evaluation of CRG stability under supercritical-CO2 conditions and CRG-plugging efficiency using a partially open fractured-sandstone model.

Flaxseed and Chia Seed Gel on Characteristics of Gluten-Free Cake

ABSTRACTThis study aimed to evaluate the effect of using flaxseed and chia gel as a gluten substitute in cakes. It was performed in four steps: cake production, 9-point hedonic scale sensory analysis, chemical composition analysis, and ink print texture analysis. Five preparations of gluten-free cake were prepared: one control cake with no added gel and four modified preparations, two preparations with gels extracted from flaxseed and chia seeds without the use of seed and two using the gels mashed with the seeds. Preparations with chia or flaxseed gels showed better acceptance. Isolated chia gel cake had better overall acceptability in sensory analysis. Isolated chia and flaxseed gels cakes had a higher percentage of moisture. Flaxseed cakes had more uniform texture. The use of flaxseed or chia gels as gluten substitute can be beneficial as they give better sensorial characteristics to the product, as well as adding nutritional value to preparations.

Use of Hydrochloric Acid To Remove Filter-Cake Damage From Preformed Particle Gel During Conformance-Control Treatments

Summary Millimeter-sized (10-µm to mm) preformed particle gel (PPG) has been used to control water flow through superhigh-permeability zones and fracture zones in mature oil fields. When the PPG is extruded into target zones, the gel can form a cake on the surface of low-permeability, unswept formations. This cake reduces the effectiveness of conformance control and the amount of oil that can be recovered from unswept oil formations. Thus, this study evaluated the effectiveness of using hydrochloric acid (HCl) to remove gel cakes induced during conformance-control treatments. The interactions between HCl and PPG were evaluated to understand the swelling, deswelling, and gel strength after adding acid. A Hassler core holder was then used to determine the core permeability after gel and acid treatments. Gels swollen in brine concentrations of 0.05, 1, and 10% were injected into a sandstone core having a variety of permeabilities. Brine was then injected in cycles through the gel into the core. The core permeability was measured after the gel-particle injection and after the core surface of the gel cake was soaked in the acid solution for 12 hours. The results indicate that particles swollen in brine concentrations of 0.05% caused more damage than those swollen in higher concentrations of brine. The damage increased as the core permeability increased for all the swollen gels. HCl removed the gel cake effectively; varying the HCl concentration did not cause a significant difference in the gel-cake removal efficiency. The gel was found to swell much less in HCl solutions than in brine. After the gel was deswollen in acid, the gel strengths were found to be higher than when the gel was swollen in brine. This work concludes that HCl can be used effectively to mitigate the damage induced by PPGs.

The performance of forward osmosis process in treating the surfactant wastewater: The rejection of surfactant, water flux and physical cleaning effectiveness

In this study, the rejection of surfactant (sodium dodecyl benzene sulfonate, SDBS) was investigated at different feed solution (FS) chemistries (ionic strengths and SDBS concentrations, with and without the presence of organic foulants BSA and Alg-Na), temperatures and flow velocities in the forward osmosis (FO) process. SDBS rejection increased with the increase of flow velocity and the decrease of temperature and SDBS concentration; while it had no obvious change with the increasing FS ionic strength. SDBS rejection of FO membrane was high (more than 99.77%), mainly due to the size exclusion. Moreover, the water flux and effectiveness of physical cleaning were also measured. SDBS impacted water flux by two ways: one was the positive role that SDBS micelles enhanced the hydrophilia of membrane; the other one was the negative role that SDBS formed a gel cake layer and increase the resistance. The membrane fouling caused by Alg-Na increased solute rejection and water flux in the FO mode, which was beneficial to the total membrane process. Though BSA fouling increased solute rejection in the PRO mode, it declined water flux, and caused a severe pore blocking which was hard to remove just by the simple rinse.

Formation of square lamellae by self-assembly of long-chain bolaphospholipids in water

The self-assembly process of the symmetric single-chain polymethylene-1,ω-bis(phosphocholine) (PC-C34-PC) with a chain length of 34 carbon atoms and two polar phosphocholine headgroups when put into water is exclusively driven by hydrophobic interactions of the long alkyl chains. This process leads to the formation of a dense network of helical nanofibers and the formation of a hydrogel (Meister et al. J. Phys. Chem. B, 2008, 112, 4506). In contrast, the single-chain bolalipids tetra- and hexatriacontane-1,ω-diyl-bis[2-(dimethylammonio)ethylphosphate] (Me2PE-Cn-Me2PE, n = 34, 36) and the partly deuterated analogue Me2PE-C11-(CD2)12-C11-Me2PE (dMe2PE-C34-Me2PE) form a different type of stable aggregate. In a first step, the self-assembly of these long-chain bolalipids in water at room temperature leads to the formation of a dense network of nanofibers which eventually form a hydrogel. Within one day, the nanofibers transform into square lamellae that grow up to an edge length of about 100 nm. Nanofibers are linked to one or two (opposite) corners of the squares leading to the appearance of a kite-like structure. After one week, all fibers have been transformed into square lamellae which are apparently stacked and form a gel cake. Within several weeks, a more compact cake is formed by syneresis, i.e. the expulsion of water.

Utilization of Hydroxypropylated Waxy Rice and Corn Starches in Korean Waxy Rice Cake to Retard Retrogradation

ABSTRACTA traditional waxy rice gel cake in Korea, Injulmi, was prepared with hydroxypropylated waxy rice and corn starches (molar substitutions 0.13 and 0.11, respectively), and the textural and retrogradation characteristics of the cake were compared with a conventional cake made of waxy rice flour. In the pasting viscogram, hydroxypropylated starches exhibited reduced pasting temperatures, but increased peak viscosities compared with the unmodified starches. Under differential scanning calorimetry, the Tg′ and ice melting enthalpy of the starch gel cakes were reduced by hydroxypropylation, which indicated that the modified starches had higher water‐holding capacity than the unmodified starches. The degree of retrogradation, as measured by the hardness of the gel cake and the melting enthalpy, was significantly reduced by hydroxypropylation and hydroxypropylated waxy rice starch was more effective in retarding the retrogradation than hydroxypropylated waxy corn starch

A fast and reliable chromatographic procedure for the purification of virginiamycin M1 factor

The goal of this study was to develop a simple, fast and reliable procedure for the preparation of highly purified virginiamycin M1 factor using readily available and low cost laboratory equipment. This was achieved by purifying M1 by reversed-phase flash chromatography after clean-up of the bulk sample by filtration on a silica gel cake. The purity of the final product determined by RP-HPLC was 99% and its identity was confirmed by IR spectroscopy and ESI mass spectrometry.

Filtration Mechanism of Gel Particle Slurry.

The filtration process of gel particle slurry was experimentally investigated with three kinds of gel particles. Gel particles have a high water content and are able to compress themselves, and so build up highly compressible filter cakes by filtration. The hydraulic pressure distributions in the gel particle cake were successfully measured by using a subminiature pressure sensor for evaluating the internal behavior of gel cake. This process was able to be divided into four different periods of separation. In this study, the separation modes were hypothesized and the methods for theoretical calculations were developed. The results of the study are useful in obtaining proper understanding of the filtration process of soft and hydrous materials.

Experimental analysis of flux decline mechanism of batch ultrafiltration (filtration characteristics of gel layer)

In order to make the so-called membrane fouling phenomena during ultrafiltration clearer, it is Important to visualise, by any means, the characteristics of the gel layer formed on the membrane surface. Unstirred dead-end ultrafiltration experiments were conducted under constant pressure, by using a newly-designed batchwise filter which had a sudden change in its filtration area. The variation in gel cake thickness with time, was determined on the basis of experimental measurements and then the overall characteristic values, such as the average specific filtration resistance, average porosity and the ratio of wet to dry cake mass were calculated on the basis of experimentally determined gel cake thickness. It has become evident that the relationship between filtration characteristics and operating conditions can be thoroughly analysed on the same basis as the conventional cake filtration theories or concept.

Disposable glucose sensor plate and disposable multi-ion sensor plate

A disposable glucose sensor plate and a disposable multi-ion sensor plate sensitive to sodium, potassium, chloride and hydrogen ions have been developed for clinical use. For a disposable-type sensor, simplicity of operation, especially the elimination of calibration, is necessary in addition to measurement accuracy and precision. To obtain a stable potential, a simple reference electrode was fabricated on a plate together with the ion-sensitive electrode using electrolyte gel cake on a Ag/AgCl electrode. The ion sensors had a sensitivity of 55–58 mV/dec and showed a linear response relative to the logarithm of each ion activity. The response to a given solution was reproducible to within approximately ±1.0 mV, corresponding to a final error of ±4% without any electrode calibration. The glucose sensor plate was prepared by immobilization of GOD over the pH electrode of the sensor plate. Responses to a given glucose solution ranging from 10 to 250 mg/dl were obtained and were reproducible to within approximately 8% in a normal glucose range without calibration before use. These results suggest that further improvement is necessary in order to obtain uniform electrode electrochemical characteristics, so that clinical application without pre-use calibration can be achieved.