Liquid injectivity in a SAG foam process:Effect of permeability

Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in facilities.Our previous studies with similar permeability cores show that during SAG injection,several banks occupy the area near the well where fluid exhibits distinct behaviour.However,underground reservoirs are heterogeneous,often layered.It is crucial to understand the effect of permeability on fluid behaviour and injectivity in a SAG process.In this work,coreflood experiments are conducted in cores with permeabilities ranging from 16 to 2300 mD.We observe the same sequence of banks in cores with different permeabilities.However,the speed at which banks propagate and their overall mobility can vary depending on permeability.At higher permeabilities,the gas-dissolution bank and the forced-imbibition bank progress more rapidly during liquid injection.The total mobilities of both banks decrease with permeability.By utilizing a bank-propagation model,we scale up our experimental findings and compare them to results obtained using the Peaceman equation.Our findings reveal that the liquid injectivity in a SAG foam process is misestimated by conventional simulators based on the Peaceman equation.The lower the formation permeability,the greater the error.

Progression of injectivity damage with oily waste water in linear flow

Numerous laboratory experiments and field cases show that even very small amount of oil in injected water can cause severe injectivity damage. Although injectivity decline caused by oil droplets has been studied experimentally, there is still lack of an easy-to-use and widely accepted model to predict the decline behavior. In this work, we developed an analytical model to predict the time-dependent progress of the water permeability reduction in linear flow by analyzing experimental data obtained from linear core flooding. The model considers mass transfer of the oil phase from the produced water to the rock due capture effects by dispersion, advection and adsorption inside the rock. As the captured oil saturation increases, permeability reduces following the relative permeability drainage relationship. The reduction stabilizes when the oil saturation comes to an equilibrium value controlled by oil droplet size and injection velocity. The model is calibrated using published experimental data from prolonged core floods with oil- contaminated waste water. Theoretical runs of the model replicate all the effects known from experimental observations. Resulting from the model is a distributed change of permeability vs. time and distance from the point of injection that can be converted to the overall injectivity damage.

Characterization of Hereditary Rings ViaInjectivity and Projectivity Classes

In this note,some characterizations of hereditary rings using injectivity classes and projectivity classes are given.These results unify many well known results.

Assessing roles of geochemical reactions on CO_(2)plume,injectivity and residual trapping

With increasing CO_(2)concentration in the atmosphere,CO_(2)geo-aequestration has become a popular technique to counter the dangers of global warming resulting from high levels of CO_(2)in the atmosphere.This paper examins sequestration parameters such as CO_(2)plume behaviour,residual gas trapping and injectivity as a means of achieving safe and successful CO_(2)storage in saline aquifers.Mineral precipitation/dissolution rates are used to establish a relationship between these parameters and geochemical reactions in saline aquifers.To achieve this,mechanistic models(6 models with different inputs,created using CMG e GEM,2016 and WINPROP,2016)are simulated using input data from literature and studying changes in fluids and formation properties as well as mineral precipitation/dissolution rates in aquifers when subjected to different conditions in the different models.The results from the models show that high CO_(2)dissolution,which creates large CO_(2)plume,leads to high mineral dissolution/precipitation as results of increased fluid-rock interactions(geochemical reactions);whereas injectivity,although enhanced by CO_(2)-water cyclic injection,does not show much increase in bottom hole pressure when mineral trapping(thus geochemical reactions)is introduced into the model.Sensitivity study on residual gas trapping shows that high residual gas saturation leads to reduced mineral precipitation/dissolution due to the reduced amount of dissolved CO_(2)in brine.Also,rapid changes in the bottom hole pressure at high residual gas saturation means that a formation that fosters high residual gas trapping,rather than CO_(2)dissolution in brine,is more likely to experience injectivity issues during the sequestration process.

A small-scale experimental study of CO_(2) enhanced injectivity methods of the high-rank coal

The attenuation of CO_(2)injectivity has become the biggest technical barrier for the application of CO_(2)enhanced coalbed methane recovery(CO_(2)-ECBM).Commonly,the intermittent CO_(2)injection,N2 displacing CO_(2)and pre-fracturing are the potential CO_(2)enhanced injectivity methods for coal reservoirs,but their mechanism and effectiveness remain to be clarified.This paper thus conducted small-scale experiments to simulate the working process of these engineering measures by an independently developed experimental device.Results show that the CO_(2)injectivity of coal is remarkably improved by the intermittent injection mode since the CO_(2)injection time is increased by folds and the loss of reservoir pressure can be complemented in time.The N_(2)displacing CO_(2)method promotes the desorption of CO_(2)and reduces the swelling strain,with the result that the permeability of coal is improved by 74.82%and 64.95%compared with the methods of the primary subcritical CO_(2)(Sub CO_(2))and supercritical CO_(2)(Sc CO_(2))injection.However,the permeability reduces again with the secondary CO_(2)injection.The permeability of the coal sample after pre-fracturing is averagely improved by 1-2 orders of magnitude,the irreversible permeability loss rate,average stress sensitivity coefficient and the permeability loss rate due to adsorption are averagely reduced by 95.885%,61.538%and 96.297%,respectively.This indicates that the permeability of coal after pre-fracturing is no longer sensitive to both the effective stress and Sc CO_(2)adsorption,the injectivity is thus improved and stable.The CO_(2)enhanced injectivity effects of the intermittent CO_(2)injection,the N_(2)displacing CO_(2)and the pre-fracturing are various,which thus can be selected individually or jointly to improve the CO_(2)injectivity according to the reservoir physical properties and geological conditions.This research deepens the understanding of the functional mechanism of CO_(2)enhanced injectivity methods and provides some guidance for their selection and application in engineering practices.

On the Flatness and Injectivity of Dual Modules(II)

For a commtative ring R and an injective cogenerator E in the category of R-modules, we characterize QF rings, IF rings and semihereditary rings by using the properties of the dual modules with respect to E.

On Maximal Injectivity

A right R-module E over a ring R is said to be maximally injective in case for any maximal right ideal m of R, every R-homomorphism f ： m → E can be extended to an R-homomorphism f^1 ： R → E. In this paper, we first construct an example to show that maximal injectivity is a proper generalization of injectivity. Then we prove that any right R-module over a left perfect ring R is maximally injective if and only if it is injective. We also give a partial affirmative answer to Faith＇s conjecture by further investigating the property of maximally injective rings. Finally, we get an approximation to Faith＇s conjecture, which asserts that every injective right R-module over any left perfect right self-injective ring R is the injective hull of a projective submodule.

A simulation study of water injection and gas injectivity scenarios in a fractured carbonate reservoir:A comparative study

Regarding the enormous demands of numerous industries to fossil fuels,it is essential to select the proper enhanced oil recovery approaches for vertical and horizontal wells to supply the demands with the optimum expenditure.Water and gas injectivity as the secondary enhanced oil recovery techniques would be preferentially considered regarding their low costs of performances rather than chemical recovery and thermal techniques.Injected gas tends to push oil through pores or cracks in the matrix block and lead them to the production well.Therefore,injection of gas may significantly increase the recovery factor in these reservoirs.In this research,different injection scenarios in a fractured carbonate reservoir in the west of Iran are being simulated by the PVT modules of Eclipse software.The purpose of this research is to analyze the possibility of gradually increasing the extent of recovery by injecting carbon dioxide,methane,and water,and different injectivity patterns are considered in this research.The selection of injectivity patterns is severely based on the highest recycling rate of gas injection on different injection scenarios,and the injectivity scenarios were being compared with the natural depletion scenario.Consequently,Co2 injection(about 60%)had the highest oil recovery factor and CH4 and TB(about 54%and 53%)injectivity scenarios had the second and third highest rate of the oil recovery factor.

Refractory lipoatrophy treated with autologous whole blood injection:A case report

BACKGROUND Intramuscular corticosteroid injection may cause adverse effects such as dermal and/or subcutaneous atrophy,alopecia,hypopigmentation,and hyperpigmentation.Although cutaneous atrophy can spontaneously resolve,several treatment options have been suggested for this condition.CASE SUMMARY In this paper,we report a case of corticosteroid injection induced lipoatrophy treated with autologous whole blood(AWB)injection,as the condition had been unresponsive to fractional laser therapy.A 29-year-old female patient visited the dermatology clinic complaining of skin depression on her right buttock area,which had appeared six months earlier.There had been only subtle improvement at the margins after fractional CO_(2) laser treatment;therefore,after obtaining informed consent from the patient,AWB treatment was initiated.One month after the first AWB injection,the size and depth of the lesion had noticeably improved,and a slight improvement was also observed in discoloration.CONCLUSION Close observation is the initial treatment of choice for steroid induced skin atrophy;however,for patients in need of immediate cosmetic improvement,AWB injection may be a safe and cost-effective alternative.

Injectivity theorems on compact complex manifolds

We use analytic methods in this paper to prove some new Enoki type injeetivity theorems on compact complex manifolds which generalize more or less the original Enoki injectivity theorem.

Injectivity radius bound of Ricci flow with positive Ricci curvature and applications

We study the injectivity radius bound for 3-d Ricci flow with bounded curvature. As applications, we show the long time existence of the Ricci flow with positive Ricci curvature and with curvature decay condition at infinity. We partially settle a question of Chow-Lu-Ni [Hamilton＇s Ricci Flow, p. 302].

Preliminary assessment of CO_(2) injectivity in carbonate storage sites

Depleted gas reservoirs are used for a large-scale carbon dioxide(CO_(2))storage and reduction of the greenhouse gas released into the atmosphere.To identify a suitable depleted reservoir,it is essential to do a preliminary and comprehensive assessment of key storage factors such as storage capacity,injectivity,trapping mechanisms,and containment.However,there are a limited number of studies providing a preliminary assessment of CO_(2) injectivity potential in depleted gas reservoirs prior to a CO_(2) storage operation.The aim of this study is to provide a preliminary assessment of a gas field located in Malaysia for its storage potential based on subsurface characterization prior to injection.Evaluation of the reservoir interval based on the facies,cores,and wireline log data of a well located in the field indicated that the pore type and fabrics analysis is very beneficial to identify suitable locations for a successful storage practice.Although the results obtained are promising,it is recommended to combine this preliminary assessment with the fluid-mineral interactions analysis before making any judgment about reliability of storage sites.

Gorenstein flatness and injectivity over Gorenstein rings

Let R be a Gorenstein ring.We prove that if I is an ideal of R such that R/I is a semi-simple ring,then the Gorenstein flat dimension of R/I as a right R-module and the Gorenstein injective dimension of R/I as a left R-module are identical.In addition,we prove that if R→S is a homomorphism of rings and SE is an injective cogenerator for the category of left S-modules,then the Gorenstein flat dimension of S as a right R-module and the Gorenstein injective dimension of E as a left R-module are identical.We also give some applications of these results.

Injectivity and projectivity in analysis and topology

We give new proofs of many injectivity results in analysis that make more careful use of the duality between abelian C*-algebras and topological spaces. We then extend many of these ideas to incorporate the case of a group action. This approach gives new insight into Hamana's theory of G-injective operator spaces and G-injective envelopes. Our new proofs of these classic results, use only topological methods and eliminate the need for results from the theory of Boolean algebras and AW*-algebras.

Gadolinium-doped injectable magnesium-calcium phosphate bone cements for noninvasive visualization

Injectable bone cements are used in minimally invasive surgical techniques including vertebroplasty and kyphoplasty.This work is devoted to the development of magnesium-calcium phosphate cements(MCPCs)doped with gadolinium ions(Gd^(3+))for bone defect repair.Interaction between cement powders and a cement liquid resulted in the formation of newberyite and brushite phases,which gave mechanical strength up to 17 MPa without a thermal effect.The introduction of Gd3+into the lattice was confirmed by electron paramagnetic resonance spectroscopy;the doping increased injectivity while giving rise to antibacterial properties against Escherichia coli.Assays of the cement samples soaking in Kokubo’s simulated body fluid revealed the formation of calcium phosphate coatings on the cements’surface.The cements manifested biocompatibility with the MG-63 cell line and significantly enhanced contrast when Gd-MCPC was placed into a bone defect and examined by X-ray micro-computed tomography.For the first time,visualization of a Gd-doped cement material was achieved in a model of a bone defect analyzed by MRI.

激素不同给药途径治疗突发性聋疗效观察

目的观察激素不同给药途径治疗突发性聋的疗效。方法回顾性分析海宁市中医院2021年4月~2024年4月间90例(90耳)突发性聋患者的病历资料,根据糖皮质激素用药方案分为静脉注射组26例(26耳)、鼓室注射组31例(31耳)、耳后注射组33例(33耳),均予以营养神经甲钴胺及认知行为疗法,此外分别予以地塞米松磷酸钠注射液静脉注射、经鼓膜穿刺注射、耳后注射,比较三组治疗疗效及治疗前后平均纯音听阈值(PTA)、主观症状视觉模拟量表(VAS)评分及不良反应。结果静脉注射组痊愈、显效、有效、无效分别为4例(15.38%)、6例(23.08%)、7例(26.92%)、9例(34.62%),鼓室注射组分别为14例(45.16%)、8例(25.81%)、4例(12.90%)、5例(16.13%),耳后注射组分别为21例(63.64%)、9例(27.27%)、2例(6.06%)、1例(3.03%)。总有效率比较,耳后注射组高于静脉注射组(P<0.05),静脉注射组与鼓室注射组、鼓室注射组与耳后注射组比较,差异均无统计意义(P>0.05);总显效率比较,鼓室注射组、耳后注射组均高于静脉注射组(P<0.05),且耳后注射组高于鼓室注射组(P<0.05);三组患者治疗后PTA及耳鸣、耳闷感VAS评分均较治疗前下降,且鼓室注射组、耳后注射组均低于静脉注射组,耳后注射组低于鼓室注射组,差异均有统计学意义(P<0.05);三组治疗期间均未见严重的全身不良反应,静脉注射组出现5例胃肠道不适,3例血小板增加,总发生率30.77%,鼓室注射组、耳后注射组仅出现局部不良反应,其中鼓室注射组治疗期间出现眩晕10例次,出血1例次,耳鸣2例次,不良反应总发生率41.94%,耳后注射组出现眩晕2例次,出血2例次,耳鸣1例次,不良反应总发生率15.15%,鼓室注射组不良反应总发生率高于耳后注射组(P<0.05)。结论耳后注射治疗突发性聋总显效率更高,治疗后听力及耳鸣、耳闷感改善均优于静脉注射和鼓室注射,且不良反应发生率显著低于鼓室注射,提示耳后注射途径在疗效和安全性方面具有优势。

Permanent Magnet Temperature Estimation for PMSMs Using Virtual Position-offset Injection

This paper proposes a virtual position-offset injection based permanent magnet temperature estimation approach for permanent magnet synchronous machines(PMSMs). The concept of virtual position-offset injection is mathematically transforming the machine model to a virtual frame with a position-offset. The virtual frame temperature estimation model is derived to calculate the permanent magnet temperature(PMT) directly from the measurements with computation efficiency. The estimation model involves a combined inductance term, which can simplify the establishment of saturation compensation model with less measurements. Moreover, resistance and inverter distorted terms are cancelled in the estimation model, which can improve the robustness to the winding temperature rise and inverter distortion. The proposed approach can achieve simplified computation in temperature estimation and reduced memory usage in saturation compensation. While existing model-based approaches could be affected by either the need of resistance and inverter information or complex saturation compensation. Experiments are conducted on the test machine to verify the proposed approach under various operating conditions.

Evaluation of the efficacy and safety of endoscopic band ligation in the treatment of bleeding from mild to moderate gastric varices type 1

BACKGROUND According to practice guidelines,endoscopic band ligation(EBL)and endoscopic tissue adhesive injection(TAI)are recommended for treating bleeding from esophagogastric varices.However,EBL and TAI are known to cause serious complications,such as hemorrhage from dislodged ligature rings caused by EBL and hemorrhage from operation-related ulcers resulting from TAI.However,the optimal therapy for mild to moderate type 1 gastric variceal hemorrhage(GOV1)has not been determined.Therefore,the aim of this study was to discover an individualized treatment for mild to moderate GOV1.AIM To compare the efficacy,safety and costs of EBL and TAI for the treatment of mild and moderate GOV1.METHODS A clinical analysis of the data retrieved from patients with mild or moderate GOV1 gastric varices who were treated under endoscopy was also conducted.Patients were allocated to an EBL group or an endoscopic TAI group.The differences in the incidence of varicose relief,operative time,operation success rate,mortality rate within 6 wk,rebleeding rate,6-wk operation-related ulcer healing rate,complication rate and average operation cost were compared between the two groups of patients.RESULTS The total effective rate of the two treatments was similar,but the efficacy of EBL(66.7%)was markedly better than that of TAI(39.2%)(P<0.05).The operation success rate in both groups was 100%,and the 6-wk mortality rate in both groups was 0%.The average operative time(26 min)in the EBL group was significantly shorter than that in the TAI group(46 min)(P<0.01).The rate of delayed postoperative rebleeding in the EBL group was significantly lower than that in the TAI group(11.8%vs 45.1%)(P<0.01).At 6 wk after the operation,the healing rate of operation-related ulcers in the EBL group was 80.4%,which was significantly greater than that in the TAI group(35.3%)(P<0.01).The incidence of postoperative complications in the two groups was similar.The average cost and other related economic factors were greater for the EBL than for the TAI(P<0.01).CONCLUSION For mild to moderate GOV1,patients with EBL had a greater one-time varix eradication rate,a greater 6-wk operation-related ulcer healing rate,a lower delayed rebleeding rate and a lower cost than patients with TAI.

Progress and prospects of EOR technology in deep,massive sandstone reservoirs with a strong bottom-water drive

The Triassic massive sandstone reservoir in the Tahe oilfield has a strong bottom-water drive and is characterized by great burial depth,high temperature and salinity,a thin pay zone,and strong heterogeneity.At present,the water-cut is high in each block within the reservoir;some wells are at an ultrahigh water-cut stage.A lack of effective measures to control water-cut rise and stabilize oil production have necessitated the application of enhanced oil recovery(EOR)technology.This paper investigates the development and technological advances for oil reservoirs with strong edge/bottom-water drive globally,and compares their application to reservoirs with characteristics similar to the Tahe oilfield.Among the technological advances,gas injection from the top and along the direction of structural dip has been used to optimize the flow field in a typical bottom-water drive reservoir.Bottom-water coning is restrained by gas injection-assisted water control.In addition,increasing the lateral driving pressure differential improves the plane sweep efficiency which enhances oil recovery in turn.Gas injection technology in combination with technological measures like channeling prevention and blocking,and water plugging and profile control,can achieve better results in reservoir development.Gas flooding tests in the Tahe oilfield are of great significance to identifying which EOR technology is the most effective and has the potential of large-scale application for improving development of deep reservoirs with a strong bottomwater drive.

An analytical model to estimate the time delay to reach spontaneous ignition considering heat loss in oil reservoirs

During air injection into an oil reservoir,an oxidation reaction generates some heat to raise the reservoir temperature.When the reservoir temperature reaches an ignition temperature,spontaneous ignition occurs.There is a time delay from the injection to ignition.There are mixed results regarding the feasibility of spontaneous ignition in real-field projects and in laboratory experiments.No analytical model is available in the literature to estimate the oxidation time required to reach spontaneous ignition with heat loss.This paper discusses the feasibility of spontaneous ignition from theoretical points and experimental and field project observations.An analytical model considering heat loss is proposed.Analytical models with and without heat loss investigate the factors that affect spontaneous ignition.Based on the discussion and investigations,we find that it is more difficult for spontaneous ignition to occur in laboratory experiments than in oil reservoirs;spontaneous ignition is strongly affected by the initial reservoir temperature,oil activity,and heat loss;spontaneous ignition is only possible when the initial reservoir temperature is high,the oil oxidation rate is high,and the heat loss is low.