Conductive polymer scaffolds to improve neural recovery

Injuries to the nervous system manifest in various forms ranging from stroke to trauma（i.e.,motor vehicle accidents,combats）to diabetic neuropathy as well as many other neurological diseases.Nerve regeneration remains a complex biological process that is challenging to address clinically.There is no effective medical treatment for central nervous system repair.

Utilization of CO2 Injection to Improve Oil Recovery of the Handsworth Bakken Formation

The Bakken formation has become a prominent oil resource for south-east Saskatchewan, especially with the advent of horizontal well technology and new hydraulic fracturing methods. As more wells are drilled, there is a desire to determine whether there is potential for improved oil recovery and to evaluate the economic feasibility. This paper evaluates the benefit of implementing waterflooding, CO2 injection or WAG （water-alternating-gas） recovery methods for improved oil recovery of the Bakken formation. A simulation model resembling the study area was built using CMG-GEM （computer modeling group-generalized equation of state model） reservoir simulation package and a history match of the primary recovery data available was performed. Based on the simulation results, it was concluded that waterflooding had a significant influence on the oil recovery factor, although COz provided the highest increase in crude oil recovery, The capital expenditure for surface facilities and cost of injected fluid was the most economically viable for implementation of waterflooding. The WAG injection simulation results were similar to CO2 injection, except that reservoir pressure was able to be better maintained. Given that high-quality source water is available, waterflooding is the most economically feasible choice according to the simulation results obtained from this study.

Enhancing recovery and sensitivity studies in an unconventional tight gas condensate reservoir

The recovery factor from tight gas reservoirs is typically less than 15%, even with multistage hydrauhc tractunng stimulation. Such low recovery is exacerbated in tight gas condensate reservoirs, where the depletion of gas leaves the valuable condensate behind. In this paper, three enhanced gas recovery （EGR） methods including produced gas injection, CO2 injection and water injection are investigated to increase the well productivity for a tight gas condensate reservoir in the Montney Formation, Canada. The production performance of the three EGR methods is compared and their economic feasibility is evaluated. Sensitivity analysis of the key factors such as primary production duration, bottom-hole pressures, and fracture conductivity is conducted and their effects on the well production performance are analyzed. Results show that, compared with the simple depletion method, both the cumulative gas and condensate production increase with fluids injected. Produced gas injection leads to both a higher gas and condensate production compared with those of the CO2 injection, while waterflooding suffers from injection difficulty and the corresponding low sweep efficiency. Meanwhile, the injection cost is lower for the produced gas injection due to the on-site available gas source and minimal transport costs, gaining more economic benefits than the other EGR methods.

Combined imbibition system with black nanosheet and low-salinity water for improving oil recovery in tight sandstone reservoirs

Nanomaterials and low-salinity water(LSW)are two popular enhanced oil recovery(EOR)methods that have been widely studied in recent years.The former is used for in-depth conformance improvement and the latter for microscopic oil displacement(by altering the potential and contact angle).However,there are few literature on combining them to achieve synergistic effects,especially for tight sandstone res-ervoirs.Based on the reservoir conditions of the Jimusar Oilfield,this study investigated the oil recovery mechanism of the combined imbibition system,which was composed of black nanosheet(BN)and LSW.Its performances including decreasing interfacial tension,emulsification,and wettability alterations were evaluated.The imbibition differences between the single system of BN and LSW and the combined BN-LsW imbibition system were then compared.Results showed that the combined imbibition system had a better emulsification effect on the crude oil and could also alter the wettability of the core surface.Moreover,the combined system could increase both the imbibition rate and the ultimate oil recovery.The nuclear magnetic T2 spectrum also indicated that the addition of black nanosheets could divert more fluid into small pores and thus improve the microscopic sweep efficiency.

Improved plasmid-based recovery of coxsackievirus A16 infectious clone driven by human RNA polymerase I promoter

Dear Editor,Coxsackievirus A16(CA16)is one of the major viral pathogens associated with hand,foot,and mouth disease.CA16 belongs to the Enterovirus genus of the Picornaviridae family and possesses a single-stranded positivesense RNA genome(Mao et al.,2014).Reverse genetics is an important tool for CA16 research.Previously,a reverse genetics T7 polymerase-based system was de-

Experimental and modeling study of CO_(2)-Improved gas recovery in gas condensate reservoir

This paper presents the effectiveness of the CO_(2) injection process at different periods during gascondensate reservoir development.Taking a real gas-condensate reservoir located in China's east region as an example,first,we conducted experiments of constant composition expansion(CCE),constant volume depletion(CVD),saturation pressure determination,and single flash.Next,a series of water/CO2 flooding experiments were been investigated,including water flooding at present pressure 15 MPa,CO_(2) flooding at 25.53 MPa,15 MPa,which repents initial pressure and present pressure respectively.Finally,the core flooding numerical model was constructed using a generalized equation-of-state model reservoir simulator(GEM)to reveal miscible flooding mechanism and the seepage flow characteristics in the condensate gas reservoir with CO2 injection.A desirable agreement achieved in experimental results and predicted pressure volume temperature(PVT)properties by the modified equation of state(EOS)in the CVD and CCE tests indicated that the proposed recombination method can successfully produce a fluid with the same phase behavior of initial reservoir fluid with an acceptable accuracy.The modeling results confirm the experimental results,and both methods indicate that significant productivity loss can occur in retrograde gas condensate reservoirs when the flowing bottom-hole pressure falls below dew point pressure.Moreover,the results show that CO_(2) treatment can improve gas productivity by a factor of about 1.39 compared with the water flooding mode.These results may help reservoir engineers and specialists to restore the lost productivity of gas condensate.

A critical review of self-diverting acid treatments applied to carbonate oil and gas reservoirs

Carbonate reservoirs generally achieved relatively low primary resource recovery rates.It is therefore often necessary to clean those reservoirs up and/or stimulate them post drilling and later in their production life.A common and basic carbonate reservoir cleanup technique to remove contaminating material from the wellbore is acidizing.The efficiency of acid treatments is determined by many factors,including:the type and quantity of the acid used;the number of repeated treatments performed,heterogeneity of the reservoir,water cut of the reservoir fluids,and presence of idle zones and interlayers.Post-treatment production performance of such reservoirs frequently does not meet design expectations.There is therefore much scope to improve acidizing technologies and treatment designs to make them more reliable and effective.This review considers acid treatment technologies applied to carbonate reservoirs at the laboratory scale and in field-scale applications.The range of acid treatment techniques commonly applied are compared.Differences between specific acid treatments,such as foamed acids,acid emulsions,gelled and thickened acid systems,targeted acid treatments,and acid hydraulic fracturing are described in terms of the positive and negative influences they have on carbonate oil production rates and recovery.Opportunities to improve acid treatment techniques are identified,particularly those involving the deployment of nanoparticles(NPs).Due consideration is also given to the potential environmental impacts associated with carbonate reservoir acid treatment.Recommendations are made regarding the future research required to overcome the remaining challenges pertaining to acid treatment applications.

Foaming supramolecular surfactants for gas mobility control in naturally fractured carbonate reservoirs at high temperature,salinity,and hardness

Oil production and mainte nance are essential issues in naturally fractured reservoirs because they are the largest and most productive on earth.However,they present early water and gas channeling but could be remediated by using foaming agents to control these phenomena through blocking channeling areas.In Mexico these reservoirs have pressure up to 5,500 psi,high temperature up to 200℃,salinity up to400,000 ppm,and hardness up to 250,000 ppm;due to these thermodynamic conditions,there has been no available technology to form stable enough foams.In this work,a foaming supramolecular surfactant with the capability to chelate Ca^(2+)ions is examined.As a result,surfactant monomers are bridged by captured Ca^(2+)cations leading to the formation of high-molecular-weight oligomers,which significantly increment the viscosity of the solution improving the foam stability,and since at this manner the Ca2+cations are no longer available to precipitate as components of solid salts,the foaming supramolecular surfactant also performs as antiscalant.These observations are explained through quantum theoretical modeling.The foam is stable,effectively blocking the gas channels,whereas in presence of oil the foam is broken leading the oil to pass into the wellbore.The characteristic rheological properties of the foam allow its injection into the formation at a range of flow rates,foam qualities,and shear stress to achieve the flooding and the blocking of a variety of fractured carbonate formations,and the change of the wettability of the matrix,which is a desirable behavior in a huff and puff process,as reported in a previous publication about a successful pilot test of this foam.

Comparison of numerical codes for coupled thermo-hydro-mechanical simulations of fractured media

Geo-energy and geo-engineering applications,such as improved oil recovery(IOR),geologic carbon storage,and enhanced geothermal systems(EGSs),involve coupled thermo-hydro-mechanical(THM)processes that result from fluid injection and production.In some cases,reservoirs are highly fractured and the geomechanical response is controlled by fractures.Therefore,fractures should explicitly be included into numerical models to realistically simulate the THM responses of the subsurface.In this study,we perform coupled THM numerical simulations of water injection into naturally fractured reservoirs(NFRs)using CODE_BRIGHT and TOUGH-UDEC codes.CODE_BRIGHT is a finite element method(FEM)code that performs fully coupled THM analysis in geological media and TOUGH-UDEC sequentially solves coupled THM processes by combining a finite volume method(FVM)code that solves nonisothermal multiphase flow(TOUGH2)with a distinct element method(DEM)code that solves the mechanical problem(UDEC).First,we validate the two codes against a semi-analytical solution for water injection into a single deformable fracture considering variable permeability based on the cubic law.Then,we compare simulation results of the two codes in an idealized conceptual model that includes one horizontal fracture and in a more realistic model with multiple fractures.Each code models fractures differently.UDEC calculates fracture deformation from the fracture normal and shear stiffnesses,while CODE_BRIGHT treats fractures as equivalent porous media and uses the equivalent Young’s modulus and Poisson’s ratio of the fracture.Finally,we obtain comparable results of pressure,temperature,stress and displacement distributions and evolutions for the single horizontal fracture model.Despite some similarities,the two codes provide increasingly different results as model complexity increases.These differences highlight the challenging task of accurately modeling coupled THM processes in fractured media given their high nonlinearity.

Improving gold recovery of Pb–Zn sulfide ore by selective activation with organic acid

Free gold and gold wrapped in sulfides are considered as the object of gold floatation. However,floatation of free gold exhibits more variables in practice.In this study, improving gold recovery of a Pb-Zn sulfide ore from Yunnan Province, China, was investigated. The results show that free gold and auriferous sulfides account for 94.99 % of total gold. Without adding organic acid in floatation, only 82 % recovery of gold could be obtained.Gold recovery in Au/Pb concentrates increases by 9.29 %with oxalate added and by 7.35 % with citric acid added,respectively, while performances of lead and arsenic nearly keep a constant. A possible reason is that free gold is of wonderful selectivity against pyrite with organic activators.A new method to enhance gold recovery is proposed.

Developing a phenomenological model to simulate single and mixed scale formation during flow in porous media:Coupling a salt precipitation model with an ion transport equation under dynamic conditions

Water flooding and pressure maintenance are recommended to improve oil recovery practices after low recovery of petroleum reservoirs occurs during primary production.Salt crystal formation is a frequent occurrence when using these techniques.Several experimental,numerical,and theoretical studies have been done on the mechanisms underlying scaling and permeability reduction in porous media;however,there has not been a satisfactory model developed.This study developed a phenomenological model to predict formation damage caused by salt deposition.Compared with existing models,which provide a scaling tendency,the proposed model predicts the profile of scale deposition.The salt precipitation model simulates reactive fluid flow through porous media.A thermodynamic,kinetic,and flow hydrodynamic model was developed and coupled with the ion transport equation to describe the movement of ions.Further,a set of carefully designed dynamic experiments were conducted and the data were compared with the model predictions.Model forecasts and experimental data were observed to have an average absolute error(AAE)ranging from 0.68%to 5.94%,which indicates the model's suitability.