Gas channeling control with an in-situ smart surfactant gel during water-alternating-CO_(2) enhanced oil recovery

Undesirable gas channeling always occurs along the high-permeability layers in heterogeneous oil reservoirs during water-alternating-CO_(2)(WAG)flooding,and conventional polymer gels used for blocking the“channeling”paths usually suffer from either low injectivity or poor gelation control.Herein,we for the first time developed an in-situ high-pressure CO_(2)-triggered gel system based on a smart surfactant,N-erucamidopropyl-N,N-dimethylamine(UC22AMPM),which was introduced into the aqueous slugs to control gas channeling inWAG processes.The water-like,low-viscosity UC22AMPM brine solution can be thickened by high-pressure CO_(2) owing to the formation of wormlike micelles(WLMs),as well as their growth and shear-induced structure buildup under shear flow.The thickening power can be further potentiated by the generation of denser WLMs resulting from either surfactant concentration augmentation or a certain range of heating,and can be impaired via pressurization above the critical pressure of CO_(2) because of its soaring solvent power.Core flooding tests using heterogeneous cores demonstrated that gas channeling was alleviated by plugging of high-capacity channels due to the in-situ gelation of UC22AMPM slugs upon their reaction with the pre-or post-injected CO_(2) slugs under shear flow,thereupon driving chase fluids into unrecovered low-permeability areas and producing an 8.0% higher oil recovery factor than the conventional WAG mode.This smart surfactant enabled high injectivity and satisfactory gelation control,attributable to low initial viscosity and the combined properties of one component and CO_(2)-triggered gelation,respectively.This work could provide a guide towards designing gels for reducing CO_(2) spillover and reinforcing the CO_(2) sequestration effect during CO_(2) enhanced oil recovery processes.

Comparative Analysis of Budesonide Treatments on Blood Gas and Inflammation in Chronic Obstructive Pulmonary Disease Remission

Objective:To investigate the effects of budesonide on blood gas and inflammation indexes in patients with chronic obstructive pulmonary disease(COPD)during remission.Methods:Fifty-one patients with COPD in remission,admitted to Zhongshan Hospital of Dalian University from July 2021 to December 2022,were selected and divided into two groups based on a randomized numerical table method.The control group(25 cases)received budesonide formoterol treatment,while the observation group(26 cases)received budesonide geforce treatment.Various indexes,including clinical efficacy,blood gas indexes,inflammation indexes,St.George’s Respiratory Questionnaire(SGRQ)scores,Chronic Obstructive Pulmonary Disease Assessment Test(CAT)scores,and 6-minute Walking Distance Test(6MWD)results,were compared between the two groups.Results:After 21 days of treatment,the total clinical effectiveness rate of the observation group was higher than that of the control group,with a statistically significant difference(P<0.05).Post-treatment,the PaO2 level and pH value in both groups were higher,and the PaCO_(2) level was lower compared to pre-treatment levels.The observation group showed better improvements in these indicators than the control group,with statistically significant differences(P<0.05).SGRQ and CAT scores for both groups were lower post-treatment,with the observation group scoring lower than the control group.Additionally,the 6MWD results were farther for both groups post-treatment,with the observation group achieving greater distances than the control group,with statistically significant differences(P<0.05).Conclusion:Budesonide can effectively improve blood gas indexes in patients with COPD in remission,alleviate related clinical symptoms,reduce inflammatory responses,and promote patient recovery.The treatment efficacy is significant.

Affecting Factors and Improving Measures for Converter Gas Recovery

To change the undesirable present situation of recovering and using converter gas in steel plants in China, the basic approaches to improving the converter gas recovery rate were analyzed theoretically along with the change curves of the converter gas component content, based on the converter gas recovery system of Baosteel No. 2 steel- making plant. The effects of converter device, raw material, air imbibed quantity, recovery restricted condition, and intensity of oxygen blowing on the converter gas recovery rate were studied. Among these, the effects of the air im bibed quantity, recovery restricted condition, and intensity of oxygen blowing are remarkable. Comprehensive measures were put forward for improving the converter gas recovery from the point of devices, etc. , and good results were achieved.

A deep-learning-based prediction method of the estimated ultimate recovery(EUR)of shale gas wells

The estimated ultimate recovery(EUR)of shale gas wells is influenced by many factors,and the accurate prediction still faces certain challenges.As an artificial intelligence algorithm,deep learning yields notable advantages in nonlinear regression.Therefore,it is feasible to predict the EUR of shale gas wells based on a deep-learning algorithm.In this paper,according to geological evaluation data,hydraulic fracturing data,production data and EUR evaluation results of 282 wells in the WY shale gas field,a deep-learning-based algorithm for EUR evaluation of shale gas wells was designed and realized.First,the existing EUR evaluation methods of shale gas wells and the deep feedforward neural network algorithm was systematically analyzed.Second,the technical process of a deep-learning-based algorithm for EUR prediction of shale gas wells was designed.Finally,by means of real data obtained from the WY shale gas field,several different cases were applied to testify the validity and accuracy of the proposed approach.The results show that the EUR prediction with high accuracy.In addition,the results are affected by the variety and number of input parameters,the network structure and hyperparameters.The proposed approach can be extended to other shale fields using the similar technic process.

Destruction mechanism of gas explosion to ventilation facilities and automatic recovery technology

In order to overcome the heavy casualties caused by gas explosion, we verified the propagation law of shock wave in pipeline and the overpressure distribution of gas explosion by similar experiments according to the analyses of reasons for casualty and ventilation system model destroyed by gas explosion in the mining face. We summarized the gas composition after the explosion and its danger, analyzed the effects of the gas explosion shock wave to ventilation system and facilities and the laws of toxic gas spread and diffusion in the ventilation network after the explosion. We presented a technical proposal to control the smoke and recover the ventilation system after a gas explosion and developed a reserve air door and control system that were embed in the lane, and could close automatically in conditions of no pressure and electricity. The results showed that the reserve air door normally opened and could close automatically controlling the smoke flow and resuming the ventilation system when the gas explosion shock wave destroyed the original shutting air door which resulted in the air short circuit.

Experimental Study of the Recovery Times of Spark Gap Switch with Different Gases

A two-pulse method is used to determine the insulation recovery time of the gas spark gap switch with different types of gas applied in a high power accelerator with a water dielectric pulse forming line. At the breakdown voltage of 450 kV, with the vacuum diode voltage of about 200 kV, and a current of 30 kA, recovery characteristics of H2, N2, SF6 were studied. The recovery percentages of the gas breakdown voltage and vacuum diode voltage were determined. The results show that hydrogen has the best recovery characteristics. At a pulse interval of 8.8 ms, the recovery percentages of both the gas breakdown voltage and vacuum diode voltage for hydrogen exceed 95%. For SF6 and N2 with an interval of 25 ms and 50 ms respectively, a 90% voltage recovery was obtained. The experiments also proved that the repetitive rate of the high power accelerator with a pulse forming line is mainly restricted by the gas switch repetitive rate; the recovery percentages of the vacuum diode voltage are limited by the recovery percentages of the gas switch breakdown voltage. The hydrogen switch can be employed for a high repetitive rate-high power accelerator with a pulse forming line.

Performance of free gases during the recovery enhancement of shale gas by CO_(2) injection:a case study on the depleted Wufeng–Longmaxi shale in northeastern Sichuan Basin,China

In this work, a novel thermal–hydraulic–mechanical (THM) coupling model is developed, where the real geological parameters of the reservoir properties are embedded. Accordingly, nine schemes of CO_(2) injection well (IW) and CH_(4) production well (PW) are established, aiming to explore the behavior of free gases after CO_(2) is injected into the depleted Wufeng–Longmaxi shale. The results indicate the free CH4 or CO2 content in the shale fractures/matrix is invariably heterogeneous. The CO_(2) involvement facilitates the ratio of free CH_(4)/CO_(2) in the matrix to that in the fractures declines and tends to be stable with time. Different combinations of IW–PWs induce a difference in the ratio of the free CH4 to the free CO_(2), in the ratio of the free CH_(4)/CO_(2) in the matrix to that in the fractures, in the content of the recovered free CH_(4), and in the content of the trapped free CO_(2). Basically, when the IW locates at the bottom Wufeng–Longmaxi shale, a farther IW–PWs distance allows more CO2 in the free phase to be trapped;furthermore, no matter where the IW is, a shorter IW–PWs distance benefits by getting more CH_(4) in the free phase recovered from the depleted Wufeng–Longmaxi shale. Hopefully, this work is helpful in gaining knowledge about the shale-based CO_(2) injection technique.

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.

CO_(2)storage with enhanced gas recovery(CSEGR):A review of experimental and numerical studies

CO_(2)emission mitigation is one of the most critical research frontiers.As a promising option of carbon capture,utilization and storage(CCUS),CO_(2)storage with enhanced gas recovery(CSEGR)can reduce CO_(2)emission by sequestrating it into gas reservoirs and simultaneously enhance natural gas production.Over the past decades,the displacement behaviour of CO_(2)—natural gas has been extensively studied and demonstrated to play a key role on both CO_(2)geologic storage and gas recovery performance.This work thoroughly and critically reviews the experimental and numerical simulation studies of CO_(2)displacing natural gas,along with both CSEGR research and demonstration projects at various scales.The physical property difference between CO_(2)and natural gas,especially density and viscosity,lays the foundation of CSEGR.Previous experiments on displacement behaviour and dispersion characteristics of CO_(2)/natural gas revealed the fundamental mixing characteristics in porous media,which is one key factor of gas recovery efficiency and warrants further study.Preliminary numerical simulations demonstrated that it is technically and economically feasible to apply CSEGR in depleted gas reservoirs.However,CO_(2)preferential flow pathways are easy to form(due to reservoir heterogeneity)and thus adversely compromise CSEGR performance.This preferential flow can be slowed down by connate or injected water.Additionally,the optimization of CO_(2)injection strategies is essential for improving gas recovery and CO_(2)storage,which needs further study.The successful K12—B pilot project provides insightful field-scale knowledge and experience,which paves a good foundation for commercial application.More experiments,simulations,research and demonstration projects are needed to facilitate the maturation of the CSEGR technology.

Investigation of flue gas water-alternating gas (flue gas–WAG) injection for enhanced oil recovery and multicomponent flue gas storage in the post-waterflooding reservoir

Flue gas fooding is one of the important technologies to improve oil recovery and achieve greenhouse gas storage.In order to study multicomponent fue gas storage capacity and enhanced oil recovery(EOR)performance of fue gas water-alternating gas(fue gas-WAG)injection after continuous waterfooding in an oil reservoir,a long core fooding system was built.The experimental results showed that the oil recovery factor of fue gas-WAG fooding was increased by 21.25%after continuous waterfooding and fue gas-WAG fooding could further enhance oil recovery and reduce water cut signifcantly.A novel material balance model based on storage mechanism was developed to estimate the multicomponent fue gas storage capacity and storage capacity of each component of fue gas in reservoir oil,water and as free gas in the post-waterfooding reservoir.The ultimate storage ratio of fue gas is 16%in the fue gas-WAG fooding process.The calculation results of fue gas storage capacity showed that the injection gas storage capacity mainly consists of N_(2) and CO_(2),only N_(2) exists as free gas phase in cores,and other components of injection gas are dissolved in oil and water.Finally,injection strategies from three perspectives for fue gas storage,EOR,and combination of fue gas storage and EOR were proposed,respectively.

A power plant for integrated waste energy recovery from liquid air energy storage and liquefied natural gas

Liquefied natural gas(LNG)is regarded as one of the cleanest fossil fuel and has experienced significant developments in recent years.The liquefaction process of natural gas is energy-intensive,while the regasification of LNG gives out a huge amount of waste energy since plenty of high grade cold energy(-160℃)from LNG is released to sea water directly in most cases,and also sometimes LNG is burned for regasification.On the other hand,liquid air energy storage(LAES)is an emerging energy storage technology for applications such as peak load shifting of power grids,which generates 30%-40%of compression heat(-200℃).Such heat could lead to energy waste if not recovered and used.The recovery of the compression heat is technically feasible but requires additional capital investment,which may not always be economically attractive.Therefore,we propose a power plant for recovering the waste cryogenic energy from LNG regasification and compression heat from the LAES.The challenge for such a power plant is the wide working temperature range between the low-temperature exergy source(-160℃)and heat source(-200℃).Nitrogen and argon are proposed as the working fluids to address the challenge.Thermodynamic analyses are carried out and the results show that the power plant could achieve a thermal efficiency of 27%and 19%and an exergy efficiency of 40%and 28%for nitrogen and argon,respectively.Here,with the nitrogen as working fluid undergoes a complete Brayton Cycle,while the argon based power plant goes through a combined Brayton and Rankine Cycle.Besides,the economic analysis shows that the payback period of this proposed system is only 2.2 years,utilizing the excess heat from a 5 MW/40 MWh LAES system.The findings suggest that the waste energy based power plant could be co-located with the LNG terminal and LAES plant,providing additional power output and reducing energy waste.

Gas injection for enhanced oil recovery in two-dimensional geology-based physical model of Tahe fractured-vuggy carbonate reservoirs:karst fault system

Gas injection serves as a main enhanced oil recovery(EOR)method in fractured-vuggy carbonate reservoir,but its effect differs among single wells and multi-well groups because of the diverse fractured-vuggy configuration.Many researchers conducted experiments for the observation of fluid flow and the evaluation of production performance,while most of their physical models were fabricated based on the probability distribution of fractures and caves in the reservoir.In this study,a two-dimensional physical model of the karst fault system was designed and fabricated based on the geological model of TK748 well group in the seventh block of the Tahe Oilfield.The fluid flow and production performance of primary gas flooding were discussed.Gas-assisted gravity flooding was firstly introduced to take full use of gas-oil gravity difference,and its feasibility in the karst fault system was examined.Experimental results showed that primary gas flooding created more flow paths and achieved a remarkable increment of oil recovery compared to water flooding.Gas injection at a lower location was recommended to delay gas breakthrough.Gas-assisted gravity flooding achieved more stable gas-displacing-oil because oil production was at a lower location,and thus,the oil recovery was further enhanced.

A novel type curve for estimating oil recovery factor of gas flooding

A novel type curve is presented for oil recovery factor prediction suitable for gas flooding by innovatively introducing the equivalent water-gas cut to replace the water cut,comprehensively considering the impact of three-phase flow(oil,gas,water),and deriving the theoretical equations of gas flooding type curve based on Tong’s type curve.The equivalent water-gas cut is the ratio of the cumulative underground volume of gas and water production to the total underground volume of produced fluids.Field production data and the numerical simulation results are used to demonstrate the feasibility of the new type curve and verify the accuracy of the prediction results with field cases.The new type curve is suitable for oil recovery factor prediction of both water flooding and gas flooding.When a reservoir has no gas injected or produced,the gas phase can be ignored and only the oil and water phases need to be considered,in this case,this gas flooding type curve returns to the Tong’s type curve,which can evaluate the oil recovery factor of water flooding.For reservoirs with equivalent water-gas cuts of 60%-80%,the regression method of the new type curve works well in predicting the oil recovery factor.For reservoirs with equivalent water-gas cuts higher than 80%,both the regression and assignment methods of the new type curve can accurately predict the oil recovery factor of gas flooding.

Technical strategies for effective development and gas recovery enhancement of a large tight gas field: A case study of Sulige gas field, Ordos Basin, NW China

Based on the analysis of influencing factors of tight gas recovery and reservoir geological characteristics, the types of remaining tight gas reserves in the Sulige gas field are summarized from the perspective of residual gas genesis to estimate residual gas reserves of different types and provide corresponding technical strategies for enhancing gas recovery. The residual gas reserves in the Sulige gas field can be divided into four types: well pattern uncontrollable, horizontal well missing, imperfect perforation, blocking zone in composite sandbodies. Among them, the uncontrolled remaining gas of well pattern and blocking zone in composite sandbodies are the main body for tapping potential and improving recovery factor, and well pattern infilling adjustment is the main means. Taking into account reservoir geological characteristics, production dynamic response and economic benefit requirements, four methods for infilling vertical well pattern, i.e., quantitative geological model method, dynamic controlled range of gas well method, production interference method and economic and technical index evaluation method, as well as a design method of combined vertical well pattern with horizontal well pattern are established. Under certain economic and technological conditions, the reasonable well pattern density of enrichment zone of gas field is proved to be 4 wells per square kilometers, which can increase the recovery rate of the gas field from 32% to about 50%. Meanwhile, five matching techniques for enhancing gas recovery aimed at interlayer undeveloped residual gas have been formed, including tapping potential of old wells, technological technology optimizing of new wells, rational production system optimizing, drainage and gas producing, and reducing waste production, which could increase the recovery rate for 5% based on well pattern infilling. The research results provide effective support for the long-term stable production of 230×108 m3/a of the Sulige gas field and production growth in the Changqing gas area.

Coupled thermo-hydro-mechanical simulation of CO2 enhanced gas recovery with an extended equation of state module for TOUGH2MP-FLAC3D

As one of the most important ways to reduce the greenhouse gas emission,carbon dioxide（CO2）enhanced gas recovery（CO2-EGR） is attractive since the gas recovery can be enhanced simultaneously with CO2sequestration.Based on the existing equation of state（EOS） module of TOUGH2 MP,extEOS7C is developed to calculate the phase partition of H2O-CO2-CH4-NaCl mixtures accurately with consideration of dissolved NaCI and brine properties at high pressure and temperature conditions.Verifications show that it can be applied up to the pressure of 100 MPa and temperature of 150℃.The module was implemented in the linked simulator TOUGH2MP-FLAC3 D for the coupled hydro-mechanical simulations.A simplified three-dimensional（3D）1/4 model（2.2 km×1 km×1 km） which consists of the whole reservoir,caprock and baserock was generated based on the geological conditions of a gas field in the North German Basin.The simulation results show that,under an injection rate of 200,000 t/yr and production rate of 200,000 sm3/d,CO2breakthrough occurred in the case with the initial reservoir pressure of 5 MPa but did not occur in the case of 42 MPa.Under low pressure conditions,the pressure driven horizontal transport is the dominant process;while under high pressure conditions,the density driven vertical flow is dominant.Under the considered conditions,the CO2-EGR caused only small pressure changes.The largest pore pressure increase（2 MPa） and uplift（7 mm） occurred at the caprock bottom induced by only CO2injection.The caprock had still the primary stress state and its integrity was not affected.The formation water salinity and temperature variations of ±20℃ had small influences on the CO2-EGR process.In order to slow down the breakthrough,it is suggested that CO2-EGR should be carried out before the reservoir pressure drops below the critical pressure of CO2.

Assessment of Hazards in Gas Hydrates Recovery

Gas hydrates are whitish balls containing enormous amount of methane gas at deep marine sediments.This energy source will account for future energy needs as it is said to be twice the value of all recoverable energy sources tapped till date.They are formed as a result of biogenic and thermogenic matters coupled with deep water conditions such as excessive pressure and diminishing temperature.Various recovery methods have been juxtaposed till date to influence the production of its reserves.However,appropriate assessment of the hazards and shortcomings hindering the large scale production of these reserve needs to be checkmated in order to facilitate the effective development of gas from methane hydrate in a near future.

Improvement in Sensitivity and Recovery of Single-Walled Carbon Nanotube-Based Gas Sensors

In this paper,an improvement in sensitivity and recovery of the single-walled carbon nanotube (SWNT)-based gas sensors was reported.The sensors were fabricated from SWNT powder by a screen-printing method,followed by annealing for 2 h in open-air at various temperatures.The Raman spectra of the SWNT bundles and the response to ammonia (NH_3) exposure of the sensors indicated that the annealing at a relevant temperature improved the sensor sensitivity.The sensor annealed at 200℃exhibited a high sensitivity in NH_3 detection.After 20 min of exposure to NH_3 at room temperature,the resistance of the sensor increased up to 12% in comparison with its initial value.By evacuating combined with maintaining the flux of carrier gas at 300 sccm,the sensor recovery was significantly speeded.The sensor resistance retrieved to its initial value after only 25 min degassing. These results would be considered in the development of the SWNT-based gas sensors.

Oscillation in Response and Recovery Properties of SnO_2 Gas Sensor

Six kinds of Sn(OH)_4 precipitates were prepared by the chemical precipitation method (liquid-phase),of which the pH values are 3.0 (sample 1),4.5 (sample 2),6.0 (sample 3),7.5 (sample 4),9.0 (sample 5) and 10.5 (sample 6),respectively. After washed and dried,the Sn(OH)_4 precipitates were first calcined into tin oxide powder.Six kinds of gas sensors were made from the obtained SnO_2 powders.The XRD patterns of all the samples were recorded.The sensing properties of all samples to C_2H_5OH and H_2 gases were measured in different gas concentrations and temperatures,including the sensitivities of all samples,their response and recovery properties.The recovery properties of all samples to C_2H_5OH exhibit the sinusoidal oscillation character.

Qualification Test for the Reliability of Diver Gas Recovery System

A qualification test for the reliability of a newly-developed Diver Gas Recovery System (DGRS) was carried out in the Naval Medical Research Institute of the People's Liberation Army, China from March 29 to April 2, 1995. A sequential test plan of high discrimination ratio for the mean time between failures (MTBF) was adopted. The test procedures simulated those of a 300 msw dive. A hyperbaric breathing machine was used for the simulation of diver's respiratory functions. Parameters, such as diving depth, respiratory minute volume (RMV), CO2 production, gas flow rate, partial pressure of carbon dioxide, and ambient temperature and himidity were all displayed and recorded with a microcomputer system. The results indicated that no failure occurred during the 91.5 h operation. According to the acceptance and rejection criteria specified in the statistical test plan, a no-failure score in the 88 h operation is acceptable. Therefore, the DGRS has been demonstrated to meet the requirements of MTBF specified in the contract.

A reservoir drying method for enhancing recovery of tight gas

Based on the study of damage mechanisms of generalized water blocking and related water-blocking removal methods, the drying agents for enhancing tight gas reservoir recovery were developed, and the basic properties, injection mode and drying effect of the drying agents were evaluated. The chemical effect, thermal effect, salt resistance, salt resistance formulas and delay mechanism of the drying agent systems for different types of tight reservoirs were investigated through lab experiment. The solubility and solubilization properties of supercritical carbon dioxide on drying agent systems were tested.The injection mode of dissolving drying agent in supercritical carbon dioxide was proposed. The mechanisms of supercritical carbon dioxide with water in micropores of formation matrix were analyzed. Micro-pore structures and seepage characteristics of reservoir before and after drying were compared. Based on the characterization in combination of NMR and laser etched pore structure model, drying effects of the drying agents on bound water of different occurrences were evaluated qualitatively and quantitatively. Lattice Boltzmann method was used to evaluate the influence of drying effect on gas micro-seepage ability.The influence of drying effect on productivity and production performance of gas well was analyzed by numerical simulation.The drying effect can greatly reduce water saturation of tight reservoir and improve the gas seepage capacity in near wellbore and fractures. This work can provide guidance for developing new measures in enhancing recovery of tight gas reservoirs.