Gas Channel Research Articles

Research on Gas Injection Limits and Development Methods of CH4/CO2 Synergistic Displacement in Offshore Fractured Condensate Gas Reservoirs

Gas injection for enhanced oil and gas reservoir recovery is a crucial method in offshore Carbon Capture, Utilization, and Storage (CCUS). The B6 buried hill condensate gas reservoir, characterized by high CO2 content, a deficit in natural energy, developed fractures and low-pressure differentials between formation and saturation pressures, requires supplementary formation energy to mitigate retrograde condensation near the wellbore area through gas injection. However, due to the connected fractures, the B6 gas reservoir exhibits strong horizontal and vertical heterogeneity, resulting in severe gas channeling and a futile cycle, which affects the gas injection efficiency at various levels of fracture development. Based on these findings, we conducted gas injection experiments and numerical simulations on fractured cores. A characterization method for oil and gas relative permeability considering dissolution was established. Additionally, the gas injection development boundary for this type of condensate gas reservoir was quantified according to the degree of fracture development, and the gas injection mode of the B6 reservoir was optimized. Research indicates that the presence of fractures leads to the formation of a dominant gas channel; the greater the permeability difference, the poorer the gas injection effect. The permeability gradation (fracture permeability divided by matrix permeability) in the gas injection area should be no higher than 15; gas injection in wells A1 and A2 is likely to achieve a better development effect under the existing well pattern. Moreover, early gas injection timing and pulse gas injection prove beneficial in enhancing the recovery rate of condensate oil. The study offers significant guidance for the development of similar gas reservoirs and for reservoirs with weakly connected fractures; advancing the timing of gas injection can mitigate the retrograde condensation phenomenon, whereas initiating gas injection after depletion may reduce the impact of gas channeling for reservoirs with strongly connected fractures.

Development characteristics and controlling mechanism of different microfracture combinations in shale reservoir: A case study of silurian longmaxi formation in Weiyuan area

Fractures in organic-rich shale are important reservoir spaces and seepage channels of shale gas, and they are closely related to the gas-bearing properties of shale. The development characteristics and laws of fractures are of great significance in the exploration and development of shale oil and gas. This study examines organic-rich shales of the Wufeng–Longmaxi Formation in the Weiyuan area of the Sichuan Basin. On the basis of two-dimensional large-area multi-scale combination electron microscopy characterization and digital core platform technology, the development degree and distribution of different fractures are quantitatively characterized. The results show the following. (1) The shale of the Wufeng and Longmaxi formations developed a variety of fractures with different occurrences, sizes, and origins. According to the number and combination relationship between fractures of different occurrences, the shale can be divided into four fracture combination types: horizontal bedding fractures; vein fractures; reticular fractures; and ring fractures. Of these, the horizontal bedding fracture group has the largest number of samples and a higher average fracture surface porosity. (2) The degree of fracture development in the shale is affected by many factors, such as the laminar type, mineral composition, mineral particle size, mineral distribution, and total organic carbon, and the controlling mechanisms of different fracture combination types differ. Factors such as horizontal stratification, high clay mineral content, and uneven mineral particle size are conducive to the development of horizontal bedding joints. (3) Differences in the sedimentary environment affect the variation laws of the vertical fracture combination types and density. The total organic carbon and organic quartz content of the Long111 layer with deeper sedimentary water is higher, and the vein fracture formation is more developed than in other small layers, while the clay mineral content of the Long112 and Long114 layers with shallower sedimentary water is higher and the horizontal layer is more developed; the fracture combination type is dominated by the horizontal bedding fracture combination. At the same time, the fractures at the junction of each layer of the Long11 sub-member are the most developed because sea level rise and fall make the mineral particle size heterogeneity most prominent at the junction of the small layer.

ENGINEERING OF LIQUID-GAS EJECTOR USING NUMERICAL SIMULATION

The article deals with the development and application of the technology of injection of low-pressure associated petroleum gas (APG) into the reservoir through the reservoir pressure maintenance system (RPMS) in connection with the entry into force of the Russian government decree on the mandatory utilization of 95 % of produced APG. The technology under consideration, the key element of which is a liquid-gas ejector (LGE), makes it possible to achieve this level with minimal investment, in the shortest possible time and to stop flaring APG at flares remote from the central oil and gas treatment facilities of oil and gas production facilities. LGEs have a relatively simple and reliable design due to the absence of moving elements.At present, there are known LGEs of classical designs, in which the level of hydrodynamic losses can reach 40–60 %. High hydrodynamic losses make it inexpedient to use such ejectors at small fields operated at a late stage of development, remote from the central oil and gas treatment facilities, due to the limitations of the existing equipment complex and the allowed operation mode of the injection well stock. To ensure the possibility of including LGE in the RPM system it was required to develop a new design of LGE, allowing to reduce hydrodynamic losses up to 30 %, as well as to ensure the maximum possible percentage of APG utilization. The article is devoted to the development, calculation of geometry and operating mode of LGE using numerical modeling in ANSYS environment.Modeling of the flowing part of the main elements of LGE (confuser nozzle, diffuser throat and gas channel width) at different values of parameters directly affecting the level of hydraulic losses is carried out. The results of calculations of numerical simulation of LGE allowed to optimize the dimensions of the internal geometry of LGE, thus it was possible to develop a new device for the required initial data, which will reduce the level of hydraulic losses up to 30 % and ensure the involvement of the maximum volume of gas in the RPM system.

Superior AlGaN/GaN-Based Phototransistors and Arrays with Reconfigurable Triple-Mode Functionalities Enabled by Voltage-Programmed Two-DimensionalElectron Gas for High-Quality Imaging.

High-quality imaging units are indispensable in modern optoelectronic systems for accurate recognition and processing of optical information. To fulfill massive and complex imaging tasks in the digital age, devices with remarkable photoresponsive characteristics and versatile reconfigurable functions on a single-device platform are in demand but remain challenging to fabricate. Herein, an AlGaN/GaN-based double-heterostructure is reported, incorporated with a unique compositionally graded AlGaN structure to generate a channel of polarization-induced two-dimensional electron gas (2DEGs). Owing to the programmable feature of the 2DEGs by the combined gate and drain voltage inputs, with a particular capability of electron separation, collection and storage under different light illumination, the phototransistor shows reconfigurable multifunctional photoresponsive behaviors with superior characteristics. A self-powered mode with a responsivity over 100AW-1 and a photoconductive mode with a responsivity of ≈108AW-1 are achieved, with the ultimate demonstration of a 10×10 device array for imaging. More intriguingly, the device can be switched to photoelectric synapse mode, emulating synaptic functions to denoise the imaging process while prolonging the image storage ability. The demonstration of three-in-one operational characteristics in a single device offers a new path toward future integrated and multifunctional imaging units.

Evaluation of Thermal and Mechanical Properties of Foamed Phosphogypsum-Based Cementitious Materials for Well Cementing in Hydrate Reservoirs

As detrimental byproduct waste generated during the production of fertilizers, phosphogypsum can be harmlessly treated by producing phosphogypsum-based cementitious materials (PGCs) for offshore well cementing in hydrate reservoirs. To be specific, the excellent mechanical properties of PGCs significantly promote wellbore stability. And the preeminent temperature control performance of PGCs helps to control undesirable gas channeling, increasing the formation stability of natural gas hydrate (NGH) reservoirs. Notably, to further enhance temperature control performance, foaming agents are added to PGCs to increase porosity, which however reduces the compressive strength and increases the risk of wellbore instability. Therefore, the synergetic effect between temperature control performance and mechanical properties should be quantitatively evaluated to enhance the overall performance of foamed PGCs for well cementing in NGH reservoirs. But so far, most existing studies of foamed PGCs are limited to experimental work and ignore the synergetic effect. Motivated by this, we combine experimental work with theoretical work to investigate the correlations between the porosity, temperature control performance, and mechanical properties of foamed PGCs. Specifically, the thermal conductivity and compressive strength of foamed PGCs are accurately determined through experimental measurements, then theoretical models are proposed to make up for the non-repeatability of experiments. The results show that, when the porosity increases from 6% to 70%, the 7 d and 28 d compressive strengths of foamed PGCs respectively decrease from 21.3 MPa to 0.9 MPa and from 23.5 MPa to 1.0 MPa, and the thermal conductivity decreases from 0.33 W·m−1·K−1 to 0.12 W·m−1·K−1. Additionally, an overall performance index evaluation system is established, advancing the application of foamed PGCs for well cementing in NGH reservoirs and promoting the recycling of phosphogypsum.

Gas channeling control with CO2-responsive gel system in fractured low-permeability reservoirs: Enhancing oil recovery during CO2 flooding

During the CO2 flooding process in fractured low-permeability oil reservoirs, the injected CO2 is prone to channeling along fractures due to severe reservoir heterogeneity, resulting in poor development effect. The CO2-responsive gel system shows dual advantages in achieving CO2 capture and plugging gas channeling to enhance oil recovery. This paper constructed a system with good CO2 sensitivity based on long-chain alkyl amide propyl dimethyl tertiary amine first. Subsequently, the properties of the system before and after the response were evaluated through rheological test, and its microstructure was characterized by Cryo-TEM. The system exhibited good CO2 responsiveness, transitioning from low-viscosity solution system to high-viscosity CO2-responsive gel system upon contact with CO2, with its viscosity increasing by nearly five orders of magnitude. The CO2-responsive gel demonstrated excellent shear resistance, viscoelasticity and shear self-repairing ability. The change of microstructure further verified the mechanism of molecules self-assembly in the system under the action of CO2. Then, a series of core physical simulation experiments were carried out to comprehensively evaluate the effects of different factors on the injection capacity, plugging characteristics, dynamic filtration damage performance and EOR effect of CO2-responsive gel. The gel maintained injectability while achieving an exceptional deep plugging effect, and the plugging rate reached 98.77%. It showed good characteristics of low filtration and permeability damage in low permeability reservoirs, effectively ensuring the fracture plugging effect. After the fracture was plugged by gel, the sweep range of CO2 to the matrix significantly expanded, and the gas flooding recovery increased by 18.19–21.7%. Finally, the matrix-fracture dual-media chip model was used to conduct microfluidic experiment, the oil displacement characteristics in different displacement stages were visually clarified, and the synergistic plugging and oil displacement mechanism between the CO2-responsive gel and CO2 was summarized. The research results can provide important insights for the green and efficient application of CO2-responsive gel in fractured low-permeability reservoirs.

Room temperature acetone gas sensing performance of ZnS-NiO nanocomposite sensor enhanced by UV activation for diabetes detection

Metal oxide semiconductors are popular in gas sensor applications.Current metal oxide-based acetone sensors struggle to deliver ppb-level acetone sensing at low temperatures for biological use. This study synthesizes 4mol% ZnS combined with NiO for acetone sensing. Nanoparticles were studied using FE-SEM, XPS, XRD, and UV-Vis spectroscopy. Mixed ZnS and NiO resulted in rapid gas channel movement and n-p heterojunction development, which increased acetone sensitivity. ZnS-NiO showed a gas sensing response of 163% for 20 ppm acetone at room temperature under UV irradiation, which is 2.3 times higher than pristine NiO (70% at 180 ∘C). ZnS improves sensor selectivity. Heterojunction sensor reaction and recovery times were 20 and 14 seconds, respectively. The composite sensor detection limit was 0.1 ppm. The increased sensitivity validates the n-p heterojunction. The sensor’s higher response values and lower detection limit point to breath analyzer applications such as diabetes detection.

Tailoring Water-Gas Ratios to Saturation Distribution for Improved Oil Recovery in Low-Permeability Reservoirs.

Water-gas alternation technology (WAG) is considered to be one of the methods that can effectively improve the effect of the CO2 flooding in heterogeneous reservoirs. The proportion of WAG and the timing of WAG adjustment are key factors affecting the oil displacement effect. This article analyzes the influence of adjusting the WAG ratio on the oil recovery effect of heterogeneous rock cores at different gas flooding stages based on gas flooding experiments. Second, the influence of WAG ratio changes on the recovery rate of displacement experiments under different saturation distributions was studied through numerical simulation. Finally, the oilfield model currently in production was used to optimize the WAG ratio adjustment of the reservoir recovery as a constraint condition. Moreover, the correlation between the fluid distribution of the reservoir and the timing of WAG adjustment was verified. The displacement experiment shows that adjusting the WAG ratio has a significant impact on the displacement effect of crude oil under the same heterogeneous conditions. After adjusting the WAG ratio from 1:2 to 2:1 at 0.5 HCPV and 1 HCPV, the final RF showed significant changes. There is an optimal timing for adjusting the WAG ratio under the same heterogeneity. If the WAG ratio is increased earlier, it will lead to a decrease in the CO2 injection volume and reduce the effectiveness of CO2 flooding. If the WAG ratio is increased later, it will lead to the formation of gas channeling channels and affect the effect of adjusting the WAG ratio on flooding.

Evaluation of mercury sorbent effectiveness using a vibration system

Gas purification is one of the important elements of many technologies. One of the methods of gas purification is the use of sorbents. The basis of the developed method is the vibratory introduction of the testing mixture (sorbent in fly ash) into the reaction chamber, which simulates the injection of the sorbent into the flue gas channel. The proposed method and stand enables a reliable comparison of powder sorbents with different rheological properties. A 0.1 % mixture of sorbent in fly ash was used for testing. The contact time can be flow regulated from 0.7-4.9 s. The measurement system enables testing of sorbents using flue gases of various compositions (λ = 1.1–2.7) at various temperatures (105–260 °C). The method was validated according EURACHEM guidelines and successfully tested in laboratory and industrial conditions. After validation the method was used to estimate the effectiveness of several new sorbents designed to remove mercury from flue gases.

A Dynamic Tanks-in-Series Model for a High-Temperature PEM Fuel Cell

A dynamic tanks-in-series model has been developed for the coupled heat, mass, and charge transfer processes in a high-temperature proton exchange membrane fuel cell. The semi-empirical model includes the heat and mass balance equations in the gas channels and the membrane electrode assembly together with the charge balance at the electrode/membrane interfaces. The outputs of the tanks-in-series model are the concentration, the temperature, and the current density with a step change from tank to tank. The dynamic non-isothermal model is capable of predicting both the transient and steady-state behavior of the fuel cell and reproducing impedance data under harmonic perturbations of the cell potential together with a comprehensive interpretation of experimental data.

Experimental Evidence of Primary Permeability at Very Low Gas Content in Crystal‐Rich Silicic Magma

AbstractEruptive dynamics is influenced by gas escape from the ascending magma. Gas pathways form in the magma via bubble coalescence, leading to gas channeling. Magmatic crystals play a key role in gas channel formation. This work constrains experimentally decompression‐induced coalescence in high‐crystallinity silicic magmas without external deformation, focusing on low gas content and bimodal crystal size (microlites and phenocrysts). All percolating samples have permeabilities of 10−14 m2 at bulk porosities of 7–10 vol% and bulk crystallinities up to 75 vol%. Our results demonstrate the possibility of coalescence‐related outgassing at high pressure (120–350 MPa) and without external strain, which corresponds to magma stagnating deep in a volcanic conduit. Channeling at such low gas content implies that bimodal crystallinity favors effusive over explosive volcanic behavior. It may also be the missing physical mechanism explaining gas transfer across magmatic systems despite high melt viscosity and low or absent magma extrusion.

Numerical Investigation of the Irreversible Behavior of GDL Under Cyclic Hygrothermal Loading

Performances of proton exchange membrane fuel cells (PEMFCs) is impacted by the physical properties of the gas diffusion layer (GDL). These properties, including thickness and porosity, are irreversibly modified by diverse processes, notably by the clamping of the PEMFC or the swelling of the membrane during cell operation. This can result in irreversible deformation of the GDL, with consequent impact on the performance and durability of the PEMFCs. This phenomenon, which is difficult to apprehend experimentally, is also challenging to investigate numerically. An elastoplastic law related to the irreversible strain of the GDL after compression is proposed in this study and implemented in a finite element model. Variations in GDL’s properties during humidity and temperature cycles are studied depending on PEMFC clamping methods using numerical simulations. The influences of processing conditions, i.e. the membrane electrode assembly hot pressing process, on GDLs properties are also investigated numerically. The results demonstrate the necessity to take into account the evolution of the mechanical properties of PEMFC components, with a significant influence of clamping process, life load and hot pressing process on the physical properties of the GDL as thickness, porosity, or intrusion in the gas channels.

High-Speed Generation of Microbubbles with Constant Cumulative Production in a Glass Capillary Microfluidic Bubble Generator.

This work reports a simple bubble generator for the high-speed generation of microbubbles with constant cumulative production. To achieve this, a gas-liquid co-flowing microfluidic device with a tiny capillary orifice as small as 5 μm is fabricated to produce monodisperse microbubbles. The diameter of the microbubbles can be adjusted precisely by tuning the input gas pressure and flow rate of the continuous liquid phase. The co-flowing structure ensures the uniformity of the generated microbubbles, and the surfactant in the liquid phase prevents coalescence of the collected microbubbles. The diameter coefficient of variation (CV) of the generated microbubbles can reach a minimum of 1.3%. Additionally, the relationship between microbubble diameter and the gas channel orifice is studied using the low Capillary number (Ca) and Weber number (We) of the liquid phase. Moreover, by maintaining a consistent gas input pressure, the CV of the cumulative microbubble volume can reach 3.6% regardless of the flow rate of the liquid phase. This method not only facilitates the generation of microbubbles with morphologic stability under variable flow conditions, but also ensures that the cumulative microbubble production over a certain period of time remains constant, which is important for the volume-dominated application of chromatographic analysis and the component analysis of natural gas.

Numerical investigation on dynamic characteristics of the droplet impacting on a random rough surface

Water management is a significant problem affecting the reliability and stability of proton exchange membrane fuel cells (PEMFC), in which droplet wall collision is the critical factor affecting the liquid water transmission in the gas channel. The surface roughness directly affects the spreading deformation of the droplet after impacting. This study's influence of surface roughness on the dynamic process of a single droplet of micrometer level impacting random rough surfaces was numerically investigated. Based on the Weierstrass–Manderlbrot (W-M) fractal theory, three-dimensional random rough surfaces with five roughness levels were established, and the dynamic process of droplet impact on the random rough surface was captured. The contour features of the droplet were analyzed, and the results showed that rough peaks hinder the spreading and retracted process of droplets, resulting in a thicker liquid film deposited on the rough surface, which is not conducive to liquid water discharge. The higher roughness level makes it difficult for droplets to gather into liquid film after hitting the wall and further hinders the discharge of liquid water from the flow channel. Therefore, when micrometer-sized droplets collide with a wall velocity of about 10 m/s, the roughness Ra should be controlled below 0.4 μm, which is conducive to the formation of thin liquid film after droplet impact and the effective discharge of water, which is crucial to maintaining the performance and life of PEMFC.

Recess-free enhancement-mode AlGaN/GaN RF HEMTs on Si substrate

Enhancement-mode (E-mode) GaN-on-Si radio-frequency (RF) high-electron-mobility transistors (HEMTs) were fabricated on an ultrathin-barrier (UTB) AlGaN (<6 nm)/GaN heterostructure featuring a naturally depleted 2-D electron gas (2DEG) channel. The fabricated E-mode HEMTs exhibit a relatively high threshold voltage (V TH) of +1.1 V with good uniformity. A maximum current/power gain cut-off frequency (f T/f MAX) of 31.3/99.6 GHz with a power added efficiency (PAE) of 52.47% and an output power density (P out) of 1.0 W/mm at 3.5 GHz were achieved on the fabricated E-mode HEMTs with 1-µm gate and Au-free ohmic contact.

Study on preparation and properties of polyurethane modified epoxy resin lotion cementing slurry

To solve the problems of poor cementing quality and weak consolidation performance of deep-water shallow cementing cement, a low-temperature curable polyurethane-modified epoxy resin lotion (WER) was prepared with epoxy resin and polyurethane as raw materials, and its hydrophilic groups (carboxyl and ether bonds) were self emulsified. The results show that the modified WER lotion cement slurry has good fluidity and stability. Its thickening transition time is less than 16 min, which can effectively prevent gas channeling. In addition, its low-temperature mechanical properties have been significantly improved, and its compressive strength has increased by 42.4% and 44.5% compared to net slurry cement within 3 and 7 days, while its elastic modulus has decreased by 34.1% and 42.4%, respectively.

CO2-responsive polymer promoted by polyether to efficient viscosity increase for CO2 plugging

A novel series of CO2-responsive polymers with unique hydrophobic structures were developed, capable of efficiently increasing viscosity in response to CO2 at low concentrations. These polymers, namely PAD-H, were synthesized by copolymerizing acrylamide, 2-(dimethylamino)ethyl methacrylate, and octadecyl polyoxyethylene ether methacrylate. In parallel, two comparative polymer sets were crafted, lacking the long polyether chains in their hydrophobic structures. DMAEMA imparts CO2-responsiveness through its tertiary amine groups, while the hydrophobic monomer contributes an alkyl structure with polyether long chains. These hydrophilic polyether long chains provide enhanced mobility to the hydrophobic alkyl chains, enabling lower concentration molecular hydrophobic association post CO2 exposure, thus leading to an increase in viscosity. This research delved into the mechanism of CO2-responsive viscosity increase, examining the impact of the polymer's intrinsic structure and external factors on its responsive behavior. Additionally, the polymer was applied in CO2 flooding, a crucial technique in carbon capture, utilization, and storage (CCUS). Simulated reservoir conditions were used to conduct in-situ CO2-responsive viscosity increase tests and CO2 gas channeling plugging experiments, substantially enhancing plugging efficiency. This advancement offers practical materials for addressing gas channeling in CO2 flooding and augments the technical methodologies for carbon utilization and storage within the CCUS framework.

Optical and Electrical Properties of AlGaN-Based High Electron Mobility Transistors and Photodetectors with AlGaN/AlN/GaN Channel-Stacking Structure.

High channel current of the high electron mobility transistors (HEMTs) and high relative responsivity of the photodetectors (PDs) were demonstrated in the AlGaN/AlN/GaN channel-stacking epitaxial structures. The interference properties of the X-ray curves indicated high-quality interfaces of the conductive channels. The AlGaN/AlN/GaN interfaces were observed clearly in the transmission electron microscope micrograph. The saturation I ds currents of the HEMT structures were increased by adding a number of channels. The conductive properties of the channel-stacking structures corresponded to the peaks of the transconductance (g m) spectra in the HEMT structures. The depletion-mode one- and two-channel HEMT structures can be operated at the cutoff region by increasing the reverse V gs bias voltages. Higher I ds current in the active state and lower current in the cutoff state were observed in the two-channel HEMT structure compared with one- and three-channel HEMT structures. For the channel-stacking metal-semiconductor-metal photodetector structures, the peak responsivity was observed at almost 300 nm incident monochromic light, which was increased by adding a number of channel layers. The channel current of the HEMT devices and the photocurrent in the PD devices were increased by adding a number of two-dimensional electron gas (2DEG) channels. By using a flat gate metal layer, the two-channel AlGaN/AlN/GaN HEMT structures exhibited a high I ds current, a low cutoff current, and a high peak g m value and have the potential for GaN-based power devices, fast portable chargers, and ultraviolet PD applications.

A Study on the Plugging Effect of Different Plugging Agent Combinations during CO2 Flooding in Heterogeneous Reservoirs

Gas channeling control is key to improving CO2-flooding efficiency. A traditional plugging system has disadvantages, such as poor adaptability and stability, leading to the poor plugging effect of CO2 channeling in heterogeneous reservoirs and difficulty in controlling the subsequent CO2 injection pressure. To achieve a significant plugging effect and effectively control the subsequent CO2 injection pressure, a heterogeneous physical model of gas channeling in a horizontal well was established, and plugging experiments were conducted using four different combinations of plugging agents during CO2 flooding. Three evaluation parameters were defined, including the temperature field variation coefficient (TFVC), medium-permeability diversion rate (MPDR), and subsequent injection pressure coefficient (SIPC). The plugging effect of different combinations of plugging agents during CO2 flooding in heterogeneous reservoirs was analyzed. The results show that the plugging effect after using a combination of plugging agents was significantly better than after using a single plugging agent, and different plugging agent combinations had distinct characteristics. The strong–medium–weak (S-M-W) combination had the best MPDR for subsequent CO2 flooding, but the SIPC was the highest. The strong–weak–strong–weak (S-W-S-W) and weak–strong–weak–strong (W-S-W-S) combinations could effectively control the SIPC. These results indicate that plugging using the S-W-S-W and W-S-W-S combinations can achieve an effective plugging effect and reasonably control the subsequent CO2 injection pressure. This work provides a personalized design scheme for effective gas channeling control and maintenance of appropriate injection pressure during CO2 flooding in heterogeneous reservoirs.

Impact of eliminating ungated access regions on DC and thermal performance of GaN-based MIS-HEMT

The impacts of eliminating access regions (AR) on DC and thermal performance of GaN-based MIS-HEMT have been studied using a device of 4 µm gate length. Nominal absence of ARs was achieved by a metal-organic chemical vapor deposition-regrown heavily n-doped GaN contact region extended to the two-dimensional electron gas (2DEG) channel (with sheet resistance as low as 14 Ω/ ◻ and ohmic contact resistance of 0.20 Ω⋅ mm) and 22-nm-thick AlN/Al2O3/HfO2 insulator layers acting as both gate dielectrics and sidewall spacers. As a result, a low knee voltage (2.5 V @ VGS = +2 V) comparable to deeply-scaled devices was attained, revealing the dominant role of ARs in knee voltages. High linearity at lower supply voltages (gate voltage swing of 7.3 V @ VDS = 5 V) and a faster GVS saturation trend with V DS increasing were observed, benefiting from the improved utility of applied lateral voltage. Moreover, a much lower thermal resistance compared to that of the conventional MIS-HEMT structure (146 vs. 202 K W−1) was extracted by a static-pulsed I-V measurement method. Simplified TCAD simulations were conducted to explain the underlying mechanisms, demonstrating that the enhanced surface heat flow covered by the gate metal as well as the more uniform electric field along the 2DEG channel accounts for the better capability of heat management in the device free of ARs. Our results indicate the size of DC and thermal performance enhancements obtained by eliminating ARs in a GaN-based MIS-HEMT structure.