Effects Of Depressurization Research Articles

Effect of Isotropic and Anisotropic Permeability on Gas Production Behavior of Site NGHP-01-10D in Krishna-Godavari Basin

This study reports an investigation into both isotropic and anisotropic permeability effects on gas production behavior during depressurization-induced natural gas hydrate dissociation at site NGHP-01-10D in the Krishna-Godavari basin. Numerical simulations were performed on a reservoir-scale model incorporating a single vertical well, examining different scenarios of permeability ratios (rrz). The investigation assessed gas and water production rates, cumulative production volumes, the gas-to-water ratio, and the spatial distribution of reservoir parameters throughout a production duration of 3 years. The findings indicate that permeability anisotropy has a substantial impact on hydrate dissociation and gas recovery. For rrz > 1, horizontal pressure propagation was promoted and gas production increased. For example, at t = 1100 days, the total gas production improved from 7.88 × 105 ST m3 for rrz = 1 to 55.9 × 105 ST m3 for rrz = 10. For rrz < 1, vertical pressure propagation resulted in higher water production with concomitantly lower rates of gas production rates. Spatial distribution analysis revealed that higher rrz values led to more extensive radial propagation of pressure drop, temperature decrease, gas saturation increase, and hydrate dissociation. The study concludes that higher horizontal permeability enhances depressurization effects, resulting in higher gas production rates and more favorable gas-to-water ratios.

Impact Tendency Characteristics of Borehole Coal Samples under Real-Time and Uniaxial Loading Conditions: Insights from Physical Experiments

Real-time drilling depressurization technology is widely used in the prevention and control of dynamic disasters, such as deep-seated rock burst. However, current coal- and rock-loading tests under drilling conditions seldom account for real-time issues associated with drilling, thus failing to fully reflect the actual stress state of the surrounding rock during the implementation of drilling depressurization technology. Therefore, this study designed and implemented a uniaxial loading scheme for coal samples incorporating real-time-drilling characteristics. The results indicate a significant reduction in the uniaxial compressive strength (RC), elastic energy index (WET), and impact energy index (KE) of the samples post-drilling. These parameters show a clear decreasing trend with increasing axial stress during real-time drilling. The weakening effect of impact tendency following real-time drilling depressurization is significant, and the depressurization effect is pronounced. The RC, WET, and KE of each real-time-drilled sample exhibit a notable decrease with increasing drilling stress, with the reduction rate significantly diminishing after the drilling stress reaches 20% of the peak strength.

Experimental study on controlling basement leakage for urban flooding mitigation

Intense summer rainstorms can result in short-term urban flooding, leading to localized groundwater level rise and subsequent floor cracking and leakage in basements. Rational control of the surrounding water level is crucial for addressing existing basement leaks caused by short-term urban flooding. In this study, a combined approach of interception and seepage control using waterproof curtains and negative-pressure wells is proposed. Four different scenarios were considered, and experimental and numerical investigations were conducted on a 1.2 m × 1.2 m × 1.1 m model. The study analyzed the influence of factors such as water content, pore water pressure, soil properties, waterproof curtain insertion depth, and length of the filter section in the negative-pressure well on controlling the upward water level in the basement.The results showed that the installation of waterproof curtains alone can impede rainwater infiltration into the basement, delaying its penetration by approximately 48 h. The combined approach of interception and seepage control outperformed the sole use of waterproof curtains, with the reduction in water level becoming smaller as the insertion depth of the waterproof curtain increased. The reduction in water level decreased at a slower rate with increasing waterproof curtain insertion depth. The recommended waterproof curtain insertion ratio was equal to or greater than 83.5 %, while the filter section length ratio in the negative pressure well should be less than 64 %. Compared to natural seepage drainage, negative-pressure pumping could maintain the basement floor's water content within the initial range 32 h earlier. The water-blocking and depressurization effect is best in sandy soil and worst in clay. Water-blocking and depressurization provide a new approach for controlling the uplift caused by summer urban waterlogging, especially offering a new method for controlling leaks in the basement.

Experimental Analysis on Thermodynamic and Kinetic Characteristics of Water‐Saturated Natural Gas Hydrates by Depressurization Decomposition

Natural gas hydrate has attracted worldwide attention for its abundant availability and clean and nonpolluting combustion products. The actual environment of marine methane hydrates is water‐saturated, but present researches on water‐saturated hydrates are relatively few. This study prepares water‐saturated hydrate sediment of ≈70% saturation and mainly focuses on the thermodynamic and kinetic characteristics of decomposition process using different depressurization rates. Compared with gas‐saturated hydrates, both the thermodynamic evolution and the decomposition kinetics of water‐saturated hydrates get weakened due to the inhibition of water molecules surrounding hydrate crystals on heat and mass transfer. In all experimental cases of water‐saturated hydrates, the temperature still decreases at most 0.5 °C in several minutes after the pressure has become constant, indicating the delay effect of depressurization in water phase. The results show that the increase in depressurization rate strengthens both temperature decrease and pressure delay of water‐saturated hydrate‐bearing sediment. In addition, the decomposition rate of water‐saturated hydrates in depressurization stage is constant and positive to the depressurization rate, while the decomposition rate in constant pressure stage is a function of residual hydrate amount. This study is significant for decomposition control of hydrate mining under actual marine environment.

Experimental study on metastable dissociation of sandy hydrate reservoirs

The depressurization method has been proven to be an energy-efficient and relatively feasible production technique for natural gas hydrates. However, during the depressurization process, especially when the hydrates reservoir approaches the quadruple point, it is inevitable to experience phenomena such as freezing and hydrates secondary formation. Therefore, most researchers think that the P-T near the quadruple point may not be suitable for the dissociation of hydrates and a series of depressurization control methods were adopted to avoid this. However, according to other researchers, the effect of depressurization near the quadruple point on the dissociation behavior of hydrates is not inhibitory, but even a promoting effect to a certain extent. In addition, A special region called metastable state appears with the decrease of pressure near the quadruple point, which makes the dissociation behavior of hydrate below the quadruple point different from that above it. Therefore, in this paper, to reveal more clearly the dissociation behavior of natural gas hydrates near the quadruple point and the influence of the existence of metastable state on the depressurization dissociation of hydrate, the dissociation experiment of natural gas hydrates in the porous medium peri-freezing point is investigated in different depressurization rates and amplitudes, peri-freezing point and pressure stabilization times quadruple point. Experimental studies have shown that the amount of dissociation of natural gas hydrates below the quadruple point is non-linearly correlated with the depressurization rate. This correlation is synergistically regulated by the depressurization magnitude per unit of time and the environmental heating efficiency. Compared with the dissociation of hydrates above the freezing point, the metastable region does not show an obvious inhibitory effect on the dissociation of hydrates, and it even effectively shortens the dissociation time of hydrates and improves the heat transfer efficiency of the reservoir. Under the dissociation pressure of 2.5 MPa (metastable state), the reservoir temperature rose from 0 °C to 1 °C in 2.9 h, 3.6 h less than that under 2.6 MPa (above the quadruple point), and 0.7 h more than that under 1.0 MPa (below the metastable state). In addition, the gas production rate of hydrates is improved when hydrates disengagement the metastable region, increasing by 65.12 % compared with those above the quadruple point. However, pressure stabilization times when hydrates are in a metastable state need to be kept within a certain interval, too long or short pressure stabilization time will inhibit the dissociation of hydrates, and reduce the promotion effect on the dissociation of hydrates.

Class-III Hydrate Reservoir Depressurization Production Enhancement by Volume Fracturing and Cyclic N2 Stimulation Combination.

The depressurization effect is limited to class III hydrate reservoir recovery. To improve the depressurization effect, a new method of volume-fracturing and cyclic N2 stimulation combination (VFCS) was proposed. The production performance of this method was investigated by using numerical models based on reservoir parameters of the SH7 hydrate site in the South China Sea. The results show that (1) VFCS can greatly enhance the production performance with the average CH4 production rate being approximately 2.85 times higher than that of pure depressurization. This method combines the effects of volume fracturing and cyclic N2 stimulation by improving the seepage environment and further reducing the CH4 partial pressure in the gas phase. (2) High reservoir permeability, medium hydrate saturation, large volume-fracturing scale, low bottom-hole pressure, and high N2 injection amount can increase CH4 production by VFCS. (3) Although VFCS has the largest CH4 production volume and the highest hydrate dissociation degree among the studied production strategies, the reservoir temperature drop is significant by VFCS and future studies can be focused on the external heat supply to the reservoir to further improve the production.

Evaluation of the Effects of Nano-SiO2 Microemulsion on Decompression and Augmented Injection in the Eunan Tight Reservoir

The residual oil saturation of the matrix near the well zone of a tight reservoir is high due to the tight reservoir’s complex conditions, such as the small pore throat radius and low permeability of the matrix and the development of microfractures, which can result in serious water channeling, even after long-term water injection development. The aim of this paper is to improve the effects of depressurization and augmented injection for tight reservoir waterflooding development by reducing the tight matrix’s residual oil saturation, increasing and maintaining its water phase permeability near the well zone using a nano-SiO2 microemulsion system with a small particle size and high interfacial activity. Therefore, four nano-microemulsion systems were evaluated and screened for their temperature resistance, salt resistance, interfacial tension, solubilization, and dilution resistance. A microemulsion system of 13% A + 4% B + 4% C + 4% n-butanol + 6% oil phase + 69% NaCl solution (10%) + 1% OP-5 + 0.5% anti-temperature agent + 0.3% nanosilica material was preferred. According to the core displacement experiment, the depressurization rate can reach 28~60% when the injection concentration of the system is 1~10% and the injection volume is 2~5 PV. The results of the on-site test show that the water injection pressure dropped to 17.5 MPa, which was lower than the reservoir fracture re-opening pressure. The pressure reduction rate was approximately 20%. The validity period of the depressurization and augmented injection has reached 23 months to date.

Investigation on unsteady thermal process of NEPE propellant based on an refined chemical kinetic model

This study presents a sophisticated investigation into the intricate heat and mass transfer mechanisms of NEPE composite propellant under realistic rocket motor conditions, with particular emphasis on the rapid depressurization effects. To accomplish this, we have developed an innovative particle packing algorithm coupled with a novel semi-global kinetics model. By integrating detailed chemical kinetics models for Ammonium perchlorate (AP) oxidizing powders, Cyclotetramethylene tetranitramine (HMX) oxidizing powders, and Nitroglycerin/1,2,4-Butane triol trinitrate (NG/BTTN) fuel-binder, we have constructed a meso-scale model of NEPE propellant based on comprehensive experimental data. Furthermore, a refined 9-step kinetic mechanism has been incorporated into the meso-scale model, along with a pressure drop model that accurately captures the intricate gas reaction domain. The predicted parameters of NEPE propellant have been meticulously compared with experimental results, demonstrating a remarkable level of agreement. Moreover, meticulous analyses have been carried out to investigate the complex thermal processes exhibited by this composite propellant under the challenging conditions of rapid depressurization combustion. These analyses primarily focus on unraveling the dynamic evolution of the gas-solid phase and the underlying thermal regression mechanism of the solid phase. Notably, our findings reveal intriguing temporal changes in local heat flux feedback spikes throughout the entire depressurization process, owing to the intricate topology structure of NEPE propellant, which comprises multiscale oxidizing micro-particles embedded within a fuel-binder matrix. This research significantly enhances our understanding of the thermal behavior and performance characteristics of NEPE composite propellant, thereby paving the way for future advancements in rocket propulsion technology.

Effect of heterogeneous hydrate distribution on hydrate production under different hole combinations

Few laboratory studies were focused on the effect of heterogeneous hydrate distribution on hydrate production. Herein, in a horizontal pressure vessel with hole density of 8.3 holes/m and hole diameter of 2.5 cm, this effect was defined by depressurization in seven samples with a hydrate saturation of 23.2% under various hole combinations. Hydrate distribution and its heterogeneity degree were represented by the net increase of the electrical resistance during hydrate formation and the corresponding variation coefficient and then compared with depressurization effects. The results showed that hydrate distribution possessed a heterogeneity degree range of 0.96–1.97. Under a large heterogeneity degree, water production was aggravated. Thus, temperature loss and the sensible heat use ratio under one-hole combination was separately increased by 0.21 °C and 0.12, while gas production and hydrate dissociation ratio was reduced by 4.332 L and 3.79%, respectively. An apparent effect of hydrate distribution on water production was observed within 1–2 holes. This effect increased temperature loss by 0.11 °C and the sensible heat use ratio by 0.084, and reduced gas production by 6.564 L. Exceeding 1–2 holes, hole amounts governed severe water production. This work may advantage to understand the influencing mechanism of hydrate distribution on hydrate production.

Effect of seawater infiltration on marine hydrate sediment exploitation by depressurization

The overburden of marine hydrate sediment is usually a permeable cover, and the presence of permeable overburden directly affects the depressurization effect. However, previous studies have mainly focused on the effect of the permeable overburden without considering seawater infiltration, and the influence of seawater infiltration on the production of hydrate cannot be ignored. In this article, a new numerical model considering seawater infiltration is developed and this study is completed by numerical simulation. The results show that seawater infiltration significantly reduces hydrate dissociation, and the presence of seawater substantially reduces cumulative gas production and increases water production compared to non-permeable overburden, with higher permeability resulting in lower gas production and higher water production. It is an effective means to extract hydrates through lower bottom-hole pressure by increasing the gas–water ratio. It is of great significance to further understand the production characteristics of hydrate reservoirs.

Structure improvement and parameter optimization of micro flow control valve

Aiming at the sticking phenomenon between the valve core and the valve sleeve when the valve core moves, and to solve the problem that the torque required to drive the valve core to rotate is large, the fluid–solid coupling simulation analysis of the valve core is carried out in this study, and then the valve core structure of the valve core is improved and its parameters are optimized based on the bird colony algorithm. The combination structure of the valve sleeve and valve core is studied, and the fluid–solid coupling model is established by Ansys WorkBench, and the static structure simulation analysis of valve sleeve and valve core before and after structural improvement and parameter optimization is performed. The mathematical models of triangular buffer tank, U-shaped buffer tank and combined buffer tank are established, and the structural parameters of the combined buffer tank are optimized by bird swarm optimization. The results demonstrate the triangular buffer tank has good depressurization effect but great impact, the pressure of the U-shaped buffer tank is stable and gentle but the depressurization effect is not ideal, while the combined buffer tank has obvious depressurization effect and good stability. At the same time, the optimal structural parameters of the combined buffer tank are cut-in angle of 72, plane angle of 60 and depth of 1.65 mm. The excellent structure and parameters of the combined buffer groove are obtained, so that the pressure buffer of the regulating valve at the key position of the valve port achieves the best effect, and an effective solution is provided for solving the sticking problem of the valve core of the regulating valve when working.

Development of Hydrophobic-Modified Nanosilica for Pressure Reduction and Injection Increase in an Ultra-Low-Permeability Reservoir

A low-permeability reservoir contains many fine pore throat structures, which result in excessive injection pressure of the water injection well and difficult water injection in the production process of a low-permeability reservoir. In this study, a new silane coupling agent was synthesized via the ring-opening reaction between dodecyl amine and KH-560 (γ-propyl trimethoxysilane). The modified KH-560 was reacted with nano-SiO2 to synthesize the modified nano-SiO2 as an antihypertensive additive. Fourier infrared spectroscopy, thermogravimetric analysis and laser scattering were used to characterize this modified nano-SiO2. The results show that the particle size of the modified nano-SiO2 is less than 60 nm. The test results of the water contact angle show that the dispersion system can increase the rock contact angle from 37.34° to 136.36°, which makes the rock surface transform from hydrophilicity to hydrophobicity and reduce the binding effect of rock with water. The dispersion test shows that the modified nano-SiO2 has good dispersion stability under alkaline conditions with TX-100 (Polyethylene glycol octylphenyl ether) as the dispersant. The antiswelling test results show that the antiswelling rate of this modified nano-SiO2 is 42.9%, which can efficiently prevent the clay expansion in the formation to reduce the injection pressure. The core displacement test results show that its depressurization rate reaches 49%. The depressurization rate still maintains 46% at a 20 PV water flow rate, indicating that its depressurization effect is remarkable and it has excellent erosion resistance.

Studying the Favorable Zone for Pressure-Relief Gas Extraction by Combining Numerical Investigation and On-Site Application

Gas extraction in the pressure-relief area using the depressurization effect of seam mining is an effective way to solve coal-mine gas problems. In this paper, we performed numerical modelling of the 204 working face via FLAC 3D, by which the stress variation of the rock mass and associated permeability evolution during the working face advancement were investigated. Furthermore, the favorable gas extraction zone for pressure relief was proposed based on the gas extraction performance of the on-site boreholes. The results show that: (1) gas extraction varies with the evolution of the three zones of the overlying rock and the associated permeability variation, which becomes stable when the height of the three zones remains unchanged; (2) the favorable zone for gas extraction of the 204 working face ranges from 13 m to 19 m of Dv, in which the gas extraction of on-site boreholes are located, presents better performance than other areas; (3) the gas extraction volume of the optimized gas extraction scheme rises to 77.46 m3/min with a 77.26% gas extraction rate, eliminating gas overrun in the working face and upper corner and increasing the advancement speed to 6.4 m/d. The on-site verification confirms the numerical simulation scope, more accurately determining the favorable zone for gas extraction. This may provide a reliable approach for improving the pressure-relief gas extraction performance and reducing the associated engineering costs.

A dynamic prediction model of reservoir pressure considering stress sensitivity and variable production

In the early stage of coalbed methane (CBM) development, a reasonable depressurization rate is beneficial for CBM wells to achieve high and stable production. The daily water production or the bottom-hole pressure (BHP) in current prediction models of reservoir pressure needs to be kept constant, while the production system is constantly changing. To explore the refined drainage strategy, a dynamic prediction model of reservoir pressure considering stress sensitivity and variable production was established. Based on actual production data, the model could achieve real-time monitoring of reservoir pressure, absolute permeability, and pressure propagation distance. Furtherly, the pressure dynamic variation law in the single-phase water flow stage of CBM reservoir development in the Baode area was quantitatively characterized and the dewatering rate was optimized. The study found that in the early stage of CBM well development, the dewatering rate mainly affects the reservoir pressure in near-wellbore areas. The effective stress of the reservoir within 20 m from the wellbore has a great influence, and the key to controlling the influence of stress sensitivity is to monitor the reservoir pressure and adjust the dewatering rate. Reducing the dewatering rate can restore pressure and reduce the effect of stress sensitivity near the wellbore during continuous drainage. Shut-in for 1–2 days during the drainage process to achieve the best effect of pressure recovery. Based on the effective verification of 20 wells, the four-stage drainage scheme (A: slow increase; B: rapid increase; C: pressure recovery; D: continuous depressurization) is formulated, and the depressurization effect of the four well groups is increased by 3.65%, 5.47%, 6%, and 3.74%, respectively.

Numerical Simulation of a Class I Gas Hydrate Reservoir Depressurized by a Fishbone Well

The results of the second trial production of the gas hydrate reservoir in the Shenhu area of the South China Sea show that the production of a gas hydrate reservoir by horizontal wells can greatly increase the daily gas production, but the current trial production is still far below the minimum production required for commercial development. Compared with a single horizontal well, a fishbone well has a larger reservoir contact area and is expected to achieve higher productivity in the depressurization development of gas hydrate reservoirs. However, there is still a lack of systematic research on the application of fishbone wells in Class I gas hydrate reservoirs. In this paper, a grid system for gas hydrate reservoirs containing fishbone wells is first established using the PEBI unstructured grid, and fine-grained simulation of reservoirs near the bottom of the wells is achieved by adaptive grid encryption while ensuring computational efficiency. On this basis, Tough + Hydrate software is adopted to simulate the productivity and physical field change of a fishbone well with different branching numbers. The results show that: the higher the number of branches in a fishbone well, the faster the free water production rate, reservoir depressurization, and free gas production rate in the initial stage of depressurization development, and the faster depressurization can effectively promote hydrate dissociation. Compared with a single horizontal well, the cumulative gas production of a six branch fishbone well can increase by 59.3%. Therefore, using multi-branch fishbone depressurization to develop Class I gas hydrate reservoirs can effectively improve productivity and the depressurization effect, but the hydrate dissociation will absorb a lot of heat and lead to a rapid decrease in reservoir temperature and hydrate dissociation rate. At the end of the simulation, the hydrate dissociation rate of all schemes was lower than 50%. In the later stage of depressurization development, the combined development method of heat injection and depressurization is expected to further provide sufficient thermal energy for hydrate dissociation and promote the dissociation of the hydrate.

Production efficiency analysis in hydrate reservoir under multi-well systems

To achieve the goal of carbon emission reduction, the hydrate is widely concerned for its outstanding advantages such as high calorific value and low pollution. As the output of natural gas still cannot meet the requirements of commercial exploitation, multi-well exploitation will become a technological trend in the future. Therefore, the depressurization mining of hydrate reservoirs under multi-well systems was simulated. The influences of the well branch number, well spacing, and wellhead radius on the soil depressurization characteristics were analyzed. Moreover, two new parameters, depressurization and decomposition areas, are defined to analyze the reservoir depressurized effect and production efficiency. The results show that the more the number of wells, the better the depressurization effect and the longer the duration. The decomposition efficiency of multi-well production in the late mining stage is much higher than that of single-well production. The gas production by multi-well cooperative production is much higher than that by single well production with the same number.

Optimization of the pressure drop produced during CO2 replacement in hydrate reservoirs: Balance between gas removal and preservation of structures

The replacement of methane molecules with a theoretical equal number of CO2 molecules, is one of the most promising opportunities for the exploitation of natural gas hydrate reservoirs. In this work, the effect of depressurization on CH4 hydrates was analysed in depth. Different pressure drops, from 5 to 15 bar were tested and described in terms of free gas removed (desired event) and hydrates destroyed (undesired event) before the injection of carbon dioxide. A few pronounced pressure drop might be not enough to ensure an effective replacement, while an excessive one might be not sustainable due to the high quantity of hydrates destroyed before the process. In this work, variation of hydrates and free gas was evaluated before and after depressurization; it was then compared and employed to define an optimum range of pressure drop to optimize the process. It was proved that the quantity of hydrates destroyed increases with the pressure drop imposed, while the removal of free gas shows a maximum. When depressurization was close to 10 bar, only 18.57% of hydrates dissociated, while the quantity of free gas removed was three times higher (59.27%). Finally, the CO2/CH4 replacement process was carried out with the optimal depressurization degree previously defined.

Comparative analysis between homogeneous and heterogeneous models of gas cooled fast reactor core (GFR-2400)

Abstract The main objective of the presented work is to investigate the effectiveness of homogenization of the GFR-2400 core in simulating its neutronic characteristics. To explore and evaluate the neutronic behavior of the large scale Gas cooled Fast Reactor GFR-2400 core, two computer models (homogeneous and heterogeneous) were designed using the MCNPX code. The designed heterogeneous model has been validated by comparing its results with a previously published paper. The results of both models were compared with each other to study the effect of fuel homogeneity on the radial flux and power distribution through the core. As part of a safety analysis of the reactor core for both designs, the reactivity worth of control rods, Effective delayed neutron fraction (ß eff), Doppler constant and Depressurization effect have been analyzed and compared. The variations of the effective multiplication factor (k eff), the minor actinides concentration and the most important fission products as a function of operation time have been investigated for the presented designs.

Effects of depressurization on gas production and water performance from excess-gas and excess-water methane hydrate accumulations

• Various water saturations simulate Classes I and II hydrate deposits in nature. • Ambient temperature controls periphery dissociation in excess-gas hydrate deposits. • Sensible heat dominates spatially uniform dissociation in excess-water deposits. • Secondary hydrate formation are prevented by adjusted gas production pressure. • Optimized depressurization is crucial to improve water production and CH 4 recovery. Depressurization is considered as the most promising technique for hydrate exploitation, as it achieves the highest energy profit ratio and is the most technologically feasible. However, the exploitation of excess-water hydrate accumulations generates high water production, leading to increased cost, poor energy efficiency, and problems with sand during operation. Thus, water management is crucial to gas recovery by the depressurization of different classes of hydrate accumulations, yet relevant studies remain limited. In this study, synthetic hydrate samples were prepared to simulate two types of natural methane hydrate sediments: Class 1 accumulations (excess-gas hydrate) and Class 2 accumulations (excess-water hydrate). Hydrate dissociation was conducted using a variety of depressurization approaches, and MRI imaging was employed to characterize water performance and methane recovery. Methane hydrate preferentially dissociated along the peripheries of the excess-gas samples due to more efficient heat dissipation. Methane hydrate dissociated more uniformly in the excess-water samples because the high specific heat capacity of water enabled the supply of extra heat. Furthermore, pressure histories, mean intensity change in MRI images, and water variations were monitored to analyze the characteristics of hydrate dissociation, changes in porosity, intrinsic permeability and reservoir heat, water and gas production rates, and possible secondary hydrate formation. The results of this study suggest that an optimized depressurization approach, such as stepwise depressurization, could improve methane recovery from Class 1 and Class 2 methane hydrate accumulations.

Experimental study on the injection of polysilicon nanomaterials in natural gas pipeline

China is a big oil country, and its oil production and storage are in the forefront of the world. However, China's oil resources are mainly low-permeability reservoirs. It is characterized by small porosity, which leads to the increase of injection pressure and seriously affects the production rate. The main solution is to use polysilicon nano injection enhancer. Polysilicon nano materials can solve the problem of high injection pressure from the micro level. At present, there are many researches on polysilicon nano injection technology at home and abroad, but the research on the application of polysilicon nano materials in natural gas pipeline materials is still blank. In order to solve this problem, this paper will further study the injection enhancement effect of polysilicon nano materials in natural gas pipeline materials. First of all, through theoretical research and analysis, this paper believes that polysilicon nano injection technology has good application, good effect in oilfield injection pressure drop, and obvious advantages over other traditional injection additives. In order to further analyze the injection enhancement effect of polysilicon nanomaterials, the corresponding experimental model is established. The experiment is divided into two parts, one is the preparation of reagents and solvents. In this paper, nano polysilicon solution and corrosion inhibitor are re optimized. The other part is the specific test steps. In order to ensure the quality and verifiability of the test, this paper explains and records the test principle and steps in detail. After sampling and analysis of many core factors such as adsorption time and permeability, it can be seen from the analysis data that when polysilicon nanomaterials are injected, when the injection volume is about 1pv, the effect of depressurization is the best, and the comprehensive effect of depressurization is good. This study has achieved ideal results, which is of great significance to the related research of oil field.