Water Injection Pressure Research Articles

Experimental research on deformation response of hot dry rock (HDR) geothermal reservoir during hydraulic modification at 300 °C and depth 2500 m

In the stages of reservoir construction and geothermal exploitation, the rock deformation is an important factor in the study of the reservoir stability. However, the existing laboratory research in this area pay far less attention to the macroscopic deformation of the reservoir rock mass. Hydraulic fracturing experiments have here been conducted at a temperature of 300 °C, an axial pressure of 65 MPa, and a confining pressure of 60 MPa. The quantitative relationship between the granite strain (axial, radial, and volumetric) and the water injection pressure during hydraulic fracturing has then for the first time been determined experimentally. Meanwhile, the deformation response of granite geothermal reservoir during hydraulic modification has also been discussed. As a result, the maximum opening of the hydraulic fractures was in the range of 10−1 μm - 10−2 μm and the maximum volumetric strain rate of the rock mass was 1.71 × 10−4 s−1. Microseismic events preferably occurred during periods of high volumetric strain rates when the injection pressure fluctuated repeatedly. During geothermal exploitation, the structural changes caused by hydraulic fractures and thermal cracks resulted in greater potential for contraction of the rock mass. These research results provide a reference for geothermal reservoir reconstruction and stability assessment.

Threshold Determination for Effective Water Injection in Coal Seams: Insights from Numerical Simulation

Coal seam water injection is the most basic and effective dust control technology used on the coal mining face. Numerical simulations are helpful for predicting the humidity range of coal seam water injection. The results can provide guidance for the field design of coal seam water injection process parameters. In order to understand the influence of coal seam water injection pressure and water injection time on the coal seam wetting effect, this paper uses the Fluent 17.0 software system to study the process parameters of the coal seam water injection seepage process under different conditions. It is found that in the process of coal seam water injection, with the increase in water injection pressure and the prolongation of water injection time, there is a specific threshold value for the change in coal seam permeability. Only when the water injection pressure and time increase to the threshold value will the permeability of the coal seam be significantly enhanced and the wetting effect improved. The pressure threshold of the mine is 15 MPa–20 MPa, and the time threshold is the first 42 h.

Evaluating the effectiveness of innovative pervious concrete pavement system for mitigating urban heat island effects, de-icing, and de-clogging

The Urban Heat Island (UHI) effect and water runoff pose significant challenges in urban environments. This research aimed to mitigate the UHI effect through the implementation of an innovative pervious concrete pavement (IPCP) system. Furthermore, the study investigated the main obstacles associated with conventional permeable pavements, such as clogging and vulnerability to freeze-thaw damage. To achieve this goal, a physical model apparatus was developed to simulate temperature variations, de-icing processes, and clogging incidents in the IPCP system. This apparatus was specifically designed with distinct sections for both the pervious concrete layer and the subbase layer. The findings revealed that careful selection of an appropriate subbase material significantly contributed to reducing the temperature rise (up to 37 %) under varying environmental conditions by enhancing evaporative cooling capacity. Additionally, the pavement simulation apparatus featured a dual-function drainage system. This system not only regulated the water level within the pavement by draining excess water but also addressed clogging (with up to 97 % permeability recovery) and de-icing concerns through the application of air pressure and hot water injection, respectively.

Analysis of asynchronous/inter-fracture injection-production mechanism under the condition of five-spot vertical and horizontal well combination in low permeability oil reservoirs

At present, low permeability resources are the focus of the development of petroleum industry. In this paper, firstly, the oil displacement mechanism under the condition of vertical and horizontal well combination is clarified. Secondly, the difference of the mechanism of enhancing oil recovery between asynchronous and inter-fracture injection and production is revealed. Thirdly, the difference of energy supplement mechanism between huff and puff and displacement is compared and analyzed. Results show that: (a) with asynchronous injection-production development, the oil saturation drop around the water injection well is greater than that of periodic injection-production and synchronous injection-production. (b) Under the dual effects of water injection pressure difference and capillary force, part of the injected water enters the reservoir with relatively small pore channels, expanding the swept volume. (c) In the soak stage of asynchronous injection-production development, capillary force is the main control factor of oil-water permeability, and its size determines the permeability level. (d) The injected water first flows through the large channel and then flows into small channel to complete the imbibition and replacement. (e) The flow field of asynchronous injection-production has a large sweep range, which is conducive to improving oil recovery.

Evaluation of near wellbore damaged conditions with an injection - falloff tests during transient flow regime in clastic hydrocarbon reservoir

Low or near zero daily oil production from a well below its potential is undesirable and should be addressed. This problem is caused by permeability reduction or impairments in the vicinity of a wellbore and could be due to one or combinations of the following factors; mud filtrate invasion, fines redeposition due to production, microbial growth, fracturing fluid, and enhanced chemical processes. The extent of this problem has to be quantitatively evaluated, using a skin factor, before an appropriate solution can be developed. A set of secondary data was simulated with a commercial software package, for a reservoir undergoing transient flow condition acting infinitely. A water injection well, fully perforated, is placed at the centre of an infinite-acting reservoir, for constant water injection. The wellbore radius of 0.5 ft fully penetrated the entire length of 190 ft, and injected water at 250 bbls per day, with water viscosities of 0.8 cP to 1.2 cP, continuously for 4 days. Water injection pressure stabilized at 1300 psi. Analysis of both injectivity and falloff were performed with an initial assumption of zero wellbore storage effects to evaluate formation permeability and skin factor, S. The result showed that skin factor increases with decreasing water viscosities. At water viscosity of 0.8 cP to 1.2 cP, a constant value of skin factor was obtained. An S value of +0.09 indicated that the near wellbore environment is slightly damaged. Therefore, it requires light acidization.

The impact of nozzle parameters and water injection pressure on the application effect of hydraulic punching enhanced permeability technology in high ground stress coal seam

High-stress coal seams are different from ordinary coal seams in terms of their low hardness, low permeability, and certain degree of fluidity, making them more difficult to enhance permeability. Hydraulic punching enhanced transmission technology can quickly create voids in coal seams, but existing hydraulic punching techniques are suitable for shallow coal seams, and the effect of creating voids is greatly reduced when applied to high-stress coal seams. To optimize the application effect of hydraulic punching enhanced transmission technology in high-stress coal seams, theoretical research was conducted on the parameters of hydraulic punching nozzles and injection water pressure. A simulation model was established using COMSOL numerical simulation software to optimize the nozzle parameters and explore the combined effect of nozzle parameters and injection water pressure on enhancing permeability. Field experiments were conducted in the Zhaotong Tunnel of the China high-speed railway to determine the optimal combination of nozzle parameters and injection water pressure, thereby increasing the overall permeability of the coal seam and improving gas extraction efficiency. The results indicate that: (1)Through theoretical calculations, numerical simulations, and experimental verification, it has been proven that the perforation effect of a jetting device with three the long oblique nozzle with an oblique length of 15 mm and a size of 3 mm × 6mm is the best among the comparative results under a water injection pressure of 5 MPa；(2)Compared to the perforation effect before optimization, the water consumption for perforation after optimization is reduced to 0.6 times that before optimization, and the perforation efficiency after optimization is 3.556 times that before optimization. The perforation efficiency has been effectively improved；(3)The similarity between the theoretical results, simulation results, and experimental results in this study is all above 85%. The consistency of the results provides mutual verification and has certain engineering guidance significance.

Analysis of mechanical response mechanism and energy evolution characteristics of saturated coal with a single pre-existing hole

It is essential to elucidate the mechanical mechanism of water injection and large-diameter drilling pressure relief measures on coal rock deformation and failure. This helps coal mines adopt more precise and effective dynamic disaster prevention and control measures. To obtain the mechanical response mechanism and energy evolution characteristics of saturated coal with a single pre-existing hole, uniaxial compression tests was carried out, and the deformation and failure process of coal samples were monitored by high-speed camera and acoustic emission monitoring systems. It is found that water saturation, single pre-existing hole measures, and their coupling effect resulted in a deterioration in the coal sample's strength by approximately 23.49%, 9.47%, and 47.95% respectively. The final failure mode of coal samples with different measures is shear failure. The law of fracture development and expansion and energy accumulation and release in different coal samples is roughly the same, the speed of energy accumulation and release in different stages is different. Water saturation and single pre-existing hole measures can affect the impact risk of coal samples, and water saturation can significantly reduce the impact tendency of coal samples, and reduce the impact energy index of complete coal samples by 56.59%. The impact tendency index of natural coal sample is slightly increased by single pre-existing hole measure, and the impact energy index of intact coal sample is reduced by 46.78% by the coupling of the two measures. These findings can provide technical support for coal mine power disaster prevention and control.

Method for predicting the injection pressure for horizontal wells in fractured tight sandstone reservoirs

Hydraulic fracturing and horizontal well drilling are the key technologies for increasing the production of continental tight sandstone reservoirs. Taking the typical fractured tight sandstone in the Yuan-287 block of the Ordos Basin as an example, a reservoir geologic model is established based on the stratigraphic correlation of 206 wells. The model and 3D paleostress field are combined to predict fracture parameters such as fracture density and strike. Using reservoir breakdown pressure (RBP) monitoring data and other data such as reservoir physical and mechanical parameters, tectonic fracture characteristics, and in situ stress parameters, a quantitative evaluation model of the RBP, which predicts the 3D distribution of RBP, is established via stepwise regression, and the factors controlling the RBP are analyzed. The rock P-wave velocity, horizontal minimum principal stress, and fracture density are found to be three key parameters that control the breakdown pressure of this tight sandstone reservoir. By comparing the fracture opening pressure of subsurface tectonic fractures with the RBP, a new method for predicting the optimal water injection pressure of this reservoir is developed. This work provides a valuable evaluation model for accelerating the efficient development of continental tight sandstone reservoirs.

Study on the Law of True Triaxial Hydraulic Fracturing by Acoustic Emission Monitoring.

Hydraulic fracturing generates fractures in a coal seam, which has been extensively used in coal mining and disaster management. To study the influences of water injection pressure and time on the propagation of hydraulic fracture, we conducted true triaxial hydraulic fracturing experiments under acoustic emission monitoring. Five briquette specimens were prepared by molding the mixture of coal powder, cement, river sand, and distilled water under 60 MPa to simulate the properties of coal seam. True triaxial loading was used to simulate the in situ stress environment of the coal seam. Hydraulic fracturing experiments on the test specimens were conducted under different water injection pressures and times. The following conclusions have been drawn. At the fixed injection time, increasing water injection pressure promotes the propagation of hydraulic fracture and the migration of water in the coal seam after the fractures are connected. The number of fractures increases from 3 to 8 as the water injected pressure increased from 3 to 9 MPa. Under the constant water injection pressure, the increase in longitudinal wave velocity in the test specimen decreases with the prolongation of water injection time. When the water reaches the action boundary of the water injection pressure, the water stops moving. At this moment, the water injection time has no effect on the longitudinal wave velocity anymore. The fracturing influence range can be increased by increasing the water injection pressure to produce a fracture network of a large radius with many fractures. Appropriately prolonging hydraulic fracturing time can ensure that the fracturing fluid fully moistens the coal seam and thus effectively reduces dust pollution.

Research on water-out mode and differential perforation in thick carbonate reservoir

The development of anti-rhythmic carbonate reservoirs in the Middle East often encounters challenges such as water hold-up and reverse coning during the water injection process, leading to premature water breakthrough and various water-out issues. The unclear understanding of these phenomena, attributed to strong reservoir heterogeneity, results in a relatively low recovery degree in water injection development. This paper investigates the mechanisms behind water hold-up and reverse coning phenomena, offering detailed solutions. Numerical models of the oil reservoirs were developed, and an extensive study of influencing factors, including reservoir types, Kv/Kh, water injection pressure differential, wettability, and perforation position, was conducted to unveil the underlying mechanisms. Key findings indicate that the water hold-up phenomenon is influenced by capillary force barriers due to wettability and high-perm streaks, while the reverse coning phenomenon depends on the combined forces of gravity, capillary force and downward production differential among which downward production differential is the dominant factor compared to capillary force and gravity. The study also proposes a differential perforation principle tailored to different water-out types to enhance vertical sweep efficiency. The differential perforation principle is as follows: the optimal perforation position is at top layer and the optimal perforation length approximately accounts for 1/4 of the total oil layer thickness for water-out in bottom; the avoidance perforation height in top accounts for 1/6 of the total oil layer thickness and the optimal perforation length approximately accounts for 1/2 of the total oil layer thickness for water-out in top; the avoidance perforation height in top and bottom accounts for 1/5 and 2/5 of the total oil layer thickness respectively for water-out in both top and bottom.

Experimental analysis of acidizing in Weizhou X low permeability reservoir

AbstractAiming at the problem of increased water injection pressure and poor water injection effect during the water injection operation of Weizhou X offshore low permeability oil reservoir. The cause of clogging was clarified using cast thin section experiments, water quality compatibility experiments and reservoir sensitivity experiments, and corresponding deblocking agents were configured based on the experimental results. The experimental results show that Weizhou X oilfield has strong velocity sensitivity (damage rate 85.35%) and strong salt sensitivity (damage rate 63.02%), and there is a phenomenon of water quality incompatibility. Analysis shows that the excessive velocity of the injected water causes the core particles to fall off and the water quality is incompatible with the calcium carbonate precipitation to cause pore throat blockage as the fluid migrates to the small roar, which is the main reason for the increase in water injection pressure. Based on the analysis results, the acid solution formula was optimized and determined to be: 12% HCl + 0.5% HF + 3% CH3COOH + 0.5% C6H12N4. Indoor test results show that the acid has good clay swelling prevention and reservoir modification effects, and the average reservoir modification rate is 129.21%. The plug‐removing effect is remarkable and can be promoted in similar oil fields.

Synthesis of temperature and salt resistance silicon dots for effective enhanced oil recovery in tight reservoir

The intensive development of tight reservoirs has positioned them as a strategic alternative to conventional oil and gas resources. Existing enhanced oil recovery (EOR) methods struggle to effectively exploring reservoir oil, resulting in low recovery rates. Novel and effective means of developing tight reservoirs are urgently needed. Nanomaterials have shown promising applications in improving water flooding efficiency, with in-depth research into mechanisms that lower injection pressure and increase water injection volumes. However, the extent of improvement remains limited. In this study, a silicon quantum dots (Si-QDs) material was synthesized via a hydrothermal synthesis method and used to prepare a nanofluid for the efficient recovery of tight reservoir. The Si-QDs, with an approximate diameter of 3 nm and a spherical structure, were surface functionalized with benzenesulfonic acid groups to enhance the performance. The developed nanofluid demonstrated stability without aggregation at 120 °C and a salinity of 60000 mg/L. Core flooding experiments have demonstrated the attractive EOR capabilities of Si-QDs, shedding light of the EOR mechanisms. Si-QDs effectively improve the wettability of rocks, enhancing the sweeping coefficient of injected fluids and expanding sweeping area. Within this sweeping region, Si-QDs efficiently stripping adsorbed oil from the matrix, thus increasing sweeping efficiency. Furthermore, Si-QDs could modify the state of pore-confined crude oil, breaking it down into smaller particles that are easier to displacement in subsequent stages. Si-QDs exhibit compelling EOR potential, positioning them as a promising approach for effectively developing tight oil reservoirs.

Experimental Study on Carbon Dioxide Displacement by Coal Seam Water Injection.

Using water to displace carbon dioxide adsorbed in coal can prevent coal and gas outbursts. However, the mechanism of continuous water injection replacing adsorbed gases in coal has not been well studied. An experiment with the same water injection pressure and different adsorption equilibrium pressures for displacing carbon dioxide was conducted. The variation patterns of the amount of displaced carbon dioxide, time, and water displacement rate, displacement ratio, and water action ratio were analyzed. The modes of water injection displacing carbon dioxide are discussed. The results show that the change in the amount of displaced carbon dioxide consists of three stages: rapid, slow, and stop growth stages. For the same displacement time, as the adsorption equilibrium pressure rises, more carbon dioxide is displaced. The time displacement rate and water displacement rate can be divided into three stages: rising, peak, and dropping stages. As the adsorption equilibrium pressure increases, the duration of the peak stage decreases, while the time and water displacement rates increase. At different adsorption equilibrium pressures, the carbon dioxide displacement ratio ranged from 45% to 54%, less than the natural desorption ratio. But the water action ratio containing the gas dissolution amount was close to or greater than the natural desorption ratio. Thus, the displacement effect of flowing water accelerated the desorption of carbon dioxide in coal. The modes of carbon dioxide displacement by water injection include water-displacement, gas-dissolution displacement, and gas-diffusion-dissolution displacement. The findings of this study provide novel suggestions for preventing and controlling coal and gas outbursts.

Influence of fracture parameters on hydraulic shear seepage characteristics of granite

To reveal the influence mechanism of different fracture parameters on the permeability characteristics of hot dry rock after hydraulic shear. The self-made high temperature true triaxial hydraulic shear test device and rock roughness profile tester were used. The granite in Daqing area of Songliao Basin is taken as the research object. The prefabricated fractured granite is subjected to high-temperature treatment. The geological characteristics of different geothermal reservoirs are simulated by changing the three-dimensional stress. The roughness coefficient of the fracture surface is used to characterize the variation characteristics of fracture before and after hydraulic shear. The influence of different fracture angles and roughness on the permeability of granite after hydraulic shear was tested. Combined with numerical simulation, the relationship between fracture parameters and geothermal mining performance is analyzed. The results show that the maximum water injection pressure of hydraulic shear decreases with the increase of fracture angle by quadratic polynomial law and increases with the increase of fracture roughness by quadratic polynomial law. The variation of fracture surface roughness coefficient fluctuates within 0–2 with the increase of volume stress before and after hydraulic shearing. The variation of fracture surface roughness coefficient increases linearly with the increase of water injection flow rate and increases with the increase of water injection time, and there is a fluctuation range of 0.38–0.44. After hydraulic shear, the permeability of granite increases first and then decreases with the increase of fracture angle. When the fracture angle is 15°, the permeability has the maximum value. The permeability increases with the increase of fracture surface roughness. The numerical simulation results show that the high fracture opening (15 mm), high fracture number, and high fracture penetration performance significantly improve the geothermal mining efficiency.

Experimental research of direct water injection characteristics over wide range of injection temperature and ambient pressure

Direct water injection (DWI) within internal combustion engine has become a promising technology due to its potential for suppressing knock, reducing emissions and lowering fuel consumption. The spray morphology shows a significant impact on the effectiveness of DWI, which makes it of great research significance. In this research, the spray characteristics of water jet under different conditions were investigated based on a constant volume vessel. The water injection temperature ranged from 30 °C to 240 °C, and the ambient pressure varied from 0.2 bar to 10 bar. The results showed that the spray width at near-field increases with water temperature. However, at ambient pressures of 0.8 bar–2.5 bar, higher superheat level resulted in severe spray collapse, manifested as significantly reduced spray width. It was identified that the collapse under flash boiling occurs as a result of the presence of the low-pressure zone at the center of the spray, and higher superheat level migrate the low-pressure zone closer to the nozzle exit, resulting in enhanced spray collapse. This could lead to excessive water mist concentration in partial region, negatively affecting combustion process and potentially causing oil emulsion in actual engine operation. This work also suggests a strong correlation between spray collapse and water injection pressure, in addition to superheat level and ambient pressure. The findings of this work have the potential to provide effective reference for high-temperature water injection strategies in internal combustion engines.

Research on the Water Injection Pressure Reducing and Increasing Injection System for Low Permeability Reservoirs in Fushan Oilfield

In response to the problems of increased injection pressure, decreased injection volume, and stopped injection caused by scaling and impurity blockage during the water injection process in the low permeability reservoir of HuaX block in Fushan Oilfield, water quality analysis and scaling experiments were conducted on the injected water in the block to determine the cause of scaling. Secondly, core displacement damage experiments were conducted using natural rock cores and on-site injected water to determine the degree of permeability damage during the water injection process, with a permeability damage rate greater than 70%, Finally, based on the causes of scaling and core displacement experiments, scale inhibitors, anti expansion agents, and surfactants were selected. Through orthogonal experiments, the optimal system formula was determined. The scale inhibition rate was greater than 90%, the anti expansion agent was greater than 90%, and the interfacial tension was less than 0.01mN/m. Core displacement experiments showed that the permeability damage rate of the system to the core was less than 15%, which can achieve the effect of reducing pressure and increasing injection in water injection wells.

Formula system of reduce pressure and increase injection working fluid in Tamtsag oilfield

Tamtsag Oilfield is a low-permeability oilfield. In the actual production process, there will be “high water injection pressure and high injection difficulty”. In order to improve the waterflood development effect of low permeability reservoir, the selection of working fluid plays a key role. By measuring the interfacial tension between the working fluid and crude oil, combined with the depressurization and injection performance evaluation test, the anion-non-ionic surfactant working fluid system suitable for the characteristics of the Tamtsag reservoir was prepared. Under the condition that the formation water pH of oil formation in the Block 21 of Tamtsag oilfield is 7.5 and the salinity is 3000 mg/L, the injection increasing formula selected in this paper is: 0.9 % coconut oil diethanolamide+0.7 % sodium dodecylbenzene sulfonate+0.5 % anhydrous ethanol+3 % clay stabilizer. For cores with permeability lower than 80 mD, the depressurization rate can reach more than 25 %; For cores with permeability less than 15.9 mD, the depressurization rate can reach more than 30 %. The working fluid system can effectively improve the effect of increasing injection in Tamtsag Oilfield.

ABOUT SOME PROBLEMS OF WATERFLOODING IN CARBONATE RESERVOIRS

The features of waterflooding of carbonate (fractured-porous) rocks, caused by the interaction of the system of fractures with the matrix (blocks) of the rock, are considered. It is shown that the slower propagation of the pressure pulse in the rock matrix in comparison with the propagation of this pulse along the fracture system of the formation leads to compression of the rock blocks in the near-wellbore zone of the injection well, as a result of which stress concentration occurs at the ends of vertical fractures, which increases the likelihood of these fractures growing into the roof of the productive formation. It is shown that in order to prevent the development of this process, the growth rate of water injection pressure should be limited in accordance with the time of liquid pressure equalization in the pore space of the rock matrix and in the fracture system. When developing production wells drilled in fractured porous media, in order to prevent the development of the process of closing fractures in the bottomhole zones of these wells, the drawdown reduction rate must also be limited in a similar way. It is noted that when applying technologies for non-stationary flooding of productive reservoirs, the main factor determining their effectiveness is the change in the direction of filtration flows in the reservoir. This leads to the activation of filtration processes in the stagnant zones of the formation and the intensification of the processes of capillary impregnation of low-permeability interlayers with water from more flooded highpermeability interlayers.At the same time, it is important to take into account that when changing the direction of filtration flows at a late stage of development of carbonate reservoirs, in order to prevent reimpregnation of hydrophobic rock blocks with oil, it is more expedient to change the operating modes of production rather than injection wells. It is shown that water flooding of hydrophobic carbonate reservoirs results in incomplete water displacement of oil as a wetting phase from rock blocks. To reduce the residual oil saturation of rock blocks, it is advisable to increase the displacement pressure gradient in the reservoir in combination with a change in the direction of filtration flows in it.

Retracted: Integrated Design Technology of Geological Engineering for Pressure Flooding and Water Injection in Low Permeability Reservoirs: Take the Reservoir of Keshang Formation in Wu2 East Area as an Example

Retracted: Integrated Design Technology of Geological Engineering for Pressure Flooding and Water Injection in Low Permeability Reservoirs: Take the Reservoir of Keshang Formation in Wu2 East Area as an Example

Experimental Study on Seawater Intrusion Law and Countermeasures within Island Underground Water-Sealed Oil Storage Caverns

Underground water-sealed oil storage caverns constructed in island environments is a promising approach for expanding oil storage caverns. However, few researchers have studied the risks of seawater intrusion and the distribution characteristics of intrusion interfaces in large underground water-sealed oil storage caverns in island environments. In this paper, we established a visualized physical simulation platform to investigate the characteristics and control measures of seawater intrusion in single fracture of rock masses within island underground water-sealed oil storage caverns. In addition, the effects of the excavation of caverns, the distance between the cavern and coast, fracture width, seawater level, oil storage stage, water curtain, and water injection pressure were evaluated. The results show that excavation of oil storage caverns carries the risk of seawater intrusion. Specifically, reducing the distance between the oil storage caverns and the coast, increasing the fracture width, and raising the seawater level all contribute to accelerated seawater intrusion into the caverns. However, the vertical water curtain can effectively inhibit seawater intrusion, and increasing the injection pressure of vertical water curtain can avoid the risk of seawater intrusion into the caverns. The research results provide an experimental basis for the study of seawater intrusion in underground oil storage caverns in island environments.