Hydraulic Operations Research Articles

Design and Test of Potato Seedling Killing and Residual Film Recycling Integrated Machine

Plastic film mulching technology can effectively enhance crop yield and quality, and the use of mulch has been increasing in recent years; however, the problem of mulch residue is worsening due to the large amount of recycling work and slow natural degradation. In this study, a potato seedling killing and residual film recycling machine is designed to provide good working conditions for potato harvesters before harvesting in response to the problems of difficult separation of film tangles, the low net rate of recycling due to the mixing of residual film with soil, and the high soil content in residual film recycling operations in northwest China. The machine is based on the potato monoculture and double row planting mode in Gansu area. This paper puts forward the overall design scheme and carries out the theoretical analysis and parameter determination of the key components, such as the seedling killing device, the film surface cleaning device, the film unloading device, and so on. Using EDEM software to carry out the virtual simulation test and Design-Expert13 to analyze the test results, we determined the optimal working scheme for the machine, with a forward speed of 0.8 m/s, a film gap of 125 mm, and a spiral stirrer speed of 600 r/min. Based on a field test for verification, the test results show that the machine’s residual film recovery rate was 83.3%, the impurity rate was 3.8%, and the rate of injury to the potatoes was 1.4%. The machine meets the requirements of national and industry standards, and it can simultaneously realize straw crushing, film surface cleaning, residual film recycling, and hydraulic film unloading operations, with better operating results and while reaching the expected results. It can also provide a reference for the design and testing of a seeding and residual film recycling machine.

Hydraulic dual-module hybrid driving system with adjustable waste energy recovery for industrial vehicles

The energy dissipation of industrial vehicle during hydraulic cylinder operations is significant, and the limitations of energy recovery and reuse further exacerbate the issue of energy waste and low energy efficiency. To address these challenges, we propose a hydraulic dual module hybrid driving system (DHDS) for cylinder. This system incorporates a Main drive module with a Power-assisting module, enabling the recovery and reuse of gravitational energy to assist in cargo lifting through the bidirectional operation of the Power-assisting module. Based on the DHDS, we design a multi-mode control strategy (MMCS) with adjustable power distribution capability, allowing for the optimization of recovered energy utilization under various conditions. Furthermore, experiments and simulations are conducted to evaluate the ability of the MMCS to redistribute recovered energy and assess the energy efficiency of the DHDS. Using a DHDS-equipped forklift as an example, simulation platform and test bench are constructed to demonstrate its performance in several designed working cycles. Compared to a 1.2-t electric forklift, the DHDS-equipped forklift with MMCS achieves a battery saving efficiency of 12.70%–40.53 % and a gravitational energy recovery efficiency of 24.80%–62.85 %.

Integrating experiments with modeling to understand key bacterial taxa dynamics after episodic mixing of a stratified water column

Hydraulic mixing of stratified reservoirs homogenizes physicochemical gradients and microbial communities. This has potential repercussions for microbial metabolism and water quality, not least in dams and hydraulically controlled waters. A better understanding of how key taxa respond to mixing of such stratified water bodies is needed to understand and predict the impact of hydraulic operations on microbial communities and nutrient dynamics in reservoirs. We studied taxa transitions between cyanobacteria and sulfur-transforming bacteria following mixing of stratified water columns in bioreactors and complemented the experimental approach with a biogeochemical model. Model predictions were consistent with experimental observations, suggesting that stable stratification of DO is restored within 24 h after episodic and complete mixing, at least in the absence of other more continuous disturbances. Subsequently, the concentration of S2− gradually return to pre-mixing states, with higher concentration at the surface and lower in the bottom waters, while the opposite pattern was seen for SO42−. The total abundance of sulfate-reducing bacteria and phototrophic sulfur bacteria increased markedly after 24h of mixing. The model further predicted that the rapid re-oxygenation of the entire water column by aeration will effectively suppress the water stratification and the growth of sulfur-transforming bacteria. Based on these results, we suggest that a reduction of thermocline depth by optimal flow regulation in reservoirs may also depress sulfur transforming bacteria and thereby constrain sulfur transformation processes and pollutant accumulation. The simulation of microbial nutrient transformation processes in vertically stratified waters can provide new insights about effective environmental management measures for reservoirs.

The Three-tank Watergy Configuration

The objective of this paper is to propose a generic mathematical model, capable of supporting the design of a custom Watergy plant and future testing of suited control algorithms. The subsystems of the Watergy system are an inside water tank, providing input water for the heat pump, accumulating watering water for plants, and acting like a buffer for the hydraulic operations between tanks, a surface water tank, collecting rain waters, accumulating warm water when the outside temperature is high and cold water when the outside temperature is low and an underground water tank, accumulating water at constant underground temperature.

ИНСТРУМЕНТЫ ЦИФРОВИЗАЦИИ В ПРАКТИКЕ ПРОЕКТИРОВАНИЯ ПРИ РЕКОНСТРУКЦИИ ПОДЗЕМНЫХ ТРУБОПРОВОДОВ БЕСТРАНШЕЙНЫМИ МЕТОДАМИ

The article focuses on the possibilities of multi-optional design of repair and rehabilitation works on dilapidated pressure pipeline networks with the use of automated complexes in order to achieve minimum energy costs in water transportation with regard to the temperature factor. Two automated programs based on hydraulic and energy calculation operations are presented as digital tools. As a basic variant of reconstruction of dilapidated pipelines, the trenchless Swagelining technology was accepted. It is realized by pulling pre-compressed polymer pipes into old pipelines with their subsequent straightening. The paper presents information on regulatory and technical documentation and the application of advanced technology, installation and operation conditions, as well as comparative assessment of energy consumption after reconstruction of dilapidated sections of pipelines with polymer pipes with the possibility of minimizing energy consumption during water transportation under non-isothermal conditions of pipeline operation.

Fluid-driven slow slip and earthquake nucleation on a slip-weakening circular fault

We investigate the propagation of fluid-driven fault slip on a slip-weakening frictional interface separating two identical half-spaces of a three-dimensional elastic solid. Our focus is on axisymmetric circular shear ruptures as they capture the most essential aspects of the dynamics of unbounded ruptures in three dimensions. In our model, fluid-driven aseismic slip occurs in two modes: as an interfacial rupture that is unconditionally stable, or as the quasi-static nucleation phase of an otherwise dynamic rupture. Unconditionally stable ruptures progress through four stages. Initially, ruptures are diffusively self-similar and the interface behaves as if it were governed by a constant friction coefficient equal to the static friction value. Slip then accelerates due to frictional weakening while the cohesive zone develops. Once the latter gets properly localized, a finite amount of fracture energy emerges along the interface. The rupture dynamics is then governed by an energy balance of the Griffith’s type. In this stage, fault slip transitions from a large-toughness to a small-toughness regime due to the diminishing effect of the fracture energy in the near-front energy balance. Ultimately, self-similarity is recovered and the fault behaves again as having a constant friction coefficient, but this time equal to the dynamic friction value. This condition is equivalent to a fault interface operating to leading order with zero fracture energy. When slow slip is the result of a frustrated dynamic instability, slip also initiates self-similarly at a constant peak friction coefficient. The maximum size that aseismic ruptures can reach before becoming unstable can be as small as a critical nucleation radius (shear modulus divided by the slip-weakening rate) and as large as infinity when faults are close to a well-defined limit that separates the two modes of aseismic sliding. In the former case, earthquake nucleation occurs unaffected by the dynamic friction coefficient. In contrast, the latter case exhibits fracture-mechanics behavior, characterized by a finite influx of elastic strain energy being supplied to and dissipated at the rupture front. We provide analytical and numerical solutions for the problem solved over its full dimensionless parameter space, including expressions for relevant length and time scales characterizing the transition between different stages and regimes. Due to its three-dimensional nature, the model enables quantitative comparisons with field observations as well as preliminary engineering design of hydraulic stimulation operations. Existing laboratory and in-situ experiments of fluid injection into simulated and natural faults are briefly discussed in light of our results.

Reactivation of variably sealed joints and permeability enhancement in geothermal reservoir rocks.

The online version contains supplementary material available at 10.1186/s40517-023-00271-5.

Investigation and Optimization of Energy Consumption for Hybrid Hydraulic Excavator with an Innovative Powertrain

This paper presents an innovative powertrain design and an energy regeneration system for hybrid hydraulic excavators to reduce energy consumption and emissions. The proposed system is designed to maximize engine efficiency and make full use of the energy gained from boom and arm retraction. The powertrain features an innovative design that incorporates a continuously variable transmission (CVT), which drives the main pump. It enables precise control of both the engine’s speed and torque, ensuring that the engine operates within the high-efficiency range. The energy regeneration system is applied to regenerate the potential energy of the boom and arm, which can be used to either charge the battery or directly supply power to the main pump. Moreover, an energy management strategy based on an equivalent consumption minimization strategy is used to distribute the power while offering maximum engine efficiency. When compared with the existing hybrid system and conventional system, the simulation results indicated that the proposed approach achieves energy-saving efficiencies of 16.9% and 77.1%, respectively, at high velocities and 22.25% and 53.5%, respectively, at medium velocities. This research signifies a promising advancement for sustainable and efficient hydraulic excavator operations.

Reservoir Ice Conditions from Multi-Sensor Remote Sensing and ERA5-Land: The Manicouagan Hydroelectric Reservoir Case Study

Reservoir ice can have an important impact on the watershed scale and influence hydraulic operations. On the other hand, hydropower generation can also impact the ice regime. In this study, multi-source satellite and ERA5-land data are used to evaluate ice conditions. Specifically, ice-controlling variables (temperature, water levels), ice regime (cover/deformation, thickness) and their interrelations are assessed for a 5-year period from 2017 to 2021. The methodology is applied to the Manicouagan reservoir, one of the largest hydropower reservoirs in Quebec, Canada. The satellite-based land surface temperatures (LSTs) suggest that winter 2021 was the hottest one. Overall, MODIS and Landsat LSTs agree with the ERA5-land temperatures. Ice backscatter from Sentinel-1 indicates that, in general, the reservoir is completely covered by ice from January to March. A correlation of 0.6 and 0.8 is observed between C- and Ku-band Synthetic Aperture Radar (SAR) signal and ice thickness, respectively. Important ice changes inferred from Differential Interferometric SAR (D-InSAR) occur approximately at the position where the largest ERA5-land ice thickness differences are observed. Winter water levels are also evaluated using satellite altimetric data to verify their influence on the ice dynamics. They show a decreasing tendency as the winter advances.

A REVIEW STUDY IN TROUBLESHOOTING OF HYDRAULIC SYSTEMS IN CEMENT INDUSTRIES

Behind every hydraulic system there exists critical components that influence power transmission. To improve talent you should recognize how these components operate and affect the system i.e. learn the kinds of filter and piping used in hydraulic systems, describe the types and functions of hydraulic seals, and explain the operating principles of different types of pumps, and further learning the types and uses of accumulators, control valves, relief valves, cylinders, and even actuators. In this research study appropriate problem-solving processes are applied, and this helps to comprehend the hydraulic concepts and hydraulic schematic representations. Therefore, it will enhance the knowledge and the capacity of troubleshooting the different hydraulics systems in the cement industry. This will enable the person to stay on top of the industry practices in hydraulics, explore the basics of a hydraulic system by reviewing the types and properties of hydraulic fluids, identifying the symbols used on hydraulic schematic representations, and explaining hydraulic circuit operations based on a schematic design.

Geochemical cycle of hydraulic fracturing fluids: Implications for fracture functionality and frac job efficiency in tight sandstone

The efficiency of the hydraulic fracturing processes is measured through its success rate in opening fracture space, fracturing fluid injectivity, and recovery rates of flowback fluid. This paper applies the volumetric ratio (RFF/FW) between recovered hydraulic fracturing fluid (FF) and formation water (FW) – besides gas production (GP) and flowback efficiency (FE) – as a third criterion and novel classification tool to quantify the loss of fracturing fluids, the inflow of formation water, and to define the type of involved fractures during hydraulic fracturing. Eight scenarios were designed to assess the performance and success rate of hydraulic fracking operations. For model calibration, geochemical time trends of flowback fluids from two horizontal wells were compared with the known composition of injected FF and local FW to quantify mixing ratios (RFF/FW) between both fluid types in produced water. The use of Na and Cl concentrations as nonreactive elements resulted in the most precise solution for endmember calculations. For the cased-hole scenario (C-1), low values of most operational parameters (gas recovery, injected fracturing fluid, recovered flowback volume, and FE of 0.37) reflect tight reservoir conditions with limited conductive capacity of induced fractures in the target zone. The elevated RFF/FW ratio (2.65) and dominant FF return during the first day of flowback suggest that injected fracturing fluids either remained close to the sealed borehole and returned immediately to surface during post-fracture production or were lost to the formation due to unconnected hydraulic fractures. In contrast, a complex fracture system at the open-hole completion (O-1) allowed the release of gas from micropores, reflected by relatively elevated ratios of 0.5 for FE and low RFF/FW ratios of 1.09. The interconnectivity between natural and induced fractures permitted the injection of larger volumes of FF with an elevated flowback of both fracturing fluid and formation water. A portion of 26% of the injected FF was recovered from well O-1 during a flowback period of 41 days, while an identical percentage was reached at well C-1 during 10 days. It is of practical importance for fracking operations that geochemical fingerprinting of flowback water can provide strategic decisions to optimize fracturing project performance beyond the capabilities of petrophysical data from well logging. In the present case, similar permeability and porosity characteristics for both targeted clastic intervals could not explain the contrasting performance of both frac jobs. Geochemical assessment can lead to avoiding water-pay zones to minimize the volume of required fracturing fluids for injection purposes, and to economize the recycling process for recoverable flowback fluids. An improved understanding of the functionality of the structural network of natural and induced fractures by the present classification is applicable to predict the success rate for upcoming frac jobs.

Analytical Solution and Simulation of Oil Deliverability Analysis for Reorientation Hydraulic Fracture in Low-Permeability Reservoirs

The hydraulic refracturing operations are often used to improve oil deliverability in the low-permeability reservoir. When the development of oilfields has entered a high water cut stage, oil deliverability can be promoted by refracturing reservoirs. The orientation of the new fracture formed by refracturing will be changed. The new formed fracture is called reorientation fracture. To calculate the oil deliverability of the refracture wells, a three-section fracture which includes reorientation fracture was established. The multiwell pressure drop superposition theory is used to derive the analytical solution of the refracture wells which includes the reorientation fracture. The numerical simulation was conducted to validate the results of the analytical solution. Comparing the refracture well deliverability of reorientation and nonreorientation, permeability, deflection angle, and the length of reorientation fracture will jointly control the productivity of refracture well. When the permeability in the direction of maximum principal stress is greater than the permeability in the direction of minimum principal stress, the capacity of reorientation fractures is relatively large. The deflection angles and the length of the reorientation fracture will directly affect the drainage area of the fracture, thus affecting productivity. The reorientation fractures generated by repeated fracturing have great potential for improving oil deliverability in the anisotropic low-permeability reservoirs.

High In Situ Stress Anisotropy Lead to Formation of Complex Fracture Patterns

During the process of water injection, due to solid particle deposition and foreign liquid intrusion, the formation near the wellbore was contaminated and blocked. As a result, water injection rate reduced and failed to meet the injection requirements. In order to improve water injection rate and improve oil recovery of offshore oilfields, hydraulic injection tests were carried out in controlled laboratory conditions. In general, the formation of complex fracture patterns is an ideal outcome of the hydraulic fracturing stimulation seeks to achieve. In situ stress condition is an inherited geological condition one can only adopt to. By comparing test results of different experiments that had varied stress and hydraulic injection conditions imposed, we can investigate their impact on the fracture patterns created. This paper presents laboratory evidences to support that if the hydraulic injection condition is managed properly, a complex fracture pattern is possible even under a high in situ stress anisotropy. Even if the in situ stress condition has a large anisotropy, proper hydraulic stimulation operations can still cause complex fracture patterns and thus provide good stimulation efficiency.

Integrating Reservoir Operations and Flood Modeling with HEC-RAS 2D

Current free to use models developed by the United States Army Corps of Engineers (USACE) perform unique functions (e.g., hydrology, hydraulics, reservoir operations, and flood impact analysis) that are widely used in numerous studies and applications. These models are commonly set up in a framework that is limited to point source connections, which is problematic in regions with flat topography and complex hydrodynamics. The separate models need to be integrally linked and jointly considered for accurate risk communication and decision-making, especially during major storm events. Recently, Hurricane Harvey (2017) exposed the shortcomings of the existing framework in West Harris County, TX, where an insufficient understanding of potential flood risk and impacts contributed to the extensive flood damages sustained in the region. This work illustrates the possibility of using a single hydraulic model, HEC-RAS 2D, to perform all hydrologic, hydraulic, and reservoir operations modeling necessary for accurate flood impact assessments. Implications of this study include a simplification of the entire flood impact analysis, which could help future flood risk communication and emergency planning.

Deep well as a facility for on-line hydraulic studies of the stress state of the rock mass in fluid-saturated fractured reservoirs

I n the south ern areas of the Siberian platform , geological and m ining conditions are highly complex for design , drilling and construction of deep wells for oil and gas. C omplicating factor s are related to specific features of deform ing cavity- fractured carbonate reservoirs. G eological model s of carbonate reservoir s should be designed on a case-by-case basis, taking into consideration the conditions of each specific field, including its complex filtration field, confirmed deformation of filter ing fractures with constant parameters of the cavern component, etc . If an incomprehensive geological model is used for production planning with a lack of a well-based approach to the development of a carbonate reservoir , design well flow rates may not be achieved , the field reserve coverage will be reduced and, consequently, the oil recovery ratio will be lower . When developing oil, gas and brine deposits , it is required to consider the natural-technical system of ‘r eservoir – reservoir ’ (mechanical impact) – ‘ reservoir fluid system and well ’ (hydrodynamic impact) on the basis of a comprehensive analysis of its in terrelated and interdependent components. Our study shows that each part of the system contributes directly to the entire complex. The stress state of the rock mass in the fluid- permeable part of the natural fracture d reservoir and fluid-saturated reservoirs is dynamically change able during the fluctuation s of the pressure field of the reservoir hydrocarbon system at the initial penetration of a well into the reservoir. The authors analyzed the natural-technical system ‘ well – fluid-saturated bed’ as a real on-line model of leaking – hydraulic fracturing based on a standard pressure v s. time curve during hydraulic fracturing. Based on the knowledge of the on-going processes in carbonate cavern-fractured reservoirs , it becomes possible to predict the reaction of the rock mass during hydraulic repression (i.e., during the initial penetration of a well into the reservoir) and depression (during testing and operations of a producti on well). All pressure effects hydraulically applied to the reservoir fluid system can lead to changes in the stress state of the natural reservoir. The stress state with significantly changing permeability parameters of filtering fractures is among the most complex states of stress [Belonin et al., 2005; Borevsky, 1986]. It is important to take into account that such stress state transition during the drilling process is uncontrollable and unpredictable, which means that the reservoir permeability and porosity may be irreversibly affected and considerably reduce d and, consequently, the oil well productivity and the final profitability of developing the hydrocarbon field will be significantly decreased . Based on the actual deep drilling data , we continue comprehensive studies of deform ing fractured reservoirs in the area of the stress state of the rock mass and investigation of pressure characteristics of fluid systems and their mutual influence during hydraulic operations in the well completion cycle . We have analyzed the stress state of the rock mass in various reservoir s . I ndicators characterizing a particular state of the rock mass are substantiated. Geological and technological recommendations a re specified for the initial penetration of wells into the reservoir, as well as for testing the well s with respect to the state of the natural-technical system ‘ well – fluid-saturated formation ’ . New geological and technological solutions are proposed .

Assessing longwall shield–strata interaction using a physical model

The stability of the longwall face and shields in thick coal seams requires a thorough understanding of shield–strata interaction, but the realistic hydraulic operations of longwall shields have been widely ignored to date. This paper reproduces the behaviour of the longwall face and shield in response to roof loading through a physical modelling study with a consideration of the basic operating principles of the shield leg cylinder. The extension and retraction of the leg cylinder and important characteristics of longwall shields are introduced. The results show that: (1) the shield vertical stiffness has a positive correlation with shield capacity, and it decreases with the extension of the hydraulic liquid inside the leg cylinder; (2) higher capacity shields develop more load in response to roof convergence, but retain an adequate reserve capacity to protect the shield from damage; (3) yielding of a modern shield represents a 10% drop in yielding pressure and produces 5–10 mm of reduction in shield height and 100–250 t of loss in support load; (4) the physical modelling study of shield–strata interaction with a consideration of leg hydraulic operation shows a step function of roof deflection. Face and roof displace at a slow rate during the initial shield loading stage but increase rapidly during the yielding events.

Fluid-structure simulations of the stochastic behaviour of a medium head Francis turbine during startup

The use of dynamic CFD and FEA simulations of hydraulic turbines for steady operation is now widespread for fatigue analysis. However, machines will undergo a major role change from the traditional base load operation in the coming years. This can have a significant impact on life expectancy. In this regard, a lot of research efforts have been recently devoted to improve understanding of hydraulic turbines transient operations such as startup and runaway. Our recent experiences have shown that almost all turbines present unique behaviour from a stochastic point of view during transient operation, and we consider there is still a lot to learn about how to correlate load patterns to life expectancy. In past work, startup simulations and no-load stochastic predictions were presented separately. To our knowledge, no one has attempted to combine them to predict stochastic stresses by simulations in the case of turbine startup. The challenge is thus to capture much more physics while respecting fluid-structure interaction modelling requirements. This paper presents specifically transient CFD and FEA simulations of a medium head Francis turbine startup aimed at getting stochastic dynamic loads on the runner. The CFD simulations involve, among other things, variable rotating speed, mesh deformation, labyrinth seals, resistive torque, roughness, SAS turbulence modelling. 1-way fluid-structure simulations with time-dependent pressure loads are used to determine the stochastic stresses. The stochastic loads are challenging, and only a part of them were captured. Encouraging results are obtained at the leading edge, but the trailing edge deformations lack most of the content. Simulations and experiments might indicate that a stronger coupling is required to get both the fluid load and the mechanical answer right.

Effect of hydraulic loading on bioremediation of municipal wastewater using constructed wetland planted with vetiver grass, Addis Ababa, Ethiopia

Gravel-based pilot horizontal subsurface flow constructed wetland planted with vetiver grass (Vitiveria zinaniodes) and unplanted operated at two hydraulic loading rates: 0.025 m/d and 0.05 m/d was carried out over a 3-year period. The aim of the study was to evaluate the effect of plant and hydraulic loading rate on the organic and nutrient removal performance of the constructed wetland system planted with vetiver grass (Vitiveria zinaniodes) in the removal of chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) from municipal wastewater. The removal efficiencies of COD, TN, and TP in the planted cell decreased from 95 to 90.8%, 95.2 to 86.8% and 95.2 to 88.5%, respectively, with an increase in HLR from 0.025 to 0.05 m/d. The estimated above-ground biomass of dry weights of vetiver harvested ranged from 10.1 to 10.3 kg DW/m2, the nutrients uptake increased with plant age from 2.4 to 14.6 g N/kg DW and 0.8 to 8.5 g P/kg DW and above-ground biomass nutrient standing stock ranged from 147.5 to 150.4 g N/m2 and 85.5 to 87.5 g P/m2 in 16 months. The higher removal efficiency of COD, TN, and TP was achieved in HSSFCW planted with vetiver grass as compared to unplanted at both hydraulic loading rate operations. The results concluded that both applications of HLR are capable of removing organic matter and nutrients efficiently and vetiver grass can be used for remediation of pollutants in municipal wastewater in Addis Ababa.

Modeling of curving hydraulic fracture propagation from a wellbore in a poroelastic medium

Understanding near-wellbore hydraulic fracture behaviors is vital for hydraulic fracturing treatments and other injection-related operations in the petroleum industry. This paper presents a fully coupled fluid flow and geomechanics model for growth of hydraulic fractures in the near-wellbore region. The model is developed within the framework of the extended finite element method (XFEM). Fracture initiation and propagation, fracturing fluid flow, rock deformation, and pore fluid flow are coupled into the XFEM framework. The model is validated against experimental results in the literature. Capabilities of the proposed model for capturing fracture geometry, fluid flow, and local stress and pore pressure distributions are illustrated with numerical examples. A parametric study is carried out using the model to investigate a few operational parameters’ effects on near-wellbore fractures. Some recommendations are provided for reducing fracture tortuosity and breakdown pressure based on the results of the parametric study. The XFEM model proposed in this paper provides an efficient tool to predict arbitrary hydraulic fracture growth in the wellbore vicinity. It can be used to aid designs of various hydraulic fracturing related operations in the petroleum industry, such as fracturing stimulations, injectivity tests, waterfloods, and waste injections.

Volumetric components in the earthquake source related to fluid injection and stress state

AbstractWe investigate source processes of fluid‐induced seismicity from The Geysers geothermal reservoir in California to determine their relation with hydraulic operations and improve the corresponding seismic hazard estimates. Analysis of 869 well‐constrained full moment tensors (Mw 0.8–3.5) reveals significant non‐double‐couple components (>25%) for about 65% of the events. Volumetric deformation is governed by cumulative injection rates with larger non‐double‐couple components observed near the wells and during high injection periods. Source mechanisms are magnitude dependent and vary significantly between faulting regimes. Normal faulting events (Mw < 2) reveal substantial volumetric components indicating dilatancy in contrast to strike‐slip events that have a dominant double‐couple source. Volumetric components indicating closure of cracks in the source region are mostly found for reverse faulting events with Mw > 2.5. Our results imply that source processes and magnitudes of fluid‐induced seismic events are strongly affected by the hydraulic operations, the reservoir stress state, and the faulting regime.