Fused breccia tuff occurs globally, but its formation mechanism is very controversial. Volcanic reservoirs have developed at the bottom of the Permian Fengcheng Formation in the Wuxia region of the Junggar Basin, and here, the lithology is fused breccia tuff. The reservoir porosity is mainly vesicles, but the development and relative filling of the vesicles vary spatially, resulting in strong reservoir

This paper presents an experimental investigation on the properties of hydraulic conductivity and permeability of conglomerates under different temperatures and confining pressures with integrated samples and samples with shear failure. Constant head tests were carried out in a temperature-controlled triaxial cell with samples obtained from the Zhuxianzhuang Coal Mine. Five levels of temperatures (10°C

Small-strain shear modulus, , is a key evaluation index to study the dynamic characteristics of soil in geotechnical engineering. It is widely adopted to evaluate the stiffness of soft soil in soil dynamic engineering. In this paper, the cyclic triaxial tests and resonance column tests were carried out to explore the variation of of soft clay with respect to various confining stresses, cyclic shear

Subsurface migration and accumulation of oil and gas have interested researchers for a long time, but these processes may occur over very long geological periods and are difficult to observe directly, so experimental simulations are warranted. In this study, an experimental method was developed to model hydrocarbon migration in the subsurface structure. Oil migration was simulated in a sandbox model

Small external disturbances may destabilize the bearing pillar, which in turn will change the stress distribution of the pillar supporting system, leading to its overall instability. Based on the engineering background of a mine and the mechanical analysis of pillar under disturbed stress, this paper investigated the stress, strain, and plastic zone of the pillar supporting system under different disturbed

Nitrate isotopic values are often used as a tool to identify sources of nitrate in order to effectively manage ground water quality. In this study, the concentrations of NO3−, NO2−, and NH4+ from 50 boreholes and shallow wells in the Singida and Manyoni Districts were analyzed during the dry and wet seasons, followed by identification of nitrate sources using the hydrochemical method (NO3−/Cl−) and

Steam-assisted gravity drainage (SAGD) is an important method used in the development of heavy oil. A heat transfer model in the SAGD production process is established based on the heat transfer effect caused by the temperature difference at the front edge of the steam chamber and the heat convection effect caused by the pressure difference. The observation well temperature method is used in this model

Based on the physical quantity of log data, the accurate identification of oil- and gas-bearing properties may be caused by the prestack inversion of fluid prediction, which will affect the success rate of exploration and development. Prestack data contain more information of amplitude and frequency. Using the frequency-dependent viscoelastic impedance equation and Bayesian inversion framework, the

This study investigated the temperature field distribution of a freezing inclined shaft. Thus, a three-dimensional physical simulation test system was developed, and the system consists of six parts, which are simulation box and shaft model, loading system, freezing system, external environment simulation system, and data acquisition system. From the results of physical and mechanical property test

Steam-assisted gravity drainage (SAGD) has been used to develop the “super heavy” oil reservoirs in Canada. The viscosity can reach more than 30,000 cp at 50°C. Moreover, owing to their continental deposit origin, the reservoirs have a low porosity and permeability. Because of these challenges, the conventional steam circulation start-up process takes 6 to 12 months before the well pair can be switched

Fractured horizontal wells have been widely used to develop unconventional oil and gas reservoirs. In previous studies, most studies on the transient pressure behavior of multistage horizontal wells were based on the assumption of single porosity medium, in which the coupling relationship of natural fractures and artificial fractures was not taken into account or artificial fractures were assumed to

This paper investigates the performance of a top-down deep excavation in soil-rock composite stratum. The behavior of the excavation bracing system, consisting of ground anchors and end-suspended piles, has not been well understood due to the lack of relevant research. Based on the observed data of a typical deep excavation case history for the May Fourth Square Station in Tsingtao, China, the characteristics

The heavy-oil flow in porous media is characterized by non-Darcy law with variable threshold pressure gradient (TPG) due to the large fluid viscosity. However, available analytical and numerical models hardly consider this effect, which can lead to erroneous results. This paper is aimed at presenting an innovative approach and establishing a numerical simulator to analyze the heavy-oil flow behavior

Clay minerals significantly alter the pore size distribution (PSD) of the gas hydrate-bearing sediments and sandstone reservoir rock by adding an intense amount of micropores to the existing intragranular pore space. Therefore, in the present study, the internal pore space of various clay groups is investigated by manually segmenting Scanning Electron Microscopy (SEM) images. We focused on kaolinite

Nature gas hydrates (NGHs) are regarded as a potential alternative energy source due to their huge reserves and wide distribution. According to the geophysical surveys, the pore-filling hydrates occupy a large proportion of the global hydrate reserves, especially for the marine regions. Therefore, with a novel pore-scale 3D morphological modeling algorithm, this study systematically studied the effect

Coal and gas outburst is still a major safety problem in the process of coal production in China. Correctly understanding of the migration law of outburst high gas and pulverized coal is an important basis for accurately predicting the occurrence time and possible scope of outburst. To reveal the airflow disturbance characteristics and coal-gas flow rule in coal and gas outburst process, outburst coal-gas

A large proportion of minable coal seams in China belong to low-permeability soft coal seams. Such coal seams suffer serious coal and gas outburst hazards and endure a high incidence of major disasters in coal mines. The adoption of the high-pressure water jet (HPWJ) hydraulic flushing cavity can effectively promote the gas drainage efficiency and volume and eliminate the hidden danger of gas disasters

In this study, the full-size pore structure characteristics of six different-rank coal samples were investigated and analyzed from three perspectives, namely, pore shape, pore volume, and pore specific surface area, by performing a high-pressure mercury injection experiment and a low-temperature nitrogen adsorption experiment. Next, the full-size pore volumes and pore specific surface areas of the

Rock compressive strength is an important mechanical parameter for the design, excavation, and stability analysis of rock mass engineering in cold regions. Accurate and rapid prediction of rock compressive strength has great engineering value in guiding the efficient construction of rock mass engineering in a cold regions. In this study, the prediction of triaxial compressive strength (TCS) for sandstone

CO2 transports in the Earth’s interior play a crucial role in understanding the deep carbon cycle and the global climate changes. Currently, CO2 transports inside of the Earth under extreme condition of pressure and temperature have not been understood well. In this study, the molecular dynamics (MD) calculations were performed to study CO2 transports under different CO2 pressures in slit-like magnesite

At present, there is a lack of necessary technical parameters for sludge vacuum reinforcement. To explore the effects of the drain board type on sludge vacuum reinforcement, the Fenton reagent was used to pretreat the landfill sludge in a sludge landfill area in Shanghai, and then, vacuum preloading contrast tests of different prefabricated vertical drainage types were carried out. During the test

The supercritical multithermal fluids (SCMTF) were developed for deep offshore heavy oil reservoirs. However, its EOR mechanisms are still unclear, and its numerical simulation method is deficient. In this study, a series of sandpack flooding experiments were first performed to investigate the viability of SCMTF flooding. Then, a novel numerical model for SCMTF flooding was developed based on the experimental

The Upper Paleozoic in the southwestern Ordos Basin has significant potential for natural gas exploration. This study investigated the diagenetic fluid evolution and hydrocarbon accumulation characteristics of He 8 section from Permian Lower Shihezi formation and Shan 1 section from Shanxi formation tight sandstone reservoirs by petrographic observation, scanning electron microscope imaging, fluid

Distributed temperature sensing (DTS) has been used for fracture parameter diagnosis and flow profile monitoring. In this paper, we present a new model for predicting the temperature profile of two-phase flow multistage fractured horizontal wells in the tight oil reservoirs. The homogeneous reservoir flow/heat transfer model is extended to the tight oil reservoir-fracture-wellbore coupled flow/thermal

Water huff and puff in horizontal wells in tight reservoirs has achieved good results in replenishing formation energy. However, after multiple rounds of treatment, a rapid decrease in formation pressure takes place making it difficult to maintain stable production. To improve the oil recovery rate of tight reservoirs, it is imminent to change the development mode. In this work, the stress distribution

As the most significant nonlinear reservoir, the rocks have complex structural characteristic. The pore structure of the rock is varied in shape and complex in connectivity. However, the prevailing methods for characterising the microstructure of rocks, such as the coordination number method and fractal theory, are still difficult to quantify the structural properties. In this study, based on the CT-scan

The deep oceanic sediments were collected from the Challenger Deep in the southwestern part of the Mariana Trench. Considering the salt in the pore water, a modified method for determining the physical and mechanical properties of the deep-sea sediments was proposed, by which the geological engineering indices were measured and corrected. Through the scanning electronic microscope (SEM), the microstructures

Lightweight cement systems are used in the weak intervals of petroleum wells. Sodium bentonite is used as an extender in lightweight oil-well cement systems as it prevents excess water and sedimentation of particles, thereby ensuring the formation of homogenous and stable cement sheaths. The extending ability of sodium bentonite is enhanced when prehydrated. However, the optimum bentonite prehydration

The 3D seismic data acquired in the central Qiongdongnan Basin, northwestern South China Sea, reveal the presence of shallow gas hydrate, free gas, and focused fluid flow in the study area, which are indicated by multiple seismic anomalies, including bottom simulating reflectors, polarity reverses, pulldowns, minor faults, and gas chimneys intensively emplaced within the shallow strata. A new cold

Carbonate reservoirs are the main reservoir types in China, which occupy the large ratio of reserves and production at present. The high-efficiency development of carbonate reservoirs is of great significance to assure the stability of national energy supply. The Lower Paleozoic reservoir in Jingbian gas field and the Sinian reservoir in Anyue gas field are two typical carbonate gas reservoirs, and

The study on hydromechanical coupling properties of rocks is of great importance for rock engineering. It is closely related to the stability analysis of structures in rocks under seepage condition. In this study, a series of conventional triaxial tests under drained condition and hydrostatic compression tests under drained or undrained condition on sandstones were conducted. Moreover, complex cyclic

The stress disturbance effect will significantly affect the propagation path of hydraulic fractures in the composite rock reservoir. To reveal the influence mechanism of stress disturbance effect on the hydraulic fracture propagation, several groups of laboratory tests and simulation tests were carried out. The test results showed that the hydraulic fracture tip formed a disturbing stress field because

Although vegetation is increasingly used to mitigate landslide risks, how vegetation roots affect the landslide threshold of slope has rarely been explored, particularly in the case of lateral runoff. In this study, we established a two-dimensional saturated-unsaturated infiltration equation considering the hydraulic effects of vegetation roots. The analytical solution for the shallow unsaturated two-dimensional

Fluid injection-induced earthquakes have been a scientific and social issue of wide concern, and fluid pressurization rate may be an important inducement. Therefore, a series of stepwise and conventional injection-induced shear tests were carried out under different fluid pressurization rates and effective normal stresses. The results show that the magnitude of fluid pressure is the main factor controlling

Generally, long-term waterflooding development often leads to the change of reservoir pore and clay mineral composition, which results in the change of permeability and wettability. In order to explore the relationship between core micropore structure and water cut, based on physical simulation experiments and fractal theory, we proposed a fractal evolutionary model to describe the evolution characteristics

Viscoelastic polymer solution shows shear thinning behavior at low shear rates and shear thickening behavior at high shear rates in reservoirs. However, models that ignored shear thickening behavior were commonly employed to interpret transient pressure data derived from tested wells in viscoelastic polymer flooding systems; although, viscoelastic polymer solutions show shear thickening behavior in

The hydrogeochemical characteristics of coalbed-produced water can provide insights into the sources of ions and water, the groundwater environments, hydrodynamic conditions, and water-rock interactions of depositional basins. To study the water-rock reaction process and reveal whether there is a microbial activity in the groundwater, a case of the Dafosi biogenic gas field was chosen by testing the

In order to explore the law of groundwater evolution, the water source connection between faults and aquifers and the main sources of mine water inrush in the deep mining area of Yangcheng Coal Mine in Jining City, 40 groups of hydrochemical samples were collected and analyzed by Piper Diagram and Durov Diagram. The results showed that the fluidity of groundwater developing to the deep became weaker

A series of qualitative descriptions and quantitative analyses was used to determine the lithofacies characteristics and recognize the favorable shale intervals of Dawuba Formation in the Ziyun area of South Qian Depression. The qualitative descriptions include core description and scanning electron microscope (SEM) observation. The quantitative analyses include X-ray diffraction, total organic content

Drilling fluid loss in depleted reservoir has been an import issue faced by further tapping the potential of old oil fields. Accurate evaluation of the fracture pressure is the foundation to avoid mud loss. Traditional views suggest that tensile failure is the only fracture mode and the fracture pressure should be determined by a tensile failure criterion, which are not suitable for wells drilled in

When a tunnel is excavated in the water-rich soft rock stratum, the strength of the soft rock is greatly reduced due to the seepage of groundwater. The condition may result in engineering accidents, such as large deformation, limit invasion, and even local collapse of the tunnel. Therefore, it is very important to research the stability of the surrounding rock in the water-rich soft rock tunnel. The

Despite their frequent natural occurrence and engineering encounter, heterogeneous rock joints (rock joints with different lithological characters on both sides of the joint surface) have been studied much less systematically. To study the shear behavior and failure mechanism of bolted heterogeneous rock joints, laboratory tests were performed on the heterogeneous rock joints having different joint

Horizontal well fracturing technology is widely used in unconventional reservoirs such as tight or shale oil and gas reservoirs. Meanwhile, the potential of enhanced oil recovery (EOR) methods including huff-n-puff miscible gas injection are used to further increase oil recovery in unconventional reservoirs. The complexities of hydraulic fracture properties and multiphase flow make it difficult and

Hydraulic flushing drilling technology can not only improve the efficiency of high-pressure and low-permeability geological reservoir coalbed methane drainage but also effectively reduce the probability of coal and gas outburst disasters through pressure relief. The main mechanism of this technology is to expand the borehole diameter through hydraulic flushing measures, increase the strain of the coal

Wellbore instabilities frequently occur in mudstone formation with weak plane bedding because of strong anisotropies. The mechanics parameters of weak plane bedding are of vital significance to the wellbore stability analysis for mudstone formations. The conventional method for determining the mechanics parameters is to fit lots of triaxial test data due to the blindness of coring. In this paper, an

The parameters of grain size, contents of silica, kaolinite, hydromica, calcite, and a geological time of tight sandstone reservoirs in Upper Paleozoic in Ordos basin were researched thoroughly, and the impact of the diagenetic evolution process of different sandstone types on porosity and throats was analyzed, based on the quantitative statistics from thin sections, measurements of porosity and permeability

Asphaltene deposition is a common phenomenon during CO2 flooding in ultralow permeability reservoirs. The deposited asphaltene occupies the pore volume and decreases permeability, resulting in serious formation damage and pore well productivity. It is urgent to investigate the asphaltene deposition mechanisms, adverse effects, and preventive measures. However, few asphaltene deposition investigations

The direct mechanical effects of seepage force on the behavior of hydrate-bearing porous media (HBPM) have commonly been neglected in previous studies. In this work, the physical nature of seepage force in hydrate-bearing porous media under saturated and unsaturated seepage conditions was adequately explained, and then, the direct effects of seepage force on the mechanical behavior of HBPM were quantified

The current formula of critical hydraulic gradient is not adapted to solve critical hydraulic gradient of cohesive soil. Assume that the seepage failure mode of the cohesive soil foundation was cylindrical or inverted circular truncated cone, based on the calculation formula of the critical hydraulic gradient of Terzaghi, the analytical formula of the critical hydraulic gradient considering the influence

It is generally accepted that the adsorbed water layer on the surface of the mineral particle has significant effects on the mechanical properties of soils. By defining the concepts of “solid water” and “particle skeleton” after a brief review on adsorbed water, therefore, the mechanical mechanism about how solid water affects the deformation and strength of particle skeleton is theoretically clarified

To explore the seepage characteristics of cut-through fractured rocks after different temperatures, sandstone in the Hunan area was selected as the research object. First, the influence degree of different temperatures on the permeability of fractured sandstone was studied, and the permeability variation of fractured sandstone with net confining pressure was revealed. The test data was nonlinearly

Lucaogou formation in Jimsar sag is host to large quantities of bedding fractures which are known to play a critical role in the enrichment, accumulation, and efficient development of tight oil. In this paper, we examine and finely characterize the development of the bedding fractures found in the upper and lower sweet spots of Lucaogou formation of tight oil reservoir through field outcrop and core

The identification of the oil-source correlation plays a significant role in petroleum exploration and development. In this study, we identify the oil-source correlation by a hierarchical cluster analysis method combined with traditional methods. The results shed light on the oil-source correlation in Minfeng area and revealed the oil migration and accumulation process. The crude oil in different structural

Human activities have greatly accelerated the input of nitrogen into waters, resulting in water quality degradation. Facing the water crisis of nitrogen pollution, the state of surface water in arid areas needs close attention. Although numerous studies have indicated that waters’ nitrogen is often impacted by land use covers, the correlation between the two remains obscure. This paper explored the

There is high uncertainty in reserve estimation during the early development of deep ultrahigh pressure gas reservoirs, largely because it remains challenging in accurately determining the formation compressibility. To overcome this, starting from the definition of compressibility, a novel gas production of cumulative unit pressure drop analysis method was established, of which the effectiveness was

The pore structure characterization and its controlling factors in overmature shales are keys to understand the shale gas accumulation mechanism. Organic matter in source rocks is a mixture of various macerals that have their own specific evolutionary pathways during thermal maturation. Pores within macerals also evolve following their own path. This study focused on petrographic characterization and

Sand column tests were conducted to investigate the seepage transport of silicon powders (SPs) with two wide particle size ranges (30-2000 nm and 2-70 μm), including the cotransport of SPs and copper ions. The results show that the graded large-scale SP has an obvious inhibiting influence on the transport of copper ions. In contrast, in the presence of the graded small-scale SP, the concentration of

An earthquake-induced landslide, mainly affected by seismic movement, is a frequent large-scale geological hazard in hydraulic engineering. This paper proposed a rate-dependent strain-softened micromechanical contact model and implemented it in discrete element method code, namely, PFC. Using the PFC-FLAC coupling scheme, the Hongshiyan earthquake landslide is analyzed as a case study. The influence

In this paper, we attempt to clarify the relationships between oilfield water and hydrocarbon distribution of the Triassic Baikouquan Formation, in the slope zone of Mahu depression, Junggar Basin, NW China, based on oilfield water mineralization degrees, diagenesis analysis, formation pressure coefficients, burial history, and thermal evolution processes. The results show that the study area can be

Both surface and underground rocks in nature often undergo repeated drying and wetting. The dry-wet cycle is a weathering effect that includes physical and chemical processes, which has varying degrees of degradation effects on the physical and mechanical properties of rocks. This paper analyzes and discusses this kind of rock degradation based on the existing literature data. First, the deterioration