Underground Oil Storage Research Articles

Oil recovery and cooling for underground salt cavern oil storage: Insights from coupled flow and thermal model

Oil recovery and cooling for underground salt cavern oil storage: Insights from coupled flow and thermal model

Oil storage and debrining process in insoluble sediment voids for underground salt cavern energy storage: An experimental study

Large salt cavern oil storage is an effective underground oil storage method, which has been widely used in the United States, Germany, and France. However, the insoluble impurity sediment particles at the bottom of the salt cavern will occupy plenty of oil storage space. To enhance the oil storage capacity, the sediment void oil storage (SVOS) method was proposed. The debrining process from the sediment void prerequisite of the SVOS. It will affect the feasibility of oil injection into the sediment void and the operation efficiency of SVOS. Thus, a self-made debrining device of SVOS was built, and the dynamic debrining process in the sediment void was investigated to explore the debrining process from the sediment void. Six debrining parameters (oil-brine interface change, oil injection rate, brine discharge rate, oil viscosity, the second oil injection quantity, and ground temperature) were proposed and considered. Two kinds of oils (diesel and petrolatum) were conducted in the SVOS debrining experiments. The experimental results showed that the debrining rate remained stable, and it was relevant to the oil injection rate and the interaction of oil and sediments. The average debrining rate of the initial diesel debrining, second diesel debrining, and petrolatum debrining were 2.5 g/s, 2.55 g/s and 2.40 g/s, respectively. The 50 °C of ground temperature sped the debrining rate of high-viscosity oil storage in the sediment void. The oil-brine interface kept balance from the macro perspective, and the oil did not penetrate the inner brine. The oil-brine interface drops ratio of the initial diesel debrining, second diesel debrining, and petrolatum debrining process were 0.586 mm/s, 0.629 mm/s and 0.592 mm/s, respectively. The oil in the sediment voids generated movable and immobile bubbles. The petrolatum flow in the sediment void was easier than the diesel due to the low viscosity at 50 °C. The research has a certain reference value for the development of underground salt cavern oil storage.

Experimental investigation on the oil extraction process for a novel underground oil storage method: Oil storage in salt cavern insoluble sediment voids

Large-scale underground oil storage is vital for addressing the energy crisis. Leveraging the insoluble sediment space at the bottoms of salt caverns for oil storage is particularly effective in high-impurity salt mines, enhancing oil storage capacity. The process of extracting oil from the sediment void is essential for utilizing this resource. Three experimental devices were developed to investigate this extraction process. We conducted experiments on oil extraction processes and rates for various oil types, analyzing weight changes and influencing factors. The sediment and water content in the extracted oil were also evaluated. Results indicated that extracting oil from the sediment void is feasible, yielding average recovery rates over 90.0 %. High-viscosity oil at 50 °C exhibited three stages: initial stability, a rapid rise, and final stability. Low-viscosity oil correlated with brine injection rates, displaying a rapid rise, stable phase, and subsequent decline. Petrolatum extraction was easier than diesel extraction, and ground temperature improved recovery rates. Changes in water and sediment content had minimal impact on oil quality. This research provides insights for large-scale underground energy storage.

The mechanism of seepage responding characteristic for the water curtain borehole injection in underground water-sealed oil storage

The mechanism of seepage responding characteristic for the water curtain borehole injection in underground water-sealed oil storage

Porous Flow of Energy and CO2 Transformation and Storage in Deep Formations: An Overview

The transformation and storage of energy and carbon dioxide in deep reservoirs include underground coal gasification, the underground storage of oil and gas, the underground storage of hydrogen, underground compressed air energy storage, the geological utilization and storage of carbon dioxide, etc [...]

Determining representative permeability coefficients of original and grouted rock mass for underground water-sealed oil storage: method and application

Determining representative permeability coefficients of original and grouted rock mass for underground water-sealed oil storage: method and application

A study on the materials of smart barrier for selectively blocked TCE and TPH

Many barrier materials are used around industries, construction areas, livestock dump sites, waste landfills, and underground oil storage tanks. In the case of barriers, even if there is no inflow of contaminants, they do not provide selective permeability, develop water barrier properties, and hinder groundwater flow when contaminants encounter groundwater. Recently, contaminated sites that are difficult to resolve with current purification technologies continue to emerge. Pollutants flow into groundwater through the advection and diffusion by leaking. The pollutants introduced in this way cause pollution to the surrounding environment, and various types of severe underground environmental pollution problems occur depending on the type of pollutants leaked. Therefore, using a material that has the property of adsorbing organic contaminants and gelling them is harmless to the environment by penetrating groundwater under normal conditions. It has the property of selectively adsorbing the pollutant and gelling it upon contact with it underground. Therefore, the authors aim to study the applicability of polynorbornene and polyolefin as components of smart barrier materials that make barrier materials impermeable through the adsorption of pollutants, swelling, and coagulation behavior in this study. The components of smart barrier materials include Ottawa sand, organo-bentonite, polynorbornene, and polyolefin. Polynorbornene and polyolefin adsorb only organic pollutants selectively. Before applying polynorbornene and polyolefin to the barrier material, TCLP was performed to evaluate environmental hazards. As a result of heavy metal analysis, it was determined that there was no environmental hazard. The pH results are 7.27 for polynorbornene and 7.31 for polyolefin, indicating that both materials are slightly alkaline. In addition, as a result of testing with TCE (stock solution) and TPH (diesel crude oil) to confirm the swelling effect when in contact with organic pollutants, the efficiency of pollutant adsorption and swelling was found to be high when the ratio of polynorbornene: polyolefin = 6:4. Therefore, when using the material used in this study, it is expected that it can be applied as a component of a smart barrier material that selectively blocks pollutants.

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.

Study on Experimental and Constitutive Model of Granite Gneiss under Hydro-Mechanical Properties

Permeability, as a critical element in making sure the underground facilities are secure, is a vital consideration in analyzing the rock material seepage. Selecting granite gneiss from underground oil storage as the research sample in this study. Triaxial mechanical property tests under different hydro-mechanical properties were carried out under the rock full-automatic triaxial servo system that controls the application of axial pressure, confining pressure, and seepage pressure. Through experiments carried out, we obtained the rock samples’ mechanical properties and permeability in three stages of the stress–strain process. The study shows that the seepage pressure considerably affects granite gneiss strength and deformation parameters under hydro-mechanical properties. On the basis of the same confining pressure, in pace with the growth in seepage pressure, elastic modulus, the deformation modulus, and the peak strength present a prominent decreasing inclination. The derived mechanical parameters are bound up with the stages we divided. This study analyzes and discusses the relationship among the strains and permeability, establishing the granite gneiss hydro-mechanical coupling constitutive model. Verification shows the results in numerical and experimental matches well, indicating that the rock hydro-mechanical properties could be effectively represented by the constitutive model.

Key issues in water sealing performance of underground oil storage caverns: Advances and perspectives

Key issues in water sealing performance of underground oil storage caverns: Advances and perspectives

The Effects of Spill Pressure on the Migration and Remediation of Dense Non-Aqueous Phase Liquids in Homogeneous and Heterogeneous Aquifers

The spill pressure of the contaminant source is an important factor affecting the amount, location, form, and behavior of the dense non-aqueous phase liquids (DNAPLs) that plume in a contaminated subsurface environment. In this study, perchloroethylene (PCE) infiltration, distribution and, remediation via a surfactant-enhanced aquifer remediation (SEAR) technique for a PCE spill event are simulated to evaluate the effects of the spill pressure of the contaminant source on the DNAPLs’ behavior in two-dimensional homogeneous and heterogeneous aquifers. Five scenarios with different spill pressures of contamination sources are considered to perform the simulations. The results indicate that the spill pressure of the contaminant source has an obvious influence on the distribution of DNAPLs and the associated efficiency of remediation in homogeneous and heterogeneous aquifers. As the spill pressure increases, more and more contaminants come into the aquifer and the spread range of contamination becomes wider and wider. Simultaneously, the remediation efficiency of contamination also decreases from 93.49% to 65.90% as the spill pressure increases from 33.0 kPa to 41.0 kPa for a heterogeneous aquifer with 200 realizations. The simulation results in both homogeneous and heterogeneous aquifers show the same influence of the spill pressure of the contaminant source on PCE behaviors in the two-dimensional model. This study indicates that the consideration of the spill pressure of the contaminant sources (such as underground petrol tanks, underground oil storage, underground pipeline, and landfill leakage) is essential for the disposal of contaminant leakage in the subsurface environment. Otherwise, it is impossible to accurately predict the migration and distribution of DNAPLs and determine the efficient scheme for the removal of contaminant spills in groundwater systems.

A comprehensive feasibility evaluation of salt cavern oil energy storage system in China

Large-scale underground oil storage has a great effect on national energy safety. China's oil dependency has exceeded 70% for four consecutive years, so it is necessary for China to build strategic oil storage. The salt cavern is a good medium to store oil, and it is widely used in foreign countries. China is rich in salt mines and has basic conditions for building salt cavern oil storage (SCOS). In this paper, the necessity and advantages of SCOS are analyzed, the salt rock mechanics experiments of SCOS are conducted, the geological feasibility evaluation model is built, the 3D numerical creep stability model in three working conditions (long-term, oil pressure dynamic, injection and production) is built, and the economic feasibility evaluation model is built. The results show that the implementation of SCOS in China is feasible, the earthquake (51%) and fault (28%) have a great effect on geological selection, the SCOS has good stability under three working conditions, the storage cost of SCOS is lower by 64.3% and 84.3% contrasted to rock cavern and storage tank in 2025. The study has a reference value for the development of SCOS in China.

Migration of Leaked Oil Vapor in Underground Water-Sealed Oil Storage Cavern Considering the Influence of Fractures

During the operation of underground water-sealed oil storage caverns, a large amount of oil vapor is generated due to volatilization. Oil vapor can easily leak into the surrounding rock, and fractures in the surrounding rock are usually the dominant channels for oil vapor leakage. To study the influence of fractures on oil vapor leakage and migration in underground water-sealed oil storage caverns during the oil storage period, a gas–liquid two-phase flow model of the fracture–pore dual medium in fractured rock mass was established. The program was implemented on the COMSOL platform by using weak-form PDE (partial differential equation). Then, taking an underground water-sealed cavern of an oil reserve as an example, the influence of the characteristic parameters of a single fracture on the evolution process of oil vapor leakage and migration during the oil storage period of the underground water-sealed oil storage cavern was studied. The results were further applied to the Huangdao underground oil depot project. The results show that the spatial distribution of oil vapor leakage is mainly affected by fractures. Through parameter sensitivity analysis, it was found that the geometric characteristic parameters of fractures will have a certain impact on the migration field of oil vapor leakage in underground caverns. Specifically, fracture permeability (kf), fracture width (df), and fracture inclination (θ) are positively correlated with oil vapor leakage parameters (oil vapor leakage range and leakage volume), while the distance between the fracture and the middle cavern (s) is negatively correlated with oil vapor leakage parameters (oil vapor leakage range and leakage volume). The relative influence of fracture geometry parameters on the migration process of oil vapor leakage during the oil storage period of the underground water-sealed oil storage cavern is in the following order: kf> df> s > θ. Engineering application shows that the existence of fractures affects the spatial distribution of oil vapor leakage and migration, and the relationship between oil vapor leakage parameters and oil storage operation time is a positive power function. The gas–liquid two-phase flow model of the fracture–pore dual medium in fractured rock mass developed in this study could offer a numerical simulation tool to assess and mitigate the risk of oil vapor leakage. The research conclusions can provide some references for related problems encountered in similar projects.

A New Approach to Identifying Preferential Seepage Channels for Underground Water-Sealed Oil Storage Cavern During Construction

A New Approach to Identifying Preferential Seepage Channels for Underground Water-Sealed Oil Storage Cavern During Construction

Analysis of the Hydromechanical Properties of Compact Sandstone and Engineering Application

The paper proposes a method to simulate the mechanical behavior of compact rock considering hydromechanics by combining physical experiments and numerical analysis. The effectiveness of the constructed method is validated by the comparison between the numerical and physical results of triaxial shear experiments on sandstone in seepage conditions. Based on the validated method, the stability of underground water-sealed oil and gas storage caverns in surrounding compact sandstone during excavation is analyzed. The main findings are as follows: The intrinsic permeability of compact sandstone has a power function relationship with the porosity; the combination of the porous media elastic model and the modified Drucker–Prager plasticity model can preciously represent the mechanical properties of compact sandstone; the proposed method can accurately replicate the hydromechanical response of compact sandstone in seepage conditions; the effects of hydromechanical effects have significant impacts on the stability of surround compact sandstone during the excavation of underground water sealed oil and gas storage caverns, which causes the obvious increase in stress, deformation and plastic deformation zones of the surrounding compact sandstone and remarkable decrease in the stability safety factor.

Hydrogeochemical characterization and analysis of the relation between underground oil storage caverns construction and hydro-environment

Hydrogeochemical environment is of critical importance for the environment-friendly operation of underground oil storage caverns. The construction of underground oil storage caverns usually has an impact on the hydro-environment. The characterization and analysis of the hydrogeochemical environment can provide information on the relation between construction and hydro-environment. The quality of water samples was detected and analyzed to determine the chemical type in an underground oil storage cavern in China. The water samples are classified using principal component analysis and cluster analysis. The source and proportion of seepage water into the storage caverns are determined with end member mixing calculation. The results show that the chemical type of groundwater is mainly HCO3 + Cl − Na type, and the two dominant factors affecting the evolution of hydrogeochemical content are rock dissolution and groundwater seepage. All water samples can be catalogued as seepage water, water curtain water, X River water and background water. The water curtain water can fully penetrate into the ground to provide containment for the storage caverns, and the water curtain system has a good performance and can basically cover the project area. Most of the seepage water into the storage caverns comes from water curtain water and X River water, while the proportion of background water is relatively low. The construction of underground oil storage caverns affects the groundwater flow regime by changing the directions of groundwater flow around the caverns. This study showcases the use of hydrogeochemical analysis in depicting the interplay between surface water and groundwater for underground rock engineering.

Rock Stress Measurement Methods in Rock Mechanics—A Brief Overview

The current brief review paper on rock stress measurement methods is very crucial factors in mining, civil infrastructure, geothermal energy, nuclear underground disposal, large underground oil storage caverns, etc as well as in geology and geophysical area. Measurement of in situ rock stress is a very challenging and difficult quantity and not possible to measure directly. Measure the deformation or displacements or hydraulic factors by perturbing the rock and converting the measured quantity into rock stress. There are two main categories for measuring methods: direct and indirect methods. The most common methods of direct in situ stress techniques are briefly described including advantages, disadvantages and limitations. Moreover, authors included the application of Artificial Intelligence (AI) for rock stress measurement methods.

Seawater Intrusion Risk and Prevention Technology of Coastal and Large-Span Underground Oil Storage Cavern

The presence of a high concentration of Cl− in saltwater will erode the structure and facilities, reducing the stability and service life of the underground oil storage cavern. In order to reduce the risk of seawater intrusion, this paper studies the risk and prevention technology of seawater intrusion based on a case study of a coastal and large-span underground oil storage cavern. A refined three-dimensional hydrogeological model that comprehensively considers permeability coefficient partitions, faults, and fractured zones are constructed. The seepage fields and seawater intrusion risks of the reservoir site in its natural state, during construction, and during operation are examined, respectively. The study quantifies the water inflow and optimizes the seawater intrusion prevention technology. The results indicate that there is no risk of seawater incursion into the cavern under natural conditions. The water inflows after excavating the top, middle, and bottom sections of the main cavern are predicted to be 6797 m3/day, 6895 m3/day, and 6767 m3/day, respectively. During the excavation period, the water supply from the water curtain system is lower than the water inflow of the cavern, providing the maximum water curtain injection of 6039 m3/day. The water level in the reservoir area decreased obviously in the excavation period, but the water flow direction is from the cavern to the sea. Additionally, the concentration of Cl− in the cavern area is less than 7 mol/m3; hereby, there are no seawater intrusion risks. When only the horizontal water curtain system is deployed, seawater intrusion occurs after 18 years of cavern operation. The concentration of Cl− in the southeast of the cavern group exceeds 50 mol/m3 in 50 years, reaching moderate corrosion and serious seawater intrusion. In addition to the horizontal curtain above the cavern, a vertical water curtain system could be added on the southeast side, with a borehole spacing of 10 m and extending to 30 m below the cavern group. This scheme can effectively reduce seawater intrusion risk and extend the service life of the cavern. The findings of this research can be applied as guidelines for underground oil storage caverns in coastal areas to tackle seawater intrusion problems.

Hydrogeological model for underground oil storage in rock caverns

For underground engineering, hydrogeological conditions of the engineering site are usually complicated, and a fine hydrogeological model is the basis for the accurate analysis of groundwater flow fields. A 3D fine hydrogeological modeling method applicable to large underground engineering was proposed in this study, which was mainly composed of data preprocessing, initial model establishment and model calibration. The modeling method adequately considers the complexity of geometric parameters and the non-uniformity of the spatial distribution of physical parameters in the geological zone. The boundaries of the model were determined based on independent hydrogeological units. The hydrogeological model is calibrated based on the monitoring data and supplementary investigation information. The 3D fine hydrogeological modeling method has been successfully applied to a large underground water-sealed oil storage engineering under construction. The groundwater level, water inflow and flow directions in four typical construction stages were used as the calibration information. Based on the fine hydrogeological model, the flow analysis was conducted to assess the containment properties of the oil storage caverns during operation. The feedback analyses of the buried depth of underground engineering and the permeability reduction ratio of the grouted zone of caverns were carried out. Through flow analyses, the complex geological conditions had obvious influence on the groundwater flow field, and the hydraulic connection between the oil storage and the river boundaries was obtained. The permeability reduction ratio of the grouted zone of caverns in this engineering was from 18% to 45%. The analysis results showed that the oil storages met the requirements of containment properties during operation. The 3D fine hydrogeological model is helpful to accurately analyze the groundwater flow field for underground engineering, and can provide scientific guidance to the design, construction and operation of underground water-sealed oil storage engineering.

Migration behaviour of LNAPL in fractures filled with porous media: Laboratory experiments and numerical simulations

With the increasing requirement of maintaining world energy security and strategic reserves, oil storage and transportation facilities are being built at a large scale. Taking the safe and efficient operation of petroleum storage projects as the goal, a set of experimental apparatus to investigate the migration of contaminants in fractures filled with media was developed to predict and evaluate the environmental risk of oil contaminants leakage. A multiphase numerical flow model based on COMSOL was built based on the laboratory experimental model. Specifically, the migration behaviour of Light Non-aqueous Phase Liquid (LNAPL) through a sand-filled fractured medium was studied by laboratory experiments and numerical simulations. Image and chemical analyses methods were used to monitor and study LNAPL migration behaviour for varying grain sizes of porous medium filling the fractures and varying groundwater table elevations. Laboratory experimental results showed that the LNAPL migration velocity in filled fracture network was significantly faster than that in adjoining porous media during the initial stage of infiltration. The migration velocity increased with the relative permeability of filled sand, which was closely related to the Van Genuchten (VG) model parameters α and n. LNAPL migrated downward with the falling groundwater table and became entrapped with the rising groundwater table, and the amount of entrapment depended on VG model parameters. Hydrogeological parameters were calibrated and LNAPL migration in filled fractured media was predicted using the calibrated numerical model. Simulation results revealed that fracture inclination had an important influence on LNAPL migration in filled fractured media and its migration velocity decreased with a decrease in fracture inclination. These research results can be applied to the control and remediation of oil-contaminated sites in fractured rock settings, such as at underground oil storage tanks and caverns, as well as at underground oil pipelines.