Underground Oil Research Articles

Asphyxiation effect analysis in confined space of B-type oil pool fire under pressure changes of nitrogen extinguishing system

Nitrogen fire extinguishing system has a significant development space in the modern fire extinguishing because of its environmental protection, energy saving and high stability. To further broaden the application field of nitrogen fire extinguishing system, a shrinkage size model was used as the research object and combined with simulated flow field analysis. A nitrogen fire extinguishing system was characterized for alcohol fire extinguishing efficacy using nitrogen injection pressure as a variable and parameters such as extinguishing time, oxygen concentration, and temperature. Furthermore, diesel and gasoline were used as combustible materials to verify the extinguishing efficacy of pressure variation on Class B oil pool fires. It was found that with the increase of nitrogen injection pressure, the nitrogen extinguishing efficacy gradually increased and then leveled off in the confined space. The asphyxiating oxygen concentrations were 12.2%, 13.2% and 13.7% for ethanol, diesel and gasoline, respectively. Asphyxiating oxygen concentration above limiting oxygen concentration (LOC). For extinguishing Class B oil pool fires in confined spaces, nitrogen extinguishing systems showed excellent fire extinguishing efficiency. They had specific application prospects in the field of protecting underground oil storage tanks and oil wells.

Cross-linked chitosan encapsulated hollow mesoporous silica nanoparticle: A dual-functional smart nanocapsule design for targeted corrosion inhibition and controlled emulsification

Research on stimuli-responsive micro-nanocontainers has gained attention for targeted corrosion inhibition and controlled emulsification-demulsification in oil recovery. However, existing nanocontainers face issues like irreversible drug release and limited functionality. This study presents a multi-functional nanocontainer design with reversible drug release and emulsification-demulsification capabilities. The fabricated nanomaterial BTA@HMSNs-CS, i.e., hollow mesoporous silica nanocontainers (HMSNs) loaded with 1H-Benzotriazole (BTA) and coated with crosslinked chitosan (CS), can transport BTA to corrosive areas in oil wells for targeted corrosion inhibition, and emulsify oil droplets in deep underground oil reservoirs for enhanced recovery. The imine bonds within the cross-linked CS layer demonstrate sensitivity to pH variations, dynamically adjusting the CS polymerization degree. This mechanism controls the BTA release from HMSNs-CS, achieving long-term corrosion inhibition of metal. When reaching deep underground oil reservoirs, the HMSNs-CS nanocontainers exhibit stable adsorption at the oil-water interface, preventing oil droplet aggregation and reducing the oil-water interfacial tension. This results in the formation of stable Pickering emulsions, facilitating demulsification in acid and emulsification in neutral/alkaline environments, and ultimately ensuring improved oil recovery efficiency. In this study, the developed nanomaterial exhibits dual-functions of corrosion inhibition and emulsification, offering an integrated strategy for metal protection and oil recovery in oil and gas operation.

Development and performance evaluation of a mechanically triggered release microcapsule based on in-situ polymerization for lost circulation control

Lost circulation is a critical technical challenge in the drilling and production process of underground oil and gas energy. In this study, a mechanically triggered release microcapsule for lost circulation control was designed and prepared with an in-situ polymerization using melamine, urea, formaldehyde, and diglycidyl ether of bisphenol A (healing agent) as raw materials. The structure and properties of the microcapsule were characterized by different techniques. The results show that the healing agent was successfully encapsulated by the resin shell, the median particle size (D50) of the microcapsules is 120.3 μm, and the thermal stability is excellent. The compatibility experiments show that the surface wettability and shear stability of the microcapsules are good in water-based drilling fluid. The compressive strength test reveals that the healing agent in the microcapsule is released and filled in the gap of the plugging zone under the contact pressure. The concentration of microcapsules and the size distribution of rigid particles are critical for the in-situ reinforcement effect. In addition, the fracture plugging performance of the microcapsule was studied. The results show that the pressure-bearing capacity of the plugging zone increases as the irregularity of the fracture surface increases. These findings indicate the microencapsulated healing agent is an effective lost circulation material (LCM), and provide a new technical idea for lost circulation control.

Monitoring Salt Domes Used for Energy Storage With Microseismicity: Insights for a Carbon‐Neutral Future

AbstractUnderground storage in geologic formations will play a key role in the energy transition by providing low‐cost storage of renewable fuels such as hydrogen. The sealing qualities of caverns leached in salt and availability of domal salt bodies make them ideal for energy storage. However, unstable boundary shear zones of anomalous friable salt can enhance internal shearing and pose a structural hazard to storage operations. Considering the indistinct nature of internal salt heterogeneities when imaged with conventional techniques such as reflection seismic surveys, we develop a method to map shear zones using seismicity patterns in the US Gulf Coast, the region with the world's largest underground crude oil emergency supply. We developed and finetuned a machine learning algorithm using tectonic and local microearthquakes. The finetuned model was applied to detect microearthquakes in a 12‐month long nodal seismic dataset from the Sorrento salt dome. Clustered microearthquake locations reveal the three‐dimensional geometry of two anomalous salt shear zones and their orientations were determined using probabilistic hypocenter imaging. The seismicity pattern, combined with borehole pressure measurements, and cavern sonar surveys, shows the spatiotemporal evolution of cavern shapes within the salt dome. We describe how shear zone seismicity contributed to a cavern well failure and gas release incident that occurred during monitoring. Our findings show that caverns placed close to shear zones are more susceptible to structural damage. We propose a non‐invasive technique for mapping hazards related to internal salt dome deformation that can be employed in high‐noise industrial settings to characterize storage facilities.

A spatio-temporal forecasting method of fracture distribution using dynamically exposed rock images in tunnel: Methodology and application

Forecasting the geometric characteristics of rock fractures in unexcavated tunnel sections is crucial for construction arrangements. This paper presents a method for predicting fracture distribution near the tunnel face from a spatiotemporal perspective. We Innovatively analogize the tunnel excavation mileage as the time series data. Using fractal geometry and geostatistics, we extract geometric features of peripheral rock fractures and establish a spatiotemporal dataset for dynamic prediction. The SCINet model, a spatial-aware recursive neural network, is employed for deterministic-stochastic dynamic prediction. Numerical simulations are conducted to validate the predictive accuracy of the model for various distributions, including trace length, dip angle, and density. Notably, the Mean Absolute Percentage Error (MAPE) for trace length prediction is remarkably low at 5.49 %, and the Kullback-Leibler (KL) divergence is as low as 4.81 %. The method is further applied to an underground oil storage cavern, China, revealing structural surface information. By incorporating continuously exposed fracture data, prediction accuracy is progressively improved, demonstrating the method's potential as a predictive tool for enhancing tunnel construction safety and efficiency.

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

Petroleum reserve in salt caverns is paying more attention to oil cooling to prevent dissolved gas release from heated crude oil. This work introduced a method for oil recovery in conjunction with cooling, along with a matching flow and heat transfer model taking changes in crude oil thermophysical parameters into consideration. An average error of 3.43% was observed between the model results and filed monitoring data. It was found that after being cooled by the heat exchanger, the temperature of extracted crude oil drops from 39.5 °C to 26.8 °C, demonstrating the effectiveness of this approach for oil cooling. Sensitivity analysis indicates that the season is the primary determining factor for the cooling efficacy of crude oil. Even worse, cooling will be useless when the ambient temperature exceeds 35 °C. However, increasing brine temperature will reduce the surface pumping pressure from 7.60 MPa to 5.17 MPa, with a decrease of up to 31.97%. A special focus was given to the brine injection rate, which seemed to have less impact on the cooling efficiency but became more significant in the pressure profile. In addition to providing further insights into the flow and thermal performance of strategic petroleum reserves in the salt cavern, this study could also be a powerful tool for determining the best process parameters to ensure the delivery temperature of crude oil and the stability of the salt cavern.

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.

“Component flow” conditions and its effects on enhancing production of continental medium-to-high maturity shale oil

Based on the production curves, changes in hydrocarbon composition and quantities over time, and production systems from key trial production wells in lacustrine shale oil areas in China, fine fraction cutting experiments and molecular dynamics numerical simulations were conducted to investigate the effects of changes in shale oil composition on macroscopic fluidity. The concept of “component flow” for shale oil was proposed, and the formation mechanism and conditions of component flow were discussed. The research reveals findings in four aspects. First, a miscible state of light, medium and heavy hydrocarbons form within micropores/nanopores of underground shale according to similarity and intermiscibility principles, which make components with poor fluidity suspended as molecular aggregates in light and medium hydrocarbon solvents, such as heavy hydrocarbons, thereby decreasing shale oil viscosity and enhancing fluidity and outflows. Second, small-molecule aromatic hydrocarbons act as carriers for component flow, and the higher the content of gaseous and light hydrocarbons, the more conducive it is to inhibit the formation of larger aggregates of heavy components such as resin and asphalt, thus increasing their plastic deformation ability and bringing about better component flow efficiency. Third, higher formation temperatures reduce the viscosity of heavy hydrocarbon components, such as wax, thereby improving their fluidity. Fourth, preservation conditions, formation energy, and production system play important roles in controlling the content of light hydrocarbon components, outflow rate, and forming stable “component flow”, which are crucial factors for the optimal compatibility and maximum flow rate of multi-component hydrocarbons in shale oil. The component flow of underground shale oil is significant for improving single-well production and the cumulative ultimate recovery of shale oil.

Seasonal large-scale thermal energy storage in an evolving district heating system – Long-term modeling of interconnected supply and demand

Given the strong seasonal nature of heating demands, peak heat is important during colder seasons. Instead of peak heat plants, seasonal large-scale thermal energy storage (TES) could be utilized. These can be charged during warmer seasons and discharged when required, decreasing the need for peak heat plants. Systems modelling studies on seasonal TES are lacking. Thus, a long-term local energy system model is applied under different scenarios to investigate the potential roles of seasonal TES in an evolving heating system. The results show that seasonal TES is economically viable for: all future electricity price cases for low TES construction costs, corresponding to repurposing of underground oil storages, and for most electricity price cases for mid- and high construction costs, corresponding to new underground excavations. Seasonal TES mainly decrease the investments in and usage of electric boilers or biogas boilers, while increase the utilization of heat pumps. Other technologies may be affected depending on the future trajectory of electricity price developments. The size of the TES is between 3 and 7% of the annual district heating heat demand, depending on construction cost and electricity price development. The expansion of district heating into new housing is mostly unaffected by the availability of TES.

Performance study of a compressed air energy storage system incorporating abandoned oil wells as air storage tank

With the rapid development of intermittent renewable energy, large-scale compressed air energy storage technology represented by Adiabatic Compressed Air Energy Storage (A-CAES) has attracted much attention. In order to simultaneously solve the problems of reuse of decommissioned oil wells and low efficiency of A-CAES system, a compressed air energy storage system incorporating abandoned oil wells as Air Storage Tank (AST) is proposed in this paper. The system performance of underground Oil Well CAES (OW-CAES), aboveground Steel Pipeline CAES (SP-CAES), and aboveground Storage Tank CAES (ST-CAES) is comparatively analyzed based on a thermodynamic model, focusing on the impact of heat transfer characteristic parameters of the AST wall on the system performance. The results show that recoverable heat and round-trip efficiency are significantly affected by the heat transfer characteristics of the AST wall. More recoverable heat and higher round-trip efficiency can be achieved by increasing the wall temperature and the surface area of the AST, respectively. The round-trip efficiency and energy storage density of the OW-CAES system are higher than those of the ST-CAES system, which are increased by 8.3 % and 18.45 % respectively. This study provides theoretical support for the feasibility of the OW-CAES system and has certain engineering guiding significance.

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

Temporal changes in soil physical properties following reclamation of underground natural gas pipeline rights-of-way on cropland

Underground oil and natural gas pipeline rights-of-way (ROWs) sometimes traverse croplands, leaving behind tracts of disturbed land characterized by poor productivity even after reclamation. This study investigated temporal post-reclamation changes in soil penetration resistance (PR), field saturated hydraulic conductivity (Kfs), near-saturated hydraulic conductivity (KΨ), soil pore indices, and wet aggregate stability (WAS) on natural gas pipeline ROWs on cropland. These attributes were measured in two fields in late summer of 2021 and 2022. Across the two fields, three ROWs that had been reclaimed four to thirteen years prior (i.e., time since reclamation (TSR) of 4 to 13 yr) were assessed along with adjacent undisturbed (off-ROW) transects located 50 m from the ROWs. Measurement locations on each ROW and on off-ROW were 25 m apart. Samples for WAS were collected from the 0–15 cm layer. The results showed a significant (p < 0.05) TSR by soil depth interaction for PR. Treatments were not significantly different in the 0- to 20-cm and 40- to 60-cm layers, but in the 20- to 40-cm depth interval, PR was 57.7–64.2 % greater on the 4.5-yr ROW than on off-ROW. Saturated hydraulic conductivity was three to four times lower on the 4.5- and 6.5-yr ROWs than on the off-ROW. Near-saturated hydraulic conductivity on the 4.5-yr ROW was 61.6 % lower than that on the off-ROW, while no significant differences were detected between the 6.5-yr and 12.5-yr ROWs and the off-ROW. Effective water conductive macroporosity was 72.5 % lower on the 4.5-yr ROW than on the off-ROW. All measured physical properties improved with increasing TSR. These results indicate a significant but slow recovery in soil physical attributes with increasing TSR of ROWs on cropland. This has implications on the productivity of these ROWs as crop yields, which depend on these soil physical properties, are also expected to recover slowly.

Use of fibre optic systems for detection of small leaks on trunk pipelines

This paper is devoted to the issue of efficiency of application of fibre optic leak detection systems for identification of small leaks on trunk pipelines. The main methods of leak detection currently in use have been considered, and parametric and fibre optic LDS have been selected for comparative analysis. In the course of the research a model of product leakage from an underground oil pipeline equipped with a fibre-optic LDS was built in the COMSOL Multiphysics software package. The result of the simulation was the estimated time of leak identification by the fibre-optic system, which turned out to be much shorter than that of the parametric LDS. Compensable environmental damage for each type of system was then calculated, confirming the effectiveness of fibre optic LDS for detecting small leaks on trunk pipelines due to the significant reduction in compensable damage.

Shear Wave Velocity Prediction Based on the Long Short-Term Memory Network with Attention Mechanism

Shear wave velocity (VS) is a vital prerequisite for rock geophysics. However, due to historical, cost, and technical reasons, the shear wave velocity of some wells is missing. To reduce the deviation of the description of underground oil and gas distribution, it is urgent to develop a high-precision neural network prediction method. In this paper, an attention module is designed to automatically calculate the weight of each part of the input value. Then, the weighted data are fed into the long short-term memory network to predict shear wave velocities. Numerical simulations demonstrate the efficacy of the proposed method, which achieves a significantly lower MAE of 38.89 compared to the LSTM network’s 45.35 in Well B. In addition, the relationship between network input length and prediction accuracy is further analyzed.

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

High-accuracy high temperature measurement based on forward Brillouin scattering of polyimide-coated optical fiber

In this paper, a novel method for high-accuracy high temperature measurement is proposed, which is based on forward Brillouin scattering (FBS) of double-coated optical fiber with polyimide outer coating. The temperature variation changes the acoustic properties of polyimide-coated fiber that is suitable for high temperature measurement in the range of 120 ∼ 220 ℃. An interesting feature is that different radial acoustic modes have different frequency responses in the polyimide-coated fiber. Another interesting phenomenon is that the temperature linearly depends on the frequency shift of FBS spectrum with high sensitivity from 120 ℃ to 220 ℃. By using one acoustic mode with a high frequency shift-temperature sensitivity, we propose a novel high temperature measurement method based on FBS with high measurement accuracy. The experimental result shows that the low temperature measurement uncertainty of 0.02 ℃ can be achieved. The proposed method is expected to be used for high-accuracy temperature measurement applications within a temperature range of 100 ∼ 200 ℃, such as underground oil layer detection, power plant monitoring and high-power electrical systems monitoring.

ОПТИМИЗАЦИЯ ПРОЦЕССА КЛАССИФИКАЦИИ ДАННЫХ ЛАЗЕРНОГО СКАНИРОВАНИЯ ДЛЯ ПРЕОДОЛЕНИЯ ИЗБЫТОЧНОСТИ

The article presents the results of analyzing existing methodologies for classifying mine surveying and geodetic data, particularly laser scanning data. Various software solutions are currently employed for modeling underground development, quarries, and oil extraction facilities. While there are algorithms designed to address specific tasks related to modeling stages, the majority of them are created as versatile tools. An evaluation of existing software algorithms for classification tasks has been conducted. In the mining industry, adapting these algorithms would significantly expedite and simplify the processes of updating mine surveying and geodetic information, indirectly impacting the overall speed and quality of deposit development. The research findings can be valuable for working with laser scanning data and selecting optimal solutions.

Versatile ionic liquid gels formed by dynamic covalent bonding and microphase separated structures.

It is challenging for ionic liquid gels to achieve the combination of rapid self-healing with high toughness. Here, ionic liquid gels (DI-PR) were prepared from readily available materials. A dynamic covalently bonded oxime-carbamate was prepared from polycaprolactone diol, isophorone diisocyanate and dimethylethyleneglyoxime, followed by addition of the "rigid-flexible" cross-linking agent rutin to chemically cross-link the polymer chains and afford the ionic liquid gels, DI-PR. The tensile strength, elongation at break and toughness of the DI-PR gels were as high as 16.5 MPa, 1132.6%, and 52.6 MJ m-3, respectively. The toughness is similar to that of natural silkworm silk (70 MJ m-3) and wool (60 MJ m-3). After stretching, the DI-PR can rebound within 1 s, their room temperature self-healing rate is as high as 92%, they remain functional over the temperature range -50 °C to 140 °C and the interface with a steel plate has an adhesion toughness of >2000 J m-2. These properties mean that the DI-PR gels are particularly suitable for use as anticorrosion coatings for submarine and underground gas and oil pipelines. The use of rutin, which combines rigid quercetin-based structural units with flexible glycoside-based structural units, as a cross-linking agent, provides a new method for improving the toughness of soft materials through its synergistic interaction with hard and soft chain fragments of polyurethanes.

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.