Exploitation Of Gas Resources Research Articles

Study on pressure fluctuation characteristics of the mixed-flow pump with the tandem misaligned blade structure

Abstract As supporting equipment for deep-sea oil and gas resource exploitation, how to improve the transmission performance and stability of the impeller of the mixed-flow pump (MFP) has become a key technical problem. This paper focuses on studying the impeller blade of the MFP. Based on the blade optimization technology, four different tandem misaligned blade (TMB) angle schemes of α=0°,15°,45°,75° are proposed. The SST k-ω turbulence model is used to simulate the different blade angles under the pure liquid condition. The pressure pulsation of the MFP and the blade load distribution are studied. This result show that the TMB structure increases the pressure fluctuation inside the MFP. The pressure coefficient inside the impeller exhibits a more consistent pattern at an angle of α=45° compared to other angles, and the internal flow field of the MFP exhibits most stable. From this analysis of blade load distribution, TMBs have a greater effect on the pressure surface of the front blade of the MFP. When α=15°, the best pressurization performance of the MFP. This study may serve as a benchmark for subsequent iterations of optimizing the MFP’s model and hydraulic design.

GDI (IoT-Based Gas Detector) As an Appropriate Technology for Gas Leak Detection in Tarakan City, North Kalimantan

Tarakan City, as the center of oil and gas resource exploitation in North Kalimantan Province, faces significant challenges related to safety and security concerning potential natural gas leaks. With its large population and the presence of 1,400 oil and gas wells, as well as being the largest consumer of natural gas networks in Indonesia with 32,000 consumers, the risk of gas leaks is a major concern. Previous gas leak incidents have demonstrated serious impacts, including fires and explosions resulting in significant losses for the community and the environment. To address these challenges, the 5.0 technology offers a potential solution, particularly implementing the Internet of Things (IoT). Based on this technology, developing an IoT-Based Gas Detector involves surveying potential tools, analyzing economic, social, and environmental factors, assembling the tools, and applying the product. IoT Gas Detectors have an advantage by utilizing connected sensor technology. The IoT-Based Gas Detector can be utilized to detect gas leaks in real-time, providing swift responses and reducing the potential impacts of gas leaks. Consequently, it can increase safety, security, and the efficient use of natural resources. The IoT-based Gas Detector (GDI) program supports several Sustainable Development Goals (SDGs), including: [1] No Poverty, [3] Good Health and Well-being, [7] Affordable and Clean Energy, [9] Industry, Innovation, and Infrastructure, [11] Sustainable Cities and Communities, [17] Partnerships for the Goals.

Temperature evolution in abandoned mines and the effect on gas adsorption properties of residual coal

ABSTRACT Abandoned mines contain a large amount of residual coal and gas resources for development and utilization. In order to accurately establish the calculation model of gas reserves and lay a foundation for the exploitation of gas resources in abandoned mines, based on the analysis of temperature evolution of abandoned mines, gas adsorption experiments and molecular simulations were carried out at temperatures of 30, 60, 90, 120, 150 °C and five different adsorption equilibrium pressures (0.5∼2.5 MPa). The test results show that the attenuation rates of gas adsorption at 30∼60 °C, 60∼90 °C, 90∼120 °C, and 120∼150 °C are 8.53%, 7.89%, 5.55%, and 1.55%, respectively. High temperature inhibits the increase of gas adsorption by residual coal, but its inhibition has a certain limit. At high adsorption equilibrium pressure, the initial adsorption rate increases with the rise of temperature. When the pressure is 2.5 MPa, the initial adsorption rates at 30, 60, and 90 °C is 1.25, 2.22, and 2.32 ml▪g−1▪min−1, respectively. Temperature affects the gas adsorption characteristics of residual coal. Therefore, the influence of temperature should be considered when establishing the gas reserves model of abandoned mines.

Characteristics of Fracturing Fluid Invasion Layer and Its Influence on Gas Production of Shale Gas Reservoirs

With the increase of shale gas resource exploitation in our country during recent decades, the situations of low gas production, fast production decline rate, and low flowback rate have been appearing in field production. It is an urgent problem to be solved in shale gas production and it is therefore necessary to study the interaction of the shale gas reservoir and the detained fracturing fluid. In this paper, the Longmaxi Formation shale samples of Sichuan Basin were selected for a water invasion experiment. The fracture propagation law, the water invasion front location, and the water invasion thickness of deep and shallow shale reservoirs after water invasion were compared and analyzed by CT scanning technology. Based on the analysis of the experimental mechanism, a numerical simulation model was established. The dimensionless permeability and thickness of the fracturing fluid invasion layer were introduced to analyze the positive and negative effects of fracturing fluid retention on the reservoir. The results show that during the hydraulic fracturing of shale gas wells, fracturing fluid can quickly enter the complex fracture network, and then slowly enter the shale matrix under various mechanisms to form the fracturing fluid invasion layer. Compared with shallow shale reservoirs, deep shale reservoirs have lower porosity and permeability, which propagates microfractures in the matrix induced by fracturing fluid retention, and results in a smaller fracturing fluid invasion layer thickness. Both the negative effect of fracturing fluid retention on shale damage and the positive effect of microfracture formation and propagation exist simultaneously. The higher the dimensionless fracturing fluid invasion layer permeability, the more complex the fracture network formed in the fractured reservoir will be, resulting in a longer stable production period and a better development effect. When the dimensionless fracturing fluid invasion layer permeability is greater than 1, that is, when the positive effect of fracturing fluid retention is greater, and the thicker the dimensionless fracturing fluid invasion layer is, the better the development effect will be. Combining reservoir characteristics and fracture development, the key to obtaining high productivity of a shale gas well is to optimize the soaking time and the speed of flowback in order to extend the stable production period. In this paper, the characteristics of the fracturing fluid invasion layer and the influence of fracturing fluid retention on gas well productivity are deeply studied, which provides a certain theoretical basis for the optimization of shale gas extraction technology and the improvement of the gas–water two-phase productivity prediction method for fractured horizontal wells.

Evaluation of Rock Brittleness Index under Dynamic Load

Rock is a typical brittle material, and the evaluation of its brittleness index has important guiding significance for hard rock resource exploitation, unconventional oil and gas resource exploitation, mechanical driving efficiency, rock burst prediction, and dynamic disaster prevention and control. At present, brittleness index often measures the brittleness of rock under static load; thus, whether it is applicable to dynamic load is worth exploring. In this study, static and dynamic uniaxial compression tests and Brazilian splitting tests were carried out on five kinds of rocks, including fine granite, coarse granite, shale, marble, and sandstone, using the INSTRON−1346 test system and split−Hopkinson pressure bar (SHPB), respectively. The brittleness index values of different rocks under static and dynamic load were determined, and the changes in the brittleness of rocks under different loading methods and different strain rates were studied. The definition of brittleness and the applicability of existing brittleness indices were also discussed. It was found that the loading rate amplified the variation of the brittleness characteristics of rock. When static load changes to dynamic load, the brittleness of rocks increases, and the brittleness relationship between different rocks remains unchanged. The more brittle the rock is under static load, the greater the range of brittleness enhancement is under dynamic load. It was also found that the brittleness of sandstone had an obvious effect on the strain rate. The brittleness of rock increases with the increase in strain rate, and the greater the strain rate, the greater the brittleness enhancement degree. These research results can provide reference values for dynamic disaster prevention and safe construction of deep rock projects such as mines and tunnels.

Experimental investigation of the fracture initiation and propagation for sandstone hydraulic fracturing under the effect of evenly distributed pore pressure

Pore pressure is disregarded in traditional laboratory rock hydraulic fracturing experiments, and the effect of pore pressure is not clear. An integrated experiment for seepage and hydrofracturing was established and used to perform sandstone hydraulic fracturing experiments under an initial evenly distributed pore pressure. The experimental results show that there is a positive correlation between the breakdown pressure and the pore pressure at the initiation stage. The data fitting results show that the breakdown pressure and pore pressure follow a linear growth trend. As the pore pressure increases, the acoustic emission energy at the moment of borehole wall fracturing correspondingly increases. After borehole wall fracturing, the reduced magnitude of the pumping pressure also increases, indicating that the initial rupture range is positively correlated with pore pressure. During fracturing propagation, the propagation range and opening of the fracture increase as the initial pore pressure increases within the same pumping time. During hydraulic fracturing, a pore pressure gradient is generated on both sides of the mineral particles. When the tensile stress or shear stress induced by the pore pressure gradient reaches the ultimate strength of the mineral particle bonding surface, the particle bonding surface breaks and opens. This experimental process is more similar to the actual hydraulic fracturing process of oil and gas reservoirs. These results provide a more comprehensive theoretical basis for resolving technical problems of unconventional oil and gas resource exploitation.

Differential development characteristics of secondary pores and effects on pore structure and movable fluid distribution in tight gas sandstones in the lower Permian, northeastern Ordos Basin, China

The lower Permian tight gas sandstones (TGSs) in the northeastern Ordos Basin have developed a complex pore network composed mainly of secondary pores with strong reservoir heterogeneity, which affects evaluation and exploitation of gas resources. In this study, lower Permian TGSs were analyzed through the thin sections, scanning electron microscopy, X-ray diffraction, He porosimetry, high-pressure mercury injection capillary pressure, X-ray computed tomography, and nuclear magnetic resonance experiments to elucidate the differential developmental characteristics of secondary pores and their effects on the pore structures and movable fluid distribution. Secondary pores in the lower Permian TGSs include dissolution pores associated with feldspar dissolution and micropores related to authigenic clay minerals. Based on fractal results, we designated the first-order dissolution pores as those with pore throat diameters greater than 1.98 μm, the second-order dissolution pores as those with pore throat diameters between 0.05 and 1.98 μm, and the pore throats diameters of micropores are mainly smaller than 0.05 μm. Both volumetric feldspar leaching calculations and petrographic statistics suggest that the secondary porosity observed in the lower Permian TGSs may not represent a net increase in porosity and more likely represents a redistribution of the original porosity. Dissolution requires sandstones with nonnegligible initial porosity and permeability: coarse-grained, quartz-rich, low proportion of ductile grains sandstones are more likely to maintain high porosity during burial, and dissolution of coarse-grained feldspar facilitates the development of first-order dissolution pores, thus generating the highest redistributed secondary porosity. The first-order dissolution pores have wide pore throat diameters, which enable seepage of movable fluids; the second-order dissolution pores have intermediate pore throat diameters, which allow moderate movable fluid seepage; and the micropores have small pore throat diameters, which are not conducive to seepage of movable fluids. Combinations of different types of secondary pores lead to differences in pore structures and distributions of movable fluids in the lower Permian TGSs. Specifically, TGSs with high first-order dissolution porosity have better pore structures, corresponding to the highest movable fluid saturation (MFS) and movable fluid porosity (MFP). When micropores dominate the pore system, the pore structure and pore network connectivity are poor, and the MFS and MFP decrease.

Identifying the Types of Loading Mode for Rock Fracture via Convolutional Neural Networks

AbstractFor decades, monitoring and identification of the dynamic stress states of rock masses in reservoirs have been challenging tasks owing to the lack of effective observation and analysis methods. In this study, we used deep learning methods to identify whether acoustic emission (AE) signals of rock fractures are created by different loading conditions. We performed Brazilian split and uniaxial compressive experiments on six different engineering materials, and we obtained the AE waveforms. To take advantage of the powerful image processing capabilities of convolutional neural networks (CNNs), we transformed the AE waveforms into time–frequency images. We used five types of CNN to identify the time–frequency images of the AE signals created in the Brazilian split and uniaxial compressive experiments. As a result, we found that Xception model had the highest recognition accuracy. We analyzed the basis of the CNN models to recognize the AE signals using local interpretable model‐agnostic explanations and found that the Xception model mainly used the patterns of the low‐energy region of the time–frequency images to determine the loading modes of the rock fractures. Furthermore, the high‐energy time–frequency region had little effect on recognition. The findings of this work can aid in automatically monitoring the dynamic stress states of fracture areas in reservoir formations and ensure the safety of oil and gas resource exploitation.

Stress-Dependent Unstable Dynamic Propagation of Three-Dimensional Multiple Hydraulic Fractures with Improved Fracturing Sequences in Heterogeneous Reservoirs: Numerical Cases Study via Poroelastic Effective Medium Model

Multistage hydrofracturing of horizontal wells is one of the key technologies for deep tight oil and gas resource exploitation. The stable and parallel propagation of multiple fractures formed by m...

Common Pool Problem: South Pars-North Dome Gas Field

The aim of this paper is to investigate possible problems of efficiency arising from the joint exploitation of the common gas pool (South Pars - North Dome, the largest natural gas reservoir in the world) by Iran and Qatar. The problem is related to the difference between private incentives and common goals. In the case of non-renewable resources, a Pareto-optimal joint extraction path could exist, but it is unlikely to occur in reality. We studied the difference in incentives for an optimal exploitation path for Iran and Qatar and found that their joint behavior was likely suboptimal from the perspective of the optimal dynamics of gas resource exploitation. In part, this is related to the difference in wealth, and in part to the sanctions against Iran, which have so far not allowed Iran to participate freely in the world market. Considering that the cost of future gas extraction in Russia's northern fields is likely to increase, a delay in the optimal presence of Iranian gas on the world market may lead to a suboptimal sequence of exploitation of various gas fields, which would mean both problems for the profitability of investments in Russia and higher world prices for natural gas in the future.

Gas flow laws in coal subjected to hydraulic slotting and a prediction model for its permeability-enhancing effect

ABSTRACT Low gas permeability of coal seams is a key factor restricting effective prevention and control of gas disasters and high-efficient exploitation of gas resources. Hydraulic slotting technology can enhance the permeability of a low-permeability coal seam with high gas content and significantly improve the efficiency of gas drainage. A gas–solid coupling model of gas flow in a coal seam was established based on changes of permeability caused by variation of gas pressures, and gas flow laws in coal subjected to hydraulic slotting under various working conditions were quantitatively elaborated. The research results demonstrated that slots increased the exposed area of a slotted borehole and allowed more gas to flow to the borehole per unit of time, so that the efficiency of gas drainage from the slotted borehole significantly improved. With the increase of slot spacing and width, enhancement index of gas drainage and cumulative gas drainage volume rose. After 90 d of gas drainage, cumulative gas drainage volume ratio after hydraulic slotting was 1.75 times that before hydraulic slotting on average. The enhancement index of gas drainage decreased with the enlargement of the permeability. When the permeability increases from 0.001 to 1, cumulative gas drainage volume ratio after hydraulic slotting drops from 3.0 to 1.1. The increase of gas pressure in the coal seam reduced the enhancement index of gas drainage. In addition, a prediction model for the ratio of cumulative gas drainage volume after slotting to that before slotting based on back-propagation neural network was constructed. The model realized the continuous and accurate prediction of enhancement effects of slotting on gas drainage under different working conditions. The research results could provide theoretical supports for revealing the permeability-enhancing mechanism of hydraulic slotting and properly determining slotting parameters in the field.

Expansion Planning Method of Offshore Multiplatform Power System With Wind Power Considering Cable Size Selection

With the expansion of the scale of subsea oil and gas resource exploitation, the offshore multiplatform interconnected power systems have become the main form of offshore platform group energy supply. The offshore multiplatform interconnected power system with wind power can effectively reduce the system fuel consumption and carbon emission, which has become an important direction for the development of future offshore multiplatform interconnected power systems. In this paper, the scenario method is adopted to portray the wind power output. System evaluation indicators considering the economy, reliability and environmental benefits of the system are proposed. Considering the nonnegligible impact of the cable size selection problem on the system economic cost, this paper introduces cable size selection variables in the expansion planning model of the offshore multiplatform interconnected power system with wind power to achieve accurate optimization of the system planning scheme but also greatly increases the difficulty of solving the model. A model linearization method is applied to linearize the nonlinear part of the model, so that the optimized model is a mixed-integer linear programming model under the determined system topology, and thus can be solved using commercial planning software. In addition, an improved genetic algorithm is proposed to optimize the system topology, which improves the efficiency of the model solution. The cases of different scale verify the validity of the model and the solution algorithm and show the impact of the maximum penetration rate of wind power on the total system cost.

Fracture Propagation Characteristics in Horizontal Wells

Field experience shows that horizontal well multi-stage fracturing technology can transform the volumetric pressure crack network in the formation and has been widely used in unconventional oil and gas resource exploitation. According to the requirements of horizontal well fracturing operations, this paper simulates the law of horizontal well fracturing in low-porosity and low-permeability sand-shale formation by large-mold fracturing tests and analyzes crack initiation and extension. The two completion methods of open-hole completion and casing perforation completion are considered, and the maximum and minimum horizontal principal stress difference is 10 and 4 MPa. The horizontal wellbore azimuth angle changes from 0° to 90°. The test results show that the principal stress difference has a great influence on fracture initiation. The smaller the stress difference, the higher the fracture initiation pressure and the more complicated the fracture initiation and extension. The fracture propagates along the axial direction of the wellbore, and then at both ends of the wellbore the fracture turns to the direction perpendicular to the direction of the minimum horizontal principal stress. The horizontal wellbore can form a transverse fracture by drilling along the direction of the minimum horizontal principal stress. This study is of great significance for understanding the fracture initiation and propagation law of horizontal well fracturing and can provide guidance for multi-stage fracturing operations of horizontal wells in unconventional reservoirs.

Approach for natural gas to be a primary energy source in China

This work reveals the positioning of natural gas in the evolution of world energy and the general law of its development. In the long-term adjustment of energy structure, natural gas has gradually become the primary energy source because of five factors: policy, resources, technology, facilities, and market. To expedite the revolution of energy production and consumption, China must urgently expand the use of natural gas toward a more positive role in complementing coal and renewable energy and prioritize its usage in three areas, namely, urban gas, power generation, and industrial fuel. Natural gas is expected to account for approximately 15% of China’s total energy consumption in the future. For natural gas to be the primary energy, the exploitation of gas resources must be expanded, resource access must be improved, a flexible trade system must be set up, infrastructure investment must be increased, and the security system must be enhanced.

Some Main Causes of Marine Pollution in Vietnam

Vietnam is a coastal country located in the central region of Southeast Asia, Vietnam has a sea area connecting the important sea transport route between the Indian Ocean and the Pacific Ocean, especially the East Vietnam Sea are oil and container shipping routes from other countries to Japan, South Korea and China, which are consuming huge amounts of energy. Vietnam is in a position to have a potential for marine economic development such as shipbuilding, sea transport, port development, and waterworks, marine product exploitation, marine and oil and gas resource exploitation, marine tourism and islands, sea services, and other related industries. With such a potential position, the exploitation of the sea and the protection of the marine environment is an extremely important issue.

Some Main Causes of Marine Pollution in Vietnam

Vietnam is a coastal country located in the central region of Southeast Asia, Vietnam has a sea area connecting the important sea transport route between the Indian Ocean and the Pacific Ocean, especially the East Vietnam Sea are oil and container shipping routes from other countries to Japan, South Korea and China, which are consuming huge amounts of energy. Vietnam is in a position to have a potential for marine economic development such as shipbuilding, sea transport, port development, and waterworks, marine product exploitation, marine and oil and gas resource exploitation, marine tourism and islands, sea services, and other related industries. With such a potential position, the exploitation of the sea and the protection of the marine environment is an extremely important issue.

A review of the current status of induced seismicity monitoring for hydraulic fracturing in unconventional tight oil and gas reservoirs

During the past decades, significant progress has been made in the development of induced seismicity monitoring for related human activities. Hydraulic fracturing and induced seismicity monitoring are operating procedures for safe and effective production of oil and gas from unconventional resources, particularly shales. Hydraulic fracturing can induce seismicity through fluid injection and disturbance of subsurface stress in tight reservoirs. Most seismic events associated with hydraulic fracturing exhibit magnitude of Mw ≤ 3 and are referred to as microseismicity, while a few larger-magnitude earthquakes (e.g. Mw > 3) could also be induced by reactivating pre-existing faults. Here, we review the current status of research concerning induced seismicity monitoring for shale hydraulic fracturing. Induced seismicity contains information relating to important subsurface characteristics, e.g. rock failure potential and seismogenic zones. Microseismic monitoring is essential for reservoir characterization, e.g. fracture geometry delineation and reservoir geomechanical analysis. It is carried out with advanced acquisition, processing, and interpretation techniques, while larger-magnitude earthquakes are mainly exploited for potential geohazard management and mitigation. Challenges and prospects associated with multi-disciplines for future research and applications of induced seismicity monitoring are identified, and it contributes to achieve safe and efficient unconventional (tight) oil and gas resource exploitation.

Energy Security prospects in Cyprus and Israel: A focus on Natural Gas

The global production of natural gas has increased from 1226 bcm in 1973 to 3282 bcm in 2010 and is projected to continue rising by an annual growth rate of 1.6% between 2010 to 2035. Cyprus and Israel have recently made major offshore discoveries of natural gas, which can supply to a great extent the two countries’ current domestic energy needs for the next few decades and still export a substantial volume. MESSAGE, a global optimization model was used to explore the possible interactions between the two countries’ energy systems. Scenarios are presented that assess the export potential for electricity (generated by gas-fired power plants), liquefied natural gas (LNG) or gas-to-liquid products (GTL). The results are compared to a scenario without any available reserves to illustrate the financial benefits that will arise from the exploitation of the gas resources in the two countries.

Meeting the challenge of uncertainty in surface microseismic monitoring

Mike Mueller discusses the essential elements of today’s successful microseismic monitoring surveys used in hydraulic fracturing operations during shale oil and gas resource exploitation, and looks ahead to the major challenge of uncertainty estimation and how it can be met.

Improving performance of a neural network model by artificial ant colony optimization for predicting permeability of petroleum reservoir rocks

Over recent years, oil and gas exploration has been beloved due to extended needs for petroleum and energy sources. In this way, the capabilities of intelligent techniques are studied by researchers in different fields of petroleum industry and geosciences, whereas it seems that these techniques can improve the prediction accuracy of exploration and production of the hydrocarbon reservoir. The performance indices of the artificial models have proven to be better than the conventional linear and non-linear statistical models. Artificial intelligence models are extremely useful for reservoir characterization, which requires a high-accuracy prediction for a good exploitation of the oil and gas resources. The present paper introduces an optimized neural network (NN) for predicting permeability based on a relatively new swarm intelligent approach, named ant colony optimization. Ant colony optimization (ACO) is a relatively new computational intelligent approach, which was initially inspired by the observation of ants. The number of neurons in hidden layer, weights and bias are optimized in the proposed NN using the ACO. The data of a gas reservoir in the South Pars Gas Field of Iran was used for analyzing the accuracy of optimized NN in a real case study. Finally, to clarify the advantages of the optimized NN, its outcomes were compared with the results of a simple NN model, in which the aforementioned parameters were determined through a try-and-error process. The MSEs of the optimized and simple NN were equal to 7.95 md and 12.84 md, respectively, which correspond to the correlation coefficient (R) of 0.94 and 0.866, respectively.