Shale Gas Exploitation Research Articles

Silicon: A Surface Dopant for Stable Alumina-Supported PtGa Propane Dehydrogenation Catalysts by Favoring Redox and Carbon Dynamics.

The exploitation of shale gas has stimulated the use of on-purpose propane dehydrogenation (PDH) technologies. These technologies rely on continuous and rapid catalyst regeneration to maintain high propene production. For Pt-based catalysts, metal promotors and additives, such as Ga and Si, have been shown to enhance the catalyst productivity and stability. While most studies have focused on understanding the role of Ga as a promoter, the effect and role of Si on the catalytic properties are less explored and understood. Therefore, tailored monometallic Pt and bimetallic Pt-Ga catalysts supported on alumina or Si-doped alumina are prepared via surface organometallic chemistry and evaluated under PDH conditions. The Pt catalyst containing both Ga and Si displays the highest propene productivity (1970 molC3= molPt-1 h-1 after 2 h) and the lowest deactivation constant (0.31 h-1 after 2 h), pointing out the critical role of both Ga and Si. While scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray absorption spectroscopy show that the catalyst structures of the as-reduced Pt-Ga catalysts are similar, postmortem analyses reveal that Si-doping of the alumina-supported Pt-Ga PDH catalyst modifies redox and carbon dynamics. This modification maintains Pt-active sites by yielding interfaces between Pt and GaOx domains along with a surface PtC structure that is correlated with increased structural dynamics and slower deactivation.

Identifying and prioritizing organic toxicants in treated flowback and produced water from shale gas exploitation sites using an integrative effect-directed analysis and nontarget screening method.

Identifying and prioritizing organic toxicants in treated flowback and produced water from shale gas exploitation sites using an integrative effect-directed analysis and nontarget screening method.

Dynamic coupling mechanism of shale drilling fluid invasion depth, fracture width, and rock strength

The dynamic coupling effects of fracture width, invasion depth, and rock strength during drilling fluid invasion into shale reservoirs constitute a key scientific issue in wellbore stability control. This study establishes a dynamic coupling theoretical model of invasion depth-fracture width-rock strength, revealing the dynamic feedback mechanisms of drilling fluid invasion. Comparative analysis between experimental and simulated data shows excellent agreement in variation patterns, where all relative deviations remain under 12%, validating the model's practical effectiveness. The study reveals that the coupled system evolves via a flow-stress positive feedback mechanism between fracture width and invasion depth, demonstrating distinctive “rapid transition-progressive stabilization” behavior; variations in original fracture width primarily determine dynamic evolution speed and balance thresholds by regulating flow cross section, while showing minimal impact on final strength equilibrium conditions; modulating drilling fluid density from 1.3 to 1.7 g/cm3 increases invasion depth by 230% and shear strength attenuation by 13.4% through pore pressure gradient adjustments that alter equilibrium thresholds; fluid viscosity governs dynamic evolution speed via flow resistance, where high-viscosity formulations (35 mPa·s) prolong stabilization time to over 20 days. The study quantitatively characterizes the tripartite dynamic coupling mechanism, establishing a theoretical foundation for drilling fluid optimization and wellbore stability management in shale gas exploitation.

The pore-network-continuum hybrid modeling of nonlinear shale gas flow in digital rocks of organic matter

Organic matter (OM) serves as the primary source of gaseous hydrocarbons in shales. Fundamental understanding of its permeability and gas production characteristics is vital to optimize shale gas exploitation. The focused ion beam scanning electron microscopy (FIB-SEM) imaging can resolve OM macropores with pore radii ranging from tens to hundreds of nanometers, while pore sizes of sub-resolution OM can be characterized using low-temperature gas adsorption. In this work, we focus on multiscale pore structures of OM and contribute to the development of an efficient pore-network-continuum model for simulating nonlinear gas flow in multiscale OM digital rocks, along with its fully coupled implicit numerical implementation. To demonstrate the influence of OM pore structures on its permeability and transient gas production, we select three types of OM featured by their distinct porosities, connectivity of macropores, and pore morphologies. We show that the high-porosity OM with interconnected macropores exhibits markedly different intrinsic permeability, mechanisms of apparent permeability, gas storage, and production behaviors compared to the medium-porosity and low-porosity OM. Moreover, we propose an empirical formula for OM apparent permeability with respect to an effective characterization length used in the calculation of Knudsen number, which will be the key input to the representative elementary volume (REV) size modeling of shale matrix.

Investigation of the Corrosion Behavior of L245 Steel in 3.5 wt.% NaCl Solution with Varying Concentrations of Na2S2O3.

In the extraction of shale gas, Cl- and S2O32- are one of the important factors causing severe corrosion and failure of equipment and pipelines. Addressing the Cl-/S2O32- corrosion challenge in shale gas exploitation pipeline steels, this study evaluates the corrosion rates of L245 steels under diverse conditions, including S2O32- concentration and exposure time, utilizing the weight loss method. The microstructural, elemental, and phase compositions of the corrosion products were examined, and the electrochemical behavior of L245 steel was scrutinized under various conditions. Findings indicate that S2O32- addition intensifies localized corrosion on L245 steel, with the corrosion nature being contingent upon S2O32- concentration in the Cl--containing solution. Concurrently, an escalation in S2O32- concentration correlates with a reduction in capacitive arc diameter and a significant decrease in film resistance, culminating in an accelerated corrosion rate.

Implications of the geochemical characteristics of post-fracturing flowback fluids for shale gas exploration and exploitation

Implications of the geochemical characteristics of post-fracturing flowback fluids for shale gas exploration and exploitation

Investigation of Pt-based Model Catalysts for Propane Dehydrogenation Reaction

Large scale exploitation of shale gas has stimulated the developments of on-purpose propane dehydrogenation (PDH) technologies. Pt-based PDH catalysts have been utilized in industry, e.g. Pt-Sn/Al2O3 and Pt-Ga/ Al2O3, where the actual role of metal dopants is not fully understood. In this regard, the development of model systems possessing tailored surface sites is necessary in order to look into the structure-activity relationships. In that context, the surface organometallic chemistry (SOMC) approach has emerged as a powerful tool to yield PDH model catalysts, revealing that the formation of alloyed particles and residual unreduced metal sites are important for high productivity and stability.

Effect of heat treatment on fatigue properties of new fracturing pump valve box material 30CrNi3MoV

ABSTRACT In the exploitation of shale oil and gas, the fracturing pump, as a key equipment for transporting liquid from the ground to the formation and increasing pressure, needs to withstand high-pressure cyclic loading, which has high requirements on the fatigue performance of the fracturing pump valve material. In this paper, different heat treatment processes are used for the new fracturing pump valve box material 30CrNi3MoV, and the fatigue properties of the material after heat treatment are studied. The results show that: (1) The samples after quenching at 840°C and tempering at 580°C show higher fatigue properties, and the fatigue limit is 681.345 MPa. On this basis, keeping the tempering temperature unchanged, increasing the quenching temperature and keeping the quenching temperature unchanged, increasing the tempering temperature will lead to the decrease of the fatigue performance of the material. (2) The increase of grain size and the precipitation of carbide particles will lead to the decrease of fatigue performance. The fatigue cracks of the specimen initiate and propagate at the stress concentration, such as dislocations, non-metallic inclusions and crack defects.

Study on the Contribution of Shale Gas Exploitation and Utilization to Carbon Emission Reduction Based on LEAP Modeling

Study on the Contribution of Shale Gas Exploitation and Utilization to Carbon Emission Reduction Based on LEAP Modeling

The Discovery of Fracture Tip-Driven Stress Concentration: A Key Contributor to Casing Deformation in Horizontal Wells

Casing deformation (CD) is generally believed to be caused by the slip of fractures in the strata and its shear effects on horizontal wells. However, the casing deformation mode based on this theory cannot fully match the measurement data, and the differential deformation characteristics and the mechanism behind this phenomenon are not completely clear. To elucidate the mechanisms of CD and enhance prevention and control measures, the CD modes in Shunan Block were identified and deformation mechanisms of these modes were comprehensively investigated. Our research shows the following: (1) Under the mechanism of penetrating fracture shear deformation, CD exhibit obvious shear deformation, and the natural fractures near the intersection point with the wellbore are prone to form a higher risk of deformation. (2) Natural fractures with tips approaching the wellbore experience intense stress concentration (1.6 times higher than shear stress) during activation, resulting in compression and asymmetrical CD. (3) The shear deformation induced by penetrating fractures is 15.52 mm, while the fracture tip-induced compression deformation demonstrates a substantially greater magnitude at 44.17 mm. This compressive deformation exceeds the shear deformation by a factor of approximately 2.85. (4) The stress concentration at the fracture tip is highly sensitive to the injection rate. Hence, adherence to the “avoiding stress concentration” principle is crucial in hydraulic fracturing operations. The conclusion indicates that in addition to penetrating fracture shear deformation, fracture tip compression deformation is another significant mechanism that causes CD. This research finding can offer theoretical guidance for developing effective measures to prevent and control CD in the exploitation of deep shale gas.

Study on anisotropic mechanics and acoustic emission response characteristics of layered shale under uniaxial compression

Deep shale has obvious bedding structure, and its complex anisotropic mechanical characteristics bring challenges to the development of shale gas resources. In order to explore the effect of bedding on the mechanical properties and failure modes of shale. This paper takes the Longmaxi Formation shale in Changning, Sichuan Province as the research object, uniaxial compression tests were conducted on shale with different bedding angles, and acoustic emission (AE) signals were monitored during the loading process. The anisotropic mechanical properties of shale under loading were analyzed, and a further comprehensive evaluation of shale brittleness characteristics and rock burst tendency was conducted. Additionally, the evolution law of statistical parameters of AE and the mechanism of rock fracture were explored. The results showed that: (1) The deformation and mechanical properties of shale containing laminations during uniaxial compression show strong anisotropic characteristics, showing significant dip angle effect. (2) The fracture morphology of shale under uniaxial loading was complex, mainly characterized by splitting tensile failure and shear tensile failure, showing a strong tendency towards rockburst. (3) The Rickman brittleness index of shale attains 45.59, manifesting strong brittleness properties that are conducive to reservoir fracturing transformation. (4) During the loading process, there is good consistency between the AE signal and the stress–strain curve. The evolution of shale AE parameters corresponds to the rock damage and failure process, and the distribution characteristics of AE spectrum RA–AF data can distinguish the type of stress-generated cracks, and it is found that the shale under uniaxial compression was dominated by shear damage on the whole, and the proportion of shear damage increases firstly and then decreases with the increase of bedding angle. The research results can provide theoretical reference and guidance for the optimization design of hydraulic fracturing and the control of drilling stability during deep shale gas exploitation.

Review of Competitive Adsorption of CO2/CH4 in Shale: Implications for CO2 Sequestration and Enhancing Shale Gas Recovery.

The injection of CO2 into shale gas reservoirs can not only enhance shale gas recovery (ESGR), but also realize CO2 geological storage (CGS). In this study, the competitive adsorption behaviors of CO2 and CH4 in shale were systematically reviewed, and the implication for shale gas recovery efficiency and CO2 storage potential were discussed. The adsorption advantage of shale for CO2 compared to CH4 provides a guarantee of the feasibility of supercritical CO2 (ScCO2) enhanced shale gas exploitation technology. The selective adsorption coefficient of CO2 and CH4 by shale (S CO2/CH4 ) is an important parameter in evaluating the competitive adsorption behavior of CO2/CH4 in shale gas reservoirs, which is closely related to the mineral composition, reservoir temperature, pressure conditions, water content, and mixed gas composition ratio. In addition, the injection type, injection mode, and injection rate of gases also exhibit different effects on CO2/CH4 competitive adsorption. Furthermore, the interaction between ScCO2 and the water-rock system will change the mineral composition and microstructure of shale, which will lead to changes in the adsorption behavior of shale on CO2 and CH4, so its influence on the competitive adsorption of CO2/CH4 cannot be ignored. Future research should integrate different research methods and combine with practical engineering to reveal the competitive adsorption mechanism of CO2/CH4 in shale reservoirs from both micro and macro aspects. This study can provide support for the integration technology of ScCO2 enhanced shale gas exploitation and its geological storage.

The adsorption and transport behavior of shale gas in nanochannels with three-dimensional random roughness

Understanding the adsorption and transport behavior of shale gas is highly critical for assessing gas-bearing properties of reservoirs and enhancing shale gas recovery. However, the underlying mechanism is still an open question due to the irregularly rough characteristic within nanochannels of reservoirs. In this paper, the migration behavior of shale gas in nanochannels with three-dimensional random roughness is studied by using molecular dynamics simulation and theoretical analysis. It is found that random roughness leads to intense gas adsorption, which contributes to the large reserve phenomenon in engineering practice. In contrast, significant obstruction of shale gas's transportation is observed due to the roughness of the walls. The exploitation of shale gas may be improved by generating channels/fractures with smoother surfaces, increasing pressure gradient, and adopting higher temperature. These results should be of importance in enhancing our knowledge of storage and exploitation of shale gas and guiding the improvement of corresponding technologies in energy engineering.

Study on the Long-Term Influence of Proppant Optimization on the Production of Deep Shale Gas Fractured Horizontal Well

As shale gas development gradually advances to a deeper level, the economic exploitation of deep shale gas has become one of the key technologies for sustainable development. Large-scale, long-term and effective hydraulic fracturing fracture networks are the core technology for achieving economic exploitation of deep shale gas. Due to the high-pressure and high-temperature characteristics of deep shale gas reservoirs, traditional seepage models cannot effectively simulate gas flow in such environments. Therefore, this paper constructs a fluid–solid–thermal coupling model, considering the creep characteristics of deep shale, the effects of proppant embedment and deformation on fracture closure, and deeply analyzes the effects of proppant parameters on the shale gas production process. The results show that factors such as proppant concentration, placement, mechanical properties and particle size have a significant effect on fracture width, fracture surface seepage characteristics and final gas production. Specifically, an increase in proppant concentration can expand the fracture width but has limited effect on increasing gas production; uneven proppant placement will significantly reduce the fracture conductivity, resulting in a significant decrease in gas production; proppants with smaller sizes are more suitable for deep shale gas fracturing construction, which not only reduces construction costs but also improves gas seepage capacity. This study provides theoretical guidance for proppant optimization in deep shale gas fracturing construction.

Effects of inclination angle and unloading rate of confining pressure on triaxial unloading-induced slip behaviors of shale fractures

The effects of inclination angle θ and unloading rate of confining pressure Uc on the unloading-induced slip behaviors of shale fractures were investigated by conducting triaxial unloading-induced fracture slip experiments. The variations in mechanical stability, frictional behavior, and morphology variation of shale fractures were systematically explored. The results show that with the continuous unloading of confining pressure, the fractures were initiated to slip, then entered the quasi-static slip stage, and eventually entered the dynamic slip stage in sequence. The occurrence of stick-slip events in the quasi-static slip stage was strongly influenced by the θ and Uc. As θ increases from 30° to 50°, the stick-slip events occurred from 0 to 3 times and from 1 to 3 times for Uc = 0.1 MPa/min and 1 MPa/min, respectively. The θ and Uc have a great influence on the interaction mode of the fractures, which directly affects the frictional behavior of the fractures. The slipping failure behavior of the fracture surfaces is mainly controlled by θ, while Uc plays different roles for the samples with different θ. With the increase in θ, the interaction form between asperities during the slip process may be changed into non-tight contact stage. The increase in θ may enhance or weanken the anisotropy of JRC, depending on whether the Uc reached a certain rate between 0.1 MPa/min and 1 MPa/min. Our results may shed light on the seismicity mitigation and safe exploitation of shale gas.

Intermittent Optimization of Shale Gas Wells Based on Reservoir–Wellbore Coupling

Shale gas, as an important component of unconventional energy, holds enormous potential value in the energy sector. However, due to the complex geological characteristics and fluid flow mechanisms of shale gas reservoirs, its exploitation faces numerous challenges. This study focuses on the optimization of intermittent production methods for shale gas wells in the Changning block. In this study, a dynamic coordination model of formation recharge and wellhead output was established using real-time pressure monitoring and historical production records as key inputs. Based on this, the dimensionless production efficiency index was optimized by finely regulating the switching timing of the wellhead, thus significantly enhancing the cumulative oil production of the well. The conclusions indicate that the optimization methods proposed in this study can effectively guide the production operations of shale gas wells in the Changning block, thereby enhancing production yield and stability. This research contributes practical value to the field by offering theoretical support and practical guidance for shale gas exploitation, addressing technical challenges in the process.

Study on the optimal scheme of shale complex cracks formation based on Xsite discrete lattice method.

In the contemporary energy industry, shale gas, as an important unconventional energy resource, has been widely concerned. However, the exploitation of shale gas is faced with complex geological conditions and technical challenges, one of the main challenges is that it is difficult to form discrete complex crack networks in shale, which greatly reduces the recovery rate. For different geological conditions and engineering needs, the criteria for evaluating the effect of reservoir reconstruction will be different. The XSite discrete lattice method can simulate the crack development process and provide detailed crack morphology and characteristic information (crack area, crack volume, etc.). The advantage of the orthogonal experimental design scheme is that it can obtain as much information as possible in a relatively small number of tests, improving the efficiency and cost effectiveness of the test. Therefore, based on Xsite design 6 factor 5 horizontal orthogonal test, this paper obtained the optimal fracturing design scheme with crack area, crack shape volume, tensile crack area and shear crack area as evaluation criteria. The standard deviation of each influencing factor was calculated to obtain the optimal fracturing scheme under different evaluation criteria. And considering a variety of quantitative indicators, calculate the influence weight of each influencing factor, and get the optimal fracturing scheme considering a variety of evaluation basis. Two Wells with different depth and natural fracture development were selected to verify the feasibility of orthogonal simulation test by changing fracturing fluid rate. To provide scientific basis and technical support for optimizing shale gas exploitation scheme.

Study of shear resistance and anisotropy of layered shales.

Characterizing anisotropy remains challenging in rock mechanics. Particularly, the strengths and failure patterns of layered shales under shear load are significantly anisotropic mainly because of the bedding planes. Meanwhile, understanding the creation and propagation of shear fractures is critical for drilling, mining, tunnelling, exploitation of shale gas, etc. In this study, the shear resistance of layered shales is comprehensively investigated based on the direct shear tests numerically. The results show that the shear parameters are greatly affected by the anisotropy induced by the normal stress and orientation of bedding planes; the shear strength, cohesion and internal friction angle generally increase with the growth of bedding plane orientation. Furthermore, three shear failure patterns are summarized, i.e., (1) the shear failure along bedding planes; (2) the shear failure crossing bedding planes; (3) the combination of tensile failure along bedding planes and shear failure crossing bedding planes. Besides, the empirical fitting formula characterizing the shear strength of layered rocks under triaxial compression is provided, and the modified Mohr-Coulomb criterion reflecting rock anisotropy is proposed.

Dynamic in-situ CT imaging to study meso-structure evolution and fracture mechanism of shale during thermal-mechanical coupling condition

Dynamic in-situ CT imaging to study meso-structure evolution and fracture mechanism of shale during thermal-mechanical coupling condition

End of tubing placement optimization for multi-stage fractured horizontal wells by transient multiphase flow simulation

End of tubing placement optimization for multi-stage fractured horizontal wells by transient multiphase flow simulation