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In some sour reservoirs and tertiary oil recovery blocks, SO42− in the well fluid can cause the corrosion and corrosion fatigue of the sucker rods. In this paper, the corrosion behaviors of super-strength sucker rod FG20 (16Mn2SiCrMoVTiA) steel in the well fluid are investigated by electrochemical measurements, and electron probe micro-analyzer (EPMA) analysis. The results show that FG20 steel has a favorable corrosion resistance in neutral solution. When the hydrogen ions increase, the hydrolysis of SO42− greatly accelerates the corrosion of FG20 steel. The energy dispersive X-ray (EDX) results demonstrate that the corrosion process of FG20 steel in neutral well fluid is an oxygen concentration process, and the protective FeCO3 and Fe2O3 on the surface of the samples can prevent the further corrosion. With the increase of the acidity in the well fluid, the corrosion process converts into a sulphide concentration process, and the sloppy FeS and mackinawite film cannot provide effective protection for the specimens, resulting in the increase of corrosion rate. Keywords: Corrosion behavior, FG20, Electrochemical measurements, EPMA, Corrosion mechanism

To address the deformation and instability characteristics of a formation after an offshore shallow gas well blowout, a theoretical model of formation deformation caused by shallow gas blowouts was constructed, based on porous elastic medium theory and incorporating the sand-out erosion criterion. The spatiotemporal dynamics of formation subsidence were then investigated, and deformation patterns during a blowout were analyzed under various factors. The results indicate that, following a blowout, a shallow gas formation near a borehole experiences significant subsidence and uplift at the upper and lower ends, with the maximum subsidence values at 12 h, 24 h, 36 h, and 48 h post blowout being 0.072 m, 0.132 m, 0.164 m, and 0.193 m, respectively. The overlying rock layer forms a distinctive "funnel" shape, exhibiting maximum subsidence at the borehole, while more distant strata show uniform subsidence. The effective stress within the shallow gas stratum and surrounding rock layers increases gradually during the blowout, with lesser impact in distant areas. The ejection rate and sand blast volume demonstrate an exponential change pattern, with a rapid decline initially and later stabilization. Formation deformation correlates positively with factors like burial depth; shallow gas layer extent; pressure coefficient; sand blast volume; gas blowout rate; and bottomhole difference pressure. Formation pressure, ejection rate, and bottomhole difference pressure have the most significant impact, followed by sand blast volume and burial depth, while the extent of the shallow gas layer has a less pronounced effect. These simulation results offer valuable theoretical insights for assessing the destabilization of formations due to blowouts. [ABSTRACT FROM AUTHOR]

Natural gas hydrate reservoir has been identified as a new alternative energy resource which has characteristics of weak cementation, low reservoir strength and shallow overburden depth. Thus, the stability of subsea equipment and formation can be affected during the drilling process. To quantitatively assess the vertical displacement of the formation induced by hydrate decomposition and clearly identify the influence laws of various factors on wellhead stability, this study established a fully coupled thermo-hydro-mechanical-chemical (THMC) model by using ABAQUS software. The important factor that affects the wellhead stability is the decomposition range of hydrates. Based on this, the orthogonal experimental design method was utilized to analyze the influence laws of some factors on wellhead stability, including the thickness of hydrate formation, initial hydrate saturation, overburden depth of hydrate sediment, and mudline temperature. The results revealed that the decomposition of hydrate weakens the mechanical properties of the hydrate formation, thus leading to the compression of the hydrate formation, further causing the wellhead subsidence. When the duration of drilling operations was 24 h and no decomposition of natural gas hydrate occurs, the wellhead subsidence is recorded at 0.053 m, this value increases with an increase in drilling fluid temperature. The factors were listed in descending order as following, according to their significance of influences on wellhead stability: the thickness of hydrate formation, initial hydrate saturation, overburden depth of hydrate sediment, and mudline temperature. Among the above factors, statistical significance of the mudline temperature was less than 15% confidence level, suggesting that the effect of mudline temperature on wellhead stability is negligible. These findings not only confirm the influence of hydrate decomposition on wellhead stability, but also suggest important implications for the drilling of hydrate-bearing formation. [ABSTRACT FROM AUTHOR]

The field monitoring data showed that the fracture of high-position thick and hard roof (THR) was the main reason for the frequent occurrence of high-energy mine earthquake events (magnitude > 2.0) in the no. 6 mining district of Dongtan coal mine. In order to study the fracture characteristics of high-level THR and seek a reasonable and effective control method, taking the 63up06 working face as the engineering background, the FLAC model was built to simulate the strata movement law before and after fracturing. The simulation results showed that the THR first breaking span was 340 m, the tensile failure runs through the whole THR, and the subsidence increased rapidly when THR reached the first breaking span. The THR breakage is related to the continuous upward transfer of horizontal compressive stress, which results in the concentration of horizontal compressive stress in THR. After ground fracturing, the first breaking span of THR decreased, and different fracturing positions have a great impact on the THR fracture form. When the fracturing position is close to the center of the first breaking span, there is no large cantilever breaking form in the THR, the THR breaks on both sides of the top and sinks along the hydraulic fracture in the middle, and the collapse degree is relatively uniform. Then, the fracturing test was carried out in the 63up06 working face, the results showed that during the first 400 m of the 63up06 working face mining after fracturing, 702 microseismic events occurred in total, including 12 high-energy vibration events which include 4 mine earthquakes of magnitude 2.0 and 8 mine earthquakes of magnitude 1.0-2.0. Compared with the adjacent working face, the quantity of high-energy mine earthquake events in the 63up06 working face has been significantly controlled. [ABSTRACT FROM AUTHOR]

Wellbore strengthening by fracture plugging is an effective method for controlling fluid leakage in a fractured formation. However, few experiments have documented the effectiveness of fracture plugging on formation leakage. In this study, fracture plugging of fractured carbonate formation was conducted using a novel plugging dynamic core device. The samples were processed into standard cores before creating fractures. Fracture plugging was assessed using the fracture pressure bearing capacity, whose higher values indicate better plugging effectiveness. A generalized linear model (GLM) has been proposed to correlate the effects of confining pressure, fracture porosity, and plugging agent content (PAC) on the fracture pressure bearing capacity. According to this model, the fracture porosity has a greater effect on the fracture pressure than the confining pressure and plugging content. The model also revealed that as the fracture porosity increased by 10%, the fracture pressure bearing capacity decreased by 10.3%, while an increase in the confining pressure by the same magnitude resulted in a 5.3% increase in the fracture pressure. The experimental results were successfully verified in the field by applying a 30% plugging agent in two wells. An improvement in the fracture pressure bearing capacity in two vulnerable sections of the wells was observed. [ABSTRACT FROM AUTHOR]

The North China Plain (NCP) has been subjected to groundwater overexploitation over the past decades as a result of rapid socioeconomic development and irrigation water demand with relatively limited renewable water resources. Operation of the middle route of the South‐to‐North Water Diversion Project (SNWD‐M) since December 2014 has provided an opportunity for groundwater sustainability in the NCP by increasing water supply and reducing groundwater abstraction. Water use changes have largely been driven by socioeconomic changes. However, impacts of water diversion, water use change, as well as climate variability in the future on groundwater storage (GWS) in the NCP have not been investigated. This study aims to simulate and project GWS in the NCP during 2005–2050 by incorporating effects of water diversion, water use, and climate variability. The high‐resolution Community Water Model with 30 arcsec spatial resolution was set up to assess interactions between water demand and availability by simulating surface water and groundwater abstraction dynamically. Results show that water diversion and reductions in water use may increase GWS over the NCP in 2050 by 144 mm (19 km3) and 573 mm (75 km3), respectively. Evaluation of GWS among different scenarios shows that combinations of factors, including water use reductions, water diversion, and precipitation variability can contribute up to 73%, 37%, and 32% to GWS stability, respectively. This study highlights the contributions of different management strategies toward sustainable GWS and the importance of water conservation along with diversions. Plain Language Summary: Human intervention (including water use reductions and water diversions) can stabilize groundwater storage in the North China Plain, which is among the most stressed aquifers globally and of great importance to food security in China. We found that water conservation (e.g., water use reductions) plays a more prominent role in groundwater stabilization than water diversions and climate variability. This has important implications for groundwater sustainability of heavily stressed aquifers globally. Regions considering large water diversion programs might reconsider the value of water conservation to address water‐resource issues, which is less costly and more environmentally benign. Key Points: The high‐resolution community water model coupled with a water diversion module was set up across the North China PlainGroundwater storage was simulated and projected until 2050 by incorporating effects of water use, water diversion, and climate variabilityWater use reductions, water diversion, and precipitation variability can contribute up to 73%, 37%, and 32% to groundwater storage stability [ABSTRACT FROM AUTHOR]

Cyanine dyes are exceptionally useful probes for a range of fluorescence‐based applications, but their photon output can be limited by trans‐to‐cis photoisomerization. We recently demonstrated that appending a ring system to the pentamethine cyanine ring system improves the quantum yield and extends the fluorescence lifetime. Here, we report an optimized synthesis of persulfonated variants that enable efficient labeling of nucleic acids and proteins. We demonstrate that a bifunctional sulfonated tertiary amide significantly improves the optical properties of the resulting bioconjugates. These new conformationally restricted cyanines are compared to the parent cyanine derivatives in a range of contexts. These include their use in the plasmonic hotspot of a DNA‐nanoantenna, in single‐molecule Förster‐resonance energy transfer (FRET) applications, far‐red fluorescence‐lifetime imaging microscopy (FLIM), and single‐molecule localization microscopy (SMLM). These efforts define contexts in which eliminating cyanine isomerization provides meaningful benefits to imaging performance. [ABSTRACT FROM AUTHOR]

To economically develop shale gas reservoirs, hydraulic fracturing treatments must be applied to artificially introduce pathways for gas to flow out. After hydraulic fracturing, both the induced hydraulic fractures and activated natural fractures provide high permeable channels for gas transport. However, the long-term production performance of shale gas reservoirs is determined by the physical properties of matrix instead of the fractures. In this work, a coupled hydro-mechanical model is developed to investigate gas flow in heterogeneous shale matrix at the microscale. This model considers the mechanical interaction and gas mass transfer between organic matter (OM) and inorganic matter (iOM) during gas depletion. The interesting results show that due to matrix heterogeneity, i.e. co-existence of OM and iOM, the gas flow and mechanical deformation behaviors in shale exhibit regional differences. Specifically, during reservoir depletion, pore pressure, Knudsen number and volumetric strain in iOM are smaller than that in OM while the intrinsic and apparent permeability of OM are smaller than that of iOM. Thus, matrix heterogeneity should be taken into account when characterizing shale gas flow. In addition, sensitivity analysis is conducted to study the influence of fractal parameters on shale apparent permeability evolution. These fractal parameters include nanopore radius fractal dimension, tortuosity fractal dimension and maximum nanopore radius. The analysis indicates that the variation of fractal parameters in iOM results in the change of apparent permeability of both OM and iOM, while the variation of fractal parameters in OM only leads to the change of apparent permeability of OM. The modeling results offer new insights into gas flow behaviors in shale matrix. [ABSTRACT FROM AUTHOR]

In order to commercially develop shale gas reservoirs, it is necessary to understand the gas transport mechanisms in shale matrix and how matrix permeability evolves during reservoir depletion. In this work, improved apparent permeability models to describe gas transport through microstructures (i.e. micropores and microfractures) in organic matter (OM) and inorganic matter (iOM) of shale matrix are proposed. The models are able to consider the combined effects of poromechanics, non-Darcy flow, gas sorption and fractal dimension of microstructures on gas flow behavior. The obtained results indicate that microfracture aperture declines by a larger margin than micropore diameter when reservoir depletes. A greater microstructure size fractal dimension and maximum microstructure size lead to a larger apparent permeability, while a greater tortuosity fractal dimension leads to a smaller apparent permeability. In shale matrix, the apparent permeability of inorganic microstructures is much larger than that of organic microstructures. In OM or iOM, when micropores and microfractures have the same cross-section area, the apparent permeability of micropores is larger than that of microfractures. Furthermore, for microstructures in OM, the contribution of different flow regimes to total gas flow varies with pore pressure and microstructure size. For microstructures in iOM, the contribution of slip flow dominates the gas transport. The obtained results provide new insights for understanding gas transport behavior in shale reservoirs from a microscopic perspective. [ABSTRACT FROM AUTHOR]