Earth and Space Sciences
Casing while drilling (CwD) technology is designed to reduce drilling time and expenses by improving the wellbore stability, fracture gradient, and formation damage while reducing the exposure time. However, for the purpose well control, the wellbore geometry and volumes differ from those obtained via a conventional drilling technique, thereby requiring a different approach. This study discusses well control principles for CwD operations. It presents a simplified method for evaluating the maximum kick tolerance and allowable well shut-in time for both conventional and CwD techniques using a mathematical model. Preliminary results revealed that the use of CwD leads to an annulus pressure loss three times higher than that observed in the conventional drilling. In addition, the kick tolerance is reduced by 50% and the maximum allowable well shut-in time is reduced by 65%, making an early kick detection system necessary.
Petroleum contamination in terrestrial environments caused by industrial activities is a significant problem that has received considerable attention. Carbon and nitrogen isotopic compositions (δ13C and δ15N) effectively describe the behavior of plants and soils under petroleum contamination stress. To better understand plant and soil responses to petroleum-contaminated soil, δ13C and δ15N values of the plants (Trifolium repens, Leguminosae with C3 photosynthesis pathway, and Agropyron cristatum with C4 photosynthesis pathway) and the soil samples under one-month exposure to different extents of petroleum contamination were measured. The results showed that petroleum contamination in the soil induced the soil δ15N values to increase and δ13C values to decrease; from 1.9‰ to 3.2‰ and from −23.6‰ to −26.8‰, respectively. However, the δ13C values of Agropyron cristatum decreased from −29.8‰ to −31.6‰, and the δ13C values of Trifolium repens remained relatively stable from −12.6‰ to −13.1‰, indicating that they have different coping strategies under petroleum-contaminated soil conditions. Moreover, the δ15N values of Trifolium repens decreased from 5.6‰ to 0.8‰ near the air δ15N values under petroleum-contaminated soil, which implies that their nitrogen fixation system works to reduce soil petroleum stress. The δ13C and δ15N values of Agropyron cristatum and Trifolium repens reflect changes in the metabolic system when they confront stressful environments. Therefore, stable isotopic compositions are useful proxies for monitoring petroleum-contaminated soil and evaluating the response of plants to petroleum contamination stress.
A more than 3 m-long deployable boom is an essential component of the Mars Orbiter Magnetometer (MOMAG) onboard the orbiter of Tianwen-1. The boom was developed to place fluxgate magnetometer (FGM) sensors away from the satellite to reduce the influence of the satellite magnetic field. It was designed as an articulated spring-driven deployable mechanism for single-shot deployment. Functionality, reliability and system constraints are fully considered in the boom design. Mechanical analyses and proof tests show that the boom has sufficient safety margin to withstand environmental conditions, even in the worst cases. After a long voyage from Earth to Mars, the boom was deployed successfully on May 25, 2021. A full deployment was performed in about 4.6 s, sending the two sensors to distances of 3.19 m and 2.29 m respectively, away from the orbiter. After deployment, the field from the orbiter decreased from 1250 nT to less than 6 nT at the sensor mounted at the tip of the boom. The MOMAG boom provides valuable engineering experience for the development of deployable structures stowed for long periods in cold temperatures in space missions.
Barium (Ba) isotopes can be used as potential tracers for crustal material recycling in the mantle. Determination of the Ba isotope composition of the depleted mantle is essential for such applications. However, Ba isotope data for mantle-derived basalts are still rare. In this study, we reported high-precision Ba isotope data of 30 oceanic basalts including 25 mid-ocean ridge basalts (MORBs) from geochemically and geologically diverse mid-ocean ridge segments and five back-arc basin basalts. The δ138/134Ba values of these samples varied from −0.06‰ to +0.11‰, with no systematic cross-region variation. Together with published data, we constrained the average δ138/134Ba of global MORBs to +0.05‰±0.09‰ (2 standard deviation, n = 51). Based on depleted MORBs that have (La/Sm)N < 0.8, low 87Sr/86Sr (< 0.70263), and low Ba/Th < 71.3, we estimated the average δ138/134Ba of the depleted MORB mantle (DMM) as + 0.05‰ ± 0.05‰ (2SD, n = 16) that is significantly lower than the DMM (≈ 0.14‰) reported previously. If a new estimation of the DMM is applied, it is unreasonable to infer that the Ba isotope signatures of the “enriched-type” MORBs (E-MORBs) could be attributed to pervasive sediment recycling in the upper mantle. We, therefore, conclude that the Ba isotope compositions of the E-MORBs could be sourced from the incorporation of subducted altered oceanic crust and/or sediments depending on the Ba isotope composition and other geochemical information of the local mantle.
A heavy dust storm originating in Mongolia and Inner Mongolia traveled to Northeast China and met a midlatitude frontal system on May 3, 2017. The potential ice nuclei (IN) effects of mineral dust aerosols on the vertical structure of clouds, precipitation, and latent heat (LH) were studied using Global Precipitation Mission (GPM) satellite observations and Weather Research and Forecasting (WRF) model simulations. The WRF simulations correctly captured the main features of the system, and the surface rain rate distribution was positively correlated with data retrieved from the GPM Microwave Imager. Moreover, the correlation coefficient increased from 0.31 to 0.54 with increasing moving average window size. The WRF-simulated rainfall vertical profiles are generally comparable to the GPM Dual-Frequency Precipitation Radar (DPR) observations, particularly in low layers. The joint probability distribution functions of the rain rate at different altitudes from the WRF simulation and GPM observations show high positive correlation coefficients of ~0.80, indicating that the assumptions regarding the raindrop size distribution in the WRF model and DPR retrieval were consistent. Atmospheric circulation analysis and aerosol optical depth observations from the Himawari-8 satellite indicated that the dust storm entered only a narrow strip of the northwest edge of the frontal precipitation system. The WRF simulations showed that in carefully selected areas of heavy dust, dust can enhance the heterogeneous ice nucleation process and increase the cloud ice, snowfall, high-altitude precipitation rate, and LH rate in the upper layers. This effect is significant at temperatures of −15 °C to −38 °C and requires dust number concentrations exceeding 106 m−3. It is important to accurately classify the dusty region in this type of case study. In the selected vertical cross section, the WRF-simulated and DPR-retrieved LH have comparable vertical shapes and amplitudes. Both results reflect the structure of the tilted frontal surface, with positive LH above it and negative LH below it. The simulated area-averaged LH profiles show positive heating in the entire column, which is a convective-dominated region, and this feature is not significantly affected by dust. DPR-based LH profiles show stratiform-dominated or convective-dominated shapes, depending on the DPR retrieval product.
Sheared E × B flow has been frequently observed to excite instability in space plasma. In this study, two methods – the interpenetrating plasma and ring electrode methods – were developed in the Keda Space Plasma EXperiment (KSPEX) device to trigger sheared E × B flow. Both methods produce sheared E × B flow by generating a radial electric field. The results of the experiment indicated that plasma instabilities in the ion cyclotron range can be excited by these methods. Therefore, the methods reported here are important for research on the mechanism for generating sheared flow-driven plasma instabilities, which may enrich our understanding of geospace physics.
The evolution of the atmospheric oxygen content through Earth’s history is a key issue in paleoclimatic and paleoenvironmental research. There were at least two oxygenation events in the Precambrian that involved fundamental changes in both biotic innovation and the surface environment. However, a large dissolved organic carbon (DOC) pool maintained in deep oceans during the Neoproterozoic may have extended the time interval between the two oxygenation events. To test the DOC hypothesis, we conducted detailed micro-drilled analyses of carbonate carbon isotopes (δ13Ccarb) of a long Ediacaran drill core (the Wangji drill core), for which whole-rock δ13Ccarb and organic carbon isotope (δ13Corg) records were available. The micro-drilled δ13Ccarb values obtained in this study are consistent with whole-rock δ13Ccarb results, precluding the influence of severe authigenic carbonate incorporation. Importantly, the multiple negative δ13Ccarb excursions in the Wangji drill core were likely linked with upwelling events, during which DOC was supplied to the surface water and oxidized. Using box models, we estimate that ~3.6 × 1019 mol and ~2.0 × 1019 mol DOC were converted to bicarbonate during two negative δ13Ccarb excursions spanning millions of years. The estimations are approximately 1000 times the modern marine DOC reservoir. Our results support a relatively high oxidation capacity (elevated atmospheric pO2 and/or oceanic [
]) of the Earth’s surface during the early Ediacaran Period.
In the inner magnetosphere, the magnetosonic waves have been proposed to transit-time scatter the radiation belt electrons over a broad range of energy and pitch-angle. Recent observations have shown that magnetosonic waves can be generated in the off-equatorial plasmasphere, whose latitudinal coverage and propagation angle are significantly different from the traditional magnetosonic waves confined near the equator. Using our previously-developed test-particle code, we here investigate the possible transit-time scattering of radiation belt electrons by the off-equatorially generated magnetosonic waves. Our results indicate that the transit-time scattering is primarily related to the perturbation near the edge of the finite wave train. The extending of wave occurrence latitudes causes the shrinking of the equatorial pitch-angle range of the transit-time scattering. Compared to the near-equatorially confined magnetosonic waves, the off-equatorially generated magnetosonic waves produce ignorable pitch-angle perturbations but slightly stronger energy perturbations.
Previous studies have documented remarkable changes in the carbon cycle during the Early Triassic. To verify these trends and improve our understanding of carbon cycling during the Early-Middle Triassic, we investigate the new δ13Ccarb record for the Early-Middle Triassic in the Tianshengqiao section of South China. Our study shows that the δ13Ccarb values in the Tianshengqiao section have received minimal diagenetic alterations. The δ13Ccarb profile initially shows a negative excursion of 2.2‰ within the Member I of the Jialingjiang Formation, followed by a positive excursion of 3.8‰ in the lower part of the Member III of the Jialingjiang Formation. After that, δ13Ccarb displays a negative excursion of 2.5‰ in the Member III of the Jialingjiang Formation, followed by a positive excursion with a maximum of +5.0‰ at the base of the Member I of the Guanling Formation. Above the maximum value, the δ13Ccarb profile exhibits a third negative excursion and then recovers and stabilizes around +1‰ to +2‰ through the Member II of the Guanling Formation to the Yangliujing Formation. The observed trend of the δ13Ccarb profile in the Tianshengqiao section can be correlated with the global C-isotopic excursions derived from the coeval sections worldwide. The similarity of the Early-Middle Triassic δ13Ccarb profile to those from other sections worldwide is indicative of the near completeness of the stratigraphic interval of the Tianshengqiao section. Our results suggest that the δ13Ccarb profile in the Tianshengqiao section represents a global carbon cycle perturbation. The stratigraphic coincidence between the carbon cycle perturbation and the limited biotic recovery has been documented in the Tianshengqiao section, suggesting that the physical mechanism of the carbon cycle perturbation may have contributed to the prolonged biotic recovery.
