Investigating water ice content at different locations on the Moon is crucial for crewed space missions and serves as a foundation for establishing lunar bases, which necessitates lunar soil sampling to gather information. Aiming to minimize the water ice loss caused by heat generation during drilling, this paper proposes a water ice highconservation sampling system based on frozen CO2 spray cooling. The thermodynamic and hydrodynamic models of the frozen CO2 generation subsystem and heat exchange subsystem are established. The impact of design parameters, flow and thermal conditions, and operation modes on water content has been analyzed. The spray cooling method indirectly affects the lunar soil temperature by reducing the drill bit temperature to increase the water conservation ratio (WCR) during drilling. The method combines frozen CO2 sublimation heat flow and jet cooling flow. Jet cooling is closely associated with the temperature difference between the fluid and the drill bit, as well as the flow velocity. Meanwhile, sublimation heat flow depends on the temperature difference between the drill bit and the saturation temperature of frozen CO2, along with the content of frozen CO2. Jet cooling is predominant at lower mass flow rates, while sublimation cooling prevails at higher rates. In addition, the time the lunar soil is at low-sublimation temperature is an important factor in WCR. Thus, to increase WCR, one can enhance flow velocity by reducing the nozzle diameter, raise sublimation heat flow by increasing mass flow and lowering the initial temperature, and maintain lunar soil at low-sublimation temperatures by increasing cooling time, duty ratio and decreasing the cooling period. Among others, increasing the cooling time has the most significant effect. The increasing slopes of WCR with cooling durations are about 20 %/100 s (at 0.4 g/s, liquid CO2) and 10 %/100 s (at 0.1 g/s, liquid CO2). However, the cooling time should not exceed the drilling time. This study provides an effective water ice conservation system that is useful for other planetary sampling missions.

A novel approach to enhance wellbore stability was put forth, based on the wellbore rock properties and instability mechanism of the hydrate reservoir, given the issue of wellbore instability when using water-based drilling fluids (WBDFs) in drilling operations, in weakly cemented muddy fine silt reservoirs of natural gas hydrates in the South China Sea. Three main strategies were used to increase the stability of reservoirs: enhancing the underwater connection between sandstone particles and clay minerals, preventing clay hydration from spreading and expanding, and strengthening the stability of hydration skeleton structure. An appropriate drilling fluid system was built with soil phase containing wellbore stabilizer. Sulfonic acid groups and electrostatic interaction were introduced based on the characteristics of underwater adhesion of mussels. Through the process of free radical polymerization, a zwitterionic polymer containing catechol groups named DAAT was prepared for application in natural gas hydrate reservoir drilling. DAAT is composed of tannic acid (TA), dimethyl diallyl chloride ammonium chloride (DMDAAC), 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and acrylamide (AM). Experimental results from mechanical property testing reveal an adhesion force of up to 4206 nN between SiO2 and 5 wt % DAAT, demonstrating its ability to bind quartz sand particles effectively. The compressive strength and cohesion of the cores treated with DAAT increased by 58.33 wt % and 53.26 wt %, respectively, at -10 degrees C, compared with pure ice particle cores. This demonstrates DAAT can significantly enhance the compressive strength and cohesion of the core. Furthermore, the adhesion force between DAAT and hydrate particles reaches up to 344.4 mN/m, significantly improving the structural stability between hydrate particles. It demonstrates excellent adhesive properties to hydrate particles. In addition to adsorbing clay minerals, rocks, and hydrate particles, DAAT also forms hydrogen bonds with argillaceous fine silt particles with its low temperature cohesiveness characteristic. As a result, it improves the cohesion between core particles, and enhances the adhesion between hydrates and rocks, thereby enhancing the stability of hydrate reservoirs. In summary, DAAT is characterized by a simple preparation process, cost-effectiveness, and environmental friendliness. It is an innovative and practical material for enhancing wellbore stability in WBDFs for natural gas hydrate exploration in the South China Sea.

With increasing water depth, marine drilling conductors exhibit higher slenderness ratios, significantly reducing their resistance to environmental loads in Arctic waters. These conductors, when subjected to combined wind, current, and ice loads, may experience substantial horizontal displacements and bending moments, potentially compromising offshore operational safety and wellhead stability. Additionally, soil disturbance near the mudline diminishes the conductor's bearing capacity, potentially rendering it inadequate for wellhead support and increasing operational risks. This study introduces a static analysis model based on plastic hinge theory to evaluate conductor survivability. The conductor analysis divides the structure into three segments: above waterline, submerged, and embedded below mudline. An idealized elastic-plastic p-y curve model characterizes soil behavior beneath the mudline, while the finite difference method (FDM) analyzes the conductor's mechanical response under complex pile-head boundary conditions. Numerical simulations using ABAQUS validate the plastic hinge approach against conventional methods, confirming its accuracy in predicting structural performance. These results provide valuable insights for optimizing installation depths and bearing capacity designs of marine drilling conductors in ice-prone regions.

Compared with the water-base drilling fluid, oil-based drilling fluid has always been one of the important technical guarantees in high temperature deep well, high-inclination directional well and all kinds of complex seismic exploration. With 5#white oil selected and taken as continuous phase, emulsifying agent, organic soil, tackifier, fluid loss agent, lime, other treatment agents and dosages are optimized and the optimal formula of oil-base drilling fluid is determined. This new type environmentally-friendly oil-base drilling fluid possesses good rheological properties, suspension capability, high temperature stability, stronger anti-pollution ability and common emulsion-breaking voltage of more than 2000 V. During the field application, this fluid possesses regular borehole diameter, good lubricity, stable borehole, simple preparation process, easy site maintenance and good reservoir protection features. Furthermore, it can solve complex formation, water expansion of clay shale, poor lubrication & drag reduction effect, poor reservoir protection effect and other technically-difficult problems.

The use of abrasive waterjets (AWJs) for rock drilling offers advantages in urbanized areas, locations that are vulnerable to damage, and piling operations. However, the overall operational cost of AWJ systems remains high compared to that of conventional drilling methods, which constrains the long-term industrial application of AWJs. For instance, the abrasive costs account for over 60% of the total process cost, but the recycling of abrasives remaining after drilling could significantly reduce machining costs. In this study, the post-impact characteristics of abrasives were explored, aiming to enhance their recyclability. The physical properties and particle distribution of used abrasives vary depending on the jet energy, ultimately affecting their recyclability and recycling rate. The particle properties of used abrasives (particle size distribution, particle shape, and mean particle size) were compared under different waterjet energy variables (standoff distance (SOD) and water pressure) and test conditions (dry and underwater). Furthermore, the collision stages of the abrasive particles within a waterjet system were classified and analyzed. The results revealed that abrasive fragmentation predominantly occurred due to internal collisions within the mixing chamber. In addition, an attempt was made to optimize the waterjet parameters for an economical and efficient operation. The findings of this study could contribute to enhancing the cost-effectiveness of AWJ systems for rock drilling applications. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

The Moon, as the celestial body closest to Earth, is a prime target for human deep space exploration. China's Lunar Exploration Project IV aims to explore and sample the lunar polar region's water-containing regolith. To effectively simulate the characteristics of this watery lunar regolith, this paper proposes a deep low-temperature preparation system. The feasibility of the system design is validated through theoretical and methodological analysis, including cold source selection, heat dissipation analysis, and energy consumption calculations. Subsequently, a deep low-temperature aqueous lunar regolith preparation system was developed, and tests were conducted to verify its performance. The results confirm that the system can generate water-containing lunar regolith at -238 degrees C and maintain its temperature during drilling. This capability is significant for subsequent research on the drilling performance of deep low-temperature watery lunar regolith.

This paper focuses on the use of rotary-percussive drilling for hard rocks. In order to improve efficiency and reduce costs, it is essential to understand how operational parameters, bit wear, and drilling performance are related. A model is presented therein that combines multibody dynamics and discrete element method (DEM) to investigate the influences of operational parameters and bit wear on the rate of penetration and wear characteristics. The model accurately captures the motion of the bit and recreates rock using the cutting sieving result. Field experimental results validate the rod dynamic behavior, rock recreating model, and coupling model in the simulation. The findings indicate that hammer pressure significantly influences the rate of penetration and wear depth of the bit, and there is an optimal range for economical hammer pressure. The wear coefficient has a major effect on the rate of penetration, when wear coefficient is between 1/3 and 2/3. Increasing the wear coefficient can reduce drill bit button pressure and wear depth at the same drill distance. Gauge button loss increases the rate of penetration due to higher pressure on the remaining buttons, which also accelerates destruction of the bit. Furthermore, a more evenly distributed button on the bit enhances the rate of penetration (ROP) when the same number of buttons is lost. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Due to the unobservable nature of underground construction and the destructive nature of horizontal directional drilling rigs with high power, this type of construction has become one of the most important causes of failure of long-distance natural gas pipelines. In recent years, horizontal directional drilling construction has caused pipeline accidents frequently. Once the accident occurs, the normal operation of natural gas pipelines cannot be ensured. Therefore, studying the damage mechanism of buried natural gas pipelines under horizontal directional drilling loads is important for the safe operation of pipelines. This paper combines the construction characteristics of horizontal directional drilling and the actual situation of natural gas pipelines to explore the relationship between horizontal directional drilling and pipelines. The force situation of pipelines after contacting directional drilling bits is analyzed by the drill bit-soil-pipe finite element model created in the ABAQUS software. The Johnson-Cook ductile damage model was utilized to determine the pipe's damage condition. The sensitivity analysis results show that he order of the impact of key parameters on the dynamic response of the pipe is bit thrust > wall thickness > bit diameter > pipe diameter > bit speed > number of bit teeth > pipe operating pressure. Therefore, priority should be given to controlling the size of the drilling thrust and the speed of the drill bit to reduce the damage to pipelines by horizontal directional drilling construction. In addition, appropriately reducing the pipeline operating pressure can also reduce the risk of the pipeline being damaged by horizontal directional drilling construction.

The surface conductor is the first structural pipe in the development of deep-water oil and gas resources, bearing the top load and suspending various casing layers. Vibrational loads can cause soil structural damage and increase pore pressure, reducing the bearing capacity of the surface conductor and threatening the safety and stability of the subsea wellhead. Based on the vertical force analysis of the surface conductor and considering the impact of vibrational loads on soil strength, a model for the vertical bearing capacity of the surface conductor was established. Utilizing the dynamic Winkler model for pile foundation horizontal dynamic response, the surface conductor was simplified as a bending beam subjected to harmonic vibration, and a control equation for lateral deformation of the surface conductor was established. The effects of vibration load amplitude and frequency on the vertical bearing capacity of surface conductors were analyzed through simulation experiments, resulting in an equivalent bearing capacity coefficient for surface conductors ranging from 0.88 to 0.97. Combining the engineering data from a deep-water block in the South China Sea, the reliability of the theoretical calculation model was validated. The analysis indicates that the maximum bending moment of the surface conductor is approximately 6m below the mudline; low-frequency(0.05Hz-0.2Hz) vibrational loads can reduce the ultimate bearing capacity of the surface conductor by 3%-11%, with the effect gradually diminishing over time. This research provides a theoretical basis for the design of surface conductor in deep-water oil and gas wells.

Relevance. Engineering-geological surveys are an integral part of mining operations for various purposes. The quality of soil core sampling has an important impact on the results of engineering geological surveys. At the same time, obtaining a frozen rock core is complicated by an increase in the bottomhole zone temperature, which arises as a result of drilling. As the temperature rises, the physical and mechanical properties of frozen soils change, which leads to a transformation of the mechanism of their destruction and an increase in the likelihood of drilling emergencies. A core obtained under conditions of rising temperature does not allow for a reliably accurate assessment of the properties and structure of soils in their natural conditions. Therefore, there is a need to develop technological and technical means that help maintain the temperature regime of a rock mass under mechanical effect on it. The analysis of the conditions of core drilling in frozen rocks showed that, along with technological reasons, the design of the rock-cutting tool affects the increase in bottom-hole temperature. The article reveals the dependence of the temperature change at well bottom when drilling on the design features of the core rock-cutting tool. Aim. To study the impact of the design features of a drilling core tool on the nature of destruction of frozen soils, represented by loose sedimentary rocks as the most susceptible to changes in physical and mechanical properties with increasing temperature. The study was based on frozen soils that make up the of Yakutia, a large industrial region that requires frequent geotechnical surveys for its development. Objects. Core drilling tool design, mechanism of frozen rocks destruction, conditions for core sampling in frozen soils. Methods. Analytical method, experimental method, production test method. Results. The authors have determined the main directions for the development of core tools for high-quality core sampling in frozen soils. They derived the dependence of the magnitude of the temperature increase at well bottom on the orientation and size of the cutters reinforcing the rock-cutting tool.