Search Results (7)

Natural gas hydrate is an important emerging strategic resource, but low permeability makes the horizontal well length a key factor limiting productivity. A prediction model for friction torque of deepwater riserless drilling strings was established, and the segmented friction coefficient of hydrate horizontal wells was inverted and applied to the Shenhu hydrate reservoir. The results show that the main limiting factor for the extreme extension length of natural gas hydrate horizontal wells is the mechanical extreme extension length. The main affecting factor of the mechanical extreme extension length is the running limit of the screen pipe. The friction coefficient is the most significant factor affecting the mechanical extreme extension of horizontal wells, with the friction coefficient inside the casing in the high-build-rate section being the largest. The research identifies the primary factors governing the limit extension during horizontal well construction. The findings provide theoretical guidance for reservoir selection, well site determination, and wellbore configuration optimization in hydrate development. Ultimately, this contributes to maximizing single-well productivity and advancing the commercialization of hydrate resources. Full article

With the steady progress of the global energy transition and the pursuit of “dual carbon” goals, Offshore Carbon Sequestration (OCS) has emerged as a pivotal strategic pathway within Carbon Capture and Storage (CCS) initiatives aimed at mitigating climate warming. Nevertheless, the drilling of OCS injection wells faces severe challenges, including narrow geological pressure windows, high risks of shallow geohazards, stringent environmental protection standards, and prohibitive construction costs. Riserless Mud Recovery (RMR) technology, as a novel and eco-friendly deepwater drilling technique, provides innovative technical support for OCS by establishing a closed-loop seafloor circulation system that achieves dual-gradient pressure control and “near-zero discharge” of drilling fluids. This paper systematically reviews the development history and technical principles of RMR. By integrating the specific requirements of OCS injection well drilling—such as wellbore integrity, environmental protection, and shallow hazard mitigation—the study provides an in-depth analysis of the application potential of RMR in drilling CO₂ injection wells within shallow formations. Furthermore, it demonstrates the engineering feasibility of RMR across technical, environmental, and economic dimensions. Building on this analysis, the paper discusses current technical challenges regarding key equipment research and development, adaptability to complex operating conditions, enhancement of intelligent control systems, and the establishment of technical standards. It also outlines the prospects for the integrated development of RMR with emerging fields, including hydrate-based carbon sequestration, intelligent drilling and completion, and carbon sequestration in far-reaching deep-sea areas. The research indicates that RMR technology can effectively resolve the dual constraints of cost control and environmental protection in OCS drilling. With breakthroughs in critical hardware, such as high-displacement subsea lift pumps, and the deepening of cross-disciplinary integration, RMR is poised to become an essential technical pillar in the field of offshore carbon sequestration. Full article

Deepwater drilling operations face critical challenges including narrow pore-fracture pressure windows, wellbore instability, and environmental concerns from drilling discharge. This paper presents a comprehensive systematic review of Riserless Mud Recovery (RMR) technology, tracing its evolution from its conceptual origins to its current applications, critically analyzing its technical limitations, and identifying future research directions. A systematic literature review was conducted covering peer-reviewed journals, SPE/IADC conference proceedings, industry technical reports, and independent academic studies from 1990 to 2025. Databases searched included Web of Science, Scopus, OnePetro, and Google Scholar, supplemented by Derwent Innovation Index for patents. After screening over 100 publications, approximately 60 references were selected following a two-step process excluding vendor-only promotional materials. Key findings reveal the following: (1) RMR technology has evolved through three distinct hardware generations—flexible hose systems, steel-pipe return lines with tandem pumps enabling deepwater breakthrough to 1419 m, and hybrid riser configurations for conceptual designs beyond 3000 m; (2) documented field benefits include 70% drilling fluid reduction, 9 days’ time savings per well, and successful mitigation of shallow geohazards across more than 1000 global well applications; (3) integration with casing-while-drilling and managed pressure cementing has enabled record-breaking performance of 1710 m in a single run; (4) independent academic validation confirms fatigue mechanisms affecting mud return lines; (5) systematic failure mode analysis identifies critical reliability issues in suction hoses, seals, and control systems; (6) quantitative economic analysis shows RMR cost-effectiveness depends on water depth, geological conditions, and environmental regulations. RMR technology has matured into a reliable drilling solution, yet its continued evolution requires addressing hardware limitations, developing dedicated well-control protocols, expanding to ultra-deepwater and emerging applications, and integrating digitalization for real-time optimization. Full article

Deepwater natural gas hydrate (NGH) exploration faces environmental and economic challenges due to the conventional seabed discharge of drilling mud. To address this, we developed an improved riserless mud recovery (RMR) system using hybrid risers to create a stable, decoupled circulation pathway. This innovative design fulfils three key operational needs: (1) closed-loop drilling fluid circulation with dual-gradient control, (2) completion fluid and test production returns, and (3) mechanical decoupling between the floating platform and subsea riser string. Numerical analysis shows that the system maintains operational stability under wave loading while effectively isolating seabed equipment from platform motion. Simulation results indicate that optimal performance requires a top tension ratio exceeding 1.5 and a submersion depth of 150–250 m, achieving a 70–80% reduction in drilling fluid consumption with full recovery capabilities. The hybrid riser-based RMR system provides a practical solution for sustainable NGH development, offering superior water depth adaptability for both drilling and completion operations in deepwater environments. Full article

Compared with traditional deepwater drilling, riserless mud recovery (RMR) drilling technology has the advantages of improving drilling efficiency, reducing risks, and minimizing environmental effects. Therefore, RMR drilling technology has been widely applied in recent years. This study primarily investigates the relationships among reverse torque, vibration, and input parameters of mud pumps in riserless mud recovery drilling. Firstly, the operating principle and the structure of the mud pump module are analyzed, and an analytical model for the reverse torque and the vibration of the mud pump is established. Secondly, relevant data are derived from theoretical calculations and experiments, and the relationships among the reverse torque, vibration, and input parameters of the mud pump are analyzed using ANSYS (Version 2020 R1) software. Furthermore, the SVR (support vector regression) algorithm is employed to predict and analyze the amplitude of the mud pump’s vibration. Finally, the conclusions are drawn based on the findings of the relationships among the reverse torque, vibration, and input parameters of the mud pump. The findings show that the reverse torque of the mud pump increases approximately linearly with an increase in rotational speed, and the vibration of the mud pump increases and then decreases with an increase in rotational speed. The predicted values obtained through the prediction algorithm closely match the actual values. The findings provide a valuable reference for the application of RMR technology. Full article

Riserless mud-recovery (RMR) drilling technology was widely applied in recent years. Compared with traditional deepwater drilling, RMR drilling can improve drilling efficiency, reduce risks, and minimize environmental effects. This paper focuses primarily on the stability of a mud-return circulation system in an RMR system. First, various factors that affect the stability of a mud-return circulation system are analyzed. An analytical model for the skid-and-mud-return line is established. Second, relevant data are derived from theoretical calculations and experiments. ABAQUS software is used to analyze the effects of each factor on the stability of the mud-return circulation system. The influencing patterns of each factor on the stability of the mud-return circulation system are summarized. Furthermore, the stability of the system under different operating conditions is analyzed based on the coupling of multiple factors. The support vector regression with derivative significance weight analysis (SVR-DWSA) algorithm is employed to perform a weight analysis of the effect on the system’s stability. Finally, based on the research findings on the stability of the mud-return circulation system, relevant conclusions and recommendations are drawn. The results of this study provide valuable references for the application of RMR technology. Full article

Riserless Mud Recovery (RMR) technology, as an emerging and efficient drilling method, is advantageous to reduce the shallow flow hazards and the number of casings. The wave current effect is one of the reasons limiting the application of RMR technology in deep and ultra-deep water, and fewer quantitative and qualitative analyses of the effect of the current are made on the stability of conductors. This paper investigates the influence of the overturning moment generated by the continuous subsea internal wave flow and the soil resistance to the conductor. The numerical simulation software ABAQUS is used to study the effects of sea state recurrence period, seabed soil properties, conductor material, driving depth in the mud, and conductor wellhead height on the stability of the conductor, and the influence weights of the factors affecting the stability of the conductor are analyzed using the weight analysis algorithm of extreme learning machine-mean impact value (ELM-MIV). Finally, the qualitative and quantitative analyses affecting the stability of the conductor are carried out, which provide reference values for the application of the RMR technology. Full article