Hao Geng

With the advancement of oil and gas exploration into ultra-deep drilling and increasingly complex downhole environments, the demand for higher downhole data transmission rates has steadily increased. Continuous wave mud pulse telemetry has emerged as a promising technology with significant potential for widespread application. While considerable research has focused on techniques for downhole signal generation and noise reduction at the wellhead in continuous wave mud pulse telemetry systems, the attenuation behavior of continuous wave transmission within the wellbore remains insufficiently explored. This study integrates transient flow theory to account for unsteady friction induced by continuous wave transmission and enhances the one-dimensional mathematical model for the generation and propagation of continuous waves. The attenuation process of continuous wave transmission, influenced by coupled drilling tools within the wellbore, is analyzed in detail, along with the fluctuation patterns of steady and unsteady friction. Furthermore, the study examines the effects of various parameters—such as frequency, displacement, mud density, viscosity, and wave velocity—on attenuation characteristics. The findings reveal that continuous wave signals in the wellbore undergo exponential attenuation, with the amplitude of the bottom hole assembly (BHA) significantly diminished. This attenuation is primarily attributed to both steady and unsteady friction, which exhibit fluctuating behaviors. High-frequency continuous waves are strongly affected by unsteady friction, resulting in rapid attenuation, whereas steady friction remains constant across varying frequencies. Notably, unsteady friction intensifies with increasing frequency. These insights establish a theoretical foundation for understanding the attenuation of continuous wave transmission under varying parameters, thereby contributing to the improvement of signal transmission efficiency.

In Coiled Tubing (CT) acoustic telemetry, the reliability of surface signal reception is severely challenged by the “contact dead zone” of traditional probes and complex nonstationary environmental noise. To address these issues, this paper proposes a hardware-software integrated solution for high-fidelity signal extraction. In terms of hardware, a novel pickup probe based on the micro-lever principle is developed. By utilizing a pivoted lever structure with an optimized arm ratio of 2.6 to 1 and a full pressure-balanced mechanism, the design physically overcomes the contact dead zone inherent in traditional pressure-compensating probes and effectively isolates low frequency common-mode interference through a lateral floating architecture. In terms of software, a joint denoising model combining Complete Ensemble Empirical Mode Decomposition with Adaptive Noise and wavelet thresholding is proposed. A cross-correlation coefficient criterion is introduced to adaptively screen intrinsic mode functions and eliminate residual fluid turbulence noise. Field experiments on a 1500 ft full-scale circulation loop demonstrate that the proposed probe improves the detection sensitivity of the radial breathing mode by approximately 20.6 dB compared to the baseline, while effectively eliminating stick-slip friction noise during dynamic tripping. Furthermore, the joint algorithm increases the Signal to noise Ratio by an additional 16.9 dB under typical pumping conditions of 0.5 bpm, with a normalized cross-correlation exceeding 0.96. These results verify that the proposed method effectively solves the bottleneck of weak signal detection in deep wells, providing robust technical support for CT telemetry operations.

Rotary Steerable System (RSS) enhances directional drilling efficiency by over 300% via dynamic bit adjustment during string rotation. This study aims to systematically address these bottlenecks, quantify technical boundaries, and propose actionable breakthrough paths for China’s RSS technology in shale gas development. To address China’s shale gas RSS bottlenecks, this study proposes a “Material-Algorithm-System” tri-level strategy centered on an innovative “Tri-loop System.” Key innovations include (1) silicon nitride–tungsten carbide composite coatings to enhance thermal resilience, tested to withstand 220 °C, reducing thermal failure risk by 40% compared to conventional materials; (2) downhole reinforcement learning optimization; (3) a “Tri-loop System” integrating downhole intelligent control, wellbore-surface bidirectional communication, and cloud monitoring, shortening downhole command response latency from over 5 s to less than 1 s. In practical shale gas development scenarios—such as the Sichuan Basin’s deep coalbed methane wells and Shengli Oilfield’s tight reservoirs—this tri-level strategy has proven effective: the high-frequency electromagnetic wave radar increased thin coal seam drilling encounter rate by 23%, while the piezoelectric ceramic micro-actuators reduced tool failure rate by 35% in 175–200 °C environments. This approach targets raising China’s shale gas RSS application rate to 60%, supporting sustainable oil and gas exploration.

In the development of tight gas reservoirs in Chuanzhong BJC Gas Field of the Sichuan Basin, running horizontal casing in ultra-long open-hole section faces challenges. These include large friction prediction errors and high casing buckling risks. These challenges significantly impede both the efficiency and safety of field development. Traditional static segmented friction models fail to accurately predict friction coefficients. The reason is that they cannot track dynamic changes in wellbore inclination, azimuth, and dogleg severity in real time. To address this bottleneck, this study develops a technical system termed AI-based dynamic friction inversion-segmented process optimization. Clustering algorithms are used to divide regions. These regions have low, medium, and high friction characteristics. The simulated annealing algorithm dynamically corrects friction coefficients. Meanwhile, the segmented processes of float collars and drilling fluid density are optimized. Verification was conducted on well J108-2H, which features an open-hole section of 4060.9 m and a horizontal-to-vertical ratio (HD/TVD) of 1.88. Results show that this system significantly reduces the mean absolute percentage error of friction coefficient prediction. It also greatly improves the accuracy of casing running feasibility assessment. As a result, the casing in well J108-2H was run smoothly and efficiently. The research results provide an innovative solution for the safe and efficient development of ultra-long open-hole sections in unconventional gas reservoirs.

As high-end oil and gas equipment, the high-temperature high-pressure (HTHP) adaptability and intelligence level of Rotary Steerable Systems (RSS) directly determine the development efficiency of deep unconventional resources. This paper reviews the technological breakthroughs and industrial chain synergy pathways of domestic RSS in China, with core conclusions as follows: (1) domestic technologies represented by the CG STEER system have achieved stable operation at 150 °C, high build rates of 15.3°/30 m, and reservoir penetration rates of 98.7%, with key indicators reaching international advanced levels; (2) collaborative innovations in material system reconstruction, hybrid steering mechanisms, and vibration suppression technology have reduced single-well drilling cycles by 50%; (3) industrial chain synergy effects are significant: a 95% localization rate reduced the cost per bottom hole assembly (BHA) run to CNY 2 million, and the “Penta-Helix” innovation model increased patent sharing rates to >60%; (4) breakthroughs in 175 °C high-temperature chips and downhole intelligent decision-making algorithms are urgently needed. This study provides technological paradigms and industrial upgrading pathways for the autonomous development of drilling equipment for extreme conditions. Recognizing the need for comprehensive improvement, the revised manuscript will strengthen three key aspects: (1) supplementing systematic comparisons between domestic technologies and international benchmarks in terms of HTHP adaptability and intelligent control; (2) elaborating technical details of hybrid steering mechanisms and vibration suppression technologies to clarify their innovation in industrial processes; (3) adding case studies of autonomous decision-making systems in ultra-deep wells to verify the practical effectiveness of the proposed methods. These revisions aim to address the current limitations and enhance the scientific rigor of the study.

To address the critical challenges of severe fragmentation in cuttings, persistent cuttings bed accumulation, and abrupt friction torque increases during horizontal well drilling of Jurassic continental shale oil formations in J Block, Sichuan Basin—rooted in the unique high clay content that induces colloidal stability of fine cuttings and resistance to conventional cleaning—this study innovatively proposes a coupled prevention–removal hole-cleaning technology. The core methodology integrates three synergistic components: (1) orthogonal numerical simulations to optimize drilling parameters, reducing the cuttings input rate by 43.48% through “hydraulic carrying + mechanical agitation” synergy; (2) a modified Moore model with horizontal section correction factors to quantify slip velocity of cuttings, lowering the prediction error from ±20% to ±5%; and (3) a helical groove cutting removal sub with 60 m optimal spacing, enhancing local turbulence intensity by 42% to disrupt residual cuttings bed. Field validation in Well J110-8-1H demonstrated remarkable improvements: a 50% reduction in sliding friction, a 25% decrease in rotational torque, and 40% shortening of the drilling cycle. This integrated technology fills the gap in addressing the “fragmentation–colloidal stability” dilemma in shale with high clay contents, providing a quantifiable solution for safe and efficient drilling in similar continental formations.