In the longstanding development of hydrate-bearing sediment (HBS) reservoirs, slow and permanent deformation of the formation will occur under the influence of stress, which endangers the safety of hydrate development projects. This paper takes hydrate-bearing sandy sediment (HBSS) as the research object and conducts triaxial compression creep tests at different saturation degrees (20%, 30%, and 40%). The results show that the hydrate-containing sandy sediments have strong creep characteristics, and accelerated creep phenomenon will occur under the long-term action of high stress. The longstanding destructive power of the specimen progressively raises with the increase in hydrate saturation, but the difference in the triaxial strength of the specimen progressively increases. This indicates that the damage to the hydrate structure during long-term loading is the main factor causing the strength decrease. Further, a new nonlinear creep constitutive model was developed by using the nonlinear Burgers model in series with the fractional-order viscoplastic body model, which can well describe the creep properties of HBSS at different saturation levels.

During drilling operations, drilling fluids undergo heat exchange with hydrate-bearing formations. The intrusion of drilling fluids affects hydrate stability, leading to variations in stress fields around a wellbore and complex scenarios such as borehole collapse, significantly hindering the efficient development of natural gas hydrate resources. This study establishes a thermo-hydro-mech model for hydrate-bearing inclined wells based on linear thermoelastic porous media theory and an appropriately high inhibitive drilling fluid temperature. This research reveals that drilling should follow directions of minimum horizontal stress or perpendicular to maximum horizontal stress during drilling operations to control wellbore stability. Hydrate decomposition due to factors like drilling fluid pressure and temperature can rapidly reduce the strength of low-saturation formations, significantly increasing the risk of wellbore instability. Therefore, selecting appropriate highly inhibitive and low-temperature drilling fluids during drilling operations helps control hydrate decomposition and reduce fluid intrusion, thereby mitigating risks associated with wellbore instability.

This paper presents an optimized economic evaluation model for intensive drilling in unconventional oil and gas development, based on the “well factory” concept. The model integrates cost components—including pre-drilling, drilling operations, drilling materials, and drilling fluid treatment—with synergy factors that capture the benefits of centralized operations. These synergy factors reflect cost savings arising from reduced land acquisition, optimized rig sharing, and enhanced reuse of drilling fluids. Furthermore, a decision timeliness component is incorporated into the objective function, ensuring that the model can dynamically balance cost minimization with rapid decision making—a critical requirement in fast-paced energy projects. The model is rigorously developed by building on conventional cost equations and is validated using field data from the Shengli Oilfield Yan 227 block. The results demonstrate significant reductions in pre-drilling and drilling operation costs under the “well factory” mode compared to conventional single-well approaches. Additionally, an optimal platform configuration is identified, highlighting the economic benefits of integrating centralized infrastructure and shared resources in large-scale drilling operations. This comprehensive framework provides a robust decision-support tool for enhancing economic efficiency and operational effectiveness in the development of unconventional resources.

Wellbore Flow Analysis of a Gas-Kick Well During Shut-In

The decomposition of hydrate during hydrate mining can reduce the strength of the formation and induce engineering geological disasters. Clarifying the decomposition characteristics of geological hydrate during hydrate mining is of great significance for preventing marine geological disasters. This study comprehensively examines the effects of various extraction conditions, including production pressure, hydrate saturation, and permeability, on methane hydrate decomposition during depressurization-based extraction. Key findings show that reduced production pressure significantly increases gas and water production rates due to an enhanced pressure differential, albeit at the cost of potential geomechanical instability. Variations in hydrate saturation reveal that lower-saturation reservoirs initially exhibit higher production due to faster pressure propagation and greater porosity, whereas high-saturation layers may sustain production in the later stages. Permeability changes impact pressure diffusion and heat transfer within the formation; higher permeability leads to faster initial production but causes rapid energy depletion, requiring supplementary energy inputs to maintain production. These findings provide essential insights for optimizing methane hydrate extraction, ensuring high productivity while mitigating formation stability risks.

When acoustic waves propagate through hydrate samples, they carry extensive information related to their physical and mechanical properties. These details are comprehensively reflected in acoustic parameters such as velocity, attenuation coefficient, waveform, frequency, spectrum, and amplitude variations. Based on these parameters, it is possible to invert the physical and mechanical indicators and microstructural characteristics of hydrate samples, thereby addressing a series of issues in hydrate development engineering. This study first provides an overview of the current applications and prospects of acoustic testing in hydrate development. Subsequently, it systematically elaborates on the progress in research on acoustic testing systems for hydrate samples, including the principles of acoustic testing, ship-borne hydrate core acoustic detection systems, laboratory hydrate sample acoustic testing systems, and resonance column experimental systems. Based on this foundation, this study further discusses the development trends and challenges of acoustic testing equipment for hydrate-bearing sediments.