To inhibit hydrate reconfiguration during deepwater dual-wall drill string dual-gradient reverse circulation drilling, accurate wellbore thermal profile characterization is critical. In this study, a novel two-dimensional transient heat field model is established. Unlike previous steady-state or one-dimensional approaches, this model explicitly captures the radial-axial thermal coupling and the transient ‘shallow-section heating’ effect unique to the dual-wall, counter-current flow architecture, providing a more accurate tool for hydrate stability assessment. A comprehensive numerical sensitivity study shows the system exhibits strong thermal decoupling. Circulating medium injection temperature governs the outlet temperature, where a 6∘C inlet rise elevates the outlet by 24.1%, while the bottom-hole temperature change is negligible at 0.011∘C. Circulation duration critically affects transient heating in the shallow seawater section; extending reverse circulation from 4 to 8 h raises the mudline annulus temperature by 24.7%. This “shallow-section heating” is diametrically opposed to conventional circulation models. Notably, the geothermal gradient is the dominant factor for bottom-hole temperature, where an incremental increase of 0.004∘C/m induces a corresponding 5.19∘C bottom-hole temperature elevation. Fluid thermal properties are main control parameters for the mudline’s hydrate-sensitive zone. High thermal inertia (from density or specific heat capacity) elevates the mudline return temperature by up to 16.9%, whereas high thermal conductivity causes a sharp 17.0% temperature reduction. These quantitative research results lay a theoretical basis for optimizing circulating medium parameters and thermal anomaly diagnosis of the dual-wall drill string dual-gradient hydrate production system, thereby improving operational safety and production efficiency.
Zhang et al. (Thu,) studied this question.