A Multiphase Wellbore Flow Model for Sour Gas “Kicks”

This study presents a new multiphase flow model with transient heat transfer and pressure coupling to simulate HTHP(high temperature and high pressure)sour gas“kicks”phenomena.The model is intended to support the estimation of wellbore temperature and pressure when sour gas kicks occur during drilling operation.The model considers sour gas solubility,phase transition and effects of temperature and pressure on the physical parameters of drilling fluid.Experimental data for a large-diameter pipe flow are used to validate the model.The results indicate that with fluid circulation,the annulus temperature with H2S kicks is the highest,followed by CO_(2),and CH_(4) is the lowest.The phase transition point of H2S is closer to wellhead compared with CO_(2),resulting in a faster expansion rate,which is more imperceptible and dangerous.With fluid circulation,the drilling fluid density and plastic viscosity both first decrease and then increase with the increase in the well depth.The bottom hole pressure when H2S kicks is greater than that for CO_(2) with the same amount of sour gas,and the pressure difference gradually increases with the increase of H2S/CO_(2) content.In addition,a parametric sensitivity analysis has been conducted to evaluate qualitatively and rank the influential factors affecting the bottom hole temperature and pressure.

Simulations of sorbent regeneration in a circulating fluidized bed system for sorption enhanced steam reforming with dolomite

In this work,the sorption enhanced steam reforming (SESR) method was developed for improved hydrogen (H2) production,and the drawbacks of conventional steam reforming processes on H2 yield and purity were overcome.However,the SESR process is discontinuous and requires regeneration after sorbent saturation with CO2.The circulating fluidized bed reactor (CFBR) system has previously been proposed for continuous H2 production,with both reforming and sorbent regeneration occurring simultaneously.The main aim of this work was to determine the feasibility and performance of SESR with a proper design and conditions in conjunction with the CFBR system.The reforming riser and bubbling bed regenerator are studied separately but related to each other.Two-dimensional transient models using the Euler-Euler approach and kinetic theory of granular flow were used for fluid dynamic simulations combined with the decarbonation kinetics of dolomite,to investigate a conceptual regenerator system and determine its key conditions.A mixture of the Ni-based catalyst and dolomite from the risers was injected with a flux of 200 kg/(m2 s) and a catalyst to sorbent ratio of 2.54 kg/kg.A double-stage bubbling bed regenerator system was designed with 1.2 m width,0.8 m bed height,a gas inlet velocity of 0.2 m/s and solid preheating at 950 ℃.The used dolomite was regenerated with an assumed CaO conversion of 3%;the almost fresh dolomite was then released with good mixing of the catalyst and sorbent.