Investigation Of Methane Hydrate Formation In Water-Continuous System With Drilling Mud Additives

Hydrate formation in the drilling fluid is the biggest challenge for the oil and gas industry,during the development of deep-water oil and natural gas resources.Once the hydrate formed during the drilling,that increases the difficulties of the wellbore pressure control system and causes difficulty for the flow assurance that reaches to block the pipeline and may cause some property damage or serious accident.Methane hydrate formation experiments were conducted in the vertical flow loop apparatus by using the aqueous solution of the xanthan gum(XG)and carboxmethylcellulose(CMC)at different concentrations and different flow velocities to imitate drilling flow conditions.The experiments divulge that during the hydration formed is mass transfer process and four different hydration formed stages were experienced,due to the kinetics and the slough of hydrate shells.The flow velocity of the aqueous solution and the concentration of the additives have a stronger impact on the hydrate formation as compared to the subcooling temperature.The increase in the fluid flow velocity can cause to increase in the rate of formation of hydrate but by increasing the concentration of the additives such as XG and CMC caused as an inhibitor.The effect of the kinetics of the hydrate shells and the slough of hydrate,flow velocity,and the mechanism of the concentration of the XG and CMC are analyzed and discussed in the detail.Based on the mechanism of methane gas molecules diffusion from the gas phase to the liquid phase we build a mass transfer model for the hydrate formation.For the influence of hydrate shell kinetics,an empirical overall mass transfer coefficient was introduced and checked the effect of fluid flow velocity and the concentration of the additives.In the XG model,the difference of the developed model was decreased from 145 to 11% by using the overall mass transfer coefficient,and in the CMC model,the discrepancy of simulated hydrate formation rate was 15 and 1.5% correspondingly.