Abstract
The flow assurance issues that will be subject of this paper are hydrates and wax. The primary objective and scope of this paper is to present the application of transient multiphase flow simulator as an aid to predicting production system performance associated with solids deposition in tubing and flow line in the Karachaganak field. The secondary objective is to be able to provide proactive solutions using modelling for results to prevent production losses.
Hydrates and wax deposition are key flow assurance challenges encountered in the Karachaganak field. The methodology employed in this study covers building up the complete model in dynamic multiphase flow simulator – Transient Simulation Model®, which includes wells and flow line. Multiflash PVT package's application includes the capability to build the fluid models and calculate hydrate/wax, precipitation curves. The well performance is matched to production liquid flowrate, wellhead temperature and plugging time to understand solids deposition rate and deposition envelope.
The simulation results show that no hydrate deposition occurred in tubing but fluid temperature drops below the hydrate formation temperature some ~ 400m from the wellhead into flow line without the application of thermodynamic inhibition. The differential temperature between hydrate formation temperature and fluid temperature (DTHYD) must be above zero for hydrate to form. The effects of methanol pumping in batch and continuous mode at different ambient temperatures provided information on the frequency and volume of proactive treatment. This paper presents the impact of seasonal weather variation on hydrate deposition.
The simulation results of wax deposition model show that wax deposition occurs inside the flow line as well as inside the tubing. Wax deposition in flow line occurs at an ambient temperature from -25°C to 0°C, while wax deposition in tubing occurs at an ambient temperature of -30° C and below. Proactive intervention by pumping mixture of organic solvent and methanol to remove wax and hydrate plugs, following observation of a drop in the slot/manifold temperature or increase in flow line pressure, has increased uptime in wells by 70%.
The scenario of heater installation with an outlet temperature of 65° C at the wellhead showed significant wax deposition reduction. Transient dynamic multiphase flow simulator is a useful tool in reproducing plugging behaviour observed in a well and flow line. The results of simulation enabled a proactive scheduling of chemical injection treatment. This is the first application of modelling approach used within management of flow assurance issues in the Karachaganak field.
