Modeling of Three-Phase Flow in the Annuli During Directional UBD Operations

Abstract

Underbalanced drilling (UBD) has several advantages compared to conventional drilling. These advantages include the elimination of formation damage, higher penetration rate, reducing circulation loss and the possibility of actually producing hydrocarbons during the drilling process. UBD technology and applications have recently been applied while drilling challenging wells in Iranian fields. It is generally accepted that the success of underbalanced drilling is dependant on maintaining the wellbore pressure in an operational window determined by the formation pressure, wellbore stability, and the capacity of the surface equipment. There are several models which can predict the wellbore pressure. Traditional models are mostly empirical and lead to acceptable results for specific conditions but fail for other conditions. In the last decade of the last century, some mechanistic models have been developed which result in an acceptable range of outcomes for a wide variety of reservoirs. On the other hand due to the dynamic nature of the process, some researchers have recently focused on development of dynamic models. This paper presents an improved, comprehensive, mechanistic model for pressure prediction through a well during UBD operations. The comprehensive model consists of a set of correlations for predicting flow pattern and estimating the pressure in addition to two-phase flow parameters in bubble, dispersed bubble, and slug flow. On the other hand the most recently developed empirical correlations have been applied to determine PVT properties. The accuracy of these correlations has been tested in more than 20 oil wells in Iran. Naseri et al. and Almarhoun correlations was applied to determine the live and dead oil viscosities. Naseri et al. model which was originally developed for Iranian reservoirs was used in our model and the results are promising.

Mechanistic Modeling of Annular Two-Phase Flow While Underbalanced Drilling in Iran

“…She found that the modified Ansari's method was shown to be superior to Hasan-Kabir's because of accurately describing slug flow parameters. Mousavi et al 16 made some alterations to the modified Ansari model to correct it for Iranian reservoirs to predict the flow patterns and estimating the BHP. They validated the results with 20 wells and found out better results (less than 5%) than Ansari's method.…”

Effect of two-phase gas-liquid flow patterns on cuttings transport efficiency

“…Effective solids transport in multiphase fluids are highly dependent on the fluid flow pattern (Oyeneyin, 2015) so the flow pattern must be taken into consideration when performing cuttings transport prediction or evaluation. The gas-liquid fluid flow patterns most likely to occur for two-phase flow in an UBD wellbore are the dispersed bubble, bubble, stratified flow and slug flow patterns (Mousavi et al, 2008). Previous experimental and theoretical studies on two-phase flow in either pipes or annuli have shown that the conservation of mass, momentum and energy for two-phase gas-liquid flow are different to that of the single-phase flow and significantly dependent on the prevailing fluid flow pattern (Caetano et al, 1992;Dukler and Hubbard, 1975;Dukler and Taitel, 1986;Mukherjee 4 and Brill, 1985;Taitel and Barnea, 1990;Xiao et al, 1990).…”

Optimization of Liquid & Gas Flow Rates For Aerated Drilling Fluids Considering Hole Cleaning For Vertical And Low Inclination Wells

“…In latter years, some studies have been conducted on two-phase flow hydrodynamics and flow pattern boundaries in annular geometries as well as hole cleaning. Mousavi et al (2008) presented a mechanistic model for two-phase flow in vertical wellbores. Hasan et al (2007) presented a model based on driftflux theory in order to express two-phase flow inside annulus, and compared the results with commercial software results.…”