Numerical Modelling of Cuttings Transport with Foam in Inclined Wells

ABSTRACT

In this study, a 1-D transient state mechanistic model of cuttings transport with foam in inclined wells has been developed. The model is solved numerically to predict the optimum foam flow rate (liquid and gas rate) and rheological properties that would maximize cuttings transport efficiency in inclined wells. A detailed sensitivity analysis of the effect of gas and liquid flow rates, drilling rate, foam rheological properties, borehole geometry, wellbore inclination and the rate of gas and liquid influx from the reservoir on the cutting transport efficiency was presented. The cuttings transport efficiency decreases with increase in well inclination from the vertical under the same flow condition. Cuttings are transported more efficiently at higher gas injection rates. The influx of gas from reservoir into the wellbore has a positive effect on the cutting transport process whereas water influx has the reverse effect. The time required for achieving stabilized bottomhole pressure increases with increasing drilling rate and with increasing inclination of the well from the vertical position. The distribution of cuttings along the annulus is found to be not uniform, even under the steady state flow condition. The highest concentration of cuttings is always at the bottom of the hole and the lowest is at the top.