Numerical Modelling of Cuttings Transport with Foam in Inclined Wells

O. Osunde, E. Kuru
2008 The Open Energy & Fuels Journal  
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
more » ... 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. In this paper, a transient mechanistic model is presented for the prediction of foam drilling performance in inclined wells. The new model considers foam rheological properties, drag coefficient of cuttings in foam, formation fluid influx, drillpipe eccentricity, inclination effect and drilling rate and thereby provides an effective numerical solution method to simulate the hydraulics of foam drilling in inclined wells. BACKGROUND Problems associated with inefficient cutting transport are; reduction in penetration rate, wear of bit, pipe stuck, high torque and drag and other hole problems [25] [26] [27] [28] [29] . The elimination or minimization of these problems associated with ineffective cuttings transport requires proper understanding of the cuttings transport mechanism. Experimental studies have shown that well inclination angle, borehole geometry, rotation of drill pipe, drill pipe eccentricity, drilling rate, cuttings size, flow rate, fluid velocity, mud type, mud rheology and flow regime are some of the most important parameters which control the cuttings transport process [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] . Based on these experimental studies, empirical models were developed [44] [45] [46] [47] [48] [49] and rules of thumb for field practices were also suggested [50] [51] [52] . Mechanistic models of cuttings transport were also developed [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] . Cuttings Transport with Foam Krug and Mitchell [63] developed charts for the determination of minimum volume of liquid and gas and the injection-pressure required for foam drilling operation. Okpobiri and Ikoku [64] used an iterative approach to develop a procedure for the determination of the minimum velocity of foam to be injected and at what wellhead injection pressure this should be done to ensure effective cuttings transport. In their study foam-cutting flow was assumed homogeneous and suggested that for effective cuttings trans-
doi:10.2174/1874248300801010019 fatcat:kb6yqmikkfbkll4yk4ue3w3dhu