Review on hole cleaning for horizontal wells

Since the demand for oil is increasing worldwide, it is expected to drill more and more wells, like vertical, horizontal and directional wells. However nowadays the economy is a bit down, where the oil price is fluctuating. To decrease the cost of drilling operations and increase the recovery performance, the parameters that control the hole cleaning must be investigated and optimized especially in horizontal and deviated wells. In these wells the cuttings concentration is higher than in straight holes, therefore a usable hole then will be obtained. Currently the hole cleaning topic become more challenging subject matter and important issue for researchers. Therefore, in this study a set of analytical and a numerical model is presented for vertical and the horizontal well- bores. The critical transport fluid flow and the subcritical fluid flow i.e. moving upward or downward of the cutting bed concentrations is a major effect on hole cleaning. Inefficient hole cleaning and formation of beds lead to problems such as, premature bit wear, high torque and drag, stuck pipe and slow drilling rates which increase drilling time and costs. For vertical wells, as addressed in the literature, the proper hole cleaning is basically dependent on drilling hydraulics which includes; mud rheology i.e. mud properties, such as mud weight /density, viscosity, gel strength, etc. Formation of cutting beds is noticed near the entry section of the annulus and the transport of the cuttings in the annular section occurs in the form of multiphase flow regime. Drilling mud flow rate, angle of inclination and rate of penetration have a major impact on cutting concentrations. Proper prediction of these parameters is important to avoid formation of cutting beds. This research will propose a numerical model for hole cleaning in the horizontal well-bores as well as the comparison between vertical and horizontal well-bore.