Wellbore Cleaning Degree and Hydraulic Extension in Shale Oil Horizontal Wells.

The efficient development and exploitation of shale oil depends on long-distance horizontal wells. As the degree of cleaning of the wellbore plays a key role in these processes, in this study, this problem is investigated experimentally by focusing on the dimensionless cuttings bed height. A method is proposed to calculate the horizontalwell hydraulic extension taking into account the influence of the wellbore cleaning degree on the wellbore pressure distribution and assess the effect of a variety of factors such as the bottom hole pressure, the circulating pressure drop, the drilling pump performance and the formation properties. The analysis shows that the hydraulic extension of horizontal wells decreases with an increase in the cuttings bed height, and the higher the displacement of drilling fluid, the faster the hydraulic extension declines. The annular pressure drop of the horizontal section increases with the increase of the cuttings bed height, resulting in a higher bottom-hole pressure. Several arguments are provided to guide the safe drilling of shale oil horizontal wells and overcome the limits of current technological approaches. [ABSTRACT FROM AUTHOR]