Study on cuttings lag calculation method in highly directional and horizontal wells

Abstract

One of the key issues for economically successful development of shale oil and shale gas is how to produce oil or gas from high productivity areas of the shale play by optimizing well arrangement and hydraulic fracturing design and, in addition, how to enhance the productivity even from low productivity areas of the play. Cuttings analysis conducted as a mud logging service is an effective method to obtain the geomechanical properties of formations required for hydraulic fracturing optimization because information about formations can be obtained directly and continuously while drilling. However, cuttings lag time and lag depth calculated by the conventional method are recognized to be different from the actual ones, particularly in highly directional and horizontal wells because of the radial distribution of cuttings velocity and cuttings accumulation in the wellbore annulus. In this paper, we theoretically derived a more precise method of cuttings lag time and lag depth calculation to improve the accuracy of depth information in cuttings analysis. We also validated the method from the results of numerical calculation made by the modified cuttings transport simulator and an experiment using large-scale flow loop system.