Experimental Study of Effective Hole Cleaning Using "Sweeps" In Horizontal Wellbores

Abstract

Abstract Drilling fluid "sweeps" are specific fluids specially formulated to transport cuttings that cannot be removed by ordinary drilling fluid circulation. There has been a lack of certainty of the "sweep" type selection in the field. Although they are in common use in vertical and deviated drilling operations, not much information is known regarding the use of "sweeps", especially in terms of "efficiency" of the "sweeps" and the specific hydraulics involved. The effect of rheology of the "sweep" fluid on "sweep efficiency" has been investigated under low pressure ambient temperature (LPAT) and elevated temperature elevated pressure (EPET) conditions. The LPAT tests were conducted on a 90-ft-long transparent test section that consists of an 8″ ID casing and 4.5″ OD drill pipe. To investigate the effect of temperature on the "sweep efficiency", EPET experiments were conducted under simulated downhole conditions. The University of Tulsa Advanced Cutting Transport Facility (ACTF) flow loop (73-ft-long test section with annular geometry of 5.76″ × 3.5″) was used to simulate downhole conditions. Three types of sweep tests were conducted with six drilling fluids that have different rheological parameters. LPAT test results are presented in terms of weight of cuttings removed from the annulus, measured cutting bed height and differential pressure. Results of EPET experiments are presented in terms of cuttings concentration in annulus and differential pressure. Through the rigorous experimental work conducted, it has been identified that within the test conditions "high viscosity" "sweeps" in the absence of drill pipe rotation proved to be ineffective in bed erosion and cuttings removal. In addition to a higher flow rate, low concentrations of polymer, i.e. "less viscous sweep" and drill pipe rotation greatly improve "sweep efficiency". Finally, recommendations are made for practical field operations.