Field Validated Hydraulic Model Predictions Give Guidelines for Optimal Annular Flow in Slimhole Drilling

Abstract

Accurate prediction of annular flow is of primary importance in slimhole drilling. A model was developed that better represents actual amular configurations. It accounts for axial variations of drillpipe eccentricity and for effeets arising from drillpipe rotation. The model is validated with data obtained from 3 industrial slimhole wells (4''3/4 and 3"3/8 phases). Based on model predictions, guidelines are given to define flow parameters and to adapt fluid rheology in order to obtain optimal hole cleaning under safe drilling conditions. introduction Flow in the reduced annular geometries of slimhole wells may give pronounced pressure losses at moderate or even low flow rates, generating thus substantially higher equivalent circulating densities than in conventioml wells. Accurate control of wellbore hydraulics and adequate choice of fluid rheology and flow parameters are therefore imponant issues of the slimhole teehrwlogy, as far as avoiding excessive pressure against the formation and efficient hole cleaning are comerned.Early field practice ] and more recent laboratory studies2 showed that the usual hydraulic models are not able to correctly predict pressure losses in slimhole armuli. These models assume a concentric annular geometry and ignore drillpipe rotation. However, the flow is extremely sensitive to the precise boundary conditions, so drillpipe actual configuration and rotation must be accounted for3.

Numerical study of temperature–pressure coupling model for the horizontal well with a slim hole

“…According to Cartalos and Song et al, 10,13 the drill column rotation, drill column eccentricity, and drill column joint size significantly affect the pressure dissipation in HW‐SH. However, their study was based only on indoor experiments ignoring temperature and pressure, that have a strong influence on the drilling fluid density and rheology.…”

“…In both laminar and turbulent flows, the annular pressure dissipation tended to decrease gradually as the eccentricity of the drilling column increased. After analyzing a large amount of field and experimental data, Cartalos 13 concluded that the annular pressure depletion in HW‐SH could not be predicted accurately, even though the drilling column rotation was considered. In addition to considering the drilling column rotation, he also considered the effect of the eccentricity of the drilling column and the variability of its eccentricity along the wellbore axial direction on the annular pressure dissipation and developed a new model for the annular pressure dissipation in HW‐SH.…”

Development of torque clutch drilling tool and evaluation of drag reduction performance

“…where DP b is bit pressure drop, Q is volumetric displacement, r m is density of drilling fluid, d 1 , d 2 , d 3 are nozzle diameters of bit. Drill string rotation factor is changed as Taylor number and Reynolds number; the Taylor number is described as follows 33,34 Ta = r(D h À D p ) n + 0:5 D p 1:…”

Numerical Simulation of Pressure Loss in Largesize Annulus of Deepwater Drilling Riser

“…Due to the fact that a fluid flowing in the annulus of a bighole well where the annular clearance is big and the annular mud velocity is low, not similar to that of the conventional wellbore's, the calculations and technology of hydraulics suitable for conventional drilling do not show a good agreement any more. This fact implies the necessity of analysis annular mud velocity,drill pipe rotation speed that cause the variation of pressure losses in annular space to predict the fluxion of helical flow and debris migration in the annular space.R.C.McCann [1],U.Cartalos [2]and Wanghaige [3] analyze the pressure loss of a fluid flowing in the narrow annulus of a slimhole well through numerical simulation and laboratory studies, but scholars seldom study annular pressure loss in largesize deepwater drilling rise, this paper has discussed annular pressure loss in largesize deepwater drilling riser using numerical simulation.…”