The new analysis technique of Annular Flow Dynamics is a simple, practical way to predict and control rheology and hydraulics in predict and control rheology and hydraulics in Drilling Fluid Systems. It is based on field experience in the sloughing shale areas of Canada and on a recently developed method of calculating Annular Pressure Losses with greater accuracy and more simplicity than previous methods. previous methods. Annular Flow Dynamics is primarily oriented towards improving drilling practices in sloughing shale situations. However, as holes become deeper, additional restrictions are imposed on casing programs and hole size. These make it even more important to be able to determine and possibly predict certain drilling fluid parameters for maximum performance. This paper shows how, by use of performance. This paper shows how, by use of a logarithmic plot of viscometer data, the following can be determined:
Effective annular viscosities at any pump rate and for any flow properties.
Flow type (laminar or turbulent).
Accurate annular pressure losses.
Approximate bit nozzle shear rates.
Upper and lower limits on both flow properties and pump rates for optimum well bore stabilization and minimum E. C. D. (Equivalent Circulation Density).
Approximate ascending velocity of cuttings.
In the past year, Annular Flow Dynamics has been used on a field basis in Canada with very positive results.
Well bore instability occurs primarily when shales absorb water. Controlled activity oil minds are presently the only way to satisfy the shales affinity for water. The mechanism of sloughing shales due to actual change in the physical and chemical properties of the shale physical and chemical properties of the shale have been thoroughly researched and discussed by the industry. Less attention has been paid to the mechanical aspect of stabilizing shales by well planned and flexible rheological and hydraulics programs.
