ABSTRACT
This paper presents a method to simulate the circulating system while drilling a well. For any given pump rate the pressure losses through the surface system, down the drill pipe, through the bit, and up the annulus can be determined. The algorithm also has the capability of simulating a washout in the drill string, losing fluid to the formation, having fluid produced into the annulus, and fracturing the formation(s).
The algorithm is general enough to calculate pressure losses for turbulent and laminar flow, simultaneously. This covers the situation where multiple flow regimes exist in the same circulation loop.
Formulation of the algorithm is presented, showing how a network type of solution is used to calculate the pressures and flows. The iterative solution converges rapidly and can be used for real time and faster than real time simulation.
Detailed surface pressure data was obtained from two wells in Texas. The circulation simulation program was used to calculate pressure losses at various depths in each well for a variety of circulation rates. Results presented in this paper show close agreement with the field data.
To show the versatility of the simulation algorithm a series of idealized circulation system simulations are presented. These include various downhole circulation situations such as lost circulation, circulation without returns, and fluid production response as a function of permeability and pressure, and circulating with a hole in the drill string.
