Development and Application of a Drilling Hydraulics Simulator Including Pressure and Temperature Dependent Fluid Density and Rheology Behavior
Determination of pressure while circulating is one of the basic drilling engineering tasks. Pressure must be kept below the maximum ratings of tubulars and equipment, and at the surface, the pumps driving the flow must be able to operate at the pressure required to generate the desired flow rate. In the annular space, the fluid pressure must be kept in the planned range to avoid a kick or damaging the formation. This thesis describes the creation and theory of a drilling hydraulics simulator to calculate pressure using standard drilling engineering inputs, operational parameters, and earth properties. As many of the properties of the circulating fluid are dependent on temperature and pressure, it is necessary to include these property variations at any point to create a realistic pressure profile. The simulation solves for the pressure, temperature and fluid density at every point using API pressure calculations, a finite difference numerical solution for a fixed volume energy balance, and density interpolation from tabular data, respectively. The three calculations include the other properties and are thus dependent on each other. Each property is solved separately using an initial guess for the other two properties or the previous step’s calculations’ results. The simulation iterates through calculating the three properties until the values converge from one step to the next. The final hydraulics program is then used to investigate the effect of changing various inputs. The changes in temperature, pressure, and fluid density are examined in various test cases. The effects of the uncertainty in the convective heat transfer coefficients are tested, as are the inclusion of a booster pump and the changing of cuttings volume.