Spline Fluid Models for Optimization

Oil production optimization is usually formulated by applying mass and momentum balances of the production network. By including temperature as a variable in pipe pressure drop, pump, and compressor models one may improve their accuracy, as well as the accuracy of the overall production system model. In addition, it is sometimes desirable to add temperature constraints to avoid flow assurance issues [e.g. wax and gas hydrates). The introduction of temperatures in the optimization problem requires thermodynamic properties of the fluid as functions of pressure and temperature. In this paper, a unifying fluid model for optimization using B-splines is presented. The fluid model can be constructed based on a Black-Oil model or from PVT simulations. The B-spline has properties that make it suitable for optimization. The applicability of the method is demonstrated in two examples, and the results are compared with realistic Olga simulator output.