Dynamic well control simulation models for water-based muds and their computer applications.

摘要

A kick is defined as an unscheduled flow of formation fluids into a wellbore. Four well control simulation models have been developed in this research to study the behavior of kicks during well control operations.;A single-phase well control model assumes that a kick fluid enters into a wellbore as a single-phase slug and remains as a single-phase slug throughout the well control operations. This model is easy to simulate and is useful for sensitivity analysis.;A two-phase well control model has been developed to analyze accurately the behavior of kick fluids based on realistic assumptions. Two new sets of finite difference equations have been derived and utilized to handle variable flow geometries. The two-phase model couples mud flow with gas influx from an infinite acting reservoir. Although the two-phase model is realistic, several numerical problems such as numerical dissipation, negative liquid velocity, instability of time step and grid sizes, and divergence due to a distinct two-phase flow map have been exposed.;An alternative two-phase well control model is proposed after comparing the dynamic two-phase model and the single-phase model. This model has been modified from the single-phase model to avoid any numerical problems that might occur in a two-phase well control model. Good matches between the alternative model and the two-phase model have been achieved for wide data ranges by considering the gas rise velocity and dynamic two-phase mixture effects at the beginning of the kick.;A user-interactive well control simulator has been developed for IBM;The simulator can handle several different well trajectories: vertical, directional, and horizontal wells including an extended reach well. Therefore, the simulator is also useful for well planning, The simulator can model the following kick and well control procedures in detail: drilling, taking a kick, detecting a kick, well shut-in, well stabilization, gas migration after well stabilization, and old mud or kill mud circulation. It also checks for possible underground blowout and pump failure.;Finally, a theoretical kill sheet is proposed and compared with a conventional kill sheet.