Adaptive and Real-Time Optimal Control of Stick–Slip and Bit Wear in Autonomous Rotary Steerable Drilling

Abstract

Deviated, horizontal, and multilateral wells are drilled to increase the contact area between the well path and the reservoir and as a result, the well productivity will be increased. Directional steering systems (DSS) are used to control the direction in nonvertical wells. Rotary steerable system (RSS) is the current state of the art of DSS. In this research, the problem of real-time control of autonomous RSS with unknown formation rock strength was presented. The aim of this study is to develop a real-time control scheme for real-time optimization of drilling parameters to (1) maximize the rate of penetration (ROP), (2) minimize the deviation from the planned well bore trajectory, (3) reduce the stick–slip oscillations, and (4) assess the degree of bit wear. Nonlinear model for the drilling operation was developed using energy balance equation, where rock specific energy (RSE) is used to calculate the minimum power required for a given ROP. A proposed mass spring system was used to represent the phenomena of stick–slip oscillation. The model parameters have been adaptively estimated at each control iteration to tackle any disturbances or variations in the formation properties. The bit wear is mathematically represented using Bourgoyne model. Detailed mathematical formulation and computer simulation were used for evaluation of the performance of the proposed technique based on real well field data. The obtained results showed excellent ability to accommodate the changes in the formation properties. In addition, the rates of bit wear and stick–slip oscillations have been optimized.