Slide-Drilling Guidance System Optimizes Directional Drilling Path
Authors: Carpenter Chris 
Published: April 2020

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 194096, “Slide-Drilling Guidance System for Directional-Drilling Path Optimization,” by Can Pehlivanturk and John D’Angelo, The University of Texas at Austin, and Dingzhou Cao, Anadarko, et al., prepared for the 2019 SPE/IADC International Drilling Conference and Exhibition, The Hague, 5–7 March. The paper has not been peer approved.
The amount of uncertainty related to directional drilling makes accurate drilling challenging, leaving much to human know-how and interpretation. Additionally, few path-planning methods in the literature consider the directional steering tool being used. The formulation of the problem of optimization varies greatly between rotary steerable systems (RSS) and mud-motor configurations. Additional cost functions and constraints exist for mud-motor use, which significantly increases the complexity of the problem. A slide-drilling-guidance system is proposed to combat this issue and to help automate directional drilling.
Introduction
Despite the numerous technological advancements that made directional drilling a reality, directional drilling is still viewed more as an art than as a science. The drillstring and penetrated rock formations are complex systems whose interaction makes prediction and planning highly uncertain.
Analytical, geometric approaches have sought to formulate the curvature of the well path in a way that eases the planning process and ensures smooth trajectories. The literature on directional drilling is rich in well-path-optimization methodologies based on operating constraints and well-path geometry. However, few of these methods seem to consider the tool used to generate the well path, and those that do typically use RSS because these yield better results from a technical perspective. Mud motors, however, are still used extensively because of cost effectiveness.
The complete paper proposes a directional-drilling guidance system targeted at downhole motors and slide drilling to generate optimal well paths and associated slide-drilling instructions. Instead of a simplistic shortest-path approach, various cost functions aimed at maximizing the value of the well are considered. For wellbore-propagation prediction, a computationally efficient and accurate model is used. The proposed methodology is built into a software package and is being developed and implemented currently for use in the real-time drilling (RTD) system of an operator.
The three main modules of the software are discussed in detail in the complete paper. The wellbore-propagation model predicts the evolution of the borehole and returns the predicted 3D path given the initial condition and a slide sheet. The fitness-evaluation module calculates the fitness of the 3D path using a cost function and returns a scalar value representing the overall value of the path. The genetic-algorithm solver generates candidate slide sheets and approaches an optimal slide sheet by iterating over generations.
Software Implementation Graphical User Interface (GUI). The GUI serves as a tool to visualize the well under consideration and to study the optimization results and the effectiveness of the approach. The GUI is written in MATLAB and uses the Runtime environment. Here, the data for the planned path and the actual survey data are loaded. The planned path and the surveyed path (up to the time for which such data are available) are displayed.