Design Considerations and Field Performance of an Advanced Automatic Driller

Abstract

Abstract Automatic Drillers have been used for decades. Most of these systems did a poor job of controlling weight on bit, which resulted in equally poor performance. Thus prompting two questions: "What is required to achieve a much better level of control of drilling parameters like weight on bit?" and "What field performance results do we see from improved control?" This paper will address these questions by examining the development and field performance of an advanced automatic drilling system. It will show how the entire system, not just the mechanics or the software, needs to be designed from a control system point of view. It will present the results of field usage of the system, and demonstrating the performance benefits resulting from improved control. Finally, it will suggest future developments for this type of advanced product. Introduction Attempts to develop Automatic Drilling controls for earth boring rigs started before the turn of the century. They were generally described as Drilling Feed Controls. Over the years many different designs were tried with limited success and the driller-operated "brake handle" feed system continued to be the preferred method. The efficiency of an automatic feed control was never denied. However, implementation proved to be illusive. With the recent advent of microprocessors and the development of proportional brake controls, the limitations experienced in the past no longer seemed insurmountable. In 1997 Helmerich and Payne approached Varco International with the challenge of developing an "electronic" feed control system. The first effort, installed on six H&P land rigs, referred to as the "six pac rigs" proved very successful. Significant improvements in drilling efficiency were recorded. Although the initial results exceeded expectations, further development of the control algorithms have greatly reduced the original design's dependency on operator's expertise. At the same time, development of improved control components resulted in another step improvement to drilling efficiency. Today's systems are highly automatic, adapting themselves to different methods of control including weight on bit (WOB), fixed rates of penetration (ROP), constant pressure (?P), and constant torque. This paper describes the evolution of this modern day design, referred to as an "Electronic Driller" and the field performance of various design irritations. History Of Feed Control Brantly in his book on History of Oil Well Drilling1, devoted a whole chapter to Drilling Feed Controls. A French mining engineer, Rololphe Leschot, developed the first "automatic" means employed for controlling bit feed-off into the formation in the early 1860's. The application was a diamond core drill used to drill blast holes for a tunneling project. Leschot used a simple hydraulic cylinder feed with a constant pressure to produce constant force on the bit. Over the subsequent years, numerous methods were tried, many of them quite novel in approach. Examples include so-called torque-based machines built by National Supply Company and Oil Well Supply Company. In the 1930's hydraulic feed rotary tables of various designs were applied. These hydraulic feed machines used cylinders that operated similar to Leschot's original design. By the 1940's most feed control machines became band brake control machines as brake performance improved. Most of these devices were pneumatically actuated and used inputs from the rig's standard weight indicating instruments. They were connected to the manual brake handle and controlled the feed by keeping the string weight constant.