Yates Field Unit in Pecos County, Texas, has recently drilled its 100th short radius horizontal drainhole. The program has been a technical as well as economic success for the field, providing efficient completions in this highly fractured reservoir.
In the early stages of the program (1986 – 1990), short radius drilling in Yates Field Unit was performed using strictly rotary drilling systems. In 1992, Odorisio and Curtis1 reported on the introduction of articulated downhole mud motors to the program and the impact of the initial modifications to the system. Since that time over 75 additional drainholes have been drilled. Two other drilling systems have been tested and many improvements have been made to the original system. This paper documents the optimization that has occurred in the drilling systems and results obtained from this work.