Advanced Electromagnetic MWD Telemetry and PDM Systems Improve Drilling Performance in a California Geothermal Well

Abstract

The service company and operating company worked together to improve penetration rates, wellbore placement and reliability in drilling operations by utilizing a specially designed positive displacement motor (PDM). The specialized PDM impacts the borehole construction process by addressing hole quality while achieving superior directional performance over conventional PDM assemblies, and an advanced electromagnetic telemetry (EMT) MWD system allows data transmission without a continuous fluid column. Operating the Coso geothermal field located in Kern County presents some of the most difficult drilling conditions in the world; the tremendously hard, abrasive and fractured formations are susceptible to lost circulation incidents and create a harmful environment to directional drilling equipment. High amounts of lost circulation material (LCM) must be pumped through the bottomhole assembly (BHA) in order to cure partial losses. At deeper depths, air drilling is utilized which renders conventional pulse tool telemetry useless.

The electromagnetic (EM) MWD system has many advantages over conventional mud-pulse telemetry including improved reliability, unlimited concentration of LCM, reduced survey time which minimizes non-productive time (NPT), and ability to operate with numerous fluid systems including air. This paper presents a case history where the EM MWD and PDM systems advantages have proven effective to help reduce drilling days and lower total well costs for the operating company.