Development of MWD System for Geothermal Wells

Abstract

In 1997, NEDO (New Energy and Industrial Technology Development Organization) commenced a new R&D project on the development of a heat-resistant MWD (Measurement While Drilling) system, which enables acquisition of real-time bottomhole data (azimuth, inclination, tool-face, temperature) while drilling geothermal wells. In 7998, we conducted a test of the MWD system at a well in the test field of JNOC-TRC (Japan National Oil Corporation Technology Research Center) in Kashiwazaki and concluded that the interference of the drilling noise with the signal was excessive and that the decoding method needed to be improved because the MWD system using mud circulation pressure changes was being developed. In 2000, we modified the format of the data transmission, decode algorithm at the surface unit, noise filter, transmission protocol, etc. Moreover, in 2001, we conducted other tests at the Kashiwazaki field and at the Ogiii geothermal field to evaluate the perfomance of each function and component of the MWD system. During the test in the Ogiii field, we. succeeded in transmitting mud pulses from a depth of about 800113 to the surface while drilling a reinjection well. In addition, the bottomhole data obtained by the MWD system wem concordant with well data. This MWD system has great heat-resistance and is expected to be put to practical use.