MWD and Downhole Motor Performance in Very High Temperature Geothermal Wells in Kakkonda, Japan

Abstract

The formation temperature in Kakkonda, northern Honshu Island, Japan, exceeds 300 below and 350 deg. C below To introduce recent deep and high temperature well drilling technologies in Kakkonda, the drilling histories of Well-20 and Well-22 are described. This paper focuses on retrievable type MWD and downhole motor performances related to drilling fluid temperatures. The temperature limitations of the MWD and downhole motors are about 150 deg. C, but those tools can survive to certain depth where formation temperature exceed 350 with the proper mud cooling system. Various temperature data are also introduced, such as temperature logs at total depth (TD), mud temperature in and out of the wells, mud circulation temperature recorded by MWD, and bottom hole temperature recorded by thermometers installed on top of the magnetic single shot tool.