SELECTION OF BEST DRILLING DESIGN FOR GEOTHERMAL DRDLLING - CASE STUDIES

摘要

Geothermal drilling technology is adapted from oil and gas drilling technology. Most geothermal wells are designed following the same principles as those used in the oil and gas industry. While geothermal reservoirs are similar to oil/gas reservoirs, the facts show that there are distinctions that cannot be marginalized in geothermal well design. The main challenges associated with geothermal drilling are related mostly to the hardness of igneous and metamorphic rocks being drilled, the high temperature of the formation (average temperature gradient for geothermal well is 12° - 13° F/100 ft but could be more) (Teodoriu et al., 2009) and the typically under-pressured strata. The non-productive time (NPT) often occurs in geothermal drilling, mainly caused by wellbore instability problems (Marbun et al., 2012). The majority of NPT occurrences are directly related to inappropriate well planning and design. The research reported herein presents a comprehensive study to evaluate drilling design and best engineering practices for geothermal fields in Indonesia. The specific aspects, NPT and productive time will be analyzed and identified related to well design, geologic, geophysics and reservoir condition, and also production attainment after drilling. The focus of the study is to create a planning management system based on drilling performance analysis, coupled with geothermal drilling research. The planning aspects consist of the details of preparation, the drilling process and evaluation management, to achieve a perfect well drilling time. Another focus of the study is to create an evaluation system for drilling execution, which can monitor the time and cost of drilling in each process, section, and total drilling operation, and link comparisons between wells.