| Abstract |
Geothermal well drilling is a complex process which frequently is leading to operational problems. From 1975 to 1988, six geothermal wells were drilled in Djibouti (Asal Rift) in an area which has high temperature potential, but also problems of low permeability and high salinity. This paper presents the analysis and interpretation of problems of wells A3 and A6 in Asal Rift, where the drilling of well A3 has presented a kick in a depth about 1000 m (weight of drilling fluid less than formation pore pressure) that has resulted the abandon of the drill string in the well, and well A6 fluid losses are observed, and the situation turns into a total lost circulation which millions of cubic meter of cement were used in order to cement each casing. The open part of the hole A6 (uncased) collapsed after fluid losses. This study focuses on the above problems which are not natural but it is due to human error, the improper handling of the tool during the operation. This may involve the improper design of drilling components regarding given geophysical data of formation, proper usage of drilling fluid to avoid bit balling, formation sloughing, maintaining hydrostatic pressure and proper usage of blow out preventer to control abnormal pressures, so that a good drilling performance will be taken into account by setting up a benchmarking process that is termed to be as “a necessity for survival”.The consequences of failure are severe. Even the most simple problem situation can result in the loss of millions of dollars in equipment and valuable natural resources. These situations can also result in the loss of something much more valuable human life. Understanding and anticipating these problems, understanding their causes, and planning solutions for the new drilling program of Asal Fialé are necessary for overall-well-cost control and for successfully reaching the target zone. |