| Title | Estimating of Equibrium Formation Temperature by Curve Fitting Method |
|---|---|
| Authors | Chiba, M., Takasugi, S., Hachino, Y. and Muramatsu, S. |
| Year | 1988 |
| Conference | Japan International Geothermal Symposium |
| Keywords | |
| Abstract | Determination of true formation temperature from measured bottom-hole temperature is important for geothermal reservoir evaluations after the completion of well drilling, and sometimes useful in selecting lost circulation materials for remedy' work. However, the original temperature field around a borehole is disturbed by circulating mud during drilling, and it takes a considerably long time to reach temperature equilibrium between the formation and drilling mud after drilling and mud circulation has ended. The Horner-plot method has popularly been in use for estimating the formation temperature. But this method requires long-period temperature logging data up to about 120 hours to get the reliable estimation, particularly in case the geothermal gradient is relative high as in geothermal wells. Several mathematical models for bottom-hole temperature stabilization have been proposed for estimation of formation temperature from short-period logging data after cessation of circulation of drilling mud. These models have been applied to determine formation temperature using the curve-fitting method. Non-linear equation reduction by least squares solution has been successfully developed in the model proposed by Middleton (1979). This study also represents some of the research achievements included in the "Research and Development of Lost Circulation Techniques in Geothermal Wellsll that is part of the "Development of geothermal hot water power generation plant," an undertaking aided by the MITI Sunshine Project. |