| Title | Utilizing Vertical Discharge Tests as an Effective Means for Well Decision Making at the Darajat Geothermal Field, Indonesia |
|---|---|
| Authors | Dian Katriya Hadi, Arias Sugandhi, Jeffrey W. Roberts, Krisnendar Martiady |
| Year | 2010 |
| Conference | World Geothermal Congress |
| Keywords | Darajat, vertical discharge, well testing, isochronal test, James lip pressure |
| Abstract | Vertical Discharge Tests using James’ Lip Pressure formula has been employed at the Darajat Geothermal Field during the 2007 – 2008 make-up well drilling program. The tests proved to be highly useful in providing preliminary estimations of newly drilled wells’ likely deliverability relatively quickly. These preliminary deliverability rates, resulting from four vertical discharge tests, were utilized in the make-up well decision making process. The ability to estimate new well flow rates in a timely manner has significantly improved the make-up well decision making quality, allowing for the efficient use of available capital. Limitations of the application of James’ lip pressure formula were experienced, as the tests were carried out using 10” and 12” diameter pipes for the tests, larger than the proscribed maximum size (8”) for James’ formula to apply. The objective of using larger diameter pipes was to minimize the restriction effects of a smaller diameter throat and to reduce potential vibration caused by the anticipated high rate steam discharges. These expected high initial flow rates were based on historical Darajat field data, where the average initial well rates in the field are capable of producing 20 MWe at a wellhead discharge pressure of 17.5 bara. Comparisons of vertical discharge and modified multi-rate isochronal tests results were undertaken out to quantify the error in measured flow rates between the two methods. This paper will make some attempt to optimize the use of the James’ formula for larger diameter pipes for future well flow rate testing capacity determination. |