| Title | Accurate location of feed zones: assessing obscuration by the liner in geothermal wells through analysis of fluid velocity profiles |
|---|---|
| Authors | J. Trent, K. McLean |
| Year | 2024 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Completion testing, stage testing, well testing, geothermal wells, cold water injection, perforated liner |
| Abstract | The location of feed zones in geothermal wells is commonly identified using pressure, temperature, and spinner (PTS) data from a downhole tool during completion testing after the slotted liner has been installed in the well. To inform drilling decisions in some wells, these data are also collected during a stage test before liner installation. In both tests, water is injected into the well at a set of fixed flow rates. It is typically expected that the presence of the liner will partially obscure feed zone locations in the data collected in completion tests. Quantifying this effect is important because a stage test is not always performed due to the additional cost and the chance of open-hole collapse. Meanwhile, completion testing is always carried out as it represents the final condition of the well. Additionally, quantifying this effect is important for situations where feed zone locations need to be known with higher accuracy. For example, to correlate the location of feed zones with geology logs, to effectively use a deflagration tool for feed zone stimulation and to assess the effectiveness of chemical clean jobs. This ‘obscuration’ effect has previously been considered for the identification of feed zones using temperature logs. In that research, the effect of the liner was found to: make feed zones appear shallower by 17 m on average, widen the feed zone by 114% on average and make close-together individual feed zones appear to be one zone. Here, we consider the follow-up to that research: quantifying the degree to which the liner obscures the feed zone locations by comparing fluid velocity profiles acquired from the spinner tool during open-hole testing (stage testing) with those acquired after liner installation (completion testing). Several field examples are presented, from liquid-dominated wells in the Taupo Volcanic Zone. |