| Title | MakBan drilling campaign offset wells monitoring and post drilling production evaluation |
|---|---|
| Authors | E. Bermido, A. Mejorada, D. Ramos, A. Fajardo |
| Year | 2023 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Mak-Ban Geothermal Field, Steam Production Enhancement Campaign, SPEC, offset wells monitoring, geochemical parameters, production evaluation |
| Abstract | A recently completed drilling campaign at the Mak-Ban Geothermal Field, Philippines (the 2021-2022 Mak-Ban Steam Production Enhancement Campaign – MB SPEC) targeted production from the deep reservoir to provide steam for the existing powerplants. The campaign included nine production wells and two injection wells, using existing active wellpads. The welltracks of the MB SPEC wells were in close proximity to active wells so there was a need for a proactive approach to monitor the drilling impact and mitigate the potential migration of drilling fluids and cement to the nearby offset wells. The Mak-Ban Resource Management Team developed an offset wells monitoring plan as a guide for recommending whether to shut-in offset wells during the drilling operations and to minimize associated generation losses. Aerated drilling fluid with bentonite and polymer were used during the drilling operations. As a general rule, when bentonite was used, all offset wells within a radius of 300 ft of the welltrack were proactively shut-in to mitigate the risk of plugging the permeable zones. When polymer was used or when the offset wells were within 300 to 800 ft, a reactive shut-in approach was implemented based on the geochemical parameters that would suggest possible interference. During cementing, all offset wells within 800 ft were proactively shut-in. The original plan was to have the steam and condensate samples from the offset wells to be analyzed for total %NCG by Wet Test Meter (WTM), Normal Gas Analysis (NGA), Total Suspended Solids (TSS) and pH. For brine samples, pH, Cl and Mg were initially planned to be analyzed. However, the monitoring plan was simplified only for the parameters with the quickest analysis turnaround time which were total %NCG and Cl. Offset wells were shut-in when the parameters increased above threshold values. The offset well monitoring plan was deemed successful as it was able to help prevent the potential breakthrough of drilling fluids and cement in offset wells. The equivalent of up to 24.5 MWe production from the offset wells was preserved after the end of the campaign and the preventive offset wells shut-in losses were reduced to 16 GWh actual from the planned 34 GWh. |