| Abstract |
Production drilling targets in geothermal wells are often biased towards faults and fracture zones. In some of New Zealand’s geothermal fields, this approach is warranted. However, in ignimbritedominated systems, formation-hosted permeability can provide excellent production. To illustrate the potential of targeting wells to intersect formation-hosted permeability, we use the results from the 2003- 2004 drilling at Mokai Geothermal Field as a case study. Six wells (MK10-MK15) were radially drilled from one wellpad to specifically target ignimbrites and sediments, and the contact zones between them. Each well intersected feedzones hosted within and/or between one or more of Ignimbrite D, Whakamaru Ignimbrite, un-named volcaniclastic sediments and Ignimbrite F. Completion test data indicated that nonwelded ignimbrite units hosted diffuse feedzones, whilst welded ignimbrite units hosted discrete, jointcontrolled feedzones. All wells were regarded as successful, and highlight the potential of targeting permeability within, or on the margins of distinct ignimbrite flow units. |