| Abstract |
This paper discusses the results of the monitoring of the changes in the physical processes of the fluid in the reservoir as well as the changes in the production well output characteristics as a consequence of the production and reinjection strategies implemented upon the full load operation of the Palinpinon I and the Palinpinon 2 power stations. The initial response of the reservoir in the Palinpinon I area was the decline of reservoir pressure which induced the expansion of the two-phase region or the Steam cap' that developed iii the shallow part of the reservoir as geothermal fluid was continuously extracted for power generation. However, cooler reinjected fluid intrusions into the production area prevented the further expansion of the shallow two-phase zone and have affected the steam production of some wells. As a stop p p measure, near-field injection at the Puhagan area was minimized. The bulk of waste brine was reinjected in the Malaunay and Ticala areas which are much farther away from the production sector. In spite of the changes in there injection strategy, reinjection breakthrough persisted and more wells were affected as the pressure differential between the production and reinjection areas became greater. The steam production in some wells was further aggregated by the intrusion of acidic inflows believed to be condensate type fluid resulting anhydrite depositions in the wellbore. Also, cooler in flows originating from the reservoir periphery at shallow levels caused calcite deposition in some production wells. This cooler inflow was the result of the cooling of the formation due to pressure drawdown. Thus, the steam production capability of the field continued to decline in spite of the work-over and in-911 production drilling. In the Palinpinon 2 area, the reservoir pressures were observed to he still declining even a after about two years since the modular power plants in the Nasuji (December 1993), Balasbalas (November1991) and Sogongon (January 1995) areas were commissioned. Reinjection fluid returns and thermal decline in the shallow levels of the reservoir similar to the Palinpinon 1 area are now being observed, however, steam production has not been greatly affected yet. Improvement in the production and reinjection strategy in Palinpinon 2 is now being undertaken. |