Deep Panuke Project Description - Encana

Injection into a Dedicated WellWater injection into a dedicated well is a proven technology on offshore oil developments and isnormally done for reservoir pressure maintenance. This concept would involve the use of all equipmentfor the overboard disposal scheme plus the addition of a dedicated flowline, a dedicated umbilical, a newinjection well, injection pumps, and filters. For this concept, the capability to discharge produced wateroverboard would be required to provide operational flexibility in times of maintenance and/oroperational issues. The concept, while technically feasible, is considerably more expensive than thesimpler overboard disposal concept. Since the overboard disposal concept provides a proven,environmentally acceptable alternative at a significantly lower cost, the dedicated injection well wasrejected based on economic considerations.Simultaneous Injection of Acid Gas and Produced WaterSimultaneous injection of produced water into the condensate/acid gas well is not commonly practicedoffshore due to risks associated with phase separation. Although the design rate of 6,400 m 3 /d [40,000bpd] is sufficient to dissolve 130 x 10 3 m 3 /d [4.5 MMscfd] of acid gas, the rate of produced water variesbetween 0 and 6,400 m 3 /d [40,000 bpd] and cannot be predicted with certainty at this time. Therefore,this option cannot be considered as a reliable solution for produced water disposal and was rejected.Injection of Produced Water into an Annular SpaceInjection into the annular space of an existing well is not widely practiced. This concept involvesinjecting the produced water into an annular space between the surface and production casing strings.The concept will require injection pumps and equipment on the topsides similar to the dedicated wellconcept as well as a special dual completion type wellhead and production tree arrangement. Thisconcept has the following technical challenges:• the annular space on any of the existing production wells will not have sufficient cross-sectionalarea to accept up to 6,400 m 3 /d [40,000 bpd]. Therefore, none of the existing wells could be reused;• well construction to accommodate this concept for either of the two new drill wells (H-99 or D-70) will be difficult and technically challenging because a special oversized surface casing willbe needed along with a custom wellhead and production tree; and• injection of the total expected quantity of produced water over the field life into a non-permeablezone, where the surface casing terminates, is questionable. There may be operational issues withthis concept.Deep Panuke Volume 4 (Environmental Assessment Report) • November 2006 2-75