Classical reservoir engineering techniques were utilised to characterise water movement in the South Brae Field and determine areas of remaining oil reserves. Exploiting these remaining oil reserves has flattened the rate of production decline in this mature North Sea peripheral waterflood. After producing over 115,000 BOPD on plateau, South Brae experienced a severe 76%/year production decline rate. Prolific oil producers experienced water breakthrough and accounted for the dramatic drop in the field oil rate. An interdisciplinary approach to describe the reservoir and review production and injection history led to identification of work to exploit bypassed oil. South Brae oil production decline rate has been arrested and is essentially flat as a result of implementing such work.
The reservoir engineering techniques used on South Brae have identified several areas of the field which were relatively unswept. Exploitation of these areas of remaining oil potential has been accomplished by through-tubing work without the need of costly rig intervention. One area identified as having remaining oil potential has resulted in raising a 200 BOPD well at a 96% watercut to over 2,100 BOPD at less than a 1% watercut. The well has been producing at this higher rate since the work was completed 5 months ago (October 1992).
The techniques used to identify areas of unswept oil potential in South Brae could be used on other mature peripheral waterfloods. Redirection of water injection to affect areas of remaining oil potential has shown positive oil rate benefits at South Brae.