| Popis: |
Andrews, I.J., and Hennington, E.R., Amoco (UK) Exploration Co. SPE Members Abstract Since 1992, Montrose, a mature waterflood field, has been rejuvenated through a multi-disciplinary full field reevaluation and the innovative, cost effective application of completion technology. Workover opportunities and areas of potentially incomplete recovery, have been identified by the full integration of all field performance, reservoir and geological data. Then workovers incorporating innovative cost effective gaslift/velocity string completions, which addressed the concerns of weak and potentially non gas-tight casing, were carried out to rejuvenate the field. This multi-disciplinary team approach to the rejuvenation of the Montrose field, has significantly increased field wide production rates, and dramatically reduced production costs per barrel, so allowing economic production in today's low oil price environment and the fulfillment of the fields long term potential. In addition the study has identified many techniques/lessons that can be readily applied to other similar mature field studies. Introduction The Montrose field, located approximately 130 miles East of Aberdeen, was discovered in 1971 with the drilling of well 22/18-2, and appraised with one further well 22/17-1 in 1972, which confirmed the potential for the field. An eight legged drilling/production platform was later installed in 1975, leading to first oil production in June 1976. Though initial production was purely from naturally flowing wells, rising watercuts and falling reservoir pressures soon led to the maintenance of production with Electrical Submersible Pumps (ESP's) of which 156 had been installed by the end of 1992, and a field wide policy of pressure maintenance through water injection. This however has not been without significant cost due to continuous ESP changeout workovers and multiple casing collapses. To date 83 MMBBLS of the 232 MMBBL STOOIP, has been produced from 22 wells, with peak production occurring in 1979 at rates in excess of 37000 bopd. In 1989 work commenced on platform modifications that would allow the Arbroath field to be brought on-line as a satellite of the Montrose field. As such, a strategic move was taken which would dramatically alter the future operation of the Montrose field through the non-availability of certain facilities (especially continuous use of a full drilling/workover rig), and open up new opportunities through lower operating costs and the availability of gas compression. Although it was initially anticipated that there would only be a minimal impact upon Montrose production, an ever expanding workscope eventually led to the total loss of all rig availability from April 1989 to Aug 1993 (with the exception of one short period in early 1992). With the average runlife of Montrose ESP completions being +/-200 days, this rapidly led to the field becoming relatively dormant from late 1989 to mid 1993. At this stage the field had many problems largely associated with its mature age and extended shut-down, i.e. all ESPs in the field had failed, so all wells bar one which was flowing naturally, were shut-in. Most of the wells also had weakened, non-gas tight casing, which had not been designed to be used with any artificial lift system. Further, a reduced size replacement living quarters meant that sustained continuous rig operation was no longer a viable option. P. 319^ |
