| Popis: |
Many Dutch gas fields are in the mature or tail-end production phase. Operating and producing these assets presents operational and financial challenges. Lower production rates, combined with ageing infrastructure, not only require effective management of expenditure but also implementation of emerging technologies to ensure sustained gas production. Liquid loading and salt precipitation are two major issues in managing mature gas fields in the Netherlands. Additionally the Dutch mining regulations require the use of sub surface safety valves (SSSV) which brings economic and operational challenges. In 2012, EBN carried out an analysis on the historical production performance of all Dutch gas fields. During the last ten years operators have implemented various "End of field life" (Eofl) techniques, which and these have proved to be very effective. The commonly applied Eofl techniques are foam injection (batch and continuous), velocity strings, fresh water injection, jet pumps, plunger lift and mobile well head compressors. Over the last ten years annual gas production from the small fields (i.e. all fields except Groningen) was between 30 to 40 Bcm/yr. (1050 - 1400 Bcf/yr.) from some 750 wells. Eofl techniques were applied to approximately 200 wells. So far an additional 2.5 Bcm (70 Bcf) has been recovered. These techniques did not only increase recoverable reserves from the specific fields, but also extended the life of infrastructure. They facilitated extra recovery whilst enabling continued operation of the assets for an extra five years. From the analysis the authors conclude that the Eofl techniques were successful, even though to date they have only been applied on a small scale. The most common production issues are: liquid loading, salt and scale deposition and water breakthrough. The focus in this paper is on liquid loading and salt and scale deposition. The potential for improvement of recovery factors has a significant economic value. It is expected that operational experience and know-how will reduce the underlying costs in the near future. |
