Application of Subsea Separation and Pumping to Marginal and Deepwater Field Developments

Abstract

SPE Members A series of studies has been undertaken in order to quantify the benefits of various alternatives for the remote production of subsea oil reservoirs. Subsea separation and production of subsea oil reservoirs. Subsea separation and pumping appears to have significant advantages for remote pumping appears to have significant advantages for remote production over longer distances and particularly in deep production over longer distances and particularly in deep water. The concept involves the separation of gas and liquids at or near the wellhead; with the liquids being pumped in single phase back to shore, or to a remote pumped in single phase back to shore, or to a remote production facility, and the separated gas flowing back to production facility, and the separated gas flowing back to the same location under wellhead pressure. A novel separation and pumping system has been conceived which allows an integrated separator and pump to be installed within a conventional 30" conductor in a dummy well. This novel configuration has been called VASPS (Vertical Annular Separation and Pumping System).A detailed series of hydraulic studies has been undertaken which indicate that the system is capable of producing over distances up to 100 km and that well producing over distances up to 100 km and that well deliverabilities are significantly enhanced at increased water depths. We believe this to be a significant conclusion as there is an increased economic incentive to employ remote subsea production in deep water. Introduction The prevailing economic conditions have increased the need for operators to develop marginal and deep water fields. Consequently the introduction of new subsea processing and transportation alternatives has been processing and transportation alternatives has been accelerated. Many marginal fields can most economically be developed using tie backs to existing host platforms, where the bulk of oil separation and processing facilities can be shared. Remote subsea production also has particular attractions for the development of reservoirs located in deep water where conventional production technologies are no longer technically or economically appropriate. Several alternatives incorporating subsea completions are available for the development of marginal fields. Reservoirs close to existing platforms have traditionally been developed by simple satellite wells or manifolded template wells and flowlines. Unfortunately more complex solutions are required for particular reservoir conditions, and/or as the distance between the marginal field and host platform increases. Multiphase insulated lines, multiphase pumps and subsea separation and pumping are the three common alternatives normally proposed for the more remote developments. Some form of subsea separation and pumping has considerable advantages as distances from the central processing facilities increase beyond 20 km. Consequently processing facilities increase beyond 20 km. Consequently several designs have been conceived; one of which is the proposed novel configuration called VASPS (Vertical proposed novel configuration called VASPS (Vertical Annular Separation and Pumping System). The VASPS Concept The VASPS concept has a number of unique features, the most significant of which is the overall geometry of the system which allows an integrated separator and pump to be installed within a conventional 30" conductor in a dummy well. P. 783