Application of Improved Oil Recovery Methods to Offshore Oil Fields: A New Philosophy
Aikman, M.J.L., Kantzas, A. and Moore, G.
DOI: 10.2118/97-34 & 10.2118/99-02-02
CIM paper 97-34, presented at the 48th Annual Technical Meeting of The Petroleum Society in Calgary, Alberta, Canada, June 8-11, 1997;
J. Can. Pet. Tech., 38(2), February 1999, Pages 27-36.
A literature survey of both improved oil recovery (“IOR”) methods, and offshore oil operations, has been performed. The survey of IOR methods examined both current field applications (commercial and pilot operations), and “horizon” research investigations. The survey of offshore oil operations has focussed upon the European North Sea, to understand the implications for marginal field development there, and also in the Canadian East Coast.
It is believed that oil recovery can be increased above a base waterflood development. This would be accomplished by earlier application of improved oil recovery methods, rather than the application of same late in the life of a watered-out field. The specific IOR method would require very early studies to design and tailor a method that is appropriate for the unique qualities of a given reservoir.
In this paper, a “Type Field”, hypothetical, but representative of a marginal field or isolated fault block, is used to illustrate this philosophy. Evaluation of various operational enhancements are performed via numerical simulation. Cases compared are a base waterflood, and IOR operations utilizing Gravity Assisted Immiscible Gas Injection (“GAIGI”). A novel operational scheme has been developed and is termed “Coupled Dual Phase Displacement” (“CDPD”). The oil recovery factor obtained for certain models using CDPD is 58%. This compares to a base waterflood recovery factor of 44% for the same models, giving an incremental recovery of 14% oil initially in place.
Hurdles that must be overcome are early characterization of the reservoir prior to production, and the identification of the optimal depletion process. This will require an integrated study team. Nonetheless, novel IOR schemes can be designed in some circumstances that can be insensitive to some forms of geological traps under displacement processes.
The benefits of early IOR applications are enhanced by the deferral of abandonment, which, on an incremental basis, will contribute positive cashflow to an already economic process.
It is pointed out that although the concept is outlined here for offshore oil fields, the natural extension of these ideas to onshore oil fields should also be considered.