Yassin, A.A.M., U. Teknologi Malaysia (Malaysia)
Whilst the incremental oil potentially recoverable by the application of enhanced oil recovery (EOR) processes can only be reliably estimated by a detailed study of each reservoir, in order to provide an early guide to the scope for EOR in Malaysia, a preliminary survey has been carried out. The approach in this preliminary survey was to develop a set of screening criteria for the various processes being developed and to use these criteria to identify possible candidate reservoirs. The potential for incremental oil recovery was then determined by applying factors obtained from the assessment studies referred to above or from published sources.
The review of EOR potential within Malaysia has suggested that only a small number of reservoirs are unsuitable for EOR and there is substantial scope for increasing the yield from known light oil and gas condensate reservoirs. The possible contribution that could be made by individual processes is fairly evenly distributed between polymer floods, surfactants, carbon dioxide and nitrogen or hydrocarbon gas.
The enforcement of strict conservation measures and depletion control had change the development strategy by integrating EOR into conventional method of production with an early implementation of EOR in order to maintain the viability of EOR projects.
What is Enhanced Oil Recovery or (EOR)? EOR implies oil recovery beyond the conventional recovery stages of primary or secondary recovery which include natural drive, waterflood and gas injection. When the EOR is implemented depends on the characteristics of the oil; for light oils, EOR refer to techniques after primary and secondary recovery which include surfactant flood, polymer floods, miscible drive and even thermal methods and for heavy oils, EOR imply to technique after primary recovery which include steam injection and in-situ combustion. So EOR is to recover more oil after conventional recovery stages.
As a starting point in considering EOR in Malaysia fields, it is important to examine existing primary/secondary recovery and determine an early initiation programme before the field reached an advanced stages of depletion by primary/secondary production. EOR need to be undertaken while the existing wells and surface equipment are still intact and useable. Very few prospects are expected to be profitable that economics will permit redrilling of wells and replacement of surface equipment since oil recoveries are expected to be substantially lower than that of primary/secondary method. Most EOR methods are heavily front-end loaded with chemical and/or equipment so timing of EOR projects is very important for it to be economical feasible.
In this paper, we shall discuss the need of EOR, the current EOR technology and the potential of EOR in the context of Malaysia.
Before understanding the purpose of EOR, it is necessary to examine the recovery efficiency by primary/secondary method. The fraction of oil recovered by secondary/primary method depends on the following factors:
areal sweep efficiency