The Effect of Rate on Recovery for Canadian Carbonate Reservoirs
Authors: Lee J.E. , Niven R.G. , Cochrane J.T.H. , Richardson J.G. 
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.
This paper was prepared for the 49th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Texas, Oct. 6–9, 1974. Permission to copy is restricted to an abstract of not more than 300 words. illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
Mathematical model studies and performance analyses of Canadian carbonate reservoirs indicate recovery will be improved when pool and well rates are increased, provided the desired water displacement mechanism is maintained. The increased recovery at increased rates is directly attributable to the ability to cycle more water through the reservoirs prior to reaching the economic limit.
Two-dimensional, two-phase (oil-water) radial and cross-sectional models were used to evaluate the impact of producing rate on ultimate recovery for bottom water drive and horizontal water displacement processes. These processes are the predominant recovery processes are the predominant recovery mechanisms operating in the reservoirs under investigation. Depletion rates were varied from 1 to 50 percent of ultimate reserves per year, which far exceeds the limits for normal withdrawal rates. The impact of reservoir heterogeneities, such as tight lenses, the KH-KV ratio, and stratification on the rate-recovery relationship were investigated. While better recoveries were obtained at low rates at a given water-oil ratio or a given water throughput, in all cases improved recovery to the economic limit was achieved at increased withdrawal-rates.
These model studies, which incorporated advanced simulation technology to account for all forces important to the recovery mechanism, demonstrate that there is no definable maximum rate within practical economic depletion rates at which recovery will begin to decrease for typical Canadian carbonate reservoirs.
In addition to the model studies, detailed performance analyses, including an evaluation of performance analyses, including an evaluation of flushing efficiency (recovery efficiency), were made of four reservoirs that had experienced substantial rate increases. Movement of the fluid interfaces in these reservoirs has been monitored extensively for several years using interface observation wells and production logs. Results of the performance analyses support the model studies conclusion that increased production rates are not detrimental to ultimate production rates are not detrimental to ultimate recovery.

Introduction
The understanding of the maximum efficient rate (MER) concept has changed considerably since the concepts were originally formulated.