Performance And Recovery Optimization Ill A Shallow Bottom Water Oil Reservoir
Authors: Sheppard Douglas A. , Robertson Dennis L. 
Published: March 2010

Efficient and economic recovery of oil m shallow bottom water oil reservoirs is recognized as a formidable task. High watercuts and rapidly decreasing oil rates early in the production life of such reservoirs have in many instances prompted their suspension or abandonment at very low levels of recovery.

Certain Basal Cretaceous bottom water oil reservoirs in southeastern Alberta exhibit features which provide for highly successful project development when the appropriate lifting and treating facilities are provided to process and reinject large volumes of produced water efficiently. This paper presents an historical evaluation of one such reservoir in the Grand Forks Field, and outlines initial reservoir characterization, analyses and numerical studies which prompted extensive development in the pool utilizing high fluid rate production to greatly enhance productivity and Significantly improve ultimate recovery of oil.

Introduction

Traditionally, shallow sandstone oil pools of thin average oil column, which are underlain by water, have presented formidable problems for most aspects of production and exploitation. Such pools, which normally contain heavier crude, generally yield low recoveries of oil in place, and typically are not capable of high average well rates. Because of potentially high costs associated with the production and disposal of water produced in conjunction with oil, there has been much hesitation toward extensive development and experimentation in such environments.

Background and History

In southeastern Alberta in the oil production areas close to the Taber area, a great deal of activity has occurred in recent years with development of the shallow oil horizons. Much of this activity has been motivated by relatively inexpensive drilling costs, and very favourable economics associated with elevated oil prices. Many new pools and extensions to existing pools have been discovered, and a very large increase in the recognizable level of recoverable oil in the area has occurred. The shallow oil zones referred to are Lower Cretaceous and Jurassic sands which drape over and fill the eroded Mississippian formations in the area. To a lesser degree, Detrital zones frequently connected to the Jurassic sands also contribute pore volume to the reservoirs to be addressed here. The main producing formations are referred to as Mannville, Sawtooth, Sunburst and, in some cases, Basal Quartz and Taber sands. The reservoir systems and associated oil accumulations are primarily connected to the defined field areas of Grand Forks, Hays, Ronalane, Enchant and Taber North. Although not all of the oil pools in these areas are bottom water pools, the majority are, and the water zones present are typically connected to extensive regional aquifers and aquifer systems, which usually provide strong and active flank and bottom water drive.

One of the earlier pools of such character to be developed in the area is the Grand Forks Lower Mannville E Pool. This pool was discovered in 1968 and placed on continuous production that same year. The main central pool area became recognized as a waterflood and qualified for enhanced recovery recognition and Good Production Practices in 1976.