The Application of Numerical Coning Models to Optimize Completion And Production Methods to Increase Oil Productivity In the Bellshill Lake Blairmore Pool
Authors: Fisher W.G. , Letkeman J.P. , Tetreau E.M. 
Published: March 2010

The Bellshill Lake pool, located in central Alberta, is a structural trap in the Lower Cretaceous Formation and contains about 250 million barrels of oil-in-place. The reservoir, which has an oil zone of 20 to 50 feet, is being pressure-maintained by a strong water drive which underlies the entire pool. Coning occurs in most wells, almost from commencement of production, and the mobility is such that water production increases to a high level before stabilized production occurs. This generally takes a period of several years. The result is a pronounced decrease in oil productivity and low recovery under primary depletion. An investigation of performance shows a typical coning relationship among production rate, stabilized water-cut and height of perforations above the oil-water contact.

A numerical coning model was used to match the coning performance of a typical well over a nine-year period. Once a match was obtained, the model was then used to investigate various completion and production techniques. The results of this study will be used to optimize oil productivity in the Bellshill Lake pool. This study demonstrates that the coning model can be a valuable tool for solving practical problems on the computer at relatively low cost, thereby eliminating costly experiments in the field.

INTRODUCTION

WATER CONING is the mechanism responsible for the rise of bottom water through the oil zone to the producing interval. The general water coning phenomenon constitutes one of the most complex problems pertaining to oil production, Coning is rate-sensitive and develops only after certain equilibrium conditions are imbalanced by increasing the pressure differential over the producing section. Since the advent of the computer and the development of digital models, it is now feasible to evaluate the water coning phenomenon and ascertain ways of controlling or eliminating its adverse effects.

The purpose of this paper is to demonstrate the use of a coning model to evaluate the effects of dually completing a well, with a second set of perforations below the oil producing interval. The object of the lower set of perforations is to introduce a second pressure gradient which will offset the gradient at the producing interval. It was anticipated that, by optimizing both the position of the lower perforations and the producing rates, the upper producing interval would revert to clean oil production, Produced water from the lower perforations would simply be injected into the underlying aquifer.

The typical performance of a producing well in the Bellshill Lake pool is shown on Figure 1. The cumulative recovery of 88,000 5tuck tank barrels occurred over a period of about nine years. During the past eight years, the total fluid production rate remained relatively constant at approximately 140 barrels per city. During this period, the oi1ln-oductivity decreased from about 40 to 20 barrels per day As this performance is typical of most wells in the pool, it is desirable to design a producing technique that will maintain high oil production rates for longer periods.