Assessing, And Compensating For, The Impact Of The Leduc D-3A Gas Cap Blowdown On The Other Golden Trend Pools
Authors: Barfoot G.L. , Ko S.C.M. 
Published: March 2010

Abstract
An aquifer model study investigated the effect of the Leduc Woodbend D-3A Pool gas cap blowdown on nine other communicating pools situated on the common Cooking Lake Aquifer. A three-dimensional, three-phase black oil model was constructed to represent the ten pools along the trend and the Cooking Lake carbonate platform on which they rest. An excellent history match of the pools' performance substantiated the investigation of several production alternatives to optimize gas cap blowdown recovery, as well as study the impact of the blowdown on the other communicating pools on the Cooking Lake chain.
Several production cases investigated the effect of void age replacement, water injection site selection and gas cap blowdown rate. The aquifer model also provided the necessary boundary conditions, such as pressure and water influx/efflux histories, for other Leduc simulation models. The primary focus of the paper, then, is on the operational impact of the blowdown, not on the mechanics to the simulator, or the simulation process.

Introduction
The ten, prolific Leduc-aged Pools that stretch for 145 km from St. Albert to Homeglen-Rimbey have come to be known as the "Golden Trend " (Fig. 1). Known too, is that these ten pools, as well as other distant D-3 reefs, receive pressure support from the vast Cooking Lake Aquifer. Being concerned about the impact the proposed Leduc-Woodbend D-3A Pool gas cap blowdown could have on the nine neighbouring pools. Esso Resources Canada Limited retained INTERCOMP to conduct an aquifer model study of the local system.
The objectives of the study were to:develop a reliable, predictive tool for the Golden Trend by obtaining a pressure match for the period 1947 to 1981 for the ten major pools (St. Albert D-3B, Big Lake D-3A, Acheson D-3A, Leduc D-3A, Glen Park D-3A, Wizard Lake D-3A, Bonnie Glen D-3A, Westerose D-3, Westerose South D-3A and Homeglen-Rimbey D-3. See Fig. 2); andpredict the pressures of these ten pools to the end of their forecasted productive lives during:—a gas cap blowdown at Leduc; and—selective water injection, designed to isolate pressure influences in other major pools along the aquifer during a Leduc blowdown.
In recognizing :the great quantity of remaining reserves in the ten pools; andthe potential to increase the reserves in some of these pools by miscible flooding;
the authors wish to make their efforts known to the industry. The approach of the writers is to summarize the work with the expectation that, if needed, the reader will reference Application 830340(1) to obtain the details desired.

Setting up the Simulator
The model used in this study was Intercomp's Beta II(2) black oil reservoir simulator. Consistent with a three-phase, three-dimensional, Cartesian application of the simulator, the following data were prepared.

Aquifer Description

Area
The area of the Cooking Lake Aquifer included in this study extends southwesterly from Edmonton for a distance of over 136 km (Fig. 1). The width of the study area varies from 7.9 to 13.1 km, following the lateral extent of the Cooking Lake platform.