Development of Operating Strategy for a Wolf Lake Satellite Underlain by a Water Leg Using Numerical Model Studies
Authors: Rubin B. 
Published: December 2007

BP Canada Inc, in partnership with Petro-Canada Inc., operates an in situ thermal project in the oil sand deposits of Cold Lake. Parts of the project area are underlain by a water-rich silt zone and a thin water sand which have the potential to limit bitumen production and increase water production. In order to minimize the water production, the operating strategy was optimized.

A detailed geological model of the oil sand-silt zone-water leg was prepared, and a numerical modelling study was initiated. The data were averaged for numerical modelling using a novel pseudoization procedure which maintained the important features of the oil sand-water leg interactions. Using the above technique, the numerical model reproduced the field performance accurately.

A pattern study was conducted to (1) duplicate field results and to (2) test several operating strategies. Analysis of the operating strategy indicated that a four well areal element could he used to model a sixteen well satellite.

The model developed was used to history match the bitumen and water production of the wells affected, using three different vertical representations. The models were subsequently used to investigate several operating strategies. Encouraging results were obtained, when the operating strategy recommended by this work was implemented in the field.

This paper describes the salient features of the pseudoization techniques used to develop the numerical model of the water leg reservoir, compares field and model results, and describes the, operating strategies investigated.

Introduction

The wolf Lake lease is located in the Cold Lake oil Sand deposit in Northeastern Alberta, Canada; and is owned equally by BP Canada and Petro-Canada. The lease covers an area of 30,000 hectares (117 square miles); and contains an estimated 600 million Cubic metres (3.8 billion barrels of bitumen in place The Wolf Lake Project is one of the first commercial in situ oil sands projects in Canada.

Bitumen is recovered at the Wolf Lake Project using Cyclic Steam Stimulation, since the bitumen at reservoir temperature is too viscous to be produced by conventional methods. This process entails injecting high pressure steam into the formation for one to two months and producing the wells for six to twelve months. The process is repeated when bitumen production is deemed too low. This process is usually complicated by the presence of bottom water which can act as a thief zone for the steam.

Portions of this oil sand project, shown in Figure 1, are underlain by sand-silt oil-water transition zones and thin water legs. Initially, field operation indicated that these water-rich zones did not result in excessive water production. Therefore, they were largely ignored until one of the Wolf Lake pads, Q1, was put into operation. Q1 was perforated in a transition zone, in an area with bottom water. The increased water mobility in the transition zone caused producing wells to water out when adjacent to wells which were injecting steam.

It was apparent that the cyclic steam technology currently used at the Wolf Lake Project was unsuitable for this type of reservoir. Therefore it was imperative that a new operating developed for this reservoir.

This paper describes the steps that were taken in order to develop the new operating strategy for Q1 Pad. In particular, this work has:Developed a consistent procedure for modelling transition zones and water legs.

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