Abstract

Gas cycling schemes have been in operation in the Kaybob South Beaverhill Lake field since the commencement of production. Their start-up dates range from 1968 to 1972. This paper outlines a study conducted to determine the behavior of the dry gas flood by simulating reservoir conditions with a two-dimensional, three-phase immiscible computer model_ The main area of the performance review centered around Units No.1 and No.2 as the majority of cycling history has occurred in these Units. Future performance was also of concern and hence, variations to the present mode of cycling were investigated.

It was determined, prior to initiating history match runs on the Kaybob South Beaverhill Lake field, that additional supplementary studies would be beneficial in defining reservoir performance. The studies, which included the use of computer simulations, were a water coning study to set individual well producing rates, an aquifer system study to quantify water influx and determine the influence of three nearby communicating gas pools, and a pseudo relative permeability study to describe miscible wet gas-dry gas flow relationships for use in the main immiscible simulator.

The predicted position of the injected dry gas is in agreement with the field data that are available to date. The prediction runs indicate that modifying the injection pattern or increasing the voidage replacement above the present value of 52 percent would not significantly improve ultimate recovery of hydrocarbons.

Introduction

The Kaybob South Beaverhill Lake reef is located about 160 miles to the northwest of Edmonton, Alberta. Discovery and development drilling has resulted in the establishment of three Units in this field (Figure 1). The most northerly Unit, Unit No.1, was developed in 1968 and a gas cycling scheme was initiated at the commencement of production. Gas cycling schemes were also established in 1970 and 1972 in Units No. 2 and No.3. This type of secondary recovery operation is intended to recover additional liquids from the original reservoir gas which would otherwise be lost due to retrograde condensation and water influx. The three Units are now approved for cycling at raw gas inlet rates of 170, 170 and 445 MMcfd with residue gas injection of 52 percent of the surface volumes produced.

This paper presents an overview of a recent performance review. The work included a history match of the behavior of the pool to date and an examination of future productivity. Previous studies of the Kaybob South BHL reservoir discussed secondary recovery applicability and design. A limitation of that work was the lack of production history. Four years of cycling operations have been completed in Unit No. 1. It Was considered that four years of history would be sufficient to provide a reliable analysis of present dry gas flood positions and to form a basis from which predictive runs could be made.

Reservoir Description

Development drilling appears to have defined most of the heaverhill lake A pool. Some 120 wells have defined a gas zone which extends approximately 32 miles and includes some 50,000 acres.

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