Abstract

This paper presents the results of an analysis of the reservoir characteristics, production performance and economics of horizontal wells drilled in conventional oil pools of the Western Canada Sedimentary Basin. The paper includes an assessment of the impact of horizontal drilling on the recoverable resources and on the supply of conventional crude oil from the basin. The major conclusions of the study are that horizontal drilling:

  1. improves the profitability of conventional crude oil production compared to vertical drilling;

  2. will increase the recoverable conventional crude oil resources of the basin by an amount in the order of 450 million cubic metres; and

  3. increased the supply of conventional crude oil by about 19 thousand cubic metres per day in 1994 and this incremental supply is likely 10 grow in the future.

Introduction

Horizontal drilling in the Western Canada Sedimentary Basin (WCSB) began in earnest in July 1987, when the first horizontal well was spudded in the Suffield area of Alberta. Since then, horizontal drilling in conventional oil pools of the basin has ncreased dramatically, from 6 wells in 1987 to 959 in 1994Figure 1). There were also 68 horizontal wells drilled in natural gas pools of the basin in 1994. Conventional crude oil roduction from horizontal wells amounted to about 13 percent of the total production for the basin in 1994. For Saskatchewan the corresponding percentage was 33 percent, for Alberta 6 percent and for B.C. 5 percent.

In view of the growing importance of horizontal well technology in exploiting Canada's petroleum resources, the Energy Resources Branch of the National Energy Board (NEB) stablished a working group in 1992 to study the impact of this technological development The study included an assessment of the reservoir characteristics conducive to the application of horizontal production wells, production performance analyses of existing horizontal wells, economic analyses for these wells and an assessment of the impact of horizontal drilling on WCSB conventional crude oil resources and supply During the course of the study the petroleum industry and provincial government agencies were consulted for information and advice.

It should be emphasized that the focus of this study is tile impact of horizontal drilling on the supply of conventional crude oil from the WCSB. No attempt has been made to integrate this work with a full analysis and projections of supply for the basin For such projections the reader is referred to the NEB's publication "Canadian Energy Supply and Demand 1993–2010" issued in 1994. This publication consists of three volumes: "Trends and Issues": "Technical Report": and "Appendix to Technical Report".

Reservoir Characteristics Suitable To Horizontal Wells

Horizontal well technology is potentially applicable to various geological formations reservoir conditions and crude types. The technology has application in infill drilling in primary recovery projects and in combination with improved recovery processes, such as waterflood, solvent flood and thermal processes. Moreover horizontal wells can be drilled in many different ways: from new surface locations, from existing vertical wells (re-entries) and from underground tunnels.

Many horizontal wells drilled in Canada have targeted thin sandstone reservoirs with oil gravity of 14–18 °API.

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