The Medicine Hat Gas Field — 100 Years After Discovery
Authors: Martin I. , Yeung G.C. 
Published: March 2010

The Medicine Har gas field in Alberta was discovered in 1890 and is the largest in Alberta with estimated initial established gas reserves of 98 191 106 m3 (3485 BCF)(1). Although gas has been found in 5 different geologic horizons, the Medicine Hat A Sand accounts for initial established reserves of 50,000 106 m3 (1775 BCF)(1). An earlier paper by Martin(2) described the history of the Medicine Hat A pool up to 1964. Since then many more wells have been drilled and a lot more has been learned about production of these shallow, thin shaly sand wells.

The purpose of this paper is to discuss application of modern techniques to estimating volumetric reserves for the Medicine Hat A pool, and to compare such estimates to those from production performance and material balance performance. The methodology applied to reserves estimating for this pool is, worthy of consideration for application to other shallow gas pools producing from shaly sands.

Introduction

Martin(2) discussed some of the earlier history of the Medicine Hat field which, at that time, was producing predominately from the Medicine Hat A Sand. Since then, large reserves of Milk River formation gas have been found with initial established reserves of 30,600 106 m3 (1086 BCF)(1), and significant quantities of gas in the Medicine Hat C Sand 2600 106 m3, (92 BCF)(1)the Medicine Hat D Sand 2390 106 m3 (85 BCF)(1), as well as varying amounts in the Second White Specks, Lower Colorado, and Bow Island formations.

The earlier paper also discussed the geology, development, reservoir properties, gas reserves, horizontal drainage, testing procedures, abandonment pressures (at the time thought to be 100 psi), and water production. In 1989 Hankel et al.(3) published a paper which discussed the general deposition of the Medicine Hat Sands and details of the rock characteristics. This geologic work was pan of a study(4) of the gas reserves and performance of the Medicine Hat A and C sands within a seven township block in the Medicine Hat field. This paper discusses the methodology used in that study applied to reserves estimating from a combination of volumetric, production decline and material balance analysis methods.

In 1985, Warren(5) presented a paper on shallow gas pool performance which included average well production declines of a very large number of Medicine Hat A wells (as well as Milk River A and Second White Specks A). Because of the usefulness of his paper and interest by him in shallow gas well performance. Warren was invited to review this paper.

Also, for completeness, because Martin has not studied the entire field in recent years, the Energy Resources Conservation Board (ERCB) was invited and have agreed to include a general field-wide structure map and porosity foot map (Figs. 4 and 5).

The Medicine Hat Sands contain gas over a large area or southern Alberta and in the Hatton area of Saskatchewan immediately east of the Alberta Medicine Hat field. The designation of the Medicine Hat A pool limits are more for administrative reasons than based on reservoir boundaries.