State-of-the-Art Tight Gas Sands Characterization and Production Technology

Abstract

Abstract As part of the activities of the ConocoPhillips-NSERC-AERI Chair in Tight Gas Engineering established in the Chemical and Petroleum Engineering Department at the University of Calgary, a comprehensive literature review has been conducted that has led to an understanding of the current status of the study of tight gas sand formations. This paper presents the results of that work, concentrating initially on Canadian and U.S. tight gas sands. The literature survey discussed in this paper is the first part of the mission-oriented research on tight gas reservoirs conducted at the University of Calgary. The planned research looks at refining the resource base and recoveries from tight gas formations in Canada. Evaluating the current status of geologic models, reservoir characterization, recovery and production technologies currently available for these types of formations is the first step in the effort to reach the final goal: finding the economic means of producing as much of this gas as possible. It is expected that the research results will prove to be of value in other parts of the world and will be exportable, creating business opportunities for Canadian companies. The program will also result in a supply of highly qualified professionals having significant knowledge of tight gas formations. Introduction The complete reference list and interpretation of tight gas sands are presented by Aguilera and Harding(1). Tight gas sands are part of what is usually known as unconventional gas, which also includes coalbed methane, shale gas and natural gas hydrates. Although tight gas production is not reported separately in Canada, interest in this resource is growing significantly. Tight gas sands have been defined in different ways by different organizations and a unique definition has proven elusive. The original definition dates back to the U.S. Gas Policy Act of 1978 that required in situ gas permeability to be equal to or less than 0.1 mD for the reservoir to qualify as a tight gas formation. At present, this is probably the most commonly accepted definition. The National Energy Board (NEB) of Canada placed tight original gas-in-place at between 89 and 1,500 Tcf in 1999(2). The Canadian Association of Petroleum Producers (CAPP) indicates that, more recently, the National Energy Board estimated that Canada has 300 Tcf of tight gas-in-place(3). Although the figures vary significantly among different estimators, the pervasive opinion among experts is that there are significant volumes of gas-in-place in Canadian tight gas sands. The estimated volumes of unconventional gas throughout the world are gigantic, as shown in a study presented by Rogner(4). He estimated tight original gas-in-place (OGIP) at 7,500 Tcf for the entire world. Our preliminary estimates suggest that this figure is conservative. For other unconventional gas sources, the volumes are even higher. The above tight gas volumes are in, at most, 271 of the 937 recognized petroleum provinces in the world. An evaluation of the resources from the remaining provinces would lead to even higher estimates, as has occurred with more conventional hydrocarbon reservoirs(5).