Publication Rights Reserved This paper was to be presented at the 40th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Denver, Colorado, October 3–6, 1965, and is considered to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Technology or the Executive Secretary. Such abstract elsewhere after publication in the Journal of Petroleum Technology or Society of Petroleum Engineers Journal is granted on request, providing proper credit is given that publication and the original presentation of the paper. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract The design procedure presented in this paper provides a method for: predicting the orientation of induced fractures from hydraulic fracturing data, thus dictating whether a vertical or horizontal treatment design method should be employed; and optimizing fracture treatment sizes for both vertical and horizontal fracture treatments. The design procedure provides for maximum flexibility in the selection of treatment variables, and both the vertical and horizontal treatment design methods are illustrated through the use of an example problem. Introduction In 1948, Stanolind Oil and Gas Company (now Pan American Petroleum Corporation) introduced their "Hydrafrac" process for increasing well productivity by hydraulically fracturing the formation. In 1949, the first commercial fracturing treatment was performed, thus initiating one of the most outstanding well stimulation procedures that the petroleum industry has ever known. Since 1949, more than 400,000 fracturing treatments have been performed in the free world as well as untold number behind the Iron Curtain. During the past 16 years, many advancements have been made in the concepts of hydraulic fracturing theory. The purpose of this paper is not to clarify the concepts of fracturing theory, but to present a sound design method of effectively employing the concepts. Discussion of theory will be confined to only that necessary to clarify the design procedure. FRACTURE ORIENTATION Since the initial development of the hydraulic fracturing process, one of the most controversial issues in hydraulic fracturing theory has been the orientation of induced fractures. Fracture orientation is very important since it dictates the procedure to be employed in designing fracture treatments. Hubbert and Wills concluded the following: If fluid pressure is applied locally within rocks and increased until fracturing of the rock occurs, the plane along which fracturing will first occur is perpendicular to the least principal stress (Fig. 1). Horizontal fractures cannot be produced by hydraulic pressures less than the total pressure of the overburden. In sedimentary rocks, a close approximation of overburden pressure is equal to 1.0 psi/ft of depth.