Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.
Production increases resulting from fracture treatments should be based on the conductivity and location of the propping agent - not on the area created by the frac fluid. Model studies show that in conventional fracture treatments propping agents settle to the bottom of a fracture forming a packed pile of prop. The location and dimensions of the pack are dependent on the physical properties of the prop, fluid and physical properties of the prop, fluid and formation, the geometry, volume and length of the fracture, and the pump rate.
This paper presents a mathematical procedure for predicting the location and procedure for predicting the location and dimensions of the prop pack in a vertical linear fracture. A computer program has been prepared and is currently being used in designing fracture treatments.
Studies we have made in models of vertical and horizontal fractures show that in conventional frac treatments props end up in a multilayer packs. We observed this in models where no leak-off occurred as well as in a vertical model with leak-off through one face. Other authors have demonstrated the same phenomena. To the best of our knowledge no one has published model studies which demonstrate that monolayer or partial monolayers are obtained in conventional frac treatments, i.e., where low viscosity gelled oil or water is used as the fracturing fluid.
With few exceptions field treatments designed on the basis of monolayer or partial monolayer concepts have not responded any better than conventionally designed treatments. Lab studies, on the other hand, show fracture conductivities of partial monolayers are much greater than conductivities of a pack. We believe this inconsistency is evidence a pack occurred.
Our model studies supplied a considerable amount of equilibrium velocity data. Earlier work had described the areal extent of a prop pack where no leak-off occurred. Our goal was pack where no leak-off occurred. Our goal was to describe both the areal extent and location of the prop pack under conditions where leak-off occurred.
