American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.
This paper presents a method of scheduling proppants in perfect or near perfect transport proppants in perfect or near perfect transport fluids to meet predetermined proppant concentrations in the fracture.
Early attempts at predicting proppant concentrations in fractures failed because of the very poor prop transporting ability of the available fracturing fluids. The formation of a sand bank in the bottom of a vertical fracture completely ruled out prediction of prop concentration based on theoretical leak-off parameters. For this reason such promising parameters. For this reason such promising techniques as partial monolayer propping and high strength proppant tail-ins were abandoned.
The development of cross-linked gel systems and ultraviscous fluids has revived interest in analytical scheduling since proppant transport in these fluids is virtually perfect.
A mathematical model of the fracture is considered with all the factors necessary to predict proppant concentration included. predict proppant concentration included. This development, in contrast to either gross averaging or finite difference solutions, has led to a closed form mathematical solution.
The technique presented allows selection of final fracture proppant concentration based on the fracture conductivity needed to meet design requirements. This concentration requirement and a fracture penetration requirement are used as computer inputs. The final computer printout presents the fluid volume required, the printout presents the fluid volume required, the required proppant amount, the pad volume needed, and a proppant addition schedule. Thus, all factors affecting reservoir improvement are considered by one computer program.
When hydraulic fracturing first began, selection of treatment volumes, sand concentration and sand scheduling was strictly an empirical art. Treatment designs relied heavily on experience and subjective judgments of what was possible. The relationships between injection possible. The relationships between injection rate, leak-off coefficients, fracture width, sand concentration, and volume pumped were not completely understood.
After this initial period, several investigators began to develop and apply various analytical tools that helped to rationalize and quantify the techniques used. Significant developments occurred in the prediction of fracture area, fracture width, and productivity improvements. productivity improvements.
