Estimated Effect of Horizontal Fractures on Production Capacity

Abstract

Abstract An electrical model study has been made of the effect of horizontal fractures on the production capacity of fractured wells. For thin reservoirs it is shown that increases in production capacity by factors of 4 to 12 may be obtained if the radius of the fracture is between 0.2 and 0.6 the drainage radius. For thick reservoirs the increases in production capacity may be near 1.4 to 3.8 if the fractures are between the same radii as indicated above. For thin reservoirs there appears to be little difference in production capacity whether the fracture is located at the top, bottom or center of the pay. However, for thick reservoirs and long fractures the center of the pay is indicated to be more responsive than other locations. One large pancake fracture is shown to be more effective for increasing the production capacity than three fractures with one-third the radius. A single horizontal fracture whose radius is 0.6 the drainage radius may result in an increase in production capacity by a factor near 6. Three fractures whose radius is near 0.2 the drainage radius are indicated to result in an increase in production by a factor near 3.5. Inclined circular fractures are indicated to be slightly less effective than horizontal fractures of the same radius. Elliptical fractures produce approximately the same effect on the production capacity as circular horizontal fractures with the same radius as the average radius of the ellipse. Introduction Commercial reservoir fracturing techniques are believed to result in the creation of vertical, horizontal and perhaps inclined fractures, depending on the nature of the formation fractured and the fracturing process applied. The creation of fractures normally results in an increase in the production capacity of the well. Qualitatively, the production capacity is believed to increase as the size of the fracture increases.