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Analysis of fracturing techniques in correlation with formation characteristics and past treatments has resulted in the development of a method to increase the flow capacity of artificially created fractures.
Glass beads,, a recently developed propping agent, have proved more effective than other rigid or deformable props in all hard formations tested. When placed in a partial monolayer in such formations, they provide a higher fracture flow capacity than any existing prop, and are hard enough to withstand the overburden pressure in any presently produced formation.
Beads can be used as a tail-in following other props, to give a high flow capacity through the critical area immediately around the wellbore. Also, they may be used alone to provide a maximum flow capacity throughout the entire fractured area.
Use of glass beads does not require any additional preparations over conventional fracture treatments. Fracture areas created are calculated in the normal manner. The increased flaw capacity is contributed by the hardness, shape, size and placement of the prop.
The first use of beads in the Uintah Basin was in April, 1962, as a prop in the Green River sand. Since then, their use has expanded to other fields and formations. Field results have proved the beads superior to conventional propping agents for hard formations in both new and old wells.
Since the introduction of hydraulic fracturing as a stimulation treatment, it has been recognized that the full potential is not always realized from this type treatment. Early investigations showed that a large fracture area is required for adequate drainage of a reservoir. More recently, it has been shown that benefits of fracturing, even where large fracture areas are obtained, are frequently limited by low capacity fractures. In order to maintain high well productivity, high conductivity drainage channels are necessary to provide easy access to the wellbore for the reservoir fluids. Special propping agents have now been developed which permit high flow capacity fractures to be placed in nearly any type of formation. The purpose of this paper will be to discuss properties and use of glass beads, a rigid, high-strength propping agent recently developed for use in hard formations.
As the fluid pressure within a formation decreases following a fracture treatment, the fracture tends to "heal". In other words, the fracture faces tend to close together and eliminate the drainage channels which have been created.