High-Permeability Fracturing: The Evolution of a Technology

Abstract

Since its introduction almost 50 years ago, hydraulic fracturing has been the prime engineering tool for improving well productivity either by bypassing near-wellbore damage or by actually stimulating performance. Historically (and in many instances erroneously), the emphasis for propped fracturing was on fracture length, culminating in massive treatments for tight-gas sands with several million pounds of proppant and design lengths in excess of 1,500 ft. More recently, the importance of fracture conductivity has become appreciated. This has led to exciting "new" applications of propped fractures in better-quality reservoira as illustrated by North Sea wells, stimulations in Prudhoe Bay, and "frac-pack" operations in the Gulf of Mexico and Indonesia, Wldle better understanding and new technologies are being used today, the actual application of fracturing to higher-permeability formations is not new. During early development of fracturing, nearly all applications were for moderateto high-permeability zones (becimse low-permeability rock was of little interest at oil prices of $3/bbl).While tremendously succeaatirl at increasing productivity index (PI), these early high-permeability treatments were doing little more than bypassing damage. More recent development of improved, artificial proppant, cleaner fluid systems, and new technologies have changed this, makhtg it possible to alter reservoir flow and stimulate production from moderate-to high-permeability reservoirs. The primary new tool in the engineer's arsenal is the development of tipscreenout (TSO) fracturing. WMle higher-permeability formations provide the new applications, the actual philosophy shift for fracturing occurred with the massive tight-gas stimulations. Traditionally applied to fracturing of poor quality reservoirs, these treatments represented the first engineering attempts to aher reservoir flow in the horizontal plane. The development of TSO fracturing to allow creation of extremely wide, highly conductive fractures has extended this ability to alter reservoir flow to better formations. However, creation of artificial, highly conductive flow paths in the earth also creates an ability to alter reservoir flow in the vertical plane, opening the way for propped fracturing to evolve from a stimulation technology to a total reservoir-management ted This paper uses field examples to trace the history, development, and application of TSO fracturing to high-permeability formations, including fracturing to increase P]. as well as appl icatiorrs aimed at improving completions in unconsolidated sands. Potential applications of fracturing to bypass the need for sand control are explored. Finally, the use of fracturing as a reservoir-management tool is examined through use of a propped fracture to alter the vertical flow profile of a well to maximize reserves. This particular use of fracturing leads to cases where careful design of both fracture length and conductivity is required: i.e., too much conductivity is as damaging to reservoir management as too...

Proving It - A Review of 80 Published Field Studies Demonstrating the Importance of Increased Fracture Conductivity

“…Although the first hydraulic fractures in 1947 were performed in moderately high permeability formations, 13 it was not until the development of TSO fracturing that the best formations could be effectively stimulated with hydraulic fractures.…”

Modeling pressure response into a fractured zone of Precambrian basement to understand deep induced-earthquake hypocenters from shallow injection

“…Coupled fluid-flow, geomechanical, and hydraulic-fracturing modeling can be used as a tool to predict the potential for fracturing in reservoirs and surrounding formations. Through applying the coupled modeling by a finite-element-based hydraulic-fracture simulator (Smith and Hannah, 1996;Smith et al, 2001), we can study whether stress changes in Basal Cambrian Sandstone and Precambrian crystalline basement during fluid injection provide different pressure-diffusion behaviors by propagation of hydraulic fractures into the basement. Table 1 shows the parameters used to build the model.…”

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