Overview of Current Hydraulic Fracturing Design and Treatment Technology--Part 1

Abstract

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to informthe general readership of recent advances in various areas of petroleum engineering. Introduction Hydraulic fracturing has made a significant contribution to the petroleum industry as a method for enhancing oil and gas producing rates and recoverable reserves. Fracturing was introduced to the industry in 1949. Since then it hasevolved into a standard operating practice, and more than 800,000 treatments have been performed. About 35 to 40% of all currently drilled wells are hydraulically fractured, and about 25 to 30% of total U.S. oil reserves have been made economically producible by the process. It has increased NorthAmerica's oil reserves by an additional 8 billion bbl. Over the years the technology associated with fracturing has increase dsignificantly. A host of fracturing fluids have been developed for reservoir sranging from shallow, low-temperature formations to those that are deep and hot. Many different types of proppants have been developed. These range from proppants have been developed. These range from silica sand, the standard, to high-strength materials for use in deep formations where fracture closure stresses exceed the ranges of sand capabilities. Fracturing treatments typically have varied in size from 500-galmini-hydraulic fracturing treatments for controlled, short, precise fracture lengths to deeply penetrating massive hydraulic fracturing (MHF) penetrating massive hydraulic fracturing (MHF) treatments that now range up to 1 million gal of fracturing fluid and more than 3 million lbm of propping agent. Over thepast decade MHF treatments propping agent. Over the past decade MHF treatments have played a significant role in developing tight (i.e., low-permeability) gasformations. To date, the only proved economical development method for tightproved economical development method for tight reservoirs has been from MHF treatments. The design difficulties and high cost of MHF have promoted a strong awareness of the need to enhance our fracture design and treatment capabilities. This discussion focuses primarily on fractures thatare oriented more orless in the vertical plane, andpropagate out ward in opposite directions from a wellbore--i.e., vertical fractures. Other types (e.g., horizontal fractures) constitute a relatively low percentage of the situations experience dto date. Part 1 percentage of the situations experienced to date. Part 1 includes economics and optimization, general design aspects, potential reservoir response, fracture propagation simulation, and some rock mechanics propagation simulation, and some rock mechanics aspects of fracture propagation. Part 2 (to appear next month) covers fracturing materials (fluids, propping agents, etc.) and field methods to obtain data applicable to predicting and analyzing fracturing behavior. Fracture design still involves a considerable amount of "judgment" engineering. After more than 30 years of fracturing experience and research, our abilities to determine in-situ fracture shapes, dimensions (lengths, widths, heights, etc.), symmetry about the wellbore, a zimuths, and fracture conductivities are still not highly developed. JPT P. 677