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

Distinguished Author Series articles are general, descriptiverepresentations that summarize the state of the art in an area of technology bydescribing recent developments for readers who are not specialists in thetopics discussed. Written by individuals recognized as experts in the area,these articles provide key references to more definitive work and presentspecific details only to illustrate the technology. Purpose: to informthe general readership of recent advances in various areas of petroleumengineering.

Introduction

Hydraulic fracturing has made a significant contribution to the petroleumindustry as a method for enhancing oil and gas producing rates and recoverablereserves. Fracturing was introduced to the industry in 1949. Since then it hasevolved into a standard operating practice, and more than 800,000 treatmentshave been performed. About 35 to 40% of all currently drilled wells arehydraulically fractured, and about 25 to 30% of total U.S. oil reserves havebeen 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 increasedsignificantly. A host of fracturing fluids have been developed for reservoirsranging from shallow, low-temperature formations to those that are deep andhot. Many different types of proppants have been developed. These range fromproppants have been developed. These range from silica sand, the standard, tohigh-strength materials for use in deep formations where fracture closurestresses exceed the ranges of sand capabilities.

Fracturing treatments typically have varied in size from 500-galmini-hydraulic fracturing treatments for controlled, short, precise fracturelengths to deeply penetrating massive hydraulic fracturing (MHF) penetratingmassive hydraulic fracturing (MHF) treatments that now range up to 1 milliongal of fracturing fluid and more than 3 million lbm of propping agent. Over thepast decade MHF treatments propping agent. Over the past decade MHF treatmentshave 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 MHFtreatments. The design difficulties and high cost of MHF have promoted a strongawareness of the need to enhance our fracture design and treatmentcapabilities.

This discussion focuses primarily on fractures that (1) are oriented more orless in the vertical plane, and (2) propagate outward in opposite directionsfrom a wellbore--i.e., vertical fractures. Other types (e.g., horizontalfractures) constitute a relatively low percentage of the situations experiencedto date. Part 1 percentage of the situations experienced to date. Part 1includes economics and optimization, general design aspects, potentialreservoir response, fracture propagation simulation, and some rock mechanicspropagation simulation, and some rock mechanics aspects of fracturepropagation. Part 2 (to appear next month) covers fracturing materials (fluids,propping agents, etc.) and field methods to obtain data applicable topredicting 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, azimuths, and fractureconductivities are still not highly developed.

JPT

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