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Abstract

Virtually all studies on transient pressure behavior of fractured gas wells assumed a single fracture of equal half-length emanating from the opposite sides of the wellbore. However, multiple fractures may result from explosive, tailored-pulse fracturing, and hydraulic fracturing treatments. This paper presents the results of using a polar-coordinate simulator to investigate the transient pressure behavior of gas wells with 4-wing, 6-wing, and 8-wing multiple fractures.

Results show that the dimensionless pressure, PwD, can be correlated with the dimensionless terms where C r is the dimensionless fracture conductivity and x fr12 is the fracture half-length ratio. The symbols, x fl and x f2, represent the half-length of the primary fracture and the auxiliary fracture, respectively. Results also show that when Cr less than 10, multiple fracture transient pressure behavior is significantly different from that of a single-plane fracture.

A family of type curves was constructed using cross-plots of p wD vs. tDxf. Transient pressure data can be analyzed using these type curves to estimate the number of multiple fractures in addition to formation permeability, fracture length, and fracture conductivity. Errors of about 5% in fracture length and 28% in formation permeability could result from the use of single-fracture type curves.

Introduction

Economic evaluation of low-permeability gas reservoirs requires reliable estimate of fracture characteristics and formation permeability. Numerous methods have been proposed to determine these parameters from transient pressure data.

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