Reservoir Permeability Determination Using After-Closure Period Analysis of Calibration Tests

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractHydraulic fracturing has generally been limited to relatively low-permeability reservoirs. In recent years, the use of hydraulic fracturing has expanded significantly to high permeability reservoirs. The objectives of fracturing low permeability reservoirs and high permeability reservoirs are different and defined by reservoir parameters.The estimation of reservoir permeability, a variable of great importance in hydraulic fracturing design is frequently unknown because candidate wells either do not flow or a pretreatment pressure transient test is required. Consequently, Nolte has introduced a new method for adding after-closure fracturing analysis to the pretreatment calibration testing sequence that defines fracture geometry and fluid loss characteristics. The exhibition of the radial flow is ensured by conducting a specialized calibration test called mini-fall test. The derivations by Nolte, based on the theory of impulse test and principle of superposition, allow the identification of radial flow and thus the determination of reservoir transmissibility and reservoir pressure.This study presents a review of the after-closure radial flow analysis. A modified method is proposed to complete the Nolte's method for the determination of the reservoir transmissibility and reservoir pressure based on the pressure derivative.The application of the modified method is demonstrated on actual field data from calibration tests performed on several oil and gas wells. The reservoir parameters determined with this method are verified by comparison with results obtained from buildup tests.

Unconventional gas reservoir evaluation: What do we have to consider?

“…Estimates of permeability are critical to assess the effectiveness of the stimulation, post-treatment. Numerous papers have tested and validated this technology in the field (Ramurthy et al, 2002;Chipperfield and Britt, 2000;Nolte, 1997;Gulrajani et al, 1998;Talley et al, 1999;Benelkaldi, 2001). Strengths and weaknesses of the DFIT technique are listed below: Strengths DFITs have an advantage over more conventional testing methods in terms of cost.…”

After-Closure Analysis To Identify Naturally Fractured Reservoirs

“…ACA Approach. Several papers have been written to determine the best methods of field implementation and the most efficient ACA analysis (Chipperfield and Britt 2000;Gulrajani et al 1998;Talley et al 1999;Benelkaldi 2001). The method used in this paper is the Nolte Diagnostic Plot (NDP) (Nolte and Economides eds.…”

Global Model for Fracture Falloff Analysis

“…After-closure analysis (ACA) following a fracture calibration test offers a workable mechanism for permeability estimation in very low permeability reservoirs. Benelkadi and Tiab (2001) and Benelkadi et al (2003) criticized Nolte's approach and the difficulties associated in the identification of after-closure linear flow regime and pseudo-radial, and provided a slightly modified approach, still based on Nolte's specialized plot, where the additional use of pressure derivative with respect to squared values of the dimensionless F-function was found to be more suitable for proper characterization of linear flow and pseudo-radial flow regimes and determination of reservoir permeability and extrapolated reservoir pressure. Gu et al (1993) presented an ACA method based on the notion of "impulse fracture", consisting of a small volume of fluid injected in order to generate a short fracture and a shut-in period afterwards to record pressure falloff.…”