Transient Pressure Analysis for Fractured Wells
- Heber Cinco-Ley (Stanford U.) | Fernando Samaniego-V. (Inst. Mexicano del Petroleo)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- September 1981
- Document Type
- Journal Paper
- 1,749 - 1,766
- 1981. Society of Petroleum Engineers
- 4.3.4 Scale, 5.6.3 Pressure Transient Testing, 5.6.4 Drillstem/Well Testing, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation
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A new technique is presented for analyzing pressure transient data for wells intercepted by a finite-conductivity vertical fracture. This method is based on the bilinear flow theory, which considers transient linear flow in both fracture and formation. It is demonstrated that a graph of p vs. t 1/4 produces a straight line whose slope is inversely proportional to h (k b )1/2 . New type curves are presented that overcome the uniqueness problem exhibited by other type curves.
A large amount of information concerning well test analysis has appeared in the literature over the last three decades. As a result of developments in this area, three monographs and one book have been published covering different aspects of pressure transient analysis. Ramey also has presented a review on the state of the art. The analysis of pressure data for fractured wells has deserved special attention because of the number of wells that have been stimulated by hydraulic fracturing techniques. A summary of the work done on flow toward fractured wells' was presented by Raghavan' in 1977. It was recognized early that intercepting fractures can strongly affect the transient flow behavior of a well and that, consequently, the application of classical methods to the analysis of transient pressure data in this situation may produce erroneous pressure data in this situation may produce erroneous results. Several methods were proposed to solve this problem. These analysis techniques consider a well intersected by either an infinite-conductivity vertical fracture or a uniform-flux vertical fracture. Cinco-Ley et al. demonstrated that the assumption of infinite fracture conductivity is valid whenever the dimensionless fracture conductivity (k b /kx ) >300; all other cases, such as those represented by long or poorly conductive fractures, must be analyzed by considering a finite-conductivity fracture model. Exploitation of low-permeability gas reserves has required stimulation of wells by massive hydraulic fracturing (MHF) techniques. Vertical fractures of large horizontal extension are created as a result of this operation; consequently, pressure drop along the fracture cannot be neglected. Several papers have been published on the behavior of finite-conductivity vertical fractures. Type-curve matching has been proposed as an analysis method under these conditions; however, some regions of the curves present a uniqueness problem in the analysis. Barker and Ramey problem in the analysis. Barker and Ramey indicated that the use of published type curves becomes practical when a large span of pressure data is practical when a large span of pressure data is available. The purpose of this work is to present a new interpretation technique for early-time pressure data for a well intercepted by a finite-conductivity vertical fracture, including the criteria to determine the end of wellbore storage effects. In addition, new type curves are discussed to overcome the uniqueness problem exhibited by previous curves at intermediate problem exhibited by previous curves at intermediate and large time values.
Transient Pressure Behavior for Fractured Wells
Consider a vertically fractured well producing at a constant flow rate, q, in an infinite, isotropic, homogeneous, horizontal reservoir that contains a slightly compressible fluid of constant compressibility c, and viscosity mu. The porous medium has a permeability k, porosity phi, thickness h, and initial pressure p .
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