New Advances in Production Data Analysis of Hydraulically Fractured Tight Reservoirs

Abstract

Tight reservoirs stimulated by multistage hydraulic fracturing are commonly described by a dual porosity model. This model consists of homogeneous matrix blocks separated by vertical hydraulic fractures. This paper hypothesizes that the production data of some fractured horizontal wells may also be described by a triple porosity model. The third medium can be either reactivated natural fractures or thin horizontal beds with a higher permeability. We test this hypothesis by extending the existing triple porosity models to develop an analytical procedure for determining the reservoir parameters. We derive the simplified equations for different regions of the rate-time plot including linear and bilinear flow regions. These equations can be used to calculate the effective fracture half-length, matrix permeability and length of micro-fractures. We use the proposed model to analyze the production data of two wells drilled in Barnett shale. The results show that a dual porosity model is more appropriate for describing Barnett shale data. Even if the micro-fractures are present they are not inter-connected and the length scale is much smaller than the hydraulic fracture spacing. The second part of this paper focuses on analyzing production data of tight oil reservoirs. We plot rate-normalized pressure (RNP) versus material balance time (MBT) of two wells drilled in Cardium and Bakken formations. We observe a half-slope followed by a unit-slope in both cases. This paper hypothesizes that the half slope reflects the linear transient flow regime, and the unit slope reflects the linear pseudosteady state (PSS) flow. We test this hypothesis by developing a new model for pseudo steady state flow when pressure interference occurs between two adjacent hydraulic fractures. We determine the reservoir properties by both PSS and transient analysis methods. For Cardium well, both methods give very close results. For Bakken well, both methods give relatively close results. We conclude that analyzing the late time production data of tight oil wells complement the linear transient analysis and can be used to calculate the stimulated reservoir volume, which can eventually help the industry to optimize the fracturing operation.

A New Model to Predict Productivity of Multiple-Fractured Horizontal Well in Naturally Fractured Reservoirs

“…Analytical flow models such as triple-linear model [1,2] and ternary-porosity model [3] were built to simulate productivity of fractured horizontal well. But these models are limited in application [17,18]; the triple-linear model is not accurate if the regions beyond the well tips control the well performance; the triporosity model could not simulate the properties of natural fractures very well.…”

Integration of Numerical Simulations for Uncertainty Analysis of Transient Flow Responses in Heterogeneous Tight Reservoirs

“…Analytical models such as Bello (2009) or Siddiqui et al (2012) can be used to derive estimates of the system parameters pertinent to a dualporosity or triple-porosity system, respectively. Analytical models such as Bello (2009) or Siddiqui et al (2012) can be used to derive estimates of the system parameters pertinent to a dualporosity or triple-porosity system, respectively.…”

“…Many authors have also proposed simplified analysis equations that can be used to estimate various system parameters such as hydraulic fracture half-length and fracturematrix contact area (Bello, 2009;Szymczak et al, 2012;Siddiqui et al, 2012). Many authors have also proposed simplified analysis equations that can be used to estimate various system parameters such as hydraulic fracture half-length and fracturematrix contact area (Bello, 2009;Szymczak et al, 2012;Siddiqui et al, 2012).…”

Volumetric Source Model to Predict Productivity of Fractured Horizontal Well in Naturally Fractured Reservoirs

“…Methods to predict the productivity of fractured horizontal wells become invaluable tools to optimize the hydraulic fracturing and determine productivity of horizontal wells. While main analytical [1][2][3][4] and semi-analytical models [5][6][7][8] are ignoring the direct flow to horizontal well, which fitted to hydraulic fractured casedhole horizontal wells. But, for hydraulic fractured open-hole horizontal wells, ignoring the flow to horizontal well will cause tremendous error, especially at early time [9][10][11][12][13].…”