Transient-Pressure Analysis of a Well With an Inclined Hydraulic Fracture Using Type Curve Matching

Abstract

Hydraulic fracturing is an important well stimulation technique that has been widely used in the oil and gas industry. Most of the pressure transient analysis techniques to analyze pressure responses of fractured wells are based on the assumption that the fracture is either vertical or horizontal. However, a hydraulic fracture could be inclined with a non-zero angle with respect to the vertical direction. Field studies have shown that most hydraulic fractures are never perfectly vertical. Thus, for an inclined hydraulic fracture, the vertical orientation assumption may lead to erroneous results in well test analysis especially when the inclination angle is significant. However, there are very few studies concerning pressure transient analysis of inclined hydraulic fracture and there is no applicable well test analysis procedure available for inclined fractures. For this reason, it is important to develop well test analysis procedures for this type of fracture. The purpose of this study is to develop a technique, based on the pressure derivative concept, for interpreting pressure transient tests in wells with an inclined hydraulic fracture. Detailed analysis of unsteady-state pressure behavior of fully penetrating inclined fracture in an infinite slab reservoir was provided. Both uniform flux and infinite conductivity models were considered. The study has shown that inclined fracture pressure data exhibit similar flow regimes as for vertical fracture counterpart. Those flow regimes are linear and pseudo-radial flow for both uniform flux and infinite conductivity models. However, for infinite conductivity model, a bi-radial flow regime is also observed. In the case of high formation thickness to fracture half length ratio and high angle of inclination, both uniform flux and infinite conductivity inclined fracture model exhibit an additional flow regime called early radial flow. Both bi-radial flow and early radial flow regimes for inclined hydraulic fracture have not been mentioned in the literature before. A type curve matching technique was developed in this study using both pressure and pressure derivative curves. This type curve matching procedures can be used to obtain the following parameters: half fracture length, inclination angle, formation permeability and the pseudo-skin factor. The results should be verified with other pressure plots such as semi-log plot of ?P vs. t and ?P vs. t 1/2 plot. A set of type curves with associated data was also provided for uniform flux and infinite conductivity inclined fracture models. Detailed explanations, tables, figures and numerical examples are included in this paper. Introduction Hydraulic fracturing technique involves creation of fracture or fracture system in porous medium to overcome wellbore damage, to improve oil and gas productivity in low permeability reservoirs or to increase production in secondary recovery operations. In this study, a new type curve matching procedure, based on the pressure derivative concept, was developed for interpreting pressure transient tests in a well with an inclined hydraulic fracture. A general literature review on inclined hydraulic fracture will be provided. Both uniform flux and infinite conductivity models will be discussed in this paper. Only the case where the fracture is symmetric in both lateral and horizontal directions was considered in this study. Analytical solution for each flow regime is explained in details. The calculation procedure and analytical model verification are illustrated using numerical examples.

Revising Transient-Pressure Solution for Vertical Well Intersected by a Partially Penetrating Fracture with Non-Darcy Flow Effect

“…The PFVF behaves like a FFVF during this period, as shown in Figure 6(c). The characteristic of this flow behavior is very similar to the compound linear flow for multistage-fractured horizontal well presented by Chen and Raghavan [4] and fractured inclined well presented by Dinh and Tiab [10], which is identified 9 Geofluids by an approximated 1/2-slope straight line on log-log plot of pressure derivative.…”

“…If the axis is in the vertical or horizontal direction, the created fracture would be horizontal or vertical, respectively; otherwise, the fracture would be inclined [1]. In addition to those time-consuming numerical simulations, numerous works using various analytical or semianalytical methods have been published for study the flow behavior of vertical fracture [2][3][4][5], horizontal fracture [6][7][8], and inclined fracture [9][10][11][12][13]. These solutions serve as a theoretical basis of the pressure-transient and rate-transient analysis for hydraulically fractured well.…”

Transient Pressure Analysis of Wells Intercepted by Partially Penetrating Finite Conductivity Hydraulic Fractures

“…Daneshy [6], Wright et al [7] investigated inclined fractures theoretically and experimentally. Anh et al [8] presented a method for interpreting pressure transient tests in wells with an inclined hydraulic fracture, considering the inclined fracture with a non-zero angle with respect to vertical direction.…”