Abstract

Drilling horizontal wells to accelerate production and increase recovery efficiency of oil and gas has now become common. With the increasing number of wells, transient well tests have been conducted in many wells with different geological settings. In this paper, we present a number of analytical models for horizontal wells with multiple fractures in homogeneous and laterally composite reservoirs. These solutions are applicable to finite-conductivity transverse fractures, and infinite-conductivity transverse and longitudinal fractures. They may also be used for the fractured reservoirs where the wellbore intersects with multiple fractures.

We examine the pressure behavior of horizontal wells with single and multiple fractures in homogeneous systems. It is shown that the wellbore cannot be neglected in the modeling of horizontal wells with fractures unless the fracture conductivity is high. If the fracture permeability (conductivity) variations in different zones are moderate, compared to the formation permeability, the multiple fractures have almost no effect on the pressure behavior of the system; the horizontal well dominates the system's pressure behavior. If the conductivities are high, the intersected fractures will dominate the behavior of the system at early times. It is also shown that multiple finite- and infinite-conductivity transverse fractures may exhibit multiple linear flow regimes before the onset of the first horizontal well radial now regime.

Introduction

Fractures and fissures are common features of many well-known reservoirs and have been of great interest in reservoir engineering. For instance, since the early sixties many studies for the pressure and production behavior of natural and hydraulic fractures have been conducted (see Earlougher1).

There are only a few studies of horizontal wells with fractures. After the Karcher et al.2 steady state solutions, Soliman, Hunt, and El Rabaa3 were the first to study the behavior of a horizontal well with a single fracture; they presented a very simple model that was a solution for a finite-conductivity disk in a one-dimensional infinite slab, where the presence of the well was disregarded. Recently, Guo and Evans4 presented a two-dimensional solution for a horizontal well with multiple fractures. Their solution was for multiple infinite-conductivity and -extent fractures with finite widths in a two-dimensional infinite medium. During the final stage of this work, three other papers on the horizontal well with multiple fractures have just appeared in the literature.5,6,7

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