INTRODUCTION

From the reservoir engineering standpoint, a horizontal wellbore is considered as an infinite-conductivity fracture, i.e., the pressure drop along the well length is very small and is negligible. Thus, the horizontal well represents a long wellbore where well pressure throughout the wellbore is constant. In practice, some pressure drop from the tip of the horizontal wellbore to the producing end is essential to maintain fluid flow within the wellbore. Consequently, the producing end of the horizontal well will be at a lower pressure than the other tip (see Fig. 10-1). Nevertheless, from an engineering standpoint, the question to be addressed is, What is the expected pressure drop along the well length? What is the magnitude of wellbore pressure drop, ? p, as compared to the pressure drop from the reservoir to the wellbore, . If the horizontal wellbore pressure drop is very small as compared to the pressure drawdown from the reservoir to the wellbore, then for all practical purposes, a horizontal well can be considered as an infinite-conductivity wellbore, i.e., a wellbore at a constant pressure. In contrast, if the pressure drop through the wellbore is significant as compared to the reservoir drawdown, then reservoir drawdown along the well length would change, and therefore, production along the well length would also change. To calculate the changing production rate along the well length, one will have to simultaneously solve pressure drop along the pipe equations with reservoir flow equations as shown in Figure 10-2.

Figure 10-1: A Schematic...