A Comprehensive Comparative Study on Analytical PI/IPR Correlations

Abstract Inflow performance is one of the significant components to quantify the reservoir's capability to produce hydrocarbon. There are two commonly-used quantities to represent reservoir inflow performance: productivity index (PI) and inflow performance relationship (IPR). Both relate fluid flow rate to pressure difference between bottomhole and reservoir. Much effort has been made on developing the PI or IPR solutions suitable for specific circumstances since Darcy proposed the simple and useful Darcy's law in 1856. As a consequence, various correlations for PI or IPR calculation have been proposed from simple analytical solutions to rigorous numerical formulations in the literature. As horizontal or multilateral wells have been occupying an ever-increasing share of hydrocarbon production since the 1980s, more accurate PI or IPR estimation has been emerging as an important issue in the petroleum industry.11 The correlations become more and more complicated and rigorous in order to accurately describe inflow performance for complex well geometries. They can provide a better prediction or estimation of inflow performance, though they would be costly and computationally demanding. On the other side, researchers have been tried to simplify the complex solutions into analytical forms through extensive case studies. These provide a useful tool for the researchers and engineers to make quick estimations although they are confined to limited conditions. In this paper, analytical correlations of PI and IPR from a comprehensive literature survey are reviewed. They have been categorized by well deviation, fluid phases and time dependence. The well deviation is divided into vertical (less than 15°), slanted (15 to 60°), highly-deviated/horizontal (60 to 90°), and multilateral wells; while fluid phases are categorized into single oil, single gas, and oil flow in two phases. For time dependence, steady state and pseudo-steady state have been considered, however the transient state has been excluded. In addition, case studies for the specific input parameters have been conducted to show the effective range, trends, and limitations of correlations as well as to provide the selection guideline for an appropriate estimation of inflow performance. All correlations of PI and IPR have been organized in the table for quick reference.