Inflow Performance Relationship

Abstract

Whenever a well is drilled and completed, it is expected to flow naturally via the wellbore to the surface, a relationship known as inflow and outflow. The inflow performance relationship (IPR) is often required for estimating well capacity, designing well completion, designing tubing string, optimizing well production, performing nodal analysis calculations, and designing artificial lift etc. This performance is commonly defined in terms of a plot of surface production rate versus bottomhole flowing pressure on a cartesian coordinate. The maximum flow rate that occurs when the bottomhole flowing pressure is zero and the maximum rate corresponding to this pressure is called the absolute open flow (AOF). In this chapter, several mathematical models for estimating the inflow performance relationship (IPR) are presented with solved example questions. Also, a case study of an improvement in IPR curve of well K35 to evaluate the efficacy of a pre and post stimulation job is also presented. Result indicates that; it is very important to determine the type of skin on each well. This help in knowing the type of solution to the problem of a well in order to increase its productivity. Thus, a well whose skin is due to completion, partial penetration or slanting of well does not require stimulation and if the field’s operators go ahead to stimulate, they will only end up wasting time and money without achieving any result because these types of skin cannot be removed by stimulation.

Exercises

Ex 9.1 :

An oil well is flowing at a rate of 420 STB/day under steady state conditions. The wellbore flowing pressure is 2750 psia. The reservoir thickness is 28 f. and permeability of 62 mD. The wellbore and reservoir radii are 0.325 f. and 700 f. respectively. A result from well test conducted on the well shows that it was damaged with skin of 2.87. PVT report gave the oil FVF as 1.356 bbl/STB and oil viscosity of 2.108 cp. Calculate:

• The reservoir pressure

• The absolute open flow potential

• The productivity index

Ex 9.2 :

The following reservoir and flow-test data are available on an oil well:

Average reservoir pressure	3560 psia
Bubble point pressure	2600 psia
Flow bottom hole pressure from flow test	2930 psia
Flow rate from flow test	300 STB/day

Generate the IPR data of the well.

Ex 9.3 :

An oil well is producing from an undersaturated reservoir that is characterized by a bubble-point pressure of 2500 psig. The current average reservoir pressure is 3750 psig. Available flow test data show that the well produced 379 STB/day at a stabilized Pwf of 3050 psig. Construct the current IPR data by using:

• Vogel’s correlation

• Wiggins’ method

• Klins and Majcher method

• Standing method