Page 240 - Introduction to Petroleum Engineering

12

TRANSIENT WELL TESTING

Transient well tests measure changes in reservoir pressure associated with changes in
well rates. Measurement and analysis of the time‐dependent pressure response can
provide information about reservoir structure and the expected flow performance of
the reservoir. Transient well tests often motivate changes in the way the well is oper-
ated or the field is managed. This chapter discusses a selection of transient well tests
for oil wells and gas wells and illustrates how transient well test information is used.

12.1 PRESSURE TRANSIENT TESTING

Pressure transient testing (PTT) is a widely used method for obtaining information
about the reservoir far from the well. The PTT method relies on measuring the
changes in pressure at the wellbore as a function of time that accompany fluid flow
rate changes in the wellbore. Changes in pressure are known as pressure transients.
For example, the flow rate at a production or injection well can be increased or
decreased. Pressure gauges measure the resulting pressure changes as a function of
time. Plots of pressure and a time derivative of pressure as functions of time are
prepared. The interpretation of these plots gives information about fluid flow through
different parts of the reservoir.
A pressure transient test can be used to estimate flow capacity (permeability times
thickness) at the well, average reservoir pressure in the drainage area of the well, the
distance to reservoir boundaries and faults from the well, and formation damage in

Introduction to Petroleum Engineering, First Edition. John R. Fanchi and Richard L. Christiansen.
© 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/Fanchi/IntroPetroleumEngineering