5.1 Introduction

Pressure buildup testing is the most familiar transient well-testing technique, which has been used extensively in the petroleum industry. Basically, the test is conducted by producing a well at constant rate for some time, shutting the well in (usually at the surface), allowing the pressure to build up in the wellbore, and recording the down-hole pressure in the wellbore as a function of time. From these data, it is possible to estimate the formation permeability and current drainage area pressure, and to characterize damage or stimulation and reservoir heterogeneity or boundaries frequently.

Knowledge of surface and subsurface mechanical conditions is important in buildup test data interpretation. Therefore it is recommended that testing and casing sizes, well depth, packer condition, etc., be determined before data interpretation starts. Usually, short-time pressure observations are necessary for the complete delineation of wellbore storage effects. Data may be needed at intervals as short as 15 seconds for the first few minutes of some buildup tests. As the test progresses, the data collection interval can be expended.

In this chapter we will discuss ideal, actual buildup tests, buildup tests in infinite-acting reservoirs and in developed (finite) reservoirs; we will also discuss multiphase buildup tests and the variable-flow-rate test analysis.