Chapter 5 - Pressure Buildup Analysis Techniques for Oil Wells

Abstract

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 a 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. In this chapter, ideal, actual buildup tests, and buildup tests in infinite-acting reservoirs and in developed (finite) reservoirs are discussed. Multiphase buildup tests and the variable-flow-rate test analysis are also covered in detail. This chapter treats pressure buildup test analysis and presents methods for estimating formation characteristics such as the reservoir permeability, skin factor, wellbore damage, and improvement evaluation, including average pressure for well drainage areas and the entire reservoir. In addition, analysis methods for after flow-dominated pressure buildup data are presented to identify a linear flow, near-wellbore permeability changes or boundaries using both accurate pressure and total after flow fluid rate.