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Sunday, August 24, 2014

Pressure Transient Analysis

Pressure Transient Analysis (PTA) is simply the measurements the change of Bottom Hole Pressure (BHP) of a well as it is opened or closed. 

In a production well,  as flow-valves is opened and fluids starts to flow, BHP decreases. Measurements of pressure drop in such a well is called "Pressure Draw-Down Test". On the other hand, when the well is closed, BHP increases. Measurements of building up of pressure of such a well is called "Pressure Build-Up Test".

In an injection well, as injection starts BHP increases. Measurements of pressure building up in such a well is called "Pressure Build-Up (Injection) Test". On the other hand, when the well is closed, injection stops and BHP decreases. Measurements of pressure fall in such a well is called "Pressure/Injection Fall-Off Test".


The event of closing or opening of a well creates an impulse in the reservoir. The pressure wave propagates into the reservoir and if a boundary is found, it reflects backs just like a stone dropped in a water body does. Thus, the fluctuations in pressure carries many important information of the boundary as well as the reservoir itself.
Figure-1: A depiction of pressure wave spreading from the well and bouncing back from a fault providing estimates of the distance of the fault from the well location.

3 comments:

  1. Sir, there probably is some typing error. The first test you mentioned about should be pressure drawdown test (not Pressure Fall Off test, which is done in a water injector after it is shut in).

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    1. Sr, I think this article was right. In injection well, when we shut in well, we measure the change of pressure vs time, it's called Fall Off test. Perhaps you're confusing.

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