The Effect of a Short Term Shut-In on a Subsequent Pressure Build-Up Test on an Oil Well
- Robert G. Nisle (Phillips Petroleum Co.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- August 1956
- Document Type
- Journal Paper
- 67 - 68
- 1956. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
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In conducting a pressure build-up test on an oil well, it is often necessary to shut-in the well for a short time prior to initiation of the test. The effect of such a short term shut-in on the resulting pressure build-up curve is derived. The derivation is based on the Kelvin point-source solution and is a straight forward extension of the fundamental theory.
The magnitude of the effect is evaluated and illustrated by an example. It is shown that if the production subsequent to the short term shut-in is at least 10 times the duration of the shut-in, the effect will be less than 10 per cent.
It often happens that before a pressure build-up test can be made an additional valve must be mounted on the wellhead, or on arrival at the well, it might be learned that the well had been shut-in several hours the previous day because of a shortage of tankage. In such cases the question is "How will such an interruption of production affect the results of a pressure buildup test?" This work explains how to take account of such a short term shut-in in order that the test can proceed without further delay.
The solution presented here makes use of the Kelvin point-source solution used by Horner in his treatment of the pressure build-up in wells. Use is also made of the super-position theorem.
The well is assumed to have been in production at a constant rate for a relatively long time (several days or more). It is then shut-in for a short time, after which it is again placed in production at the previous constant rate. It continues to produce at this rate until shut-in for a pressure build-up test.
The Kelvin point-source solution is expressed by Eq. 1.
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