Understanding the Muskat Method of Analysing Pressure Build-up Curves
- V.C. Larson (Imperial Oil Ltd.)
- Document ID
- Petroleum Society of Canada
- Journal of Canadian Petroleum Technology
- Publication Date
- September 1963
- Document Type
- Journal Paper
- 136 - 141
- 1963. Petroleum Society of Canada
- 5.6 Formation Evaluation & Management
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- 440 since 2007
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The somewhat neglected Muskat method is an excellent way to obtain staticpressure from build-up curves. A re-examination of the technique, accountingmore rigorously for fluid compressibility, shows why the early part of theMuskat pressure plot actually curves upward, so that it sometimes seems to giveunsatisfactory results. A straight line, indicating a correct static - pressureguess, should be expected only for later data; however, the time at which theline stops curving can be estimated simply. The study also revealed thatreservoir transmissibility and expansibility can be obtained from the plot.Three other methods of estimating static pressure from build-up curves arecompared to the Muskat method. They are less precise because they either do notaccount adequately for compressibility or they need more accurate reservoirinformation than is usually available.
The Muskat method of analysing build-up curves seems to have been neglectedin favour of other methods. This paper should renew confidence in the Muskatmethod in that it provides a new theoretical basis for its use, adds to itsscope, shows why and when it will sometimes fail and compares it with someother techniques.
Applied to wells in a uniform, bounded system, the Muskat method is shown togive static pressure with very good resolution and without the need for priorknowledge of any reservoir parameters; however, the plot behaves as a straightline only for the later build-up data. A modification to the method permitsdetermining drainage-area transmissibility and expansibility from the plot.
The Basic Muskat Method
In 1937 Muskat published a method for finding static pressure from abuild-up curve.
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