Test Method8212;The pulse test method is used to determine the transmissivity and storativity of low-permeability formations surrounding the packed-off intervals. This test method is considerably shorter in duration than the pump and slug tests used in more permeable rocks. To obtain results to the desired accuracy, pump and slug tests in low-permeability formations are too time consuming, as indicated in Fig. 1 (from Bredehoeft and Papadopulos (1)).
Analysis8212;The transient pressure data obtained using the suggested method are evaluated by the curve-matching technique described by Bredehoeft and Papadopulos (1), or by an analytical technique proposed by Wang et al (2). The latter is particularly useful for interpreting pulse tests when only the early-time transient pressure decay data are available.
Units:
Conversions8212;The permeability of a formation is often expressed in terms of the unit darcy. A porous medium has a permeability of 1 darcy when a fluid of viscosity 1 cP (1 mPax00B7;s) flows through it at a rate of 1 cm3/s (10x2212;6 m 3/s)/1 cm2 (10x2212;4 m2) cross-sectional area at a pressure differential of 1 atm (101.4 kPa)/1 cm (10 mm) of length. One darcy corresponds to 0.987 x03BC;m2. For water as the flowing fluid at 20x00B0;C, a hydraulic conductivity of 9.66 x03BC;m/s corresponds to a permeability of 1 darcy.
Viscosity of Water8212;Table 1 shows the viscosity of water as a function of temperature.
Temperature, x00B0;C | Absolute Viscosity, mPax00B7;s |
---|---|
0 | 1.79 |
2 | 1.67 |
4 | 1.57 |
6 | 1.47 |
8 | 1.39 |
10 | 1.31 |
12 | 1.24 |
14 | 1.17 |
16 | 1.11 |
18 | 1.06 |
20 | 1.00 |
22 | 0.96 |
24 | 0.91 |
26 | 0.87 |
28 | 0.84 |
30 | 0.80 |