Changes

==Capillary test procedure==

==Capillary test procedure==

In a mercury capillary pressure test, a rock with a measured [[porosity]] is immersed in a mercury pressure cell. The pressure in the cell is raised to a predetermined pressure level (P1, figure below). When the cell comes to equilibrium, the volume of injected mercury is measured (V2). Since the porosity of the test sample is known prior to the test, the volume of injected mercury can be converted to the percent of the total pore volume filled with mercury (for example, 10% at [[pressure::10 psi]] for point M1). All the pores filled with mercury at this point in the test have at least one 10μ pore throat radius or larger and represent 10% of the sample's pore volume. This procedure is repeated several more times at different pressures (for example, points M2 through M5).

 

 

In a mercury capillary pressure test, a rock with a measured [[porosity]] is immersed in a mercury pressure cell. The pressure in the cell is raised to a predetermined pressure level (P1, [[:file:predicting-reservoir-system-quality-and-performance_fig9-11.png|Figure 1]]). When the cell comes to equilibrium, the volume of injected mercury is measured (V2). Since the porosity of the test sample is known prior to the test, the volume of injected mercury can be converted to the percent of the total pore volume filled with mercury (for example, 10% at [[pressure::10 psi]] for point M1). All the pores filled with mercury at this point in the test have at least one 10μ pore throat radius or larger and represent 10% of the sample's pore volume. This procedure is repeated several more times at different pressures (for example, points M2 through M5).

==Pore throat profiles==

==Pore throat profiles==

[[file:predicting-reservoir-system-quality-and-performance_fig9-12.png|thumb|{{figure number|2}}Curve drawn through the points in Figure 1.]]

 

[[file:predicting-reservoir-system-quality-and-performance_fig9-12.png|thumb|{{figure number|2}}See text for explanation.]]

A curve is drawn through the measured points at test completion. This capillary pressure curve also represents a pore throat size profile for the tested sample. It relates a given pore throat size to its capillary resistance (P_c). [[:file:predicting-reservoir-system-quality-and-performance_fig9-12.png|Figure 1]] shows the curve drawn through the points in [[:file:predicting-reservoir-system-quality-and-performance_fig9-11.png|Figure 1]].

A curve is drawn through the measured points at test completion. This capillary pressure curve also represents a pore throat size profile for the tested sample. It relates a given pore throat size to its capillary resistance (P_c). [[:file:predicting-reservoir-system-quality-and-performance_fig9-12.png|Figure 1]] shows the curve drawn through the points in [[:file:predicting-reservoir-system-quality-and-performance_fig9-11.png|Figure 1]].

==Example==

==Example==

Using the curve in the diagram below, if S_w = 20% (point 1), then the mercury capillary pressure (P_c) that must be overcome to enter pore throats at that point on the curve is [[pressure::200 psi]] (point 2). Converting mercury P_c to hydrocarbon column height (''h''):

 

 

Using the curve in [[:file:predicting-reservoir-system-quality-and-performance_fig9-13.png|Figure 3]], if S_w = 20% (point 1), then the mercury capillary pressure (P_c) that must be overcome to enter pore throats at that point on the curve is [[pressure::200 psi]] (point 2). Converting mercury P_c to hydrocarbon column height (''h''):

:<math>\mbox{h}  = 200 \mbox{ psi} \times 0.7 = 140 \mbox{ ft of oil column}</math>

:<math>\mbox{h}  = 200 \mbox{ psi} \times 0.7 = 140 \mbox{ ft of oil column}</math>

The minimum pore throat radius entered when S_w is 20% and P_c is [[pressure::200 psi]] is 0.5μ.

The minimum pore throat radius entered when S_w is 20% and P_c is [[pressure::200 psi]] is 0.5μ.

==See also==

==See also==