Method and apparatus for balanced pressure sampling
First Claim
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1. A method of sampling reservoir fluid from a rock formation penetrated by a borehole, comprising:
- positioning a downhole tool having a flow line in the borehole;
establishing an inlet port through which fluid passes from a first point in the formation into the flow line;
establishing an outlet port through which fluid passes from the flow line into a second point in the formation;
passing fluid between the formation and the flow line through the inlet and outlet ports until the fluid in the flow line is of sufficient quality to be sampled; and
after the fluid in the flow line is of sufficient quality to be sampled, pumping the fluid in the flow line into a fluid chamber in the downhole tool;
wherein pumping the fluid comprises exposing a first side of a movable barrier disposed in the fluid chamber to fluid pressure at the inlet port and exposing a second side of the movable barrier to fluid pressure at the outlet port.
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Abstract
A method of sampling fluid from a rock formation penetrated by a borehole includes positioning a downhole tool having a flow line in the borehole, establishing an inlet port through which fluid passes from a first point in the formation into the flow line, establishing an outlet port through which fluid passes from the flow line into a second point in the formation, and passing fluid between the formation and the flow line through the inlet and outlet ports.
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Citations
14 Claims
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1. A method of sampling reservoir fluid from a rock formation penetrated by a borehole, comprising:
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positioning a downhole tool having a flow line in the borehole; establishing an inlet port through which fluid passes from a first point in the formation into the flow line; establishing an outlet port through which fluid passes from the flow line into a second point in the formation; passing fluid between the formation and the flow line through the inlet and outlet ports until the fluid in the flow line is of sufficient quality to be sampled; and after the fluid in the flow line is of sufficient quality to be sampled, pumping the fluid in the flow line into a fluid chamber in the downhole tool; wherein pumping the fluid comprises exposing a first side of a movable barrier disposed in the fluid chamber to fluid pressure at the inlet port and exposing a second side of the movable barrier to fluid pressure at the outlet port. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A formation evaluation tool for positioning in a borehole penetrating a subterranean formation, comprising:
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a tool body having at least one flow line; a plurality of fluid communicating devices coupled to the tool body, the fluid communicating devices comprising an inlet device which provides an inlet port through which fluid passes directly from a first point in the formation into the flow line and an outlet device which provides an outlet port through which fluid passes directly from the flow line into a second point in the formation; a fluid chamber disposed in the tool body for collecting fluid from the flow line, wherein the fluid chamber comprises a movable barrier disposed therein and wherein a first side of the movable barrier is in selective communication with the inlet port, and wherein a second side of the movable barrier is in selective communication with the outlet port; and a pump positioned in the flow line to pump fluid from the flow line into the fluid chamber and to draw fluid out of the fluid chamber. - View Dependent Claims (10, 11, 12, 13)
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14. A formation evaluation tool for positioning in a borehole penetrating a subterranean formation, comprising:
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a tool body having at least one flow line; a plurality of fluid communicating devices coupled to the tool body, the fluid communicating devices comprising an inlet device which provides an inlet port through which fluid passes directly from a first point in the formation into the flow line and an outlet device which provides an outlet port through which fluid passes directly from the flow line into a second point in the formation; a fluid chamber disposed in the tool body for collecting fluid from the flow line, wherein the fluid chamber comprises a movable barrier disposed therein and wherein a first side of the movable barrier is in selective communication with the inlet port, and wherein a second side of the movable barrier is in selective communication with the outlet port; and a pump positioned in the flow line to pump fluid from the flow line into the fluid chamber and to draw fluid out of the fluid chamber; wherein a separation distance is maintained between the inlet and outlet devices such that interaction between fluid at the first and second points of the formation as a result of passing fluid between the formation and the flow line is minimized; wherein the inlet and outlet devices are arranged in diametrically opposing relation on the tool body; and wherein the fluid communicating devices are selected from the group consisting of single probes, dual probes, probes having multiple ports, and packers.
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Specification