Using screened pads to filter unconsolidated formation samples
A fluid-sampling system that includes a downhole tool string with a fluid-sampling tool coupled thereto, and a fluid sampling probe coupled to the tool via a probe extension arm, the fluid sampling probe having an oval pad that contacts a borehole wall, one or more fluid inlets which receive a formation fluid, and a plurality of screens between the borehole wall and the one or more fluid inlets which filter the formation fluid. The fluid-sampling system further including one or more offset arms coupled to the tool which contact the borehole wall.
1. A fluid-sampling system, comprising:
a downhole tool string with a fluid-sampling tool coupled thereto;
a fluid sampling probe coupled to the tool via a probe extension arm, the fluid sampling probe having a pad that contacts a borehole wall, one or more fluid inlets which receive a formation fluid, and a plurality of screens between the borehole wall and the one or more fluid inlets which filter the formation fluid, the plurality of screens having a major surface portion configured to align with the borehole wall and an angled standoff portion coupled thereto and extending into a hole in the fluid sampling probe, wherein the standoff portion creates a cavity between the plurality of screens and the one or more fluid inlets, the plurality of screens creating a cross flow effect in the cavity to increase the ability for the formation fluid to reach the one or more fluid inlets; and
one or more offset arms coupled to the tool which contact the borehole wall.
2. The fluid-sampling system of claim 1 , wherein the downhole tool string further comprises a downhole pump which draws the formation fluid from the formation via the one or more fluid inlets.
3. The fluid-sampling system of claim 1 , wherein the downhole tool string further comprises a fluid analyzer which receives and analyzes the formation fluid via the one or more fluid inlets.
4. The fluid-sampling system of claim 1 , wherein the downhole tool string further comprises a fluid storage chamber which receives and stores the formation fluid via the one or more fluid inlets.
5. A method of sampling a formation fluid, comprising:
deploying a fluid sampling tool having a fluid-sampling probe downhole;
pressing a pad of the fluid-sampling probe against a borehole wall;
drawing a formation fluid from a formation with one or more inlets of the fluid-sampling probe; and
filtering particulates from the formation fluid with a plurality of screens arranged between the borehole wall and the one or more inlets, the plurality of screens having a major surface portion configured to align with the borehole wall and an angled standoff portion coupled thereto and extending into a hole in the fluid sampling probe, wherein the standoff portion creates a cavity between the plurality of screens and the one or more inlets, the plurality of screens creating a cross flow effect in the cavity to increase the ability for the formation fluid to reach the one or more inlets.
6. The method of claim 5 , wherein pressing the pad against the borehole wall further comprises extending a probe extension arm.
7. The method of claim 6 , further comprising extending a tool extension arm to assist pressing the pad against the borehole wall, the tool extension arm being coupled to the fluid sampling tool.
8. The method of claim 5 , further comprising dispersing the formation fluid within a fluid cavity with the plurality of screens.
9. The method of claim 5 , wherein pressing the pad against the borehole wall forms a seal.
10. The method of claim 5 , wherein filtering particulates further comprises filtering a first size particulate prior to filtering a second size particulate, wherein the first size is larger than the second size.
11. The method of claim 5 , further comprising dissipating the particulates with a chemical coupled to the plurality of screens.
12. The method of claim 11 , wherein the dissipating the particulates occurs prior to filtering the particulates.
13. A fluid-sampling probe, comprising:
a pad that contacts a borehole wall, the pad having a recessed area;
a body carrying the pad and defining one or more inlets that receive a formation fluid; and
a plurality of screens between the borehole wall and the one or more inlets which filter particulates from the formation fluid, the plurality of screens having a major surface portion configured to align with the borehole wall and an angled standoff portion coupled thereto and extending into a hole in the fluid sampling probe, wherein the standoff portion creates a cavity between the plurality of screens and the one or more inlets, the plurality of screens creating a cross flow effect in the cavity to increase the ability for the formation fluid to reach the one or more inlets.
14. The fluid-sampling probe of claim 13 , wherein the pad is oval shaped.
15. The fluid-sampling probe of claim 13 , wherein the pad is circularly shaped.
16. The fluid-sampling probe of claim 13 , wherein the pad contacting the borehole wall forms a seal.
17. The fluid-sampling probe of claim 13 , wherein multiple of the plurality of screens have different screen sizes.
18. The fluid-sampling probe of claim 17 , wherein the largest screen size is arranged closest to the borehole wall and screen sizes decrease with the smallest screen size being furthest from the borehole wall.
19. The fluid-sampling probe of claim 17 , wherein the plurality of screens are of a size ranging from 1000 microns to 1400 microns.
20. The fluid-sampling probe of claim 13 , wherein the screens are mounted to the probe using one of the group of spot welding or friction fitting or screwing or bolting.
21. The fluid-sampling tool of claim 13 , further comprising a chemical coating coupled to the plurality of screens.
22. The fluid-sampling probe of claim 21 , wherein the chemical coating is one of polylactic acid or glycolic acid.