Apparatus and method for controlling well fluid sample pressure
AssigneeBaker Hughes Incorporated
InventorPaul Andrew Reinhardt
Life of this patent
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Abstract
An apparatus and method for maintaining the pressure of a well fluid sample as the sample is transported to the well surface from a downhole wellbore location. The invention collects a formation fluid sample under pressure. The fluid sample is further pressurized with a traveling piston powered by the hydrostatic wellbore pressure. The pressurized formation fluid sample is contained under high pressure within a fixed volume chamber for retrieval to the well surface. Multiple collection tanks can be lowered into the wellbore during the same run to sample different zones with minimal rig time. The tanks can be emptied at the well surface with an evacuation pressure so that the fluid sample pressure is maintained above a selected pressure at all times.
Claims35
An apparatus for controlling pressure on a pressurized sample of formation fluid collected downhole in a well, comprising:
- a housing having a hollow interior;
- a piston within said housing interior for defining a fluid sample chamber, wherein said piston is moveable within said housing interior to selectively change said fluid sample chamber volume;
- a pump for delivering a sample volume of formation fluid into said fluid sample chamber by displacement of said piston in a first direction;
- and,
- a valve that is operatively responsive to movement of said piston in said first direction for admitting pressurized wellbore fluid against said piston to bias movement of said piston in a second direction wherein said second direction piston movement pressurizes the fluid sample within said fluid sample chamber so that the formation fluid sample remains pressurized when the fluid sample is moved to the well surface.
An apparatus for controlling pressure on a pressurized formation fluid sample collected downhole in a well, comprising:
- a housing having a hollow interior;
- a piston within said housing interior for defining a fluid sample chamber, wherein said piston is moveable within said housing interior to selectively change said fluid sample chamber volume, and wherein said piston comprises an outer sleeve and an inner sleeve moveable relative to said outer sleeve;
- a pump for introducing a formation fluid sample under pressure into said fluid sample chamber;
- retainer means for securing a displaced position of said piston outer sleeve relative to said housing;
- and,
- a valve for selectively admitting pressurized wellbore fluid against said piston to displace said piston inner sleeve relative to said piston outer sleeve so that formation fluid in said fluid sample chamber is compressed.
A method for controlling pressure on a pressurized formation fluid sample from a wellbore, comprising:
- lowering a housing into the wellbore, wherein said housing has a piston within a hollow interior of said housing which is moveable to define a fluid sample chamber;
- pumping formation fluid into said fluid sample chamber to collect a formation fluid sample;
- operating a valve to introduce wellbore fluid at a downhole hydrostatic pressure into contact with said piston to move said piston for pressurizing the formation fluid sample within said fluid sample chamber;
- retaining the formation fluid sample within said fluid sample chamber as said piston moves to compress the well fluid sample within said fluid sample chamber;
- locking said piston relative to said housing to fix the volume of the formation well fluid sample within said fluid sample chamber when the well fluid reaches a selected pressure above the downhole hydrostatic pressure;
- and,
- withdrawing said housing from said wellbore.
A process for transferring a sample of earth formation fluid from a downhole production depth to a wellbore surface, said process comprising:
- (a) lowering a unitized assembly of downhole tools into a wellbore, said assembly including a formation fluid extraction tool, a formation fluid sample retrieval tank and a surface controlled pump for selectively charging said sample retrieval tank with formation fluid;
- (b) positioning said fluid extraction tool at a first wellbore depth;
- (c) extracting formation fluid at said first wellbore depth;
- (d) charging a first sample volume in said sample retrieval tank with a corresponding volume of the first depth formation fluid;
- (e) applying in situ wellbore pressure to an element of said sample retrieval tank to reduce the first sample volume of said first sample tank to a second sample volume less than said first sample volume without displacement of fluid from said sample retrieval tank whereby the first sample volume of first depth formation fluid is compressed to a pressure substantially greater than said in situ wellbore pressure;
- (f) structurally securing said second sample volume;
- and,
- (g) retrieving the downhole tool assembly to the wellbore surface.
A process for extracting a sample of earth formation fluid comprising:
- (a) preparing a sample retrieval tank with a variable volume sample chamber;
- (b) placing said sample retrieval tank in a wellbore;
- (c) filling, in situ, a first volume of said sample chamber with a first volume of formation fluid;
- (d) applying in situ wellbore pressure against a structural component of said sample retrieval tank to reduce said sample chamber to a second volume less than said first volume without displacement of fluid from said sample chamber whereby said formation fluid therein is compressed to a pressure substantially greater than said in situ wellbore pressure;
- (e) securing the second volume position of said structural component;
- and,
- (f) removing said sample retrieval tank from said wellbore.
An apparatus for retrieving a sample of earth formation fluid from a wellbore comprising:
- (a) a cylinder having a moveable piston therein to define a variable volume sample chamber, said piston having relatively moveable first and second pressure bearing elements, each of said pressure bearing elements having respective sample chamber pressure bearing areas and wellbore pressure bearing areas wherein the wellbore pressure bearing area of said second pressure bearing element is greater than the sample chamber pressure bearing area of said second pressure bearing element;
- (b) a pump for extracting fluid from an earth formation and for discharge of said fluid through a transfer conduit into said sample chamber;
- (c) a first valve in said transfer conduit for preventing fluid flow reversal from said sample chamber;
- and,
- (d) a second valve for admitting wellbore fluid against the wellbore pressure area of said second pressure bearing element, said second valve being positioned on said first pressure bearing element and operable by arrival of said first pressure bearing element at a position corresponding to a maximum sample chamber volume.
Dependencies are inferred from the claim text.