Apparatus and method for providing a fluid sample in a well

Abstract

Apparatus and a method are provided for bringing a well-fluid sample in a well through a sampling device which is in fluid communication with the apparatus. The apparatus includes: a dump chamber for receiving the well-fluid sample; a first hydraulic piston arranged in a first cylinder housing; a second hydraulic piston arranged in a second cylinder housing; a piston rod for mechanically connecting the first piston to the second piston to form a piston arrangement, the dump chamber being defined by the first piston and a portion of the first cylinder housing. The apparatus further includes at least one holding device arranged to switch between an active position, in which the piston arrangement is held fixed against movement, and an inactive position, in which the piston arrangement is allowed a movement relative to the cylinder housings.

What is claimed is: 
     
         1 . An apparatus for bringing a well-fluid sample in a well through a sampling device which is in fluid communication with the apparatus, the apparatus comprising:
 a dump chamber for receiving the well-fluid sample;   a first hydraulic piston arranged in a first cylinder housing;   a second hydraulic piston arranged in a second cylinder housing;   a piston rod for mechanically connecting the first piston to the second piston to form a piston arrangement, characterized in that the dump chamber is defined by the first piston and a portion of the first cylinder housing, and that the apparatus further comprises at least one holding device which is arranged to switch between an active position, in which the piston arrangement is held fixed against movement, and an inactive position, in which the piston arrangement is allowed a movement relative to the cylinder housings, said movement of the piston arrangement being brought about by means of a well fluid which, in a position of application, is in fluid communication with the second hydraulic piston so that the movement brings about an increase in a volume of the dump chamber when the holding device is in its inactive position.   
     
     
         2 . The apparatus according to  claim 1 , wherein the area of a piston face of the first piston is larger than the area of the piston face of the second piston. 
     
     
         3 . The apparatus according to  claim 1 , wherein the first cylinder housing is provided with an end plug, wherein the end plug, a piston face of the first piston and a portion of the first cylinder housing define a first cylinder-housing chamber which is arranged to accommodate a pressurized fluid, and wherein the holding device is a valve arranged for selectively bleeding off the pressurized fluid. 
     
     
         4 . The apparatus according to  claim 1 , wherein the second piston is in continuous fluid communication with the well fluid when the apparatus is in its position of application. 
     
     
         5 . The apparatus according to  claim 1 , wherein the area of a piston face of the first piston is smaller than the area of the piston face of the second piston. 
     
     
         6 . The apparatus according to  claim 5 , wherein the second cylinder housing is provided with an end plug, wherein the end plug, the piston face of the second piston and a portion of the second cylinder housing define a second cylinder-housing chamber which is provided with the holding device in the form of a valve which, in its active position, shuts off fluid communication of well fluid into the second cylinder-housing chamber and, in its inactive position, allows fluid communication of well fluid into the second cylinder-housing chamber. 
     
     
         7 . The apparatus according to  claim 1 , wherein the piston rod has a cross-sectional area which is smaller than the area of a piston face of the first piston and the area of a piston face of the second piston, and wherein a chamber wall with an opening complementarily adapted to the piston rod provides a partition between the dump chamber and a partition-wall chamber defined by a portion of the piston rod, the second cylinder housing and the second piston. 
     
     
         8 . The apparatus according to  claim 7 , wherein at least the first cylinder housing is provided with an end plug, wherein the end plug, the piston face of the first piston and a portion of the first cylinder housing define a first cylinder-housing chamber which is arranged to accommodate a pressurized fluid, and wherein the holding device is a valve arranged for selectively bleeding off the pressurized fluid, the valve, in its active position, shutting off fluid communication of the pressurized fluid out of the first cylinder-housing chamber and, in its inactive position, allowing fluid communication of the pressurized fluid out of the first cylinder-housing chamber, and wherein a pressure in the partition-wall chamber is lower than atmospheric pressure at least when a volume in the dump chamber is at a minimum. 
     
     
         9 . The apparatus according to  claim 8 , wherein a second cylinder-housing chamber defined by the second piston face and the second cylinder housing is arranged to receive the well fluid. 
     
     
         10 . The apparatus according to  claim 9 , wherein the second cylinder housing is provided with an end plug which is provided with a holding device in the form of a valve to control the inflow of well fluid into the second cylinder-housing chamber, the valve, in its active position, shutting off fluid communication of well fluid into the second cylinder-housing chamber and, in its inactive position, allowing fluid communication of well fluid into the second cylinder-housing chamber. 
     
     
         11 . A system for collecting a well sample from a well, comprising:
 a sampling device comprising a measuring device provided with at least one sensor; and   an apparatus configured to bring a well-fluid sample in a well through the sampling device, wherein the sampling device is in fluid communication with the apparatus, and wherein the apparatus comprises:
 a dump chamber for receiving the well-fluid sample; 
 a first hydraulic piston arranged in a first cylinder housing; 
 a second hydraulic piston arranged in a second cylinder housing; 
 a piston rod for mechanically connecting the first piston to the second piston to form a piston arrangement, characterized in that the dump chamber is defined by the first piston and a portion of the first cylinder housing, and that the apparatus further comprises at least one holding device which is arranged to switch between an active position, in which the piston arrangement is held fixed against movement, and an inactive position, in which the piston arrangement is allowed a movement relative to the cylinder housings, said movement of the piston arrangement being brought about by means of a well fluid which, in a position of application, is in fluid communication with the second hydraulic piston so that the movement brings about an increase in a volume of the dump chamber when the holding device is in its inactive position. 
   
     
     
         12 . The system according to  claim 11 , wherein the sensor includes a chromatograph selected from the group of a gas chromatograph, a liquid chromatograph and an ion chromatograph, or a combination thereof. 
     
     
         13 . The system according to  claim 11 , wherein the sampling device comprises a tracer sample chamber which, by means of valves, is arranged to isolate a fluid sample which is drawn from the well by means of the dump chamber, and wherein the sampling device, the valves and a fluid line upstream of the tracer sample chamber is provided with an internal surface which consists of a material which is substantially non-reactive in relation to substances carried from the well into the tracer sample chamber, so that trace elements that are carried into the tracer sample chamber can be brought out of the tracer sample chamber when the well-fluid sample is analysed. 
     
     
         14 . The system according to  claim 11 , wherein the measuring device is placed upstream of the tracer sample chamber, and wherein the tracer sample chamber is arranged to be isolated from the measuring device and the dump chamber by means of valves. 
     
     
         15 . The system according to  claim 14 , wherein the tracer sample chamber includes a portion of a fluid line extending between an outlet portion of the sampling device and the dump chamber. 
     
     
         16 . The apparatus according to  claim 1 , wherein the holding device is a releasable mechanical holding device which, in its active position, is configured to lock the piston arrangement in an initial position in which the volume of the dump chamber is at a minimum. 
     
     
         17 . A method of bringing a well-fluid sample through a sampling device ( 3 ) in a well, comprising:
 providing an apparatus configured to bring the well-fluid sample in the well through the sampling device, wherein the sampling device is in fluid communication with the apparatus, and wherein the apparatus comprises:
 a dump chamber for receiving the well-fluid sample; 
 a first hydraulic piston arranged in a first cylinder housing; 
 a second hydraulic piston arranged in a second cylinder housing; 
 a piston rod for mechanically connecting the first piston to the second piston to form a piston arrangement, characterized in that the dump chamber is defined by the first piston and a portion of the first cylinder housing, and that the apparatus further comprises at least one holding device which is arranged to switch between an active position, in which the piston arrangement is held fixed against movement, and an inactive position, in which the piston arrangement is allowed a movement relative to the cylinder housings, said movement of the piston arrangement being brought about by means of a well fluid which, in a position of application, is in fluid communication with the second hydraulic piston so that the movement brings about an increase in a volume of the dump chamber when the holding device is in its inactive position; 
   arranging the dump chamber with a smallest possible volume and then activating the holding device of the apparatus;   bringing the apparatus together with the sampling device to a desired location in the well; and   initiating movement of the piston arrangement by deactivating the at least one holding device so that a well fluid sets the piston arrangement in motion in order thereby to increase the volume of the dump chamber and suck the well-fluid sample through the sampling device.   
     
     
         18 . The method according to  claim 17 , wherein the method further comprises stopping the movement of the piston arrangement by reactivating the holding device comprising a valve, so that well fluid is no longer sucked via the sampling device and into the dump chamber. 
     
     
         19 . The method according to any one of  claim 17 , wherein the movement of the piston arrangement is facilitated by means of a fluid in a partition-wall chamber, the fluid having a pressure which is lower than atmospheric pressure at least when the volume of the dump chamber is at a minimum. 
     
     
         20 . The method according to  claim 17 , wherein the dump chamber is arranged with the smallest possible volume before the apparatus is run into the well.