Wells – Submerged well – Testing
Reexamination Certificate
2000-04-10
2002-08-20
Tsay, Frank (Department: 3672)
Wells
Submerged well
Testing
C166S351000
Reexamination Certificate
active
06435279
ABSTRACT:
BACKGROUND TO THE INVENTION
This invention relates to a method and apparatus for sampling fluids from a wellbore, and in particular to a method and apparatus used to recover a quantity of production fluids such as produced oil, gas and/or water from the wellhead of an underwater well.
Wells for hydrocarbons and other valuable fluids are normally drilled in a cluster with a number of wellbores having their surface wellheads grouped together. The wellbore may diverge away from each other the deeper they become. The wellheads in a group of wells are typically connected to a manifold or other subsea structure via conduits, and the hydrocarbons recovered from each individual well are conveyed along the conduits to the manifold where they usually co-mingle before flowing along a single main pipeline to the production platform. The quality and quantity of the fluids produced from each well may vary; for example, one wellbore may produce production fluids that are rich in crude oil and relatively free from produced water and corrosive gasses such as H
2
S, whereas a neighbouring well drilled to a different depth in the same formation may produce more water, or may have a high content of noxious and corrosive gasses; such a well would be less economically productive and may have higher maintenance costs. Furthermore, different wells tied back to the same manifold may be owned and/or operated by different operators. It is therefore useful to know the quantity and quality of wellbore fluids that are produced from each respective wellbore before they are mixed in the manifold or main pipeline leading from the manifold to the production platform, so that the relative benefits and liabilities of the respective wells can be calculated.
Traditionally this has been done by sampling the fluids produced at each respective wellbore by providing separate sampling conduits or lines that run parallel to (and usually along the outside of) the conduits between the respective wellbores and the manifold, and from there along the main pipeline back to the production platform, where they can be analysed and graded. Separate sampling lines are of course needed for each wellbore, and this causes several problems in that the additional small bore lines often become blocked by viscous fluids and cuttings, or damaged by corrosive agents like H
2
S, and to address this several lines are normally installed for each wellhead all the way back to the platform, so that backup lines can be brought into operation if the main sampling line for a particular wellhead fails or becomes blocked. This is very expensive and the infrastructure of the extra lines needs to be installed at the beginning of the life of a well, but is seen as the only solution to the problems of being able to sample continuously throughout the life of the well.
SUMMARY OF THE INVENTION
According to the present invention there is provided a method for sampling a fluid from a wellbore, the method comprising
a vehicle having a drive means for moving the vehicle, a collecting device for collecting a sample of the fluid and a storage facility for the collected fluid;
using the collecting device to recover a sample of the fluid to the vehicle's storage facility at a first location on a subsea structure;
storing the sample in the storage facility of the vehicle; and
carrying the sample in the vehicle's storage facility to a second location.
The present invention also provides a sampling device for collecting samples of fluid produced from a subsea wellbore, the sampling device having;
a drive means for moving the sampling device, a collection device for collecting a sample of fluid and a storage container for holding the collected fluid.
The first location is typically a wellhead but can be other positions of a well such as a wellbore, pipeline from the wellhead, side-track manifold, or main pipeline, storage tank or gravity base structure. The first position typically has a collection port to mate with the collection apparatus. The second position can be onshore, underwater or on a platform or ship such as a remotely operated vehicle or “ROV”.
Preferably the vehicle is an ROV. Preferably the storage tank and collection device are housed on a frame or skid attached to the ROV. Typically the collecting device comprises at least one sampling bottle, but two or more can be provided.
Typically the vehicle is adapted to interface with the wellhead at the first position, and can be provided with a collecting and sampling probe for insertion into e.g. an aperture on the wellhead. The probe can be connected to the storage tanks or bottles etc by means of conduits. Typically production fluids are extracted via the male/female connection between the probe and the aperture. The collecting device can be arranged to collect and discard a portion of the fluids being sampled, and typically recovers an initial sample of fluid from the collection port of the wellhead to a first sampling bottle. This is done because the fluid lying in the collection port of the wellhead may be static and may not represent a true sample of the fluid flowing through the wellhead. Therefore, the first sample of fluid from the collection port of the wellhead is drawn off to a first sampling bottle and can be kept separate from later samples. Any number of later samples e.g. 3-10 can be taken from the fluid flowing through the wellhead, depending on the number of sampling bottles or partitions in the collection tank that are available. Typically a waste tank is provided at the second position into which the initial samples of static fluid can be discarded.
Typically the vehicle has an array of valves which can be activated independently of each other. Typically different configuration of the valves will direct liquid into each sampling bottle as required. Typically the sampling bottles each contain a piston. Normally a pressure gauge is connected to each sampling bottle. Normally a piston indicator is provided so the position of the piston can be determined from a remote position outside the bottle. Typically the piston indicator moves with the piston, but it may be an electronic indicator that is monitored elsewhere on the ROV or remote from it. Typically the piston indicator is a rod which extends from the piston outside the bottle. Typically the sampling bottles are connected to the male connector via a hose of e.g. {fraction (1/4+L )}″ diameter. The sampling bottles, valves and hose are typically designed to operate in pressure of up to 230 barg and at temperatures of −50 to 130° C.
During transportation of the ROV prior to use, the sampling apparatus is typically filled with a liquid. Preferably the liquid is bio-degradable. Typically the liquid is a mixture of water and glycol.
Typically the liquid is contained in the sampling bottles when the vehicle dives. Typically the liquid is expelled from a second end of the sampling apparatus as fluid is recovered from the wellhead. Preferably a control means such as a throttle is provided on the second end of the sampling apparatus to control the rate of expulsion of the liquid. This typically controls the rate of introduction of the fluid from the wellhead into the first end of the sampling apparatus, typically via the piston.
When production fluids have been extracted from the first wellhead the vehicle typically disengages the probe from the collection port on the wellhead and moves (in ROV terminology it “flies”) to the second position. The second position can typically be an offshore platform, a ship or an inshore facility. The vehicle typically docks at the second position where the sample(s) collected may be removed by e.g. removing the sampling bottles and replacing them with empty bottles. Typically only the second and subsequent sampling bottles are replaced. Typically the fluid(s) contained in the second or further sampling bottle is analysed for fluid chemistry.
In several important embodiments of the invention the collection device has several separate containers such as bottles for collecting samples and the v
Howe David Charles
Robb Kevin Fraser
Halliburton Energy Service,s Inc.
Tsay Frank
LandOfFree
Method and apparatus for sampling fluids from a wellbore does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for sampling fluids from a wellbore, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for sampling fluids from a wellbore will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2905919