CROSS-REFERENCE TO RELATED APPLI CATI ONS

[0001] This application claims benefi t of U.S. provisional patent application Serial No. 61/384,806 fi led September 21 , 2010, and entitled "Low Cut Water Sampler," which is hereby incorporated herein by reference in its entirety.

STATEM ENT REGARDI NG FEDERALLY SPONSORED RESEARCH OR DEVELOPM ENT

[0002] Not applicable.

BACKGROUND

Field of the Invention

[0003] This invention relates generally to the produclion of hydrocarbons from an earthen formation. - More particularly, the invention relates to a method and system for sampling a low water-cut hydrocarbon stream.

Backtiround of the Technolouv

[0004] In hydrocarbon production operations, water may be produced along with the hydrocarbons. ^" Hi e water is typically intermixed with, or in suspension with crude oil, gas, or other hydrocarbon fluids, but does not form a solution with the hydrocarbon fluids. In general, the percentage of water mixed with hydrocarbons produced from hydrocarbon producing wells, also referred to as the "water cut," is greater than 10% (by volume). However, some wells produce a very low water cut stream of hydrocarbons. Separation of the water and hydrocarbons in such low cut production streams is typically more dilTicult as compared to high cut production streams.

[0005] Sampling and analysis of the water produced from a well serves several purposes. For example, during production, the well may be treated with certain compounds to improve production or to prevent certain adverse conditions. Such treatments may include injection of water containing surfactants or polymers. In addition, these treatments may include anticorrosion treatments (corrosion inhibitor added), or treatments to prevent the formation of hydrates or deposition of paraffi ns or salts. These treatments facilitate transport of the fluid to the surface and/or prevent oil deposits. The relative volumes of the physical and/or chemical characteristics of these treatments in water or other fluids can vary considerably as a function of time. One way to monitor and adjust such treatments is to sample and analyze the produced water to determine the quantities and characteristics of the additives in the water. The water characteristics analyzed and evaluated typically include without limitation, resistivity, density, pH, conductivity, bicarbonate alkalinity, and quantitative elemental analysis. Water samples can also be used to analyze the source of the fluids produced for multi-zonal completion wel ls. This in formation may be used in reservoir development and depletion plann ing.

[0006] One conventional method for sampling water from a produced hydrocarbon stream is to take an isolated direct sample from the pipeline at a single point in time, separate the water, and then analyze the separated water. Thus, with this approach, conti nuous sampling and analysis of the produced water over time cannot be obtained without repeatedly taking discrete samples from the pipeline. Furthermore, in produced well fluids with low water cut, it is di ffi cult to separate the water and hydrocarbons.

[0007] Accordingly, there remains a need in the art for improved systems and methods for sampling water from a produced hydrocarbon stream. Such systems and methods would be particularly well-received i f they offered the potential for continuous sampling over time and could be employed wi th low water cut hydrocarbon streams.

BRI EF SUMMARY OK TH E DI SCLOSU RE

[0008] These and other needs in the art are addressed in one embodiment by an apparatus for sampling well production fluids. In an embodiment, the apparatus comprises a vessel having an inner chamber. In addition , the apparatus comprises a hydrocarbon fluids outlet conduit in fluid communication with the inner chamber. Further, the apparatus comprises a well fluids inlet conduit coaxially disposed within the hydrocarbon fluids outlet conduit and in fluid communication with the inner chamber. The well fluids inlet conduit has a fi rst portion extending from the vessel and a second portion extending into the inner chamber. The second portion of the well fluids in let conduit includes a plurality of openings con fi gured to direct the well production fluids radially outward from the well fluids inlet conduit. Still further, the apparatus compri ses a sample fluids outlet in fluid commun ication with the inner chamber.

These and other needs i n the art arc addressed in another embodiment by a method of sampling produced well fluids. I n an embodiment, the method comprises (a) continuously flowing produced well fluids lo a sampling device. The sampling device compri ses a vessel having an inn er chamber, a hydrocarbon fluids outlet conduit in fluid communication with the inner chamber, and a well fluids inlet conduit coaxially disposed within the hydrocarbon fluids outlet conduit and in fluid communication with the inner chamber. In addition, the method comprises (b) flowing the produced well fluids through the well fluids inlet conduit into the inner chamber of the vessel. Further, the method comprises (c) allowing a sample fluid i n the produced well fluids to separate from one or more hydrocarbon fluids in the produced well fluids to a lower portion of the inner chamber under the force of gravity. Sti ll further, the method comprises (d) withdrawing a sample of the sample fluid from the vessel through the sample fluids outlet.

[0009] These and other needs in the art are addressed in another embodiment by an apparatus for sampling well production fluids. In an embodiment, the apparatus comprises a vessel having an inner chamber. In addition, the apparatus compri ses a hydrocarbon fluids outlet conduit coupled to the vessel. Further, the apparatus comprises a well fluids inlet conduit extending coaxially through the hydrocarbon fluids outlet conduit into the i nner chamber. Still further, the apparatus comprises a sample fluids outlet positioned at a lower end of the vessel and in fluid communication with the inner chamber. Moreover, the apparatus comprises an annulus radially disposed between the hydrocarbon fluids outlet conduit and the well fluids inlet conduit. The annulus has an inlet end in fluid communication with the inner chamber.

[0010] The foregoing has outlined rather broadly the features and technical advantages of the invention i n order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modi fying or designing other structures for carrying out the same purposes of the invention. I t should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

[0011] Embodiments descri bed herein compri se a combination of features and advantages intended to address vari ous shortcomi ngs associated with certain pri or devices, systems, and methods. The various characteristics described above, as wel l as other features, will be readily apparent to those ski lled in the art upon reading the following detailed descri ption, and by referring lo the accompanyi ng drawings. BRI EF DESCRI PTI ON OF THE DRAWI NGS

[0012] For a detailed description of the preferred embodiments of the invention, reference wil l now be made to the accompanying drawings in which:

[0013] Figure 1 is a schematic view of an offshore installat ion including an embodiment of a low cut water sampler in accordance with the pri nciples described herein;

[ 0014] Figure 2 is a front view of the low cut water sampler of Figure 1 ;

[0015] Figure 3 is a front view of the low cut water sampler of Figure 1 being supplied produced well fluids and before oulputting separated hydrocarbon fluids or water; and

[0016] Figure 4 is an enlarged view of the lower end of (he inlet conduit of the low cut water sampler of Figure I being supplied produced wel l fluids and oulputting separated hydrocarbon fluid and water.

DETAI LED DESCRI PTI ON OF TH PREFERRED EMBODIMENTS

[0017] The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have braad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to thai embodiment.

[0018] Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not in tend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certai n features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

[0019] In the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to... ." Also, the term "couple" or "couples" is intended to mean cither an indirect or direct connection. Thus, i f a fi rst device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections. In addition, as used herein, the terms "axial" and "axially" generally mean along or parallel to a central axis (e.g., central axis of a body or a port), whi le the terms "radial" and "radially" generally mean perpendicular to the central axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radi al distance means a distance measured perpendicular to the central axis. As used herein, the phrase "low cut" refers to produced well fluids with less than about 10% water composition (by volume), and the phrase "high cut" refers to produced well fluids with greater than about 10% water composition (by volume).

[0020] Referring now Figure 1 , an offshore system 10 for producing a completed subterranean wellbore 1 1 is schematically shown. In this embodiment, system 10 includes an offshore platform 20 at the sea surface 12, a subsea production manifold 30 mounted to a wellhead 31 at the sea floor 13, and a production riser 40 extending from mani fold 30 to platform 20. In general, riser 40 is a large-di ameter pipe that connects mani fold 30 to the floating platform 20. During production operations, well fluids are produced through riser 40 to platform 20, where the produced fluids may be stored, processed, offloaded or combinations thereof. Casing 32 extends from wellhead 3 1 into subterranean wellbore 1 1 .

[0021] System 10 also includes a water sampling device 100 for sampling low cut well fluids produced through riser 40. As will be describe in more detail below, device 100 receives samples of produced well fluids from riser 40, separates the water from the produced well fluids, outputs the separated water for subsequent analysis, and outputs the balance of the produced well fluids (following separation of the water). The produced well fluids flowing through riser 40 typically comprise hydrocarbon fluids (e.g. liquid hydrocarbons such as crude oil and/or hydrocarbon gases such as natural gas) and water. Thus, the balance or remainder of the produced well fluids after separation of the water in device 100 is predominantly hydrocarbon fluids, it being understood that such fluids may include small quantities of water, solids (e.g., sand), or other fluids. In Ihts- embodiment, a production sample conduit or flowline 50 supplies produced wellbore fluids from ri ser 40 to sampling device 100. Samples of the water in the produced well fluids i n riser 40 may be obtained continuously with device 100 via flowline 50 to determi ne the composition of the water therein . Although sampling device 100 is shown disposed on platform 20, device 100 may be disposed at any suitable offshore or onshore location. For examples, sample flowline 50 may extend from platform 20 to a different offshore or onshore location for sampling with device 100 and subsequent analysis of the separated water. [0022] Referring now to Figure 2, water sampling device 100 includes a produced well fluids inlet conduit 1 10, a separator containment vessel 120, a sample fluid outlet 130, a separated hydrocarbon fluids outlet conduit 140, and a hydrocarbon fluids outlet fi tting or coupling 150. Vessel 120 has an inner chamber 12 1 . In ti n ^' s embodiment, water is sampled and separated from the produced well fluids, and thus, sample fluid outlet 130 may also be referred to as a water outlet. Inlet conduit 1 10, water outlel 130, and hydrocarbon outlet condui t 140 are each in fluid communication with inner chamber 12 1. As will be described in more detail below, produced well fluids, designated with reference numeral 160, enter chamber 121 via inlet conduit 1 10; separated water samples, designated with reference numeral 161, may be taken from chamber 121 via outlet 130; and hydrocarbon fluids, designated with reference numeral 162 and resulting from the separation of water 161 from well fluids 160, exit chamber 12 1 via outlet conduit 140 and fi tting 1 50. Flowline 50 previously descri bed is coupled to inlet conduit 1 10, and thus, supplies produced well fluids to chamber 12 1 via inlet conduit 1 10.

[0023] In general, separator vessel 120 may be any suitable vessel or container compatible with potentially corrosive well fluids and capable of withstanding relatively high pressures. In particular, vessel 120 is preferably a containment vessel or tank designed and con fi gured to wi thstand pressures of at least about 285 psi, alternatively about 1 ,000 psi, alternati vely about 5,000 psi, alternatively about 10,000 psi, and alternatively about 20,000 psi. I n this embodiment, vessel 120 is an elongate upright generally cylindrical tan k having an upper end 120a and a lower end 120b opposite upper end 120a. Upper end 120a includes a port 122 and lower end 120b includes a port 123. Conduits 1 10, 140 extend through port 122 into inner chamber 121 , and water outlet 1 0 is in fluid commun ication with port 123. Although vessel 120 is a cylindrical upright vessel in this embodiment, in other embodiments the separator vessel (e.g., vessel 120) may have other suitable geometries such as rectangular, spheri cal, etc. In general, vessel 120 and inner chamber 121 may have any suitable volume. However, for embodiments described herein, vessel 120 is preferably sized such that chamber 121 has a volume between 1 liter and 4 liters.

[0024] Referri ng still to Figure 2 , as previously described, outlet conduit 140 extends through port 122 and is secured to vessel 120. For instance, conduit 140 may be positioned in port 122 and then welded to vessel 120. In this embodiment, outlet conduit 140 is a tubular having a central axis 1 45, a fi rst or upper end 140a disposed outside and above vessel 120, and a second or lower end 1 40b disposed within chamber 121 . As will be descri bed in more detail below, hydrocarbon fluids 162 flow from chamber 121 into end 140b, through conduit 140, and out end 140a into fi tting 150. Thus, lower end 140b may also be referred to as an inlet end, and upper end 140a may also be referred to as an outlet end.

[0025] Filling 1 50 is coupled to upper end 140a of conduit 140. In this embodiment, fi tting 150 is a tubular mani fold including a main bore or passage 15 1 , a fi rst lateral bore or passage 1 52 extending from main bore 15 1 , and a second lateral bore or passage 153 extendin g from main bore 151. Main bore 1 51 is coaxially aligned with outlet conduit 140 and has a fi rst or upper end 151 a distal conduit 140, and a second or lower end 15 1 b in fluid communication with conduit 140. As wi ll be described in more detail below, lower end 151 b receives hydrocarbon fluids 162 from chamber 12 1 via conduit 140, and thus, may also be refen ed to as hyilrocarbon fluids inlet end 1 51 b. Each lateral bore 152, 153 has an inlet end 1 52a, 153a, respectively, in fluid communication with main bore 1 51 between ends 1 51 a, b, and an outlet end 152b, 153b, respectively. In this embodiment, outlet end 152b is in fluid communication with a sensor 154. In general, sensor 154 may comprise any suitable type of sensor or gauge for monitoring one or more parameters of the fluids in chamber 122 such as pressure, temperature, flow rate, etc.

[0026] Referring still to Figure 2 , well fluids inlet conduit 1 10 extends through main bore 151 of fi tting 150 and outlet conduit 140 into vessel 120. In this embodiment, inlet conduit 1 10 is a tubular having a central axis 1 1 5, a fi rst or inlet end 1 10a extending from main bore 151 distal vessel 120, and a second or closed end 1 10b disposed in chamber 12 1. Conduit 1 10 is coaxially aligned with main bore 1 51 of fitting 1 50 and outlet conduit 140, and thus, central axes 1 15, 145 arc coincident. Conduit 1 10 is preferably positioned such that end 1 10b is disposed in the upper half of separator chamber 12 1.

[0027] The outer diameter of inlet conduit 1 10 is less than the inner diameter of main bore 151 and outlet conduit 140, and thus, an annulus 1 14 is radially positioned between inlet conduit 110 and fi tting 150, outlet conduit 1 40. Annulus 1 14 extends from end 140b of conduit 140 to upper end 151 a of main bore 151 . Thus, annulus 1 14 has a first or upper end 1 14a coincident with upper end 151 a of main bore 15 1 and a second or lower end 1 14b coinciden t with inlet end 140b of conduit 140. Annulus 1 14 is closed off and sealed at upper end 1 1 4a with a cap 1 16 that extends radially across main bore 151 from inlet conduit 1 10 lo fi tting 1 50. However, lower end 1 14b of annulus 1 14 is open lo chamber 120. Lateral bores 152, 153 are in fluid communication with annulus 1 14. As will be described in more detail below, hydrocarbon fluids 162 (low from chamber 12 1 into end 1 14b of ann ulus 1 14, through annulus 1 14, and out end 1 14a of annulus 1 14 into lateral bores 152, 153. Thus, lower end 1 14b may also be referred to as an inlet end.

[0028] Referri ng now to Figures 2 and 4, the portion of inlet conduit 1 10 extending into chamber 121 includes a plurality of through bores or open ings 1 12 proximal closed end 1 10b. Openings 1 12 extend radially through conduit 1 10 proximal end 1 10b and allow produced well fluids 160 flowing through conduit 1 10 to exit inlet conduit 1 10 in a radial fashion to minimize agitation and mixing of fluids within chamber 12 1. Accordingly, each opening 1 12 may be described as an outlet port. As best shown in Figure 4, in this embodiment, openings 1 12 arc arranged in a plurality of axially spaced rows 1 12a, b, c, d. Openings 1 12 within each row 1 12a, b, c, l are circumferentially spaced about conduit 1 10, and further, openings 1 12 in each row 1 12a, b, c, d are circumferentially offset or staggered relative to the openings 1 12 in the adjacent row(s) 1 12a, b, c, d. In this embodiment, each row 1 12a, b, c, d includes two openings 1 12 spaced 180° apart, with openings 1 12 in adjacent row s 1 12 a, b, c, d being circumferentially staggered 90° apart. However, in other embodiments, each row (e.g., each row 1 12a, b, c, d) may have more or less openings (e.g., openings 1 12) and/or the openings in each row may be circumferentially spaced by more or less than 180°. Although openings 1 12 are shown as circular holes in Figure 4, in general, openings 1 12 may have any suitable geometry (e.g., oval, rectangular, elliptical, etc.).

[0029] Referring again to Figure 2, water outlet 130 is coupled to vessel 120 and extends from port 123. In this embodiment, outlet 130 includes a valve 1 1 for selectively opening and closing outlet 130. More speci fi cally, valve 131 has a closed position restricting and/or preventing fluid flow through outlet 130, and an open position allowing fluid flow through outlet 130.

[0030] Referring now to Figures I and 2, duri ng production operations, produced well fluids 160 are supplied to inlet conduit 1 10 via production sample flowline 50. Fluids 1 60 flow through conduit 1 10 and radially outward through open ings 1 12 into chamber 12 1. As previously described, the radial ejection of the produced well fluids 160 from conduit 1 10 offers the potential to reduce and or prevent mixing and agitation of the separated water 161 and hydrocarbon fluids 162 within separator chamber 121 . As desired, produced well fluids 160 may be provided to vessel 120 continuously or on a periodic basis.

[0031 ] As best shown in Figure 2, without being limited by this or any particular theory, due to the difference in densities and the immiscibility between water 161 and hydrocarbon fluids 1 62 in produced well fluids 160, any water 161 in the produced well fluids 160 begins to migrate or settle to the bottom of separator chamber 12 1 and the hydrocarbon fluids 162 move to the upper portion of chamber 121 . fn other words, gravity naturally drives the separation of the heavier water 161 from the lighter hydrocarbon fluids 162.

[0032] Moving now to Figure 3, as produced well fluids 160 are supplied to chamber 121 and water 161 separates from hydrocarbon fluids 162, the level of hydrocarbon fluids 162 in chamber 12 1 begins to ri se. ^" When the level of hydrocarbon fluids 162 in chamber 121 is suffi cient, the hydrocarbon fluids in the upper portion of chamber 121 exit chamber 121 through an nulus 1 14. The pressure and/or flow of produced hydrocarbon fluids 160 in condui t 1 10 into chamber 121 prevents hydrocarbon fluids 162 from backflowing into conduit 1 10 via openings 1 12. However, hydrocarbon fluids 162 are free to flow through i nlet end 1 14b and annulus 1 14 to outlets 152b, 153b. Outlet 152b supplies hydrocarbon fluids 162 to sensor 154. Outlet 153b may be connected to a flowline or conduit that may direct the separated hydrocarbon fluids to any desired location (e.g., back into the produced well fluids downstream of conduit 50). Cap 1 16 prevents hydrocarbon fluids 162 from exiting annulus 1 1 4 at upper end 1 14a. Separated water 161 in the lower portion of chamber 121 may be drawn off through outlet 130 for testing by opening valve 131 . Initially, and between sampling of water 161 within chamber 12 1, valve 131 is preferably closed.

[0033] In the manner descri bed, embodiments of sampling devices for sampling produced well fluids (e.g., device 100) rely on gravity separation to cost effi ciently separate water or other fluids from the produced hydrocarbon fluids for sampling purposes. In contrast to conventional low cut water sampling devices limited to periodic water sampling, embodiments of device 100 allow for continuous sampling of produced well fluids over a period of lime. Furthermore, embodiments of the apparatus provide a very low cost solution to separating the small percentage of water in low cut produced fluids. In addition, embodiments of the apparatus are capable of withstanding extremely high pressures. Although embodiments disclosed herein (e.g., device 100) have been described with respect to separating and sampling water from a produced well fluids stream, it is contemplated that other fluids having a higher density than the produced hydrocarbons may also be separated. Further, although embodiments disclosed herein have been shown and descri bed in conjunction with offshore hydrocarbon producing wells, they may also be used to separate and sample fluids from a produced well fluids in a pipeline, on land, etc. [0034] While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limi ting. Many variations and modifications of the systems, apparatus, and processes described herein arc possible and are within the scope of the invention . For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments descri bed herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Un less expressly stated othen vise, the steps in a method claim may be performed in any order. The recitation of identi fi ers such as (a), (b). (c) or ( 1 ), (2), (3) before steps in a method claim are not intended to and do not speci fy a particular order to the steps, but rather are used to simply subsequent reference to such steps.

[0035] The discussion of a reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priori ty date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated herein by reference in their entirety, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein .