Product sampling system within subsea tree

Patent metadata

Field	Value
Publication number	US-9057252-B2
Application number	US-201113302796-A
Country	US
Kind code	B2
Filing date	Nov 22, 2011
Priority date	Nov 22, 2011
Publication date	Jun 16, 2015
Grant date	Jun 16, 2015

Abstract

A method and system for producing fluid from a subsea wellbore. An amount of fluid is sampled from fluid being produced and retained for a period of time until constituents in the fluid stratify. A fluid characteristic is sensed at spaced apart vertical locations in the sampled fluid. A water fraction as well as gas content can be ascertained from sensing the sampled fluid. The fluid characteristic is used for calibrating a multi-phase flowmeter that measures flow of the fluid being produced from the wellbore.

First claim

What is claimed is:

1. A method of producing fluid from a subsea wellbore through a subsea production tree mounted over the subsea wellbore and out a production flow line extending from the tree, comprising:
a. connecting an inlet of a sampling conduit into the flow line and an outlet of the sampling conduit into the flow line at a location downstream from the inlet;
b. providing the sampling conduit with an inlet valve and an outlet valve downstream from the inlet valve, defining a container between the inlet valve and the outlet valve that has sensors at vertically spaced apart locations inside the container;
c. opening the inlet and outlet valves, thereby diverting some of the fluid flowing through the flow line into the sampling conduit, then closing the inlet and outlet valves, thereby isolating an amount of sampled fluid in the container from the fluid flowing through the flow line;
d. sensing the sampled fluid with the sensors over a period of time;
e. identifying a constituent of the sampled fluid based on the step of sensing; then
f. opening the inlet and outlet valves to allow the sampled fluid to flow through the outlet valve into the flow line.

2. The method of claim 1 , wherein step (e) further comprising identifying stratification of the sampled fluid into phases.

3. The method of claim 1 , wherein the flow line has a choke through which the well fluid flows, and wherein step (a) compises placing the outlet of the sampling conduit upstream from the choke.

4. The method of claim 1 , wherein the fluid flowing through the flow line flows through a flowmeter, the method further comprising adjusting a value of a measurement obtained with the flowmeter based on the constituents identified in step (e).

5. The method of claim 4 , wherein step (e) comprises identifying an amount of water in the sampled fluid and calibrating the flowmeter based on the amount of water identified in the sampled fluid.

6. The method of claim 1 , wherein step (e) further comprises estimating a percentage that the identified constituent makes up of the total sampled fluid.

7. The method of claim 1 , wherein step(e) comprise identifying whether the sampled fluid contains water, oil and gas.

8. The method of claim 1 , wherein step (d) further comprises communicating data signals from the sensors to a controller, which performs step (e).

9. The method of claim 8 , wherein the subsea production tree further comprises a service control module mounted to the subsea production tree; and
the controller provides data signals resulting from step (e) to the service control module.

10. A subsea wellhead assembly comprising:
a wellhead housing mounted over a subsea wellbore;
a subsea production tree coupled to the wellhead housing;
a production flow line in fluid communication with the production tree;
a sample conduit having an inlet connected into the production flow line and an outlet connected into the production flow line downstream from the inlet, defining a container between the inlet and the outlet;
an inlet valve at the inlet of the sample conduit and an outlet valve at the outlet of the sample conduit;
the inlet and outlet valves having an open position that selectively diverts some of the well fluid flowing through the production line into the container and from the container back into the production flow line;
the inlet and outlet valves having a closed position that isolates a sample of the well fluid in the container from the well fluid flowing through the production flow line; and
a sensor system comprising fluid sensors in the container at vertically spaced apart locations and that are in communication with vertically spaced points along an inside of the container,the sensors being configured to identify constituents of the sample of the well fluid.

11. The wellhead assembly of claim 10 , wherein the fluid sensors are configured to identify stratification of the sample of the well fluid that occurs when the inlet and outlet valves are in the closed position over a selected period of time.

12. The wellhead assembly of claim 10 , further comprising:
a flow meter located in production flow line that provides a value characterizing flow rate through the production flow line; and
means for adjusting the value based on an output of the sensor system.

13. The wellhead assembly of claim 10 , wherein the sensor system further comprises a controller that receives signals form the sensors.

14. A method of producing well fluid from a subsea well through a subsea production tree and out a production flow line extending from the tree, comprising:
a. connecting an inlet of a sampling conduit into the flow line and an outlet of the sampling conduit into the flow line at a located downstream from the inlet;
b. diverting a portion of the well fluid flowing through the flow line into the inlet of the sampling conduit; then
c. trapping a sample of the well fluid within the conduit and allowing the sample to stratify over a period of time; then
d. sensing a characteristic of the sample at discrete vertically spaced apart locations and determining whether the sample contains oil, water and gas occurring in stratified layers within the sampling conduit;
e. measuring a rate of flow of the well fluid flowing through the flow line;
f. adjusting the measured rate of flow based on the determination from step (d); and
g. flowing the sample trapped in step (c) from the sampling conduit through the outlet back into the flow line.

15. The method of claim 14 , wherein a multi-phase flowmeter is used to measure a rate of flow in step(e) and wherein step (f) comprises calibrating the flowmeter.

16. The method of claim 14 , wherein the period of time in step (c) may be up to 10 hours.

17. The method of claim 14 , wherein step (c) comprises isolating the sample from contact with the well fluid flowing through the flow line.

18. The method of claim 14 , wherein the characteristic of the sample sensed is selected from the group consisting of fluid density, fluid composition, fluid pressure, fluid viscosity, and fluid temperature.

Assignees

• Bell Robert
• Vetco Gray Inc

Inventors

• Bell Robert

Classifications

• E21B49/086 Primary

  Withdrawing samples at the surface · CPC title

• E21B49/08 Primary

  Obtaining fluid samples or testing fluids, in boreholes or wells · CPC title

• E21B34/02

  in well heads · CPC title