HK1135179B - Method and apparatus for measuring the density of one component in a multi-component flow - Google Patents

Description

Method and apparatus for measuring density of one component in multi-component stream

Technical Field

The present invention relates to the field of well flow measurement, and more particularly, to an oil flow calculation device.

Background

Gas and oil wells may have multiphase flow out of the well head. A measurement of the total flow out of the wellhead is required. To measure the total flow, the gas stream is typically separated from the liquid stream, and the gas and liquid streams are measured separately. The gas and liquid flows may be measured using different Coriolis (Coriolis) flow meters. The liquid stream typically contains both oil and water. In order to accurately measure the amount of oil in the flow, the amount of water in the flow must be determined. In order to determine the amount of water in the stream, the density of the water needs to be determined. Currently, the density of water is determined by periodically sampling the water flowing out of the wellhead and determining the density using a densitometer. This approach has a number of problems. One problem is that the density of water may change over time. If the density of the water changes and the old density measurement is used, the calculated value for the amount of oil in the stream becomes inaccurate. This inaccuracy problem is more severe in high water cut fluids than in low water cut fluids. One way to minimize this inaccuracy is to sample the water density frequently. However, removing the sample from the system and testing the density is a laborious and time consuming task.

Therefore, a need exists for a better system and method for determining the amount of oil in a flow.

Disclosure of Invention

A method and apparatus have been disclosed for determining the density of one component of a multi-component stream passing through a conduit. The multi-component stream is split into two streams, with the first stream having substantially all of the stream of the first component. The density of the second stream is measured.

Aspects of the invention

One aspect of the invention includes a method for determining the density of a component in a multi-component stream, comprising directing a flow of liquid to a conduit, the flow consisting of at least a first material and a second material, the steps of the method characterized by:

dividing the liquid stream into a first stream and a second stream, wherein the flow rate of the first stream is greater than the flow rate in the second stream, and wherein the first stream comprises substantially all of the first material;

the density of the liquid in the second stream is measured.

Preferably, the method further comprises wherein the first material is an oil.

Preferably, the method further comprises wherein the second material is water.

Preferably, the method further comprises wherein the second material is denser than the first material.

Preferably, the method also has the following features:

the temperature of the liquid flowing in the second stream is measured.

Preferably, the method also has the following features:

measuring a total flow of material through the conduit;

the amount of the first material flowing in the conduit is determined based in part on the density of the liquid in the second stream. Preferably, the method further comprises the feature that gravity is used to divide substantially all of the first material into the first stream.

Another aspect of the invention includes a method for determining the density of a component in a multi-component stream, the method comprising directing a flow of liquid into a conduit, wherein the liquid consists of at least oil and water, wherein the steps of the method are characterized by:

a small sample of water is continuously separated from the liquid flowing in the pipe and the density of the water is measured.

Preferably, the method is characterized by measuring the density of the water using a coriolis flowmeter.

Preferably, the method is characterized by continuously measuring the density of the water.

Preferably, the method also has the following features:

the amount of oil flowing in the conduit is determined based in part on the measured water density.

Preferably, the method also has the following features:

the water content of the liquid is determined by the density of the water.

Another aspect of the invention includes an apparatus for determining the density of a component in a multi-component stream, the apparatus having a first conduit configured to contain a liquid composed of at least a first material and a second material, the apparatus characterized by:

the second conduit is connected to the first conduit and is configured to extract a sample of the second material from the liquid.

The first coriolis flowmeter is coupled to the second conduit and is configured to measure a density of a second material sample in the second conduit.

Preferably, the apparatus with the second conduit also has the following features:

a separator tank having a top half and a bottom half, wherein the first conduit flows into the separator tank and the second conduit is connected to the bottom half of the separator tank.

Preferably, the device also has the following features:

a second coriolis flowmeter connected to the first conduit and configured to measure a density of the liquid flowing in the first conduit;

a processor coupled to the first and second coriolis flowmeters and configured to determine a ratio of the first material relative to the second material in the liquid in the conduit based in part on density measurements obtained from the first coriolis flowmeter.

Preferably, the apparatus is characterised in that the first conduit has a first diameter and the second conduit has a second diameter, and the first diameter is greater than the second diameter.

Preferably, the apparatus is characterized by 1/10 where the second diameter is less than the first diameter.

Preferably, the apparatus is characterised in that the first conduit has a first flow rate and the second conduit has a second flow rate, and the first flow rate is greater than the second flow rate.

Another aspect of the invention includes an apparatus for determining the density of a component in a multi-component stream, the apparatus having a conduit containing a flowing liquid of at least a first material and a second material, the apparatus characterized by:

an apparatus for dividing a flowing liquid into a first stream and a second stream, wherein the flow rate of the first stream is greater than the flow rate in the second stream, and wherein the first stream comprises substantially all of a first material;

an apparatus for measuring the density of a material in a second stream.

Drawings

FIG. 1 is a schematic diagram of an oil and gas measurement system 100 in an example embodiment of the invention.

FIG. 2 is a schematic view of a knock out leg in another example embodiment of the invention.

FIG. 3 is a schematic view of a knock out leg utilizing a separator tank in another example embodiment of the invention.

FIG. 4 is a flow chart of a method of determining the density of one component of a multi-component stream in an example embodiment of the invention.

Detailed Description

Fig. 1-3 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will recognize variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. Accordingly, the present invention is not limited to the specific examples described below, but only by the claims and their equivalents.

FIG. 1 is a schematic diagram of an oil and gas measurement system 100 in an example embodiment of the invention. Oil and gas measurement system 100 is connected to wellhead 102 and includes: separator 104, liquid outlet pipe 108, gas outlet pipe 106, water knock out leg 110, flow meters 116, 114, and 112, system outlet pipe 118, and oil calculation device 120.

In operation, wellhead 102 produces a multiphase flow that may include gas, oil, water, and debris, such as silt or sand. The multiphase flow is passed to a separator 104 where gas is separated from the liquid. The separator 104 may be any type of separator including a gas-liquid cylindrical cyclone (GLCC) separator. Gas outlet pipe 106 discharges gas from the top of separator 104. The flow meter 112 measures the gas flowing through the gas outlet pipe 106. The flow meter 112 may be any type of flow meter including a turbine flow meter, a coriolis flow meter, and the like. Liquid is removed from separator 104 through liquid outlet pipe 108. The liquid flowing in liquid outlet pipe 108 may contain oil and water. Knock out leg 110 is configured to separate a small flow of water from liquid outlet pipe 108. Flow meter 114 measures the flow rate of the liquid in liquid outlet pipe 108. In an exemplary embodiment of the invention, the flow meter 114 is a coriolis flow meter. When flow meter 114 is a coriolis flow meter, flow meter 114 can be used to measure the density of the liquid flowing through liquid outlet pipe 108. The water cut value of the liquid flowing in liquid outlet pipe 108 can be determined using the measured liquid density and equation 1.

Equation 1

Where ρ (mix) is the density of the liquid, ρ (oil) is the density of the oil in the liquid, and ρ (water) is the density of the water in the liquid. The density of the oil may be input by the user or measured separately. Equation 1 depends on the density of the water flowing in the liquid. The density of the water may vary as a function of salinity.

Flow meter 116 measures the flow of water in water knock out leg 110. Flow meter 116 is a coriolis flow meter. Flow meter 116 also measures the density of the water flowing in water knock out leg 110. The flow from knock out leg 110 may be reinserted back into liquid outlet pipe 108 after flow meter 114 (as shown), or may be reinserted before flow meter 114 (not shown). When the flow from knock out leg 110 reenters liquid outlet pipe 108 before flow meter 114, then flow meter 116 need not be used to measure flow, its use may be dedicated to measuring the density of the material flowing in knock out leg 110. The oil calculation device 120 monitors the flow meters 112, 114, and 116 to determine the total flow through the system. In an exemplary embodiment, the gas and liquid outputs may be recombined into one system outlet pipe 118. In other exemplary embodiments of the invention, the gas and liquid may be transported to separate destinations through separate pipeline systems (not shown).

Oil computing device 120 monitors the flow through flow meters 112, 114, and 118. The liquid flowing in liquid outlet pipe 108 comprises a mixture of oil and water. In order to determine the amount of oil flowing through liquid outlet pipe 108, the amount of water must be determined. In order to determine the amount of water flowing through liquid outlet pipe 108, the density of the water must be determined. Coriolis flowmeters can be used to measure the density of a material flowing through the flowmeter as well as the amount of material flowing through the flowmeter. Knock out leg 110 is configured to separate a substantially oil-free or other hydrocarbon-free stream from the main stream of liquid flowing in liquid outlet pipe 108. The flow of liquid in the knock out leg may be composed of water, sediment and other water soluble materials such as salt. Changes in the salinity of the water will change the density of the water. Coriolis flowmeter 116 is used to measure the density of the liquid flowing in water knock out leg 110. The measured density is then fed back into the calculation of the amount of oil flowing in the outlet pipe 108 as determined by the water cut formula.

Knock out leg 110 can be configured in a variety of ways to produce a liquid stream that is substantially free of oil or lighter liquids that separate from the main liquid stream in outlet pipe 108. In an exemplary embodiment of the invention, outlet pipe 108 is a horizontal pipe having a length relative to the flow rate sufficient to allow hydrocarbons to rise to the top of the outlet pipe. A knock out leg 110 will be connected to the bottom of outlet pipe 108, extracting only some of the heavier liquid from the outlet pipe. Knock out leg 110 may be smaller in diameter than outlet pipe 108 so that flow into the knock out leg is restricted. In an exemplary embodiment of the invention, knock out leg 110 is 1/10 the diameter of outlet pipe 108. Only a small stream or sample of the heavier liquid flowing in outlet pipe 108 needs to be drawn into water knock out leg 110. In some cases, a majority of the heavier liquid remains flowing in outlet pipe 108.

Fig. 2 is a schematic view of another configuration of a knock out leg in another example embodiment of the invention. The knock out leg includes a separator tank 222 and a knock out pipe 210. Outlet pipe 208 flows into separator tank 222. An outlet pipe leads from the separator tank 222 near the top of the separator tank 222. Knock out pipe 210 exits at or near the bottom of separator tank 222. The separation tank has a volume which allows a certain retention time of the liquid, which is sufficient for the liquid to stratify inside the tank. The knock out leg 210 may also be smaller in diameter than the outlet pipe 208 so that flow into the knock out leg 210 is restricted. Only a small stream or sample of the heavier liquid flowing into separator tank 222 needs to be drawn into knock out leg 210. In most cases, the majority of the heavier liquid is discharged from separator tank 222 through outlet pipe 208.

Fig. 3 is another configuration of a knock out leg in an example embodiment of the invention. The knock out leg includes separator pipe 334 and knock out pipe 310. Outlet tube 308 has a separator tube 334 extending from the bottom of outlet tube 308. The diameter of separator tube 334 may be smaller than the diameter of outlet tube 308. Separator tube 334 extends a short distance below outlet tube 308 before rejoining outlet tube 308. Knock out tube 310 is incorporated into separator tube 334 at the bottom of separator tube 334. Only a small stream or sample of the heavier liquid flowing in separator pipe 334 needs to be drawn into knock out pipe 310. Knock out tube 310 may be the same size as separator tube 334 or smaller than separator tube 334. Other configurations may be used to separate small samples from a multi-phase liquid flowing in an outlet tube to utilize the present invention.

Because the density of water flowing in a multiphase flow can be measured continuously, salinity changes in the water can be compensated for in real time. This will help reduce inaccuracies in the water cut measurement. The present invention is not limited to measuring the density of water in oil and water streams. The invention can also be applied to any mixed flow in which the components can be separated during flow. The knock out leg may be designed to separate any heavier liquid from the lighter liquid.

FIG. 4 is a flow chart of a method for determining a component density of a multi-component stream. At step 402, a stream comprising at least a first material and a second material is directed into a conduit. At step 404, the liquid stream is divided into a first stream and a second stream, wherein the first stream comprises substantially all of the first material. At step 406, the density of the liquid in the second stream is measured.

Claims (12)

1. A method for determining the density of a component in a multi-component stream comprising directing a flow of liquid into a conduit, wherein the liquid is comprised of at least oil and water, the steps of the method characterized by:

a small sample of water is continuously separated from the liquid flowing in the pipe and the density of the water is measured.

2. The method of claim 1 wherein the density of the water is measured using a coriolis flowmeter.

3. The method of claim 1, wherein the density of the water is measured continuously.

4. The method of claim 1, further characterized by:

the amount of oil flowing in the conduit is determined based in part on the measured water density.

5. The method of claim 1, further characterized by:

the water content of the liquid is determined by the density of the water.

6. An apparatus for determining the density of a component in a multi-component stream, the apparatus having a first conduit (108) configured to contain a liquid composed of at least a first material and a second material, the apparatus characterized by:

a second conduit (110) connected to the first conduit (108) and configured to extract a sample of a second material from the liquid flowing within the first conduit (108), wherein the density of the second material is different from the density of the first material, and the second material is substantially insoluble in the first material;

a first coriolis flowmeter (116) coupled to the second conduit (110) and configured to measure a density of the second material sample in the second conduit (110).

7. The apparatus of claim 6, wherein the second conduit further has the following features:

a separation tank (222) having a top half and a bottom half, wherein the first conduit (208) flows into the separation tank (222) and the second conduit (210) is connected to the bottom half of the separation tank.

8. The apparatus of claim 6, wherein:

a second coriolis flowmeter (114) connected to the first conduit (110) and configured to measure a density of the liquid flowing in the first conduit;

a processor (120) is coupled to the first and second coriolis flowmeters and is configured to determine a ratio of the first material relative to the second material in the liquid in the conduit based in part on density measurements obtained from the first coriolis flowmeter.

9. The apparatus of claim 6, wherein the first conduit has a first diameter and the second conduit has a second diameter, and the first diameter is greater than the second diameter.

10. The apparatus of claim 9, further characterized by: the second diameter is less than 1/10 of the first diameter.

11. The apparatus of claim 6, wherein the first conduit has a first flow rate and the second conduit has a second flow rate, and the first flow rate is greater than the second flow rate.

12. The apparatus of claim 6, wherein: the multi-component stream includes at least oil and water, and the second conduit (110) is configured to extract a water sample from the first conduit (108).