Double-capillary viscometer for measuring viscosity of acid natural gas

Abstract

The present disclosure provides a device and method for measuring viscosity of acid natural gas with high precision and a wide temperature range. The device is based on the theoretical basis of gas measurement of double-capillary method. Ground conditions (low temperature and low pressure) or formation conditions (high temperature and high pressure) can be simulated by presetting different temperatures and pressures. The viscosity change of acid gas with changes in temperature and pressure is measured. The device has fewer measuring steps, is easy to operate and has high precision, and can provide valid reference data for actual projects or experiments.

Claims

1. A double-capillary viscometer for measuring viscosity of acid natural gas, comprising: an inlet shutoff valve (2) connected to a gas cylinder (1), a measuring line connected to the inlet shutoff valve (2), a solid particle filter (3) and a gas dryer (4), an upstream inlet piezoelectric valve (5) connected in sequence an upstream capillary (7), a intermediate piezoelectric valve (11), a downstream preheating capillary (13), a downstream measuring capillary (14), a downstream outlet piezoelectric valve (18), an outlet shutoff valve (19), a H.sub.2S absorption bottle (20), and a vacuum pump (21) connected in a main measuring line; the main measuring line being divided into an upstream line and a downstream line; wherein the upstream capillary tube (7) is spirally wound on a cylindrical aluminum block and immersed in an alcohol thermostat (8), and the downstream preheating capillary (13) and the downstream measuring capillary (14) are immersed in an oil bath heating device (12) in a same manner; the upstream inlet pressure gauge (6) is connected behind the upstream inlet piezoelectric valve (5), and an upstream outlet pressure gauge (10) is arranged before the intermediate pressure piezoelectric valve (11), the upstream inlet pressure gauge (6) and the upstream outlet pressure gauge (10) being connected by an upstream differential pressure gauge (9); a downstream inlet pressure gauge (15) is arranged between the downstream preheating capillary (13) and the downstream measuring capillary (14), and a downstream outlet pressure gauge (17) is arranged before the downstream outlet piezoelectric valve (18), the downstream inlet pressure gauge (15) and the downstream outlet pressure gauge (17) being connected by an downstream differential pressure gauge (16).

2. The double-capillary viscometer for measuring viscosity of acid natural gas according to claim 1, wherein the upstream capillary (7), the downstream preheating capillary (13) and the downstream measuring capillary (14) are of a same dimension.

3. The double-capillary viscometer for measuring viscosity of acid natural gas according to claim 1, wherein the upstream capillary (7), the downstream preheating capillary (13) and the downstream measuring capillary (14) are respectively spirally wound on a cylindrical aluminum block with a radius of 0.1 mm.

4. The double-capillary viscometer for measuring viscosity of acid natural gas according to claim 1, wherein the upstream capillary (7), the downstream preheating capillary (13) and the downstream measuring capillary (14) are all made of Hastelloy, with a uniform nominal inner diameter of 0.500 mm.

5. A double-capillary viscometer for measuring viscosity of acid natural gas according to claim 1 wherein the gas cylinder (1) is capable of providing a sufficient and stable gas output.

6. The double-capillary viscometer for measuring viscosity of acid natural gas according to claim 1, wherein the alcohol thermostat (8) maintains a temperature of 298.15 K through alcohol bath heating method; the oil bath heating device (12) provides a temperature in a range of 298.15-513.15K through silicone oil bath heating method.

7. The double-capillary viscometer for measuring viscosity of acid natural gas according to claim 1, wherein the upstream differential pressure gauge (9), the downstream differential pressure gauge (16), three-way connections and the valves are all made of Hastelloy and have excellent corrosion resistance.

8. The double-capillary viscometer for measuring viscosity of acid natural gas according to claim 1, wherein the upstream inlet piezoelectric valve (5), the upstream outlet pressure gauge (10), the downstream inlet pressure gauge (15) and the downstream outlet pressure gauge (16) use Y-100BFZ stainless steel anti-vibration pressure gauge produced by Shanghai Automation Instrument Factory Four, with a scale range of 0 to 2.4 MPa and good vibration and corrosion resistances.

9. The double-capillary viscometer for measuring viscosity of acid natural gas according to claim 1, wherein the viscometer is measured by steps of: step 1: flushing the line with standard helium gas for 30 minutes; step 2: keeping the alcohol thermostat and the oil bath thermostat at 298.15K, introducing a helium gas when temperature is stable, obtaining (P.sub.1.sup.He,P.sub.2.sup.He).sub.0,298.15.sup.He when flow is stable, keeping the temperature constant and pumping the line to vacuum, introducing a gas to be measured, controlling an inlet pressure by the upstream inlet piezoelectric valve to be constant, obtaining (P.sub.1.sup.mea,P.sub.2.sup.mea).sub.0,298.15.sup.mea when flow is stable, and calculating a viscosity ratio of the helium gas to the measured gas at 298.15 K by a following formula, $\begin{array}{cc}\frac{{\eta }_{0,298.15}^{\mathrm{mea}}}{{\eta }_{0,298.15}^{\mathrm{He}}}=\frac{{\left(P_1^{\mathrm{mea}}-P_2^{\mathrm{mea}}\right)}_{0,298.15}^{\mathrm{mea}}}{{\left(P_1^{\mathrm{He}}-P_2^{\mathrm{He}}\right)}_{0,298.15}^{\mathrm{He}}}& \left(1\right)\end{array}$ in the formula (1): He represents the helium gas; Mea represents the gas to be measured; η represents dynamic viscosity, mPa.Math.s; P represents pressure, MPa; step 3: warming the oil bath thermostat to temperature T at which the measurement is to be performed, introducing the gas to be measured when temperature is stable, controlling an inlet pressure by the upstream inlet piezoelectric valve to be constant, adjusting the outlet piezoelectric valve, controlling a pressure difference between P3 and P4 to be an experimental pressure difference, obtaining (P.sub.1,P.sub.2,P.sub.3,P.sub.4).sub.0,T.sup.mea when flow is stable, pumping the line to vacuum, introducing the helium gas, repeating above operations, obtaining (P.sub.1,P.sub.2,P.sub.3,P.sub.4).sub.0,T.sup.He when flow is stable, calculating a viscosity rate R.sub.T,298.15.sup.mea,He based on obtained data by a following formula; $\begin{array}{cc}{R}_{T,298.15}^{\mathrm{mea},\mathrm{He}}=\frac{{\left(P_1^2-P_2^2\right)}^{\mathrm{He}}}{{\left(P_1^2-P_2^2\right)}^{\mathrm{mea}}}\frac{{\left(P_3^2-P_4^2\right)}^{\mathrm{mea}}}{{\left(P_3^2-P_4^2\right)}^{\mathrm{He}}}& \left(2\right)\end{array}$ step 4: calculating a theoretical value of the viscosity of helium gas at temperature T by formula (3):
η.sub.0,T.sup.He=−8.7272×10.sup.−11T.sup.4+1.38504×10.sup.−7T.sup.3−9.80906×10.sup.−5T.sup.2+7.622×10.sup.−2T+2.84835  (3) in the formula (3): T represents the temperature at which the measurement is to be performed, K; step 5: calculating a dynamic viscosity of the measured gas at a simulated temperature and pressure by formula (4): $\begin{array}{cc}{\eta }_{0,T}^{\mathrm{mea}}={\eta }_{0,T}^{\mathrm{He}}\left(\frac{{\eta }_{0,298.15}^{\mathrm{mea}}}{{\eta }_{0,298.15}^{\mathrm{He}}}\right)R_{T,298.15}^{\mathrm{mea},\mathrm{He}}.& \left(4\right)\end{array}$

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of the structure of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

(2) As shown in the accompanying drawings, the present disclosure provides a double-capillary viscometer for measuring viscosity of acid natural gas, including: an inlet shutoff valve (2) connected to a gas cylinder (1), a measuring line connected to the inlet shutoff valve (2), a solid particle filter (3) and a gas dryer (4), an upstream inlet piezoelectric valve (5) connected in sequence an upstream capillary (7), a intermediate piezoelectric valve (11), a downstream preheating capillary (13), a downstream measuring capillary (14), a downstream outlet piezoelectric valve (18), an outlet shutoff valve (19), a H.sub.2S absorption bottle (20), and a vacuum pump (21) connected in a main measuring line; the main measuring line being divided into an upstream line and a downstream line; wherein the upstream capillary tube (7) is spirally wound on a cylindrical aluminum block and immersed in an alcohol thermostat (8), and the downstream preheating capillary (13) and the downstream measuring capillary (14) are immersed in an oil bath heating device (12) in a same manner; the upstream inlet pressure gauge (6) is connected behind the upstream inlet piezoelectric valve (5), and an upstream outlet pressure gauge (10) is arranged before the intermediate pressure piezoelectric valve (11), the upstream inlet pressure gauge (6) and the upstream outlet pressure gauge (10) being connected by an upstream differential pressure gauge (9); a downstream inlet pressure gauge (15) is arranged between the downstream preheating capillary (13) and the downstream measuring capillary (14), and a downstream outlet pressure gauge (17) is arranged before the downstream outlet piezoelectric valve (18), the downstream inlet pressure gauge (15) and the downstream outlet pressure gauge (17) being connected by an downstream differential pressure gauge (16).

(3) The upstream capillary (7), the downstream preheating capillary (13) and the downstream measuring capillary (14) are of a same dimension.

(4) The upstream capillary (7), the downstream preheating capillary (13) and the downstream measuring capillary (14) are respectively spirally wound on a cylindrical aluminum block with a radius of 0.1 mm.

(5) The upstream capillary (7), the downstream preheating capillary (13) and the downstream measuring capillary (14) are all made of Hastelloy, with a uniform nominal inner diameter of 0.500 mm.

(6) As a preferred embodiment of the present disclosure, the cylindrical aluminum block has a large specific heat capacity, and a high system thermal inertia, thus making the temperature field of the capillary more stable.

(7) As a preferred embodiment of the present disclosure, the gas cylinder (1) is capable of providing a sufficient and stable gas output.

(8) As a preferred embodiment of the present disclosure, the oil bath heating device (12) provides a temperature in a range of 298.15-513.15K through silicone oil bath heating method.

(9) As a preferred embodiment of the present disclosure, the upstream capillary (7) and the downstream measuring capillary (14) are wound on the cylindrical aluminum block by a same winding method, which can offset the errors caused by deviation of the actual gas from the ideal state, gaseous slip, change in the kinetic energy at the inlet, and the centrifugal force.

(10) As a preferred embodiment of the present disclosure, the downstream preheating capillary (13) is wound on a cylindrical aluminum block in a same manner as the upstream capillary (7) and the downstream measuring capillary (14), thereby reducing errors caused by gas expansion and radial temperature field change.

(11) As a preferred embodiment of the present disclosure, the lines, the valves and the three-way connections are all made of Hastelloy and have excellent corrosion resistance.

(12) As a preferred embodiment of the present disclosure, the pressure gauges (6) (10) (15) (17) use Y-100BFZ stainless steel anti-vibration pressure gauge produced by Shanghai Automation Instrument Factory Four, with a scale range of 0 to 2.4 MPa; the differential pressure gauges (9) (16) use CYP-150B stainless steel differential pressure gauge produced by Shanghai Automation Instrument Factory Four, with a differential pressure measurement range of 0 to 60 KPa and good corrosion resistance by which the vibration generated by rapid flow of gas can be effectively resisted.

(13) The working principle of the present disclosure is as follows:

(14) The gas to be measured flows from the gas cylinder (1) through the inlet shutoff valve (2), the solid particulate filter (3), the gas dryer (4), to the upstream inlet piezoelectric valve (5) into the upstream capillary (7). Through combined regulation of the sliding piezoelectric valve (5) and the intermediate piezoelectric valve (11), the molar flow rate of the gas (corresponding to the difference between the upstream inlet pressure gauge (6) and the upstream outlet pressure gauge (10) is controlled. At a set molar flow rate, the gas enters the downstream preheating capillary (13), the downstream measuring capillary (14), and the downstream outlet piezoelectric valve (18). Through regulation of the downstream outlet piezoelectric valve (18), the volumetric flow rate of the gas (corresponding to the value of the downstream outlet pressure gauge (17) is controlled. The difference between the downstream inlet pressure gauge (15) and the downstream outlet pressure gauge (17) is the simulated pressure, and the temperature set by the silicone oil thermostat (12) is the simulated temperature. The gas to be measured enters the downstream outlet piezoelectric valve (18), the outlet shutoff valve (19), the H.sub.2S absorption bottle (20), and is finally safely recovered by the vacuum pump (21). The helium gas is subjected to the same operations to obtain the corresponding pressure data. The viscosity ratio

(15) $\frac{{\eta }_{0,298.15}^{\mathrm{mea}}}{{\eta }_{0,298.15}^{\mathrm{He}}}$
and rate R.sub.T,298.15.sup.mea,He of helium gas to the gas to be measured at 298.15K are obtained by calculation using the formulas (1) and (2), the viscosity value η.sub.0,T.sup.He of helium gas is obtained by calculation using formula (3), and the dynamic viscosity of the gas to be measured is obtained by calculation using formula (4).