GAS-LIQUID SEPARATOR
A gas-liquid separator separates free water at a downhole position of a gas well. The separator includes a centrifugal separator within a tubular portion defining a gas inlet and a gas outlet. Upstream of the centrifugal separator, the tubular portion is provided with a plurality of drain holes through which free water which was centrifugated to the tubular portion enters an annular duct allowing the collected water to flow off due to gravity. Upstream of the drain holes, a jet pump is arranged. The jet pump is driven by the gas stream to create underpressure in the duct and to suck back gas which has entered the annular duct through the drain holes. The gas-liquid separator has no moving parts and avoids monitoring or controlling of the separating process.
1 . Gas-liquid separator comprising:
a) a tubular portion having a circumferential wall which defines a gas inlet and a gas outlet at an axial distance from the gas inlet;
b) a centrifugal separator arranged coaxially within the tubular portion axially between the gas inlet and the gas outlet;
c) a duct provided outside the tubular portion; and
d) at least one drain channel extending through the circumferential wall of the tubular portion adjacent to a gas outlet region of the centrifugal separator,
wherein the at least one drain channel connects a liquid-collecting inner surface of the circumferential wall at the gas outlet region of the centrifugal separator with the interior of the duct; and
e) suction means having at least one suction port connected to the duct to create underpressure in the duct and to suck off gas from the duct.
2 . Gas-liquid separator as claimed in claim 1 , wherein the suction means is a jet pump arranged within the tubular portion to be driven by gas flowing in the tubular portion,
wherein the jet pump is arranged axially between the at least one drain channel and the gas outlet of the tubular portion and has at least one suction port connected to the duct to create underpressure in the duct and to suck off gas from the duct.
3 . Gas-liquid separator as claimed in claim 1 , wherein the duct comprises a duct portion extending downwards from the at least one drain channel to allow flowing off of separated liquid due to gravity.
4 . Gas-liquid separator as claimed in claim 1 , wherein the at least one suction port of the jet pump is connected to the duct at a position located above the at least one drain channel.
5 . Gas-liquid separator as claimed in claim 1 , further comprising at least one baffle inside the duct axially in between the at least one drain channel and the at least one suction port of the suction means.
6 . Gas-liquid separator as claimed in claim 1 , wherein the duct is an annular duct formed radially between the circumferential wall and a tubular casing which coaxially surrounds the circumferential wall at a radial distance thereto.
7 . Gas-liquid separator as claimed in claim 6 , wherein a plurality of drain channels are provided in at least one row, wherein the drain channels are spaced from each other within the row around the circumference of the circumferential wall.
8 . Gas-liquid separator as claimed in claim 7 , wherein the drain channels are provided in a plurality of rows and the drain channels of adjacent rows are staggered in the circumferential direction with respect to the drain channels of an adjacent row.
9 . Gas-liquid separator as claimed in claim 6 , wherein the at least one drain channel is an elongated hole provided with its longitudinal direction transverse to a helical line defined by the at least one helical baffle of the centrifugal separator.
10 . Gas-liquid separator as claimed in claim 1 , wherein the centrifugal separator comprises at least one helical baffle arranged in a stationary manner within the tubular portion with its helical axis coaxial to an axis of the tubular portion.
11 . Gas-liquid separator as claimed in claim 10 , wherein the at least one helical baffle surrounds a central free space which extends throughout the centrifugal separator and is accessible from the gas inlet and the gas outlet of the tubular portion.
12 . Gas-liquid separator as claimed in claim 11 , wherein the centrifugal separator comprises a plurality of helical baffles staggered in axial direction.
13 . Gas well tubing construction comprising:
a production casing;
a production tubing provided within the production casing and at least the tubular portion, the centrifugal separator and the at least one drain channel associated with the centrifugal separator of at least one gas-liquid separator as claimed in claim 1 , wherein at least one gas-liquid separator is arranged to separate water entrained by gas flowing upwards through the production tubing, and wherein the tubular portion is arranged downhole in the production tubing.
14 . Gas well tubing construction as claimed in claim 13 , wherein the gas-liquid separator is dimensioned to be movable within and along the production tubing.
15 . Gas well tubing construction as claimed in claim 13 , wherein the duct is arranged in between the production tubing and the production casing.
16 . Gas well tubing construction as claimed in claim 15 , wherein the duct extends up to the surface level of the gas well and the suction means is arranged at the surface level.
17 . Gas well tubing construction as claimed in claim 13 , wherein the suction means is a jet pump provided within the tubular portion.
18 . Gas well tubing construction as claimed in claim 13 , wherein the gas-liquid separator is positioned at a height (L) of more than 40 m above a gas production zone of the well, preferably close to a safety valve of the well.
19 . Gas well tubing construction as claimed in claim 13 , wherein a plurality of gas-liquid separators are arranged one behind the other in the production tubing.