Hydrate removal in hydrocarbon wells
A process for removing an obstruction ( 13 ) caused by gas hydrates or water ice from the tubing ( 12 ) of a hydrocarbon production or injection well or a riser using a microwave. The process comprises passing a microwave generating and emitting tool ( 5 ) on wireline ( 8 ) down the tubing ( 12 ) and supplying electrical power to the tool via the wireline ( 8 ) or from a battery to produce microwave energy and direct it to the gas hydrate and/or water ice deposit ( 13 ), thereby melting deposit and unblocking the well.
1 . A process for removing an obstruction caused by gas hydrates or water ice from tubing of a hydrocarbon production or injection well or a riser, wherein the process comprises:
a) passing a microwave generating and emitting tool on wireline down the tubing;
b) supplying electrical power to the microwave generating and emitting tool either from b) a battery package in the tool or via the wireline, to produce microwave energy and direct it distally along the tubing to a gas hydrate and/or water ice deposit, thereby at least partially melting and/or decomposing the gas hydrate and/or water ice deposit; and
c) recovering the tool by directing microwave energy proximally to melt or decompose re-formed hydrate or ice to allow the tool to be withdrawn.
2 . The process according to claim 1 , wherein the electrical power supplied to the tool is between 500 and 10,000 Watts.
3 . The process according to claim 1 , wherein, after melting or decomposing a portion of hydrate or ice, the tool is advanced through the melted or decomposed hydrate or ice, along the well or riser, to melt or decompose further hydrate or ice.
4 . The process according to claim 3 , wherein the weight of the tool is sufficient to advance it along the tubing until it reaches solid hydrate or ice.
5 . The process according to claim 1 , wherein the hydrate or ice is in a subsea well.
6 . The process according to claim 1 , wherein the tool is delivered from a surface vessel with a wireline facility.
7 . The process according to claim 1 , wherein the deposit comprises a region of water ice and a region of hydrate.
8 . The process according to claim 1 , wherein the process includes sensing slackening of tension in the wireline or sensing proximal acceleration of the tool and then activating a braking system to restrain proximal movement of the tool.
9 . A tool for removing an obstruction caused by gas hydrates or water ice from tubing of a hydrocarbon production or injection well or a riser, wherein the tool is adapted for delivery on wireline into the tubing and wherein the tool comprises:
a) a microwave generator adapted to receive electrical power from a battery pack in the tool or via the wireline; and
b) a microwave antenna adapted to deliver microwave energy in a distal direction when the tool is located in the tubing; and
c) an antenna for directing microwave energy in a proximal direction to melt or decompose re-formed hydrate or ice to allow the tool to be withdrawn.
10 . The tool according to claim 9 , including a ground/earth contact member arranged to contact the interior surface of the tubing of so that the tubing acts as a Faraday cage.
11 . The tool according to claim 9 , wherein the microwave generator has an input power rating between 500 Watts and 10,000 Watts.
12 . The tool according to claim 9 , wherein the tool further comprises at least one additional antenna for directing microwave energy.
13 . The tool according to claim 9 , wherein the tool comprises:
a) a sensor for sensing slackening of tension in the wireline or a sensor for sensing proximal acceleration of the tool; and
b) a system for braking the tool in response to sensed slackening of tension in the wireline or in response to sensed proximal acceleration.
14 . The tool according to claim 13 , wherein the system for braking comprises a braking member engageable with the interior tubing wall to restrain movement of the tool.