Nitrogen-carbon dioxide mixed gas jetting apparatus for horizontal well and exploitation method

A nitrogen-carbon dioxide mixed gas jet apparatus for a horizontal well, used in a hydrate exploitation process and comprising:

• an offshore platform;
• a natural gas processing unit disposed on the offshore platform and extending deep into a hydrate layer of a natural gas reservoir through a gas exploitation pipe;
• and
• a pressurizing unit disposed on the offshore platform and extending deep into the hydrate layer of the natural gas reservoir through a gas injection pipe, wherein
• a portion of the gas exploitation pipe in the hydrate layer is provided with a gas injection horizontal well;
• a mixed gas jet unit and a nozzle assembly are disposed in the gas injection horizontal well;
• the mixed gas jet unit is configured to mix nitrogen and carbon dioxide, and then inject the mixed gas into a hydrate deposition layer of the hydrate layer through the nozzle assembly in a dispersed manner, so that the mixed gas of nitrogen and carbon dioxide replaces methane gas in the hydrate deposition layer;
• the portion of the gas exploitation pipe in the hydrate layer is provided with a gas exploitation horizontal well;
• and the gas exploitation horizontal well is configured to collect the methane gas and convey the methane gas to the natural gas processing unit;
• and wherein
• the mixed gas jet unit comprises several cylindrical parts connected in series;
• each of the cylindrical parts comprises a high-pressure water-proof chamber and a high-pressure gas injection chamber, wherein the high-pressure gas injection chamber is used as a gas passage of the mixed gas of nitrogen and carbon dioxide;
• the high-pressure water-proof chamber is used to isolate the high-pressure gas injection chamber from the outside world;
• and
• two adjacent high-pressure water-proof chambers are movably connected to each other through a hinge;
• and two adjacent high-pressure gas injection chambers are connected to each other through a flexible connector.