Hydrate solid-state fluidization mining method and system under underbalanced reverse circulation condition

Patent metadata

Field	Value
Publication number	US-11053779-B2
Application number	US-201816604109-A
Country	US
Kind code	B2
Filing date	Nov 20, 2018
Priority date	May 25, 2018
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

A hydrate solid-state fluidization mining method and system under an underbalanced reverse circulation condition are used for solid-state fluidization mining on a non-rock-forming weak-cementation natural gas hydrate layer in the ocean. Equipment includes a ground equipment system and an underwater equipment system. The construction procedure includes an earlier-stage construction process, pilot hole drilling construction process, reverse circulation jet fragmentation process, underbalanced reverse circulation fragment recovery process and silt backfilling process. Natural gas hydrates in the seafloor are mined through an underbalanced reverse circulation method. Problems such as shaft safety, production control and environmental risks faced by conventional natural gas hydrate mining methods such as depressurization, heat injection, agent injection and replacement are effectively solved. By using the method, the weak-cementation non-rock-forming natural gas hydrates in the seafloor can be mined in environment-friendly, efficient, safe and economical modes, more energy resources can be provided, and energy shortage dilemmas are solved.

First claim

The invention claimed is:

1. A mining system for hydrate solid-state fluidization mining method under an underbalanced reverse circulation condition,
wherein the hydrate solid-state fluidization mining method comprises the following steps:
S1, an earlier-stage construction process: performing first spudding on a well by a conventional drilling mode, forming a shaft subjected to the first spudding, setting a guide pipe, injecting cement to an annulus between the shaft subjected to the first spudding and the guide pipe to form a cement ring, and installing a packer on the guide pipe;
S2, a pilot hole drilling construction process: after the guide pipe and the packer are installed, setting an oil pipe, drilling a pilot hole by adopting an underbalanced drilling mode, and taking a drill bit out after the drilling;
S3, a reverse circulation jet fragmentation process: setting the oil pipe down to the wellbore again and injecting seawater, performing high-pressure jet fragmentation on a hydrate reservoir, and storing hydrate particles formed by the fragmentation and silt in a cavity formed by a jet;
S4, an underbalanced reverse circulation fragment recovery process: injecting a mixed fluid of seawater and natural gas into the pilot hole and forming an under pressure at the bottom of the well; performing prefractionation on fragments formed in S2, then mining the hydrate particles and part of silt out along with the mixed fluid, and backfilling the remaining silt to the bottom of the well; separating the mixed stream of the mined hydrate particles and the silt to obtain natural gas, seawater and silt;
S5, after the process S3 is performed for a period of time, performing the process S2 again, and repeating the reverse circulation jet fragmentation process and the underbalanced reverse circulation fragment recovery process till reaching a designed well depth; and
S6, a silt backfilling process: injecting the mined silt and the seawater into the pilot hole, forming a certain overpressure at the bottom of the well to achieve backfilling of the silt in a mined bed, and meanwhile, dragging the oil pipe upwards slowly to complete the backfilling of the entire shaft,
wherein the mining system comprise a ground equipment system and an underwater system;
the ground equipment system comprises a drilling machine, a ground separation system, a liquefaction system, a liquefied natural gas tank, an offshore platform, a sand feeding tank, a gas injection tank, a booster pump, a seawater injection pipeline, and a seawater pump; the drilling machine is installed on the offshore platform; the liquefied natural gas tank, the liquefaction system and the ground separation system are connected in sequence; the ground separation system is connected to the underwater system; the booster pump is connected to the gas injection tank; the seawater pump, the gas injection tank and the sand feeding tank are respectively connected to the seawater injection pipeline; a valve G is installed on the seawater injection pipeline; the seawater injection pipeline is connected to the underwater system;
the underwater system comprises a coiled tubing outer tube, a coiled tubing inner tube, a drill bit, an underwater separator, a jet nipple, the pilot hole, a rotary guiding system, and a pilot hole drill bit; the coiled tubing outer tube is disposed inside the coiled tubing outer tube; the rotary guiding system is connected to the lower end of the coiled tubing inner tube in the pilot hole drilling construction process; the pilot hole drill bit is connected to the lower end of the rotary guiding system; the coiled tubing inner tube and the coiled tubing outer tube are respectively connected to an inner tube and an outer tube of the jet nipple in the reverse circulation jet fragmentation process, the underbalanced reverse circulation fragment recovery process and the silt backfilling process; the lower end of the jet nipple is connected to the underwater separator; and the lower end of the underwater separator is connected to the drill bit.

2. The mining system for the hydrate solid-state fluidization mining method under the underbalanced reverse circulation condition according to claim 1 , wherein the liquefied natural gas tank and the liquefaction system are connected through a liquefaction system and liquefied natural gas tank connecting pipe; a valve C is installed on the liquefaction system and liquefied natural gas tank connecting pipe; the liquefaction system and the ground separation system are connected through a separation system and liquefaction system connecting pipe; a valve B is installed on the separation system and liquefaction system connecting pipe.

3. The mining system for the hydrate solid-state fluidization mining method under the underbalanced reverse circulation condition according to claim 1 , wherein in the reverse circulation jet fragmentation process, the underbalanced reverse circulation fragment recovery process and the silt backfilling process, the ground separation system is connected to an inlet of the coiled tubing inner tube through a seawater recovery pipeline; a valve A is installed on the seawater recovery pipeline; an outlet end of the seawater pump is connected to the seawater injection pipeline; and the other end of the seawater injection pipeline is connected to an outlet of the coiled tubing outer tube.

4. The mining system for the hydrate solid-state fluidization mining method under the underbalanced reverse circulation condition according to claim 1 , wherein in the pilot hole drilling construction process, the ground separation system is connected to the outlet of the coiled tubing outer tube through the seawater recovery pipeline; the outlet end of the seawater pump is connected to the seawater injection pipeline; and the other end of the seawater injection pipeline is connected to the inlet of the coiled tubing inner tube.

5. The mining system for the hydrate solid-state fluidization mining method under the underbalanced reverse circulation condition according to claim 1 , wherein an inlet end of the seawater pump is connected to a seawater suction pipe; the middle of the seawater suction pipe is connected with the sand feeding tank through a sand feeding pipeline; and a valve D is installed in the middle of the sand feeding pipeline.

6. The mining system for the hydrate solid-state fluidization mining method under the underbalanced reverse circulation condition according to claim 1 , wherein the booster pump and the gas injection tank are connected through a booster pump and gas injection tank connecting pipe, and a valve F is disposed on the booster pump and gas injection tank connecting pipe; an outlet end of the gas injection pipe is connected to a gas injection pipeline, and a valve E is disposed on the gas injection pipeline and connected to the seawater injection pipeline.

7. The mining system for the hydrate solid-state fluidization mining method under the underbalanced reverse circulation condition according to claim 1 , wherein the underwater system further comprises a packer, a guide pipe, a cement ring, and a shaft subjected to first spudding; the packer is installed on the guide pipe; the guide pipe is fixedly connected to the shaft subjected to first spudding through the cement ring; the coiled tubing outer tube and the coiled tubing inner tube pass through the packer and the guide pipe and enter the hydrate reservoir; and the coiled tubing inner tube is located inside the coiled tubing outer tube.

Assignees

• Univ Southwest Petroleum

Inventors

• Zhao Jinzhou
• Wei Na
• Li Haitao
• Zhang Liehui
• Zhou Shouwei
• Li Qingping
• Sun wantong

Classifications

• E21B43/166

  Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium (CO2 injection E21B43/164; steam injection E21B43/24) · CPC title

• E21B33/14

  for cementing casings into boreholes · CPC title

• E21B43/29

  Obtaining a slurry of minerals, e.g. by using nozzles · CPC title

• E21B41/0099 Primary

  specially adapted for drilling for or production of natural hydrate or clathrate gas reservoirs; Drilling through or monitoring of formations containing gas hydrates or clathrates · CPC title

• E21B43/26

  by forming crevices or fractures · CPC title