Apparatus for preventing and controlling secondary generation of hydrates in wellbore during depressurization exploitation of offshore natural gas hydrates and prevention and control method

Patent metadata

Field	Value
Publication number	US-12000245-B2
Application number	US-202318341813-A
Country	US
Kind code	B2
Filing date	Jun 27, 2023
Priority date	Sep 14, 2022
Publication date	Jun 4, 2024
Grant date	Jun 4, 2024

Abstract

An apparatus for preventing and controlling secondary generation of hydrates in a wellbore during depressurization exploitation of offshore natural gas hydrates includes a gas recovery pipe column, a water recovery pipe column, a gas-liquid mixed transportation pipe section, a data collecting and processing unit, and a reaction control apparatus; according to characteristics of different exploitation pipe columns, three injection pipelines and three monitoring points are arranged to predict dynamic changes in a secondary generation risk of the hydrates throughout the wellbore; measures for preventing and controlling the secondary generation of the hydrates are taken at different pipe column positions by the integrated utilization of inhibitor injection, heating for pipe columns, the additional arrangement of electric submersible pumps, and other methods.

First claim

What is claimed is:

1. An apparatus for preventing and controlling secondary generation of hydrates in a wellbore during depressurization exploitation of offshore natural gas hydrates, wherein the apparatus comprises a gas recovery pipe column, a water recovery pipe column, a gas-liquid mixed transportation pipe section, a data collecting and processing unit, and a reaction control apparatus; tail ends of the gas recovery pipe column and the water recovery pipe column are connected with a top of the gas-liquid mixed transportation pipe section; the gas-liquid mixed transportation pipe section is positioned in hydrate reservoirs; and the gas recovery pipe column and the water recovery pipe column recover gases and water decomposed by the natural gas hydrates in the reservoirs respectively, a joint of the water recovery pipe column and the gas-liquid mixed transportation pipe section and a joint of the gas recovery pipe column and the gas-liquid mixed transportation pipe section are provided with a casing pipe, the first electric submersible pump is positioned in the casing pipe, and a blowout preventer is arranged on a tail end of the gas recovery pipe column;
the data collecting and processing unit comprises a first data monitoring point, a second data monitoring point, a third data monitoring point, and a computer terminal; the first data monitoring point is positioned on a top of the gas recovery pipe column, and collects a temperature, pressure and gas flow of the top of the gas recovery pipe column; the second data monitoring point is positioned on a top of the water recovery pipe column, and collects a temperature, pressure and gas flow of the top of the water recovery pipe column; the third data monitoring point is positioned on a tail end of the gas-liquid mixed transportation pipe section, and collects a temperature and pressure of a well bottom; and the computer terminal receives and processes temperature, pressure, and flow data collected from the first data monitoring point, the second data monitoring point, and the third data monitoring point;
the reaction control apparatus comprises a signal actuator, a hydrate inhibitor storage tank, a hydrate inhibitor injection pump, a first inhibitor injection point, a second inhibitor injection point, a third inhibitor injection point, a first electric submersible pump, a second electric submersible pump, and a heater; one end of the signal actuator is connected with the computer terminal, and the other end of the signal actuator is connected with the hydrate inhibitor injection pump; the hydrate inhibitor injection pump is respectively connected with the first inhibitor injection point, the second inhibitor injection point, and the third inhibitor injection point via injection pipelines, and a control valve is arranged on each of the injection pipelines; the first inhibitor injection point is positioned on the top of the gas recovery pipe column, the second inhibitor injection point is positioned at a bottom of the gas recovery pipe column, and the third inhibitor injection point is positioned on the tail end of the gas-liquid mixed transportation pipe section; the first electric submersible pump is positioned at a bottom of the water recovery pipe column, and the second electric submersible pump is positioned in the middle of the water recovery pipe column; and the heater is positioned at the bottom of the gas recovery pipe column; and
the apparatus collecting, by the three data collection points installed on the top of the gas recovery pipe column, the top of the water recovery pipe column, and the tail end of the gas-liquid mixed transportation pipe section, temperature, pressure and flow data at different positions, the different data collection points being connected with the computer terminal for transmitting the collected data to the computer terminal in real time; performing, by the computer terminal, analysis and processing on the data collected from the different data collection points, sending instructions to the signal actuator to control inhibitor injection rates of different hydrate inhibitor injection points, and to control power of the heater in the gas recovery pipe column and power of the different electric submersible pumps in the water recovery pipe column to prevent and control the secondary generation of the hydrates in the gas recovery pipe column and the water recovery pipe column.

2. The apparatus for preventing and controlling secondary generation of hydrates in a wellbore during depressurization exploitation of offshore natural gas hydrates according to claim 1 , wherein a water storage pipe section is arranged in the middle of the water recovery pipe column, the middle of the water recovery pipe column is divided into a first half and a second half of the water recovery pipe column, a tail end of the first half of the water recovery pipe column and a top of the second half of the water recovery pipe column are positioned in the water storage pipe section, and the second electric submersible pump is positioned on the tail end of the first half of the water recovery pipe column.

3. The apparatus for preventing and controlling secondary generation of hydrates in a wellbore during depressurization exploitation of offshore natural gas hydrates according to claim 1 , wherein the apparatus performing
(i) real-time monitoring of data at different positions
monitoring temperature, pressure and flow data at different positions via the first data monitoring point on the top of the gas recovery pipe column, the second data monitoring point on the top of the water recovery pipe column, and the third data monitoring point on the tail end of the gas-liquid mixed transportation pipe section, and transmitting the collected data to the computer terminal in real time;
(ii) analysis of a secondary generation risk of hydrates throughout wellbore
performing real-time calculation in real time by the computer terminal according to the temperature, pressure and flow data received thereby at different positions to obtain temperature and pressure distributions throughout the wellbore; judging, by combining a phase equilibrium calculation result of the natural gas hydrates, whether the secondary generation of the hydrates happens at different positions, and determining the secondary generation risk of the hydrates throughout the wellbore; and
(iii) prevention and control reaction of secondary generation of hydrates in different pipe columns
sending, by the computer terminal, prevention and control instructions of the secondary generation of the hydrates according to the secondary generation risk of the hydrates in different pipe columns obtained by calculation, and taking corresponding measures for preventing and controlling the secondary generation of the hydrates for different pipe columns, wherein inhibitor injection is used as the measure for preventing and controlling the secondary generation of the hydrates at the gas-liquid mixed transportation pipe section, the collaborative prevention and control of the inhibitor injection+the heating of the pipe column bottom is used as the measure for preventing and controlling the secondary generation of the hydrates in the gas recovery pipe column, and the collaborative prevention and control of depressurization by double pumps+inhibitor is used as at the measure for preventing and controlling the secondary generation of the hydrates in the water recovery pipe column.

4. The apparatus for preventing and controlling secondary generation of hydrates in a wellbore during depressurization exploitation of offshore natural gas hydrates according to claim 3 , wherein in step (ii), distinct heat transfer processes are set between a fluid flow in the exploitation wellbore and an external environment: (1) well section below mud line-gas-liquid mixed transportation

Assignees

• Univ China Petroleum East China

Inventors

• Zhang Jianbo
• Wang Zhiyuan
• Sun Xiaohui
• Sun Baojiang
• Liu Hui
• Tong Shikun
• Kong Qingwen
• Liu Peng

Classifications

• 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

• E21B43/01 Primary

  specially adapted for obtaining from underwater installations · CPC title

• E21B43/16

  Enhanced recovery methods for obtaining hydrocarbons · CPC title

• E21B47/00

  Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) · CPC title

• E21B47/06

  Measuring temperature or pressure · CPC title