Underwater laying device for offshore oil and gas pipelines and laying method thereof

An underwater laying device for offshore oil and gas pipelines, comprising:

• a box-shaped main body (1), a first mud-plowing rake (2), a first mud-plowing hoe (3), a second mud-plowing rake (4), a second mud-plowing hoe (5), propellers (6), a mud collection hood (7), an elongated pipeline-delivery cylinder (8), a mud delivery plate (9), and a control system (10), wherein the box-shaped main body (1) has an opening facing downwards;
• the first mud-plowing rake (2), the first mud-plowing hoe (3), the second mud-plowing rake (4), and the second mud-plowing hoe (5) tilt in same direction on bottom of the box-shaped main body (1) along its length direction, and are arranged at intervals and separately fixed on the bottom of the box-shaped main body (1);
• the first mud-plowing rake (2) and the first mud-plowing hoe (3) are equal in height, the second mud-plowing rake (4) and the second mud-plowing hoe (5) are equal in height, and vertical height of the second mud-plowing rake (4) is greater than that of the first mud-plowing rake (2);
• the propellers (6) are mounted respectively at two sides opposite in the length direction of the box-shaped main body (1) on its front end;
• the mud collection hood (7) has an opening facing downwards, is fixed to the rear end of the box-shaped main body (1) and is communicated with the inside thereof;
• the elongated pipeline-delivery cylinder (8) diagonally penetrates the box-shaped main body (1) along the length direction of the box-shaped main body (1);
• the mud delivery plate (9) is fixed on the bottom of the box-shaped main body (1), and spans between the first mud-plowing hoe (3) and the second mud-plowing hoe (5);
• and the control system (10) is mounted on the box-shaped main body (1), and the propellers (6) are in signal connection with the control system (10).