Combined mining method with decompression and heating in multi-branched horizontal wells for marine hydrate

Abstract

The invention discloses a multi-branch horizontal well depressurization and heating united mining method for marine hydrates. For the 'congenital' defects that the marine hydrates are distributed in ascattered manner and cannot self flow and get together, based on well type structure improvement of a 'main borehole + a multi-branch horizontal well', an ore body reservoir is hydraulically cut by avertical hydrate layer to improve the hydrate decomposition efficiency and achieve the design objectives of connecting three-dimensional scattered ore bodies and relieving the problems of a large amount of sand, instability of the reservoir and blockage formed by secondary hydrates. The united mining method comprises the following steps: (1) forming a well by a main borehole; (2) drilling a multi-branch horizontal well: forming a plurality of multi-branch horizontal wells, which form a certain included angle and are distributed in a fixed direction, around the main borehole, and arranging thehorizontal wells in the middle region of a hydrate reservoir, wherein joints between the multi-branch horizontal wells and between the multi-branch horizontal wells and the main borehole are all of sleeve and conventional sand control sieve tube structures; (3) performing limited sand control and reservoir supporting; (4) transforming the reservoir by hydraulic jetting; (5) performing heating toprevent blockage.

Description

technical field [0001] The invention relates to a combined mining method based on fractal theory, which is aimed at marine hydrate reservoirs by performing depressurization and heating in a main well and multi-branched horizontal wells, and belongs to the technical field of marine resource development engineering. Background technique [0002] As a new, efficient and environmentally friendly energy source, natural gas hydrate is widely distributed in terrestrial permafrost zones and continental margin seabeds, and the amount of marine hydrate resources is conservatively estimated to be two orders of magnitude higher than that of permafrost hydrate resources. However, compared with permafrost hydrate reservoirs, the exploitation of marine hydrate reservoirs faces more severe technical and environmental problems, which makes the research of marine hydrates both opportunities and challenges. In 2007 and 2015, my country conducted drilling in the Shenhu Sea area on the northern ...

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Problems solved by technology

However, it can also be seen that compared with sandy reservoirs, the average daily gas production of hydrates in silty reservoirs has a greater gap with the industrial gas flow standard, and the extraction efficiency still needs to be greatly improved

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