A method for constructing a high-strength chamber at the bottom of a vertical well

Abstract

A method for constructing a high-strength chamber at the bottom of a vertical well, which is used for exploiting natural gas hydrates in sea areas, comprising the following construction steps: drilling into the stratum overlying the hydrate; drilling into the stratum below the hydrate floor; expanding the cavity in the stratum below the hydrate floor High-strength cement primary piles are formed by pouring high-pressure cement slurry without drilling; drilling of high-strength cement primary piles; secondary cavity expansion; chamber slag cleaning; cavity expansion inspection; The invention adopts the technology of reaming cast-in-place piles, through two times of cavity expansion and two times of pouring into piles, the diameter of the initial pile is relatively large, and the final pile is filled with cavity expansion on the basis of the initial pile, and the final pile has high strength and regular shape. The bottom hole chamber of the vertical well is built on the terminal pile, and the formation strength around the chamber is high, which can meet the requirements of gathering gas from horizontal wells to vertical wells in multiple well groups.

Description

technical field [0001] The invention relates to the technical field of marine natural gas hydrate, in particular to a method for constructing a high-strength chamber at the bottom of a vertical well for natural gas hydrate in the sea. Background technique [0002] Although the test production of natural gas hydrate in the Shenhu area of ​​the South China Sea in 2016 has achieved great success, due to the limitation of the controllable reservoir area of ​​vertical wells, the daily gas production and the continuous stable production time are far from enough, and there is still a long way to go before the industrialization of hydrate production. For long distances, it is an inevitable trend to apply horizontal well drilling technology and multi-well group connection and convergence production technology to the pilot test area for gas hydrate test production. The current global sea area natural gas hydrate test production plan adopts the test production technology of the vertica...

AI Technical Summary

Problems solved by technology

For drilling in sea areas, due to the softness of the seabed, if you want to obtain a cavity with standard shape, high strength and stability, you must build a pile body whose strength gradually decreases from the center to the periphery. Stability plays a vital role. If the form of reaming cast-in-situ piles is directly used, the strength in the reaming cavity will be high, and the sudden transition to the soft seabed stratum is not conducive to the stability of the chamber; irregular in shape

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