Pressure-control well-drilling method and device based two gradients

Abstract

The invention relates to a drilling methods and devices based on double gradient control pressure including: 1. surveying underground pressure data and then transmitting to the Sea Central Control System; 2. The Sea Center Control System after calculation, analysis and processing, transmitted the control signals to device that control flow of sea low-density fluidand underground while drilling joint; 3. device that control flow of sea low-density fluid control the volume and flow of fluid through the pump transmitting to the double-wall drill pipe underground, 4. According to the directive of the central control system , adjusting the size of the injection while drilling joint entrance, and the low-density fluid between inside and outside of the drilling hole pipe will injecte between the drill pipe and borehole 5. the drilling fluid returning from the bottom will be diluted by the low-density fluid and in the air shaft ring formed at least two different pressure gradient; 6. drilling fluid can recycle after dealing with the devices. The invention can be used for offshore drilling and earth drilling.

Description

technical field [0001] The invention relates to a method and device for controlling pressure drilling, in particular to a method and device for controlling pressure drilling based on dual gradients. Background technique [0002] In conventional deepwater drilling, the drilling ship and the subsea wellhead are connected by a riser, and the drilling fluid flows downward through the drill pipe, passes through the drill bit, and then flows upward through the annulus between the drill pipe and the wellbore, and the lowered casing section ( conduit section), the riser above the seabed, and circulate back to the drilling ship. There is only one pressure gradient of mud in the whole drilling circuit. When drilling in deep water exceeding 500m, the conventional drilling using the riser system will be prone to technical difficulties that are difficult to overcome with conventional drilling equipment and methods, including: 1. The mooring rig itself must bear the weight of the mooring...

AI Technical Summary

Problems solved by technology

[0009] Among the various technical solutions mentioned above, the continuous circulation system cannot solve the problem of the narrow gap between the wellbore formation pore pressure and fracture pressure; the effect of using tools with reduced equivalent circulation density is not obvious; pressure mud cap drilling and controllable mud cap systems will waste a lot of The drilling fluid is limited, and the formation conditions are limited. The dual gradient is better to solve the problem, but the cost is higher

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