Where exactly, are we supposed to focus on the inhibition of hydrate-dissociation?
Should the focus be confined only within the drill-pipe associated with the gas-hydrate bearing sediments?
Or
In the regime, where the low-temperature drilling fluid keeps circulating up to BOP?
Or
In both the above regions?
Background:
It is known that hydrate dissociation would lead to varieties of engineering problems during drilling through a hydrate-bearing sediment. The enhanced heat generation from the drill bit cutting and its associated accelerated friction between the drilling-tool and the well-bore (apart from the variations in geo-static stress) make it very difficult to maintain the required low-temperature condition for hydrate stability, while the released-gas from hydrate-dissociation leads to an enhanced pore-pressure within the hydrate-bearing sediments; and in turn, leads to a mitigated effective stress; and in turn, leads to a reduction in hydrate-bearing formation strength. In addition, released-gas from hydrate-dissociation dilutes the drilling fluid, which has an adverse effect. Further, dissociated-gas might clog the drill pipe-line as well as BOP during shut-in. Requires an understanding on the inhibition of hydrate-dissociation rather than on the promotion of hydrate-dissociation.
I totally agree with your background information. In addition to the points you raised, the gas released from the dissociation of hydrate can gasify the drilling mud. This will create a gas cut mud which has a reduced mud weight. Reduction in the drilling mud density will definitely affect the fluid hydrostatic pressure, change the rheological properties of the drilling mud and lead to wellbore instabilities. However, hydrate dissociation in a confined state such as a shut-in well, can create excessive pressure which can fracture the formation and cause stuck pipe.
I think the best practice is to focus on both regions, and the real-time pressure and temperature profiles of the well for effective inhibiting procedure.
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