Industrial feasibility study for the use of barite as a permanent well barrier element
Master thesis
Permanent lenke
https://hdl.handle.net/11250/2976408Utgivelsesdato
2021Metadata
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Sammendrag
As more and more wells reach the end of their production life, the focus on permanentplug and abandonment has increased in interest. Cost-efficient abandonment of wellswith ceased production is an important economic goal for the oil and gas industry. Adominant part of the plug and abandonment operation is the removal of steel tubularand casing to establish a rock-to-rock cross-sectional barrier in the well. This process isaggravated by settled barite and other mud solids accumulated at the bottom of the casingannulus, increasing over-pull and resulting in several cut and pull runs. If the settledbarite, which is already in place behind the casing, could function as a part of a barrierenvelope, it could significantly reduce such operations.
This thesis’s primary objective is to investigate if industrial field data support the utilizationof settled barite as a feasible annulus barrier element. A total of 307 wellboreswere analysed for cut and pull operations, where attempts to circulate settled barite outof the annulus were performed. A three-layered model was suggested using theories ofbarite segregation and settling regimes in drilling mud. The model was used to calculatethe hydrostatic pressure of an annulus column of drilling mud settlements to accuratelypredict the differential pressure excreted through the settled barite plug. Twenty-two ofthe investigated wellbores showed potential for further analysis, and four wells displayedplugs of settled barite that would prevent fluids from a re-pressurised reservoir to flowunintentionally to the surface or other formations.