Schlumberger

Technical Paper: Live Fiber-Optic Telemetry Downhole Measurements on Coiled-Tubing-Enabled High-Efficiency Sand Cleanout in a Subhydrostatic Well for the First Time in the Gulf of Mexico

Society: SPE
Paper Number: 141249
Presentation Date: 2011
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Abstract

Gulf of Mexico (GoM) reservoirs consist mainly of unconsolidated sandstones. Elevated production rates and high near-wellbore fluid velocities increase the possibility of dragging the unconsolidated sand grains into the wellbore and surface production equipment. Formation sand invasion into wellbore is a common problem in the GoM, especially in wells not completed with sand control features or wells where initial sand control failed. Wellbore sand cleanouts, therefore, represent the majority of coiled tubing (CT) interventions in the GoM. As the reservoirs mature, the number of through tubing well interventions (TTWI) in sub-hydrostatic wells is constantly growing. These types of wells cannot sustain a full column of fluid which presents a significant challenge to maintain circulation and sufficient annular fluid velocity required to transport the solids to surface. Nitrified and foamed cleanouts can provide at-balance or slightly over-balanced downhole conditions necessary to minimize the fluid losses into formation. Nitrified cleanouts are normally considered as more cost effective solution which is quite important since most of the sub-hydrostatic wells are very marginal producers. However, planning and execution of nitrified jobs require accurate well information which is not always accurate or available. This drives the operators to make the most common decision; to utilize the more expensive and extensive cleanout technique - the foamed cleanout - in order to ensure job objectives with reduced risks.Real-time downhole measurements provided by a fiber-optic enabled telemetry CT helps overcome the typical challenges and operational risks associated with sub-hydrostatic well cleanouts; it also helps reduce the overall operational costs by making the job more efficient in terms of time, equipment and product usage. This paper will present a case study of the first optimized CT sand cleanout in the Gulf of Mexico.

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