Declining of shallow reservoir reserve urges efficiency effort to switching well architecture from zone-selective gravel pack completion to non-selective tubingless completion. However, zone management in tubingless completion is not as simple as sliding sleeve manipulation in gravel pack well. It requires proper zone isolation of closed zone such as setting plug, tubing patch, or squeezed cement. Therefore, optimum zone management need to be identified to be consistent with cost efficiency effort.

Study in determining optimum zone management captured two nearly identic case of 3 zones of selective well and non-selective well. The well cost, production, and its net present value was compared to evaluate how the reservoir production is managed.

Although selective well has higher initial well cost, but operation cost during the production is significantly low. On the other hand, even non-selective well has lower initial well cost, due to complication on zone management, non-selective well has higher operation cost. The total cost of problematic non-selective well could nearly reach the selective well cost. The complication is identified as downward movement, i.e. re-accessing previously isolated lower zone and isolating upper zone at once. However, this study suggests that strictly following bottom-up production strategy could potentially avoid the complication by 23% more efficient in production and cost index.

Well cost efficiency is not only determined by lower initial well cost. All operating cost during production must be also considered. Optimum well management for both type of completion is a key parameter in order to control the cost efficiency effort. Therefore, well completion design selection must consider not only the cost and production, but also the operation excellence and capability during managing well production in its lifetime.

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