Abstract

Sand production caused the abandonment of two production wells out of four in a gas field located in the Netherlands sector of the North Sea. The forced two abandoned wells due severe sand production accounted for 75% of total gas production from the field. The loss production was unexpected. This paper describes how geomechanics was applied to develop a screenless completion design for one well, and cased-hole with gravel packs for three others, to re-establish economic sand-free production rates for the field.

A geomechanics study of the reservoir sections of the abandoned wells examined the mechanical properties, including rock strength and plasticity, as well as the state of stress acting on the producing sections. The study predicted the sanding history of both wells accurately. Modelling indicated that a thin sand layer with low rock strength was the main contributor to the overall sand production. This was later validated with a Downhole Sand Detector Tool. The modelling also indicated that sand production was likely from other, stronger sections of the reservoir as the field continued to deplete

Once a validated prediction of sand failure had been constructed for the reservoir, the study investigated improvements to the well design that would give both economic production rates and sand-free production for the lifetime of the field. In addition to considering geomechanical properties, the study investigated the geometry of the completion to find the most stable orientations for the wellbore and the perforations.

After an economic feasibility study, one of the abandoned wells was sidetracked along the optimally selected trajectory and perforated with oriented guns, isolating identified weak zones. The field has been producing since this remedial work without any sand production, and the missed production has been recovered. As the results, this meets the operator production and recovery objectives for the field.

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