Mechanical plugging—solid expandable tubular refracturing technology

Abstract

To solve the three major problems of low production, low efficiency and low permeability of oil fields, it is necessary to develop new tight oil layers or shale oil outside the original perforated section in the well that has been perforated. The key to the success of repeated fracturing operations is the ability to block the original perforation of the well. At present, with tubing fracturing construction, volume fracturing of the target reservoir cannot be achieved due to limited displacement, and the effect of reservoir transformation is not obvious, affecting the productivity of the old well. Based on the above problems, this paper proposes a new blocking method suitable for fracturing wells - solid expansdable tubular (SET) plugging. In this paper, it established SET-expansion cone-casing-rubber ring 2D dynamic model which considers the friction, and contact, to analyze the effect of compression and length of rubber ring and the constraint condition of SET on sealing performance; laboratory experiments were carried out and data on driving force, sealing capacity and suspension force were obtained. The results show that optimizing the parameters of expansion cone structure can effectively reduce the residual stress of SET and driving force after expansion; the construction method of SET and the parameters of rubber ring are the main factors that affect the suspension sealing ability, and paper proposes an effective solution; in addition, experiment results show that the SET meets the requirements of fracturing construction with internal pressure greater than 60 MPa and suspension force greater than 600 kN after expansion, and can be used to seal the well body structure of refracturing wells with fewer perforations and shorter distances, and the diameter can be guaranteed to reach 112 mm. The research results provide new ideas and solutions for repeated pressure wells and high-pressure plugging.