Abstract:

During oilfield workover, it is necessary to control the gel breaking speed of the temporary plugging agent, so that the gel is not broken during the workover to ensure the completion of the operation and is broken quickly after the workover to resume production. For traditional gel breakers, it is difficult to achieve a slow release at the initial stage and a fast release at the late of the workover. This paper describes a cellulose-based sustained-release encapsulated gel breaker with a double-layer film. This gel breaker is evenly mixed with molted Carnauba wax and the solid dispersion pellet is made using the extrusion-speronization method. In the Wurster fluidized bed, a double-layer film with different components is put on the pellet to prepare the sustained-release encapsulated gel breaker. The result of the orthogonal test shows that this method is reliable, the yield of the pellet is 93.2%. SEM result shows that the film on the surface of the pellet is smooth and uniform, and the sealing and unblocking of the film pores are crucial to sustained-release. The results of sustained-release test and simulation test of reservoir gel breaking exhibit that the sustained-release encapsulated gel breaker has an excellent controlled-release effect and reservoir permeability recovery effect. Herein, the preparation method is simple and efficient. The sustained-release of drugs is mainly controlled by the double-layer film.

Key words: double-layer sustained-release film, solid dispersion, extrusion-spheronization, Wurster fluidized bed