Formation Scaling Characteristics During Waterflooding Development in Gaskule Oilfield

Gasikule oilfield is one of the main oil fields in Qinghai oilfield with a long period of waterflood development. In the process of development, the scaling problem of well shaft, ground system and waterflood formation is serious, which brings great challenges to production. Therefore, it is of great significance to explore the compatibility of formation water and injected water and the characteristics of formation scaling in the process of waterflood development. In this study, the compatibility experiment of injected water and formation water was carried out by simulating the formation environment, and the long sand-filling model was developed according to the physical parameters of the target reservoir. The pressure changes at different positions of the core during the water injection process were studied experimentally, so as to investigate the scaling position of the core and its influence on the injected water pressure. Moreover, the mineral composition at the pressure changes were analyzed by X-ray diffraction. The results show that calcium carbonate is the main component of scaling sample at different layers, and scaling mainly occurs at the inlet end of core (near well zone). With the increase of injection amount and waterflooding time, more scale is generated, and blockage is formed at the inlet of core, resulting in increased water injection pressure and water injection difficulty. By comparing the inlet pressure values of deep and shallow layers, it can be found that scale is formed in the core of deep layer at the early stage of water injection, and water injection pressure rises slowly. After 80 h, since the scaling generated, the water injection pressure increased by nearly 50% to 24 MPa. At the initial stage of water injection in core of shallow layer, there was rarely scale formation, until 180 h later, the pressure began to rise gradually. In addition, under the same injection rate, temperature has a great influence on the scale generation. It is easier to generate scale with higher temperature. This study can provide theoretical guidance for the optimization of injection water quality and the prevention of scale formation in the process of waterflooding development.