The Scaling Tendency Prediction in Water Injection

摘要

In the process of the oil production, the temperature, pressure and the balanced state among oil, gas and water are changing in every part of the whole production system. If the injected water is incompatible with formation water, or that the pressure, temperature and chemical components of the fluid change in the process of flowing, there is a possibility that scales may form. According to the exploration practice in many oilfields, there can be scale formation in every part of passage through which the oil, gas and water pass from the layer to the surface. This can cause the reservoir damaged, borehole and surface pipes blocked and equipment failure, which will further affect the normal oil production and impair the benefits of oilfields seriously. In the secondary recovery, if the injected water doesn' t match the formation water, there will usually happen a heavy scale formation. In North Sea, the injected water is incompatible with formation water, so is it in Changqing Oilfield. Because of that, CaSO_4 and BaSO_4 seals form in the layer, borehole, oil pipe and tube e-quipment, which lowers the physical condition of the reservoir and reduces the percolation conditions, which in the end results in the reduction of output and the ability to inject water. So, in order to secure that the exploration or production benefit of the oilfield will not be affected by scale for-mation, it is necessary to make the scaling tendency forecast so as to take measures in advance to prevent the scale from happening. To guide the field production, this article sets up the forecast models of common scales found in the field. Partly the model of coexistence of many scales is fully studied here. Now the principles and methods to carry out them are detailed elaborated here.