A dynamic scale location monitor method to predict oilfield blockage during water flooding

Scale formation of oil and gas production is a serious problem as major causes of formation damage affecting recovery efficiency. Investigation the permeability reduction caused by scale formation of sandstone cores by mixing formation water and injection water with different ratio under various temperatures and differential pressure is conducted in this study. X-ray diffraction (XRD) technique is used to investigate to judge the types of inorganic scale by analyzing its crystalline composition. Scale prediction and beaker test results show that the inorganic scale produced by poor compatibility of formation water and injection water in XX oilfield is calcium carbonate. With the increase in the ratio of injection water to formation water, the scale of calcium carbonate scale first increases and then decreases. The scale of calcium carbonate is gradually increasing with the decrease of pressure and increase of temperature. The dynamic scale location monitoring method is proposed to predict the degree of oilfield blockage based on the pressure difference between multi-pressure measuring points of the core. Dynamic scale location monitor tests show that inorganic scale blockage occurs in the position range of 0-1/10 around injection well in the early stage of water flooding, and further increase of injection rate will result in migration leading the blockage occurs in the position range of 1/10-6/10 near the injection wells. The prediction results are consistent with the actual blockage in the oilfield, proving that this method guides significance of predicting blockage in water flooding. This method can be used in both onshore and offshore oilfields using water flooding as a secondary oil recovery.