ANALYSIS ON THE PHYSICAL PROPERTY CHANGES OF CEMENT RING AND ITS INFLUENCING FACTORS

For the extending of testing time after cementing, the cementing quality of adjustment wells in Daqing Oilfield decreases dramatically, and this can not meet the requirements of Oilfield development. Combining the physical property of Grade A cement slurry with the formation characteristics, the causes that influencing the acoustic changing differences in time-delaying condition are analyzed. By analyzing the section-increasing curve of cement strength, and studying the changing tendency of cement volume contraction, permeability, porosity, capillary force, elastic modulus and the washing out of formation fluid seepage flow vs. time, it is proposed that the differences of acoustic change is caused by the variation of formation fluid conditions and formation stress conditions. By adjusting and controlling the underground conditions, the differences of acoustic change can be amended.The boundary conditions for good cementing quality of Grade A cement are recommended, i.e., the formation pore pressure is lower than 12MPa, the differential between layers is lower than 3MPa, and the formation elastic modulus is higher than 20GPa.