Study On Cementation Quality In Fat Sand Casing Hole

Daqing oil field had been developing for many years and it was being in the late stage. As the subdividing exploitation technology increased gradually, there were more and more requirements on cementing quality in adjustment well. But the recent data base shows that there is poor coordination between the merit factor of cementing quality and the needs of field exploration. The subsequent techniques are determined directly by cement job quality, which affects the recoverability of crud oil. For fine cementing job, the displacing efficiency of cement slurry and the cementing strength of interface are two important factors.The main problem in fat sand casing was that when casing was adhered by sand already, the remained slurry among sand grain couldn't be fully replaced, which increased the casing roughness-the flowing resistance of slurry on casing boundary. The remained slurry couldn't be replaced which decreased the replacing efficiency of cement slurry. Sometimes sand size was too big to flow-back cement slurry, and as the sand size increased the displacing efficiency dropped gradually.In this paper, three factors are analyzed of fat sand casing well those are replacing efficiency, eccentric annular replacing efficiency and cement strength. The Delayed acoustic variable density logging method was adopted to detect cementing quality. From the result it is found that cement slurry is poor displaced, and the flowing resistance of cement slurry from sand grain is the main cause of oil, gas and water channeling. The effect of adhering sand size on displacing efficiency is studied, and then the displacing efficiency model is built which is about the sand size and the sand density that is verified to be correct from experiment. From the experiment of cementing strength, the relationship between cementing strength and surrounding environment and gel-time is determined. A new method is proposed that is used to calculate the cement strength of fat sand casing well. At last, the method of studying and evaluating is built and the measuring standard is put forward.