井内水泥环物性变化及影响因素分析

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

大庆油田调整井固井质量由于检测时间的延长 ,固井质量优质率大幅度降低 ,已不能满足油田开发对固井质量的要求 ,调整井固井质量亟待提高。结合A级油井水泥原浆的物性和地层的物性 ,分析了在延时条件下影响声变差异的原因。通过水泥强度分段增长曲线分析 ,水泥浆 (石 )表观体积收缩、渗透率、孔隙度、毛细管力、弹性模数以及地层水渗流的冲蚀作用等随时间的变化规律研究 ,提出了在延时条件下声变的差异是由于地层流体状态、地层应力状态等的不同而引起的。建议通过调整和控制地下情况 ,来改善声变差异。结合大庆油田调整井的实际情况 ,给出了采用A级油井水泥原浆固井保证固井质量的边界条件是地层压力小于 12MPa ,层间压差小于3MPa ,地层弹性模数大于 2 0GPa。萨南油田的矿场试验表明 ,若地下环境相对稳定 ,固井后 15d测声变的固井质量是能够保证的。

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.