高温高压下油井水泥环胶结强度测试新方法

A new bonding strength measurement method for oil well cement sheath under high temperatures and high pressures

固井注水泥完成后,水泥环与套管(Ⅰ界面)、与地层(Ⅱ界面)的胶结强度是影响固井质量的重要因素,但目前的水泥环胶结强度测量方法不能很好地模拟井下条件水泥环的形成以及泥饼的冲洗过程,致使测量出的胶结强度数据不能很好地为现场施工提供参考。为此,在分析现有测量水泥环胶结强度方法的基础上,提出了一种能够模拟井下条件的水泥环胶结强度的测量新方法,并且研制了相应的测量装置。该装置能够模拟高温高压环境下不同钻井液在岩心上形成泥饼、钻井液泥饼的动态冲洗、水泥环的养护形成过程,并测量出水泥环与岩心、水泥环与模拟套管的界面胶结强度等。结论认为,利用该装置能够开展水泥环动态冲洗与高温高压养护实验,还能测量第一界面与第二界面的胶结强度,较之于以前的方法更能贴合现场的实际,更具有实用价值;但要评价地层岩性、冲洗液体系等因素对胶结强度的影响还需要利用该装置做进一步的深入研究。

The bonding strength of cement-casing interface （interface I） and cement-formation interface （interface II） is an important factor affecting cementing quality. However, the current cement bonding strength measurement methods cannot simulate appropriately the formation of cement sheath and the flushing process of mud cake in wellbore conditions, so the measured bonding strength cannot be well used as the reference for field operation. In this paper, the existing cement bonding strength measurement methods were analyzed. Then, a new method which can simulate the cement bonding strength under the condition of the well was put forward, and the corresponding measurement device was developed. The device can be used to simulate the curing process of cement sheath, the dynamic flushing of mud cake and the mud cake which is made of drilling fluids on the cores under high temperatures and high pressures （HTHP）. It can also be used to measure the bonding strength of cement-core interface and cement-simulated casing interface. To sum up, this device can be used for the experiments on dynamic flushing and HTHP curing of cement sheath and the bonding strength measurement of interfaces I and II. Compared with the previous methods, this new method is more applicable and practical, whereas a further study by use of this method and device is needed to evaluate the impact of lithology, flushing fluid system, etc. on the bonding strength.