热采井用固井水泥石养护方法及力学性能研究

如何模拟稠油热采井井下环境，对评价稠油井用固井水泥石能否满足热采工况的需求具有重要意义。然而，以往用马弗炉超高温干燥条件养护水泥石的方法，与稠油热采井下的超高温水蒸气环境、水泥石受套管和地层约束等实际情况不符。为此，提出了一套可模拟稠油热采井下超高温水蒸气环境的固井水泥石养护装置及方法，并对比研究了超高温干燥与水蒸气条件下，试样尺寸、加热速率对固井水泥石抗压强度和完整性的影响。研究结果表明，小尺寸水泥石试样、低升温速率和水蒸气环境有利于保证在加热过程中试样受热更均匀，从而有利于缓解因受热不均导致开裂的现象，进而维持水泥石更高的抗压强度及完整性。因此，通过该研究结果，建议室内实验模拟方法应充分考虑实验条件对模拟结果的影响；同时，基于此研究结果，建议在实际生产过程中，可适当优化注蒸汽的工艺过程及参数，以降低注蒸汽过程对固井水泥石的加热速率、减少对水泥石的不利影响。 

Curing Method and Study on the Mechanical Performance of Set Cement in Cementing Thermal Production Wells

Simulation of downhole conditions in thermally producing heavy oils is of great importance to the determination of weather the set cement is able to satisfy the needs of thermal production. In the past, set cement was cured in a dry muffle oven with ultra-high temperatures, and this curing environment is not conforming to the conditions encountered downhole a heavy oil thermal production well, such as ultra-high temperature with vapor, and the set cement is constrained by casing string and formation. A new apparatus and a new method have been developed to make the conditions of laboratory experiment more similar or equivalent to the conditions prevailing downhole. With this new apparatus and the new method, the effects of the sample size and rate of heating on the compressive strength and integrity of set cement were studied at ultra-high temperatures with and without vapors. It was found that set cement of small size, low rate of heating and vapor are favorable to the uniform heating of the sample, and this in turn is favorable to the prevention of set cement fracturing by uneven heating and the maintenance of higher compressive strength and integrity of the set cement. It is thus suggested that, based on the study as said above, laboratory simulation should consider the effects of experiment conditions on the simulation results. It is also suggested that the process and parameters of vapor injection be optimized to reduce the rate of heating of set cement by the injection of vapor and to minimize the adverse effects of vapor injection on the set cement.