Li Yanming, Liu Kaiqiang
China Coal Technology Engineering Group (CCTEG) Chongqing Research Institute, Chongqing 400039, China.
School of New Energy and Materials, Southwest Petroleum University, Chengdu 610500, China.
ACS Omega. 2023 Feb 24;8(9):8346-8354. doi: 10.1021/acsomega.2c07090. eCollection 2023 Mar 7.
In a heavy oil thermal recovery well, cement paste experiences the cyclic elevated temperature and steam of steam stimulation, the elevated temperature and steam of steam driving, and the high-concentration CO (HCC) of in situ combustion conditions in sequence. To understand the effects of different conditions of heavy oil thermal recovery wells on the properties and microstructure of the cement paste, this paper investigated the influence of the cyclic elevated temperature, elevated temperature, and high-concentration CO conditions on the compressive strength of the cement paste. Then, low-field nuclear magnetic resonance, scanning electron microscopy, and X-ray diffraction were used to test the pore structure, microstructure, and crystal type of the cement paste cured under different conditions. Experimental results showed that the elevated temperature curing loosened the microstructure of the cement paste and increased its pore size and porosity, resulting in reducing the compressive strength to 21.04 MPa, compared with that of the cement paste at cyclic elevated temperature. For the cement paste cured under high-concentration CO conditions, the calcium hydroxide and calcium-silicate-hydrate reacted with CO to generate granular vaterite, aragonite, and calcite in the pores and cracks, which repaired the cement paste by reducing the porosity and pore size of the cement paste and increasing its compressive strength. When the carbonation time increased to 28 days, the cement paste was completely carbonized, and the compressive strength of the cement paste increased by approximately 169%, compared with that of the cement paste cured at an elevated temperature.
在稠油热采井中，水泥浆依次经历蒸汽吞吐的循环升温与蒸汽、蒸汽驱的升温与蒸汽以及火烧油层条件下的高浓度CO（HCC）。为了解稠油热采井不同条件对水泥浆性能和微观结构的影响，本文研究了循环升温、升温及高浓度CO条件对水泥浆抗压强度的影响。然后，利用低场核磁共振、扫描电子显微镜和X射线衍射测试了不同条件下养护的水泥浆的孔隙结构、微观结构和晶体类型。实验结果表明，与循环升温下的水泥浆相比，高温养护使水泥浆微观结构疏松，孔径和孔隙率增大，导致抗压强度降低至21.04MPa。对于在高浓度CO条件下养护的水泥浆，氢氧化钙和硅酸钙水化物与CO反应，在孔隙和裂缝中生成粒状球霰石、文石和方解石，通过降低水泥浆的孔隙率和孔径并提高其抗压强度来修复水泥浆。当碳化时间增加到28天时，水泥浆完全碳化，与高温养护的水泥浆相比，其抗压强度提高了约169%。
