Search

During the thermal recovery of heavy oil thermal recovery wells, improving the mechanical properties and integrity of the cement ring is of great significance for the safe and efficient exploitation of heavy oil resources. This paper studies the relative properties of calcium aluminate cement and three kinds of slags under the conditions of 50°C × 1.01 MPa and 315°C × 20.7 MPa. CAC-slag composite material performance was evaluated using the cement paste compressive strength and permeability tests to study the physical properties of CAC with blast furnace slag. X-ray diffraction analysis, scanning electron microscopy (SEM), and thermal analysis (DSC/TG) were carried out to investigate the mineralogical composition of CAC with blast furnace slag. Results show that adding blast furnace slag did not affect the performance of cement slurry. Moreover, C2ASH8 curing occurred at low temperature, the microstructure of CAC paste was compact, and the permeability resistance was improved, thus improving the low-temperature properties of neat CAC. When cured at a high temperature, the CAC paste was mainly hydrated with C3ASH4 and AlO(OH), which had a well-developed crystal structure. Adding blast furnace slag can improve the CAC resistance to high temperature.

The gas lift in the offshore M field will be performed with high CO2‐content associated gas, but the change of wellbore temperature and pressure during the injection process will lead to the change of phase and physical parameters of associated gas, which has a great impact on the design of gas lift. To ensure the smooth implementation of gas lift in the offshore M field, this paper conducts a study on the physical parameters of associated gas considering the change of CO2 phase state. We obtained the density, viscosity, compression factor, constant pressure specific heat capacity, thermal conductivity, and Joule Thomson coefficient at each temperature and pressure by Hysys calculation, and regression analysis to obtain the regression model of the physical parameters; finally, the regression model was compared with the flash experiment and Hysys calculation results. The results show that the CO2 phase change has a large influence on the physical parameters; R2 > 0.8, which indicates that the regression model has sufficient reliability; the results of the comparison show that the empirical formulas of all physical properties have sufficient accuracy and superiority except Joule–Thomson coefficients. In addition, the empirical formula of the Joule–Thomson coefficient also has good accuracy and superiority at the pressure not exceeding 22 MPa. The study of phase changes and physical parameters of associated gas with high CO2 content provides a basis for subsequent gas lift design in the offshore M field and multiphase flow calculations in the wellbore during the gas lift. Although this study is only applicable to this sample, it also provides a feasible research method for other samples. [ABSTRACT FROM AUTHOR]

Carbon dioxide capture and storage is the primary way to reduce greenhouse gas emissions on a large scale. Carbon dioxide storage is the critical link of this technology, and the way in which to achieve long-term storage is a problem to be considered. The elastic and anti-corrosion cement slurry is the key for the successful storage of carbon dioxide. In order to develop the cement slurry for carbon dioxide storage, the influence of resin with both elastic and anti-corrosion properties on the performance of a cement slurry was investigated. The dispersant, retarder, and filtrate reducer suitable for the cement slurry were studied, and the performance of the designed cement slurry for carbon dioxide storage was evaluated. The experimental results show that the resin can reduce water loss and improve the elasticity and corrosion resistance of cement paste. The elastic modulus and corrosion depth of the resin cement slurry were significantly lower than those of the non-resin cement slurry. By studying the dispersant and retarder, the performances of the cement slurry for carbon dioxide storage was found to be able to meet the requirements of the cementing operation. The water loss of the designed cement slurry was low, the thickening time was more than three hours, and the rheological property was excellent. The elastic modulus and corrosion depth of the designed cement slurry was very low. The cement paste had a strong resistance to damage and corrosion. The structure after corrosion was denser than the conventional cement slurry, and the characteristic peak of corrosion products was weaker. The designed elastic and anti-corrosion cement slurry was well suitable for the cementing operation of carbon dioxide storage wells. [ABSTRACT FROM AUTHOR]