Abstract: In cementing operation in ultradeep wells with long cementing sections, there is a large difference between the temperature at the top of the cement slurry and that at the bottom of the cement slurry. The low temperature at the top of the cement slurry retards the development of the strength of the set cement. To solve this problem, an early strength additive named EDTA-LDH (EDTA intercalated hydrotalcite) was developed through water solution polymerization. A cement slurry for working at big temperature difference conditions was formulated with EDTA-LDH. Laboratory experimental results show that this early strength additive has retarding effect to some extent; at a concentration of 2.0% EDTA-LDH and 4.0% retarder, a cement slurry has thickening time of 509 min at 240 ℃. After aging at 60 ℃ for 1 d or at 30 ℃ for 6 d, the cement slurry has compressive strengths of both greater than 7 MPa, and experiences maximum temperature difference of 210 ℃. The use of EDTA-LDH is beneficial to the development of the strength of the cement slurry column in low temperature without affecting the adjustability of the thickening time of the cement slurry. This early strength additive can work normally at temperatures above 300 ℃, and is suitable for cementing wells with large temperature differences.
LIU Jingli, LIU Pingjiang, REN Qiang, et al.A cement slurry for large temperature difference in wells of ten thousand meter depth[J]. Drilling Fluid & Completion Fluid，2023, 40（6）：1-9. doi: 10.12358/j.issn.1001-5620.2023.06.012.
Abstract: In well cementing operation, to ensure that the cement slurry is safely pumped int the hole, the cement slurry shall have an appropriate thickening time. The circulating temperature of the cement slurry is one of the important factors affecting the thickening time of the cement slurry. The methods for calculating the circulating temperature of a cement slurry in the API Recommended Practice do not satisfy the need for calculating the circulating temperature in different areas and different borehole conditions. Thus, an unsteady state flow heat transfer model is established. By measuring the thermal physical parameters, the coefficients of heat conductivity and specific heat capacities of the drilling fluid, the casing strings, the rocks and the cement slurry are determined, and the temperature field of the cement slurry during injection and displacement is thus simulated. The simulation results show that increasing the coefficients of heat conductivity of the cement slurry and the spacer fluid reduces the circulating temperature of the cement slurry. Decreasing the coefficients of heat conductivity of the casing string and the rocks, the circulating temperature of the cement slurry changes in less than 1 ℃. Data acquired from the Zhejiang Oilfield and the Tarim Oilfield show that the difference between the measured well cementing temperatures and the simulated well cementing temperatures is less than 5 ℃, indicating that the simulated data is accurate and has good consistency with the measured data. Studies on the factors affecting the circulating temperatures of a cement slurry during injection and displacement in well cementing operations provide theoretical supports to the design of the properties of the cement slurry, thereby ensuring the efficient and safe well cementing operations.
ZHENG Rui, GUO Yuchao, ZHANG Chunhui, et al.Effects of thermal physical parameters on circulation temperature of cement slurries[J]. Drilling Fluid & Completion Fluid，2023, 40（6）：1-6. doi: 10.12358/j.issn.1001-5620.2023.06.013.
Competent Authorities：China National Petroleum Corporation Ltd
Sponsored by：CNPC Bohai Drilling Engineering Co. LtdPetroChina Huabei Oilfield Company
Address： Editorial Department of Drilling Fluid and Completion Fluid, Bohai Drilling Engineering Institute, Yanshan South Road, Renqiu City, Hebei Province