WU Zhiqiang¹， ZHANG Xingquan¹， XIN Fubin²， LING Xingjie²， HUANG Zhiqiang² 

1. CNOOC Research Institute Co. ， Ltd. ， Beijing 100028， China； 2. College of Petroleum Engineering， Yangtze University， Wuhan 430100， China

Abstract

Objective　To reduce the liquid column pressure in cement slurry and prevent formation rupture and loss，low-density cement slurry incorporating micro silicon，fly ash，and hollow glass microspheres is widely used in shallow deep-water cementing operations in the South China Sea.Ensuring the quality of cementing and sealing under low temperatures and low-density conditions is a key technical issue in developing deep-water oil and gas resources in this region. However，there is a lack of in-depth research on the relationship between the particle characteristics of the density reducers and the cement stone-casing interface.

Methods　The study tested micro silicon low-density cement slurry with densities of 1.70 and 1.50 g/cm³ ，fly ash low-density cement slurry， hollow glass microspheres low-density cement slurry，and composite low-density cement slurry combining hollow glass microspheres with micro silicon and hollow glass microspheres with fly ash， both with densities of 1.50 g/cm³ . The compressive strength，volume shrinkage rate，and cement stone-casing interface bonding strength were tested under the curing conditions of 15 ℃. The effects of different density reducers on the phase composition of the cement were analyzed using X-ray diffraction（XRD）.The microstructure and hydration product characteristics of the cement stone with different density reducers were observed using scanning electron microscopy （SEM）. The porosity and pore size distribution of the cement stone were measured using mercury intrusion porosimetry（MIP）.

Results and Discussion　Cement stone using hollow glass microspheres as a density reducer exhibited the highest compressive and interfacial bonding strengths.Both micro silicon cement and micro silicon-hollow glass microspheres cement demonstrated higher compressive and interfacial bonding strengths compared to fly ash cement.After 7 days of curing，the compressive strength of the 1.70 g/cm³ hollow glass microspheres cement stone was 18.54 MPa，with an interfacial bonding strength 61.5% higher than that of the fly ash cement stone. The compressive strength of 1. 50g /cm³ hollow glass microspheres cement stone was 14.56 MPa，with an interfacial bonding strength 112.5% higher than that of fly ash cement stone.Volume shrinkage rate tests showed that the linear volume shrinkage rate of hollow glass microspheres cement stone was lower than that of the micro silicon and fly ash cement stones. At a density of 1.50 g/cm³ ，the linear volume shrinkage rates of the three types of low-density cement stones over 7 d were -0.05%，-0.1%，and -0.08%，respectively.XRD analysis showed that the CH diffraction peak intensity of micro silicon cement stone was lower than that of other cement stones with the same density，indicating that micro silicon could further participate in secondary hydration reactions while adjusting to the cement slurry density， consuming part of the CH and generating C-S-H gel，which enhanced interface bonding. SEM analysis showed that the microstructure of the low-density cement stone with hollow glass microspheres was the densest， with the microspheres closely cemented with the hydration products，while the microstructure of the fly ash low-density cement was the loosest.Micro silicon could optimize the pore structure through pozzolanic and filling effects. At densities of 1.70 g/cm³ and 1.50 g/cm³ ，pores smaller than 20 nm accounted for 55.6% and 49.6% of the total，which were higher than 52.1% and 48.3% observed in fly ash cement stones.

Conclusion　Hollow glass microspheres with low density demonstrate excellent weight reduction capacities，enabling a significant decrease in the water-cement mass ratio of the cement slurry，reducing free water content in pores， optimizing the pore structure of the cement stone，and inhibiting shrinkage. This improves both the compressive and interfacial bonding strengths of the cement stone. Micro  silicon optimizes the pore structure through pozzolanic effect and filling effects，thereby improving the interfacial bonding strength of low-density cement. Conversely，the weaker pozzolanic activity and filling effect of fly ash lead to the lowest interfacial bonding  strength for low-density fly ash cement.

Keywords：weakly consolidated formation； low-density cement slurry；density reducer；compressive strength；interface bonding properties

Get Citation:WU Zhiqiang，ZHANG Xingquan，XIN Fubin，et al.Influence of density reducer particle characteristics on bonding properties of low-density cement stone-casing interface［J］.China Powder Science and Technology，2025，31（3）：1−10.

Received:2024-06-10.Revised:2024-08-09,Online:2025-03-03.

Funding Project：国家重点研发计划项目，编号：2022YFC2806504；国家自然科学基金项目，编号：52274026；中海油科技项目，编号：KJGG-2022-17-04、KJGG-2022-17-05。

First Author:武治强（1985—），高级工程师，博士，研究方向海上钻完井技术。E-mail：wuzhq2@cnooc. com. cn。

Corresponding Author:黄志强（1964—），教授，硕士，研究方向油气井工程与材料。E-mail：huangzq1356@163. com。

DOI：10.13732/j.issn.1008-5548.2025.03.014

CLC No:TE256； TB4                Type Code:A

Serial No:1008-5548（2025）03-0001-10