Performance evaluation of ultrafine cement as a grout for reservoir impermeability improvement

Abstract

Although Ordinary Portland Cement (OPC) has been widely used as one of the significant grouting materials, there are many drawbacks to its application in the field. In this study, an ultrafine cement mixed with an expansive agent is proposed as a new grout material by extensively examining its characteristics and performance over conventional grout material (OPC). Both laboratory and field tests were performed, including expansion ratio test, swelling pressure test, compressive strength test, laboratory permeability test, fish toxicity test, scanning electronic microscope (SEM) test, and X-ray diffractometry (XRD) test. Moreover, the electrical resistivity survey was performed on an actual reservoir site grouted partly by OPC and ultrafine cement to compare the efficacy of their impermeability improvement. The test results revealed that the ultrafine cement mixed with an expansive agent manifested superior performance than the OPC. The SEM and XRD analysis results show that a fine needle-like ettringite crystal was produced in the grout material mixed with the expansive agent resulting in the swelling effect. Also, the field permeability test results show that the grout mixed with the expansive agent was able to improve the ground permeability to about $\frac{1}{100}$ and $\frac{1}{10}$ at K = $\mathrm{\alpha }$  × 10⁻³ cm/s and K = $\mathrm{\alpha }$  × 10⁻⁴ cm/s, respectively, which exceeds the target value suggesting that the ground voids are satisfactorily filled with grout materials.