The effective cementing of oil and gas wells in deep water weakly consolidated formation is vital for the stable supply of world energy. During the cementing operation, the cement slurry was injected into the formation under pressure differential, and thereby forms a strength transition zone in the adjacent area of wellbore. To properly guide the formation cementing operation, a unified model for predicting the diffusion distance of cement slurry in weakly consolidated formation considering different diffusion patterns was proposed in this paper. The unified model described the diffusion process of cement slurry by the governing equation of compaction grouting, penetration grouting and fracture grouting. The criterion to identify the diffusion pattern was proposed as well. Results show that, when the pump pressure is below the threshold for penetration, compaction grouting is the sole diffusion form, with its distance influenced by the wellbore radius, the shear modulus of the soil, and the stress within the formation boundaries. Exceeding this pressure allows for both compaction and penetration grouting to coexist, where the penetration grouting's diffusion distance depends on the rheological properties of the cement slurry, the formation's physical properties, and operational conditions. Upon reaching the initial cleavage pressure, significant cracking occurs, and the diffusion of the cement slurry extends to the length of these cracks, with the fracture grouting model being based on the Drucker-Prager criterion and influenced by the formation properties and operational factors. The proposed model was validated by numerical simulation results, which showed good performance to predict the diffusion distance of cement slurry. This model provides a costeffective approach to guide the cementing operation of weakly consolidated formation in deep water.

来源平台：CONSTRUCTION AND BUILDING MATERIALS