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.

Drylands impacted by energy development often require costly reclamation activities to reconstruct damaged soils and vegetation, yet little is known about the effectiveness of reclamation practices in promoting recovery of soil quality due to a lack of long-term and cross -site studies. Here, we examined paired on -pad and adjacent undisturbed off -pad soil properties over a 22 -year chronosequence of 91 reclaimed oil or gas well pads across soil and climate gradients of the Colorado Plateau in the southwestern United States. Our goals were to estimate the time required for soil properties to reach undisturbed conditions, examine the multivariate nature of soil quality following reclamation, and identify environmental factors that affect reclamation outcomes. Soil samples, collected in 2020 and 2021, were analyzed for biogeochemical pools (total nitrogen, and total organic and inorganic carbon), chemical characteristics (salinity, sodicity, pH), and texture. Predicted time to recovery across all sites was 29 years for biogeochemical soil properties, 31 years for soil chemical properties, and 6 years for soil texture. Ordination of soil properties revealed differences between on- and off -pad soils, while site aridity explained variability in on -pad recovery. The predicted time to total soil recovery (distance between on- and offpad in ordination space) was 96 years, which was longer than any individual soil property. No site reached total recovery, indicating that individual soil properties alone may not fully indicate recovery in soil quality as soil recovery does not equal the sum of its parts. Site aridity was the largest predictor of reclamation outcomes, but the effects differed depending on soil type. Taken together, results suggest the recovery of soil quality - which reflects soil fertility, carbon sequestration potential, and other ecosystem functions - was influenced primarily by site setting, with soil type and aridity major mediators of on -pad carbon, salinity, and total soil recovery following reclamation.