Application of Big Differential Temperature Low Density Cement Slurry in Well NP36-3804

In the Well NP-36-3804 drilled in the Xinpu Gu-2 platform, 4,714 m of production casing was required to be cemented in on cementing operation. Conventional cement slurry was unable to meet the requirement of cementing such a long casing string because of low slurry density and big differential temperature. Success of the cementing job required the low density cement slurry to have lower density, to be less affected by temperature difference, and to become set more quickly at normal temperatures. Two high density low density cement slurries, having densities of 1.35 g/cm³ and 1.50 g/cm³ respectively, were formulated by selecting competent lightweight materials, developing high performance anti-gas migration agent, and selecting the best close packing calculation model. It was found in field application that the two slurries had no free water. The cement slurries were stable and had good rheology at operational conditions. API filter loss and thickening performance all met the requirement of field application. The low temperature early strength and the compressive strength of set cement were all satisfactory.