Cementing technology for high-pressure salt-anhydrate bed in HFY Oilfield

In light of the characteristics of long cementing section(about 2 000 m) of ?244.5 mm casing in high-pressure salt-anhydrate bed in HFY Oilfield of Iraq, high pore pressure (2.15~2.20 g/cm3), narrow safe cementing window (0.08 g/cm3)and low cementing section temperature (30~70 ℃), as well as the problems existing in previous cementing operation, the test and research have been carried out, the optimal salt concentration for salt-tolerant high-density cement slurry of which the density is 2.28 g/cm3 has been determined as 10%~15% (BWOW). In light of the characteristics of weighting and close packing compressible packing model and through calculation and evaluation of solid-phase water demand, the reasonable composition of weighting hematite and BCW500S (4∶1) as well as the concentration (80%~83% (BWOC) ) under such density have been determined. The salt-tolerant carboxylate based dispersant has been introduced, the concentration of filtration loss reducer has been optimized from 10% to 6%~8% (BWOW), and the HFY high-density salt-tolerant cement slurry system so formed has the characteristics such as high slurry stability, good rheological property, controllable thickening time, and quickly-developing early-stage compression strength at low temperature. On the basis of the optimization of cementing program, the cementing of ?244.5 mm casing is simplified from double-stage cementing to single-stage cementing, and the cementing quality is obviously improved. The successful application in 28 wells indicates that, this technology settles the cementing difficulty in high-pressure salt-gypsum bed with narrow-density window.