Cementing of Wells with Lost Circulation in Rumaila Oilfield

Low fracturing pressures of the Damman and Hartha formations in the Rumaila Oilfield have been causingmud losses in cementing the technical casing strings. The existence of borehole wall washout (erosion) and tight holes have resulted in poor cement slurry displacement. To overcome these problems, a plug flow low friction prepad fluid has recently been developed. This prepad fluid, having densities between 1.00 g/cm³ and 1.80 g/cm³, was formulated with non-polymeric suspending agent DF-1, flushing agent DF-3, and organic solvent, DF-4, as flow pattern modifier. It has low flow friction, high flushing performance and easy-to-control rheology, which help improve the displacement efficiency of cement slurry at low flow rates. A low density (1.00-1.35 g/cm³) cement slurry was formulated with nano silicon sol as the stabilizer to improve the settling stability of the slurry. The compressive strength of the set cement at room temperature after 48 h is greater than 14 MPa. Cementing techniques using the prepad fluid and the cement slurry were developed as guidance for proper field operation. The prepad fluid and the cement slurry have been successfully used on 5 wells, with no lost circulation. Number of well sections cemented with acceptable job quality is increased by 21%.