Fine cementing technique for matured oilfield production tail

For the matured fields produced for more than 50 years, they have gone through the processes of production ascending, peak oil rate, stable production, multi-time drilling infill wells, pressured water/polymer injection, and high strength production. And some unfavorable features have been formed vertically, which are high pressure and low permeability, low pressure and high permeability, ultra high pressure, underpressure andlow pressure loss, multipressure strata coexistence, etc., resulting in a lot of difficulties of recover residule oil in production tail stage. Based on analyzing and experimentally studing the effect factors, taking system engineering as direction, stressing the combination of exploration, development, geology, drilling, completion and cementing, the complex structure well drilling, the special process completion and cementing techniques, and multi-function slurry are taken, which can suit for the reservoir characteristics, protect formation, and enhance oil recovery, with the aim of guarantee the effective sealing between different pressure or different permeability layers and the consolidating quality between the first and second interfaces. The results show that the first interface cementing quality excellence ratio increase by 26.3%, and the second interface cementing quality increase by 18.5%. It is carried out that the effect separation between different pressure layers, expecially between thin layers or rhythmic units, which satisfy with the requirement of effectively and finely develop matured fields.