Evaluation and Field Applications of Water Treatment Residue as a Profile Control Agent

摘要

A great amount of residue from water treatment process in water-flooded oilfields has gradually accumulated and thus caused serious environmental pollution. The water treatment residue is a grey suspension with its density of 1.08g/cm~3, and mainly contains over 65% light CaCO_3, MgCO_3, CaSO_4, Fe_2S_3 and Ca(OH)_2, etc. We made laboratory tests, such as microphotograph and the comparison of the core permeability to kerosene, cast model image analysis parameters, mercury injection capillary pressure curve parameters and scanning electron microscope porosity variation before and after profile control. The results indicate that the water treatment residue is of strong profile control and plugging capability, resistance to erosion and long effective period, and thus can be used as a cheap raw material for profile control. In the past 8 years, totally 60164m~3 water treatment residue has been used for profile control of 151 wells, with the success ratio of 98% and effectiveness ratio of 83.2%. The field tests show that the starting pressure and injection pressure of the injection wells increased, the apparent injectivity coefficient decreased, the injection profile was obviously improved, and the injection wells achieved long average service life. Thus, more 28381 tons of oil was recovered from the corresponding oil wells, with 3069.55×10~4 Yuan benefits and a remarkable input output ratio of 1:8.6. The successful application of the water treatment residue as a profile control agent both reduces environmental pollution and converts bane into boon.