Research of Blocking Removal Technology of Shunting Multi-hydrogen acid with Intralayer CO₂ Generation in Offshore Oil Fields

Aiming at problems of strong heterogeneity in part of Bohai Oilfield reservoir and ineffectively starting the low permeability layer by general acidizing, an blocking removal technology of shunting multi-hydrogen acid with intralayer CO₂ generation was proposed. The plugging capacity of intralayer CO₂ generation and the removing blockage of multi-hydrogen acid system were researched by plugging performance evaluation, physical and chemical properties evaluation, acid performance evaluation and core displacement experiments. The results showed that the CO₂ foam generated by the intralayer CO₂ system could effectively seal the high permeability layer when the permeability ratio was less than 7.8, which increased the proportion of subsequent acid entering into the low permeability layer. The performance evaluation results of multi-hydrogen acid system showed that the dissolution rate of asphalt was 7.2755 mg/(mL·min) and the dissolution rate of wax was 0.599 mg/(mL·min). And the core permeability recovery rate is 200% after acidizing. The field test results showed that the technology could increase the liquid production of the oil well by 90% after the measure. The technology is simple in construction and needed less equipment, which is no damage to the reservoir. It is a good removing blockage reference for offshore oilfield.