Research and Application on Horizontal Well Sectional Acidizing Technology

摘要

Horizontal well technology is a technological revolution in oil industry, and it is one of the most important methods of thick layer sustainable production and marginal low permeable formation exploitation in Daqing Oilfield. Usually, horizontalwells will suffer damage during the course of drilling, completion and production due to the mud and other organism’s pollution. Therefore, acidizing is an effective method to improve conductivity near the wellbore and enhance overall production. However, commingled acidizing cannot guarantee acid being pumped into polluted intervals uniformly owing to long horizontal length (583.7m on average) and heterogeneity formation. A new composite acid fluid and a novel sectional acidizing technology by inject sealing ball to build the pressure to open sliding sleeves were developed to solve the problem of long interval acid placement. Composite acid system features long corrosion inhibition period, which can improve core permeability by 160% and restore the damaged core permeability by 203%. Sectional acidizing string can resists pressure up to 40MPa and temperature up to 90°C. Four stages ball injection and five intervals treatment can be done in one trip. Moreover, residual acid can be reverse flushed after acidizing. Up to now, this technology has been applied on 5 wells (18 intervals in total) in Daqing Oilfield. Now satisfactory stimulation results have been achieved. Technical success ratio is 100%; average single well liquid production is increased by 5.2m~3/d; oil production is increased by 4.5t/d; and average production enhances by 168%.