Abstract
Water injection is one of the countermeasures against ground subsidence in the Southern Kanto Natural Gas Field. Generally, injection water contains suspended solids (SS) which could reduce the injectors' injectivity. The SS may pile up at the bottom of injectors. Furthermore they may plug pores of the formations for injection and the perforation holes of the casing. Accordingly injectors' injectivity declines due to such plugs. It is indispensable to increase the injectivity for the sustainable production operation with minimizing the ground subsidence in this field.
In fact there was a conventional technique to recover the injectivity by use of jetted water. Though the flock of SS was removed from the inside of the casing by the jetted water, the effect was not remarkable if the plugging occurred in the formations.
This study presents a new technique which can remove the plugs from the formation by use of compressed air. This method was improved to be more practical after trial execution at some fields. Finally this new technique was completed and the considerable results were yielded. As the permeability of the formation near the borehole was increased by the formation cleaning, the injectivity was enhanced substantially.
