Bulalo Well No. 30 Geothermal Residue Subsurface Injection

Abstract

In I999 and 2000 PGl finalized a plan and injected solid residues that had accumulated through continuous operation of the Bulalo geothennal field. T;he disposal process used was designed to be consistent with both UNQCAL environmental policy and that of the local environmental regulators, and was a d$ect application of the principles of solids injection and hydraulic fractwing. Over a period of seven months, a total of around 7,560,000 kilograms of solid residues was successfully injected into an injection well located at the south of Bulalo Gebtherrnal Field. Bulalo Well No. 30 was chosen among other candidate injectors for this project* The well was selected through a process %hat considered various factors such as wellbore integrity, distance from nearby water sources and formation characteristics. The wection was carried out in batch modes where the solid residues were ground into finer particles, made into a slurry, and then hjected into the weU. The initial response of the well was characterized by low wellhead pressure injection. This is typical of natural fracture fill-up. During the latter stages of the injection project, higher injection pressures caused hy&aulic fracturing which contributed to the success of the injection process.