Alteration of Permeability by Fine Particle Movement - A Water Injectivity Problem

Abstract

Abstract Siri field is located off shore of Iran in Persian Gulf. It was discovered in 1972. The field is producing from a formation called Mishrif which is common between Iran and United Arab Emirates. Existence of an active aquifer and other appropriate conditions led to the decision of a water injection program. The design and the implementation of the water injection program was performed by Elf Aquitaine and water injection started in 1984. The sea water from the Persian Gulf was found to be compatible with the formation water and was directly injected into the formation after passing through 10 micron filters. Water injectivity was drastically decreased and it reached from an initial injection rate of 9100 bbl/day to 2200 bb1/day within six years. Because of the severe injectivity loss, the water injection was stopped. An experimental investigation was undertaken to look into the possible causes of the injectivity loss. Two sets of experimental investigation were undertaken with different objectives in mind. In the first part glass bead packs were used to test the experimental set up and to observe the general behavior of fine particle movement in porous media. In the second part core plug from the field and sea water were used to determine the possible cause of injectivity loss in the field. The experiments were conducted with a range of injection rate of 0.9 cm3/s to 3.1 cm3/s. Particles of bentonite were suspended in the injected water to simulate fine particles migration in porous media. The particles were injected at concentrations ranged from 20 g/l to 40 g/l. It was observed that the build up in flow resistance was mostly due to the frontal face plugging. Particles of bentonite and alumina were added to the glass beads to study the effect of particles initially present in the glass beads pack medium. Field and the laboratory data clearly indicate the importance of the water quality in a waterflood project. Experimental data suggest that a smaller size filter should have been implemented to avoid the injectivity loss. P. 655