Abstract
Formation damage can occur through migration of drilling fuid particles and polymers into porous formations. A methodology for assessing formation damage was applied to measure invasion of CaCO3 and polymers into porous formations, where the CaCO3 particles size had been selected using established particle size selection methods. Tests were conducted with and without the presence of a cellulose-based additive, to study if the fbres could reduce the fuid loss and limit the formation damage. Input factors such as applied differential pressures, ranging from 6.9 to 34.9 MPa (1000-5000psi), and median pore-throat openings of discs were also varied to investigate which parameters affected the signifcance of the formation damage. The results showed invasion of CaCO3/ground marble into the formation and that particle size selection methods used to reduce fuid loss also led to formation damage. Further it was discovered that the presence of fbres limited the invasion of both CaCO3 and polymers into the porous formations when the D90 of the fbres were ≥3/2 times the pore-throat size, and that higher applied pressures led to larger formation damage. The fuid loss tests also showed both lower total fuid losses and lower fuid loss rates over time with the fbres added to the fuids, indicating that the flter-cake permeability was reduced with the addition of the fbre particles.
NSTL