Page 276 - Reservoir Formation Damage

256 Reservoir Formation Damage

500 1000 1500 2000 2500 3000
Volume of Injected Fluid (ml)

Core #26 Core #27 Simulation
Figure 11-6. Instantaneous to initial permeability ratio (or permeability
alteration factor) vs. pore volume during external fines invasion (Liu and Civan,
©1996 SPE; reprinted by permission of the Society of Petroleum Engineers).

alteration along the core was measured after one hour of mud con-
tamination. Data for the core test and values of model parameters for
simulation are presented elsewhere by Liu and Civan (1993). Experi-
mental and simulated results for drilling fluid loss versus time and
permeability alteration versus core distance after one hour of mud con-
tamination are illustrated in Figures 11-7 and 11-8. Simulation results
indicate that the model can favorably represent the process of mud filtration.
Another laboratory test involving dynamic mud filtration was con-
ducted by Jiao and Sharma (1992). A fresh water-based mud was circu-
lated over the surface of core inlet and infiltrated into a Berea core under
an average differential pressure of 6.29 atm across the system. This Berea
core sample was previously saturated with 3% NaCl brine. Formation
damage in this test is caused by external solid invasion and formation
fines migration. Pressure taps were placed at different locations along the
core of 20.34 cm in length to measure permeability change during the
test. Experimental and simulated mud filtration volumes are in good
agreement, as presented in Figure 11-9. As shown in Figure 11-10,
experimental results of permeability alteration in the core section between
6.35 cm and 11.43 cm from core inlet compare quite well with simulation
results. Further discussion on the simulation of this test is presented
elsewhere (Liu and Civan, 1993).