Page 36 - Enhanced Oil Recovery in Shale and Tight Reservoirs

26 Enhanced Oil Recovery in Shale and Tight Reservoirs

increased oil recovery, but not effectively as the soaking became long from
12, 24e48 h. Especially, after 4th cycle, the difference for different soaking
times was marginal. Logically, there should be an optimal soaking time. In
this example, 12 h seems to be an optimal.
Fig. 2.17 compares the experimental data with the simulation results. It
can be seen that the simulation results match the experimental data,
confirming the conclusions from the experiments. Using a simulation
model, we can investigate more mechanisms by analyzing simulation data.
Fig. 2.18 shows the matrix-fracture system pressure in the first six cycles
for the test of 12 h of soaking and 3 h of production. Nitrogen is injected

Figure 2.17 Comparison of experimental data and simulation results on soaking time
effect.

Figure 2.18 System pressure profile for 6 cycles of the test of 12 h of soaking time and
3 h of production time.