Page 88 - Enhanced Oil Recovery in Shale and Tight Reservoirs

Asphaltene precipitation and deposition in a huff-n-puff process 75

Figure 3.14 Comparison of the predicted oil recovery with experimental data.

small peak. At later cycles, because less oil flows into this block, and oil flows
slower, the asphaltene precipitation show-up in this block delays the puff
period. And the peaks become lower and lower with cycle.
For the asphaltene deposition (dotted red curve), more and more asphaltene
deposits with cycle in this block. In other words, asphaltene deposition ac-
cumulates in this block. The asphaltene precipitation and deposition in
different blocks may change differently. How they change depends on the
net changes of CO 2 , oil, and asphaltene content in the oil.

3.5 Effect of asphaltene deposition on huff-n-puff
optimization
Asphaltene deposition is affected by pressure. The huff-n-puff perfor-
mance strongly depends on the optimization of huff pressure, puff pressure,
huff time, and puff time. Sheng (2017) proposed that a huff-n-puff should be
optimized so that the huff time should be long enough for the pressure near
the wellbore to reach the set maximum injection pressure, and the puff time
should be long enough for the pressure near the wellbore to reach the set
minimum production pressure. In other words, to improve or optimize