The Roles of Fluid Properties, Half‐Cycle Slug Size, and Timing of Cyclic Injection on Water Alternating Gas Injection Performance in Near‐Miscible and Miscible CO2 Flooding Hertanto Adidharma Department of Chemical and Petroleum Engineering University of Wyoming Laramie WY 82071 Hertanto Adidharma, Department of Chemical and Petroleum Engineering, University of Wyoming, Laramie, WY 82071 The overall goal is to experimentally study the effects of fluid properties (brine salinity and gas composition), CO2 and water half‐cycle slug size, and timing of cyclic injection on the performance of Water Alternating Gas (WAG) injection in near‐miscible and miscible conditions. The effect of salinityy of the injection j brine on WAG p performance in tertiaryy miscible CO2 floodingg has been investigated. The core flooding experiments in Berea sandstone core are conducted at 60oC and at miscible condition, i.e., 20% above the minimum miscible pressure of the oil sample. A model oil and a crude oil from Cottonwood Creek field in Wyoming are used. Six alternate cycles of brine and CO2 with a half‐cycle slug size of 0.25 pore volumes and a CO2/water volume ratio of 1:1 are injected in every core flood test. At the same miscible condition, the tertiary recovery factor of WAG is demonstrated to be higher than that of continuous CO2 flooding, i.e., to recover the same amount off oil,l WAG flooding fl d requires less l volume l off CO2 than h continuous CO2 flooding. fl d The h tertiary oill recovery and d recovery factor of both model and crude oils are found to increase slightly with the salinity of the injection brine due to the decrease in the CO2 solubility in brine. The CaCl2 in the injection brine is found to have similar effect as NaCl. WAG Tertiary Oil Recovery
Tertiary Oil Recovery: CGI vs. WAG
at Various Injected Brine Salinity
40
Cottonwood Creek Oil
Model oil
60
30
25
20
15
10
WAG (salinity: 8000 ppm) Continuous Gas Injection (CGI)
5
Tertiary Oil Recoverry [% OOIP]
Tertiary Oil Recoverry [% OOIP]
35 50
40
30
1000 ppm 2000 ppm 4000 ppm 8000 ppm 16000 ppm 32000 ppm
20
10
0
0 0.0
0.2
0.4
0.6
0.8
1.0
CO2 Injected [PV]
1.2
1.4
1.6
0.0
0.2
0.4
0.6
0.8
1.0
CO2 Injected [PV]
1.2
1.4
1.6
