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Research Papers: Petroleum Engineering

# An Experimental Study of the Post-CHOPS Cyclic Solvent Injection Process

[+] Author and Article Information
Zhongwei Du

Faculty of Engineering and Applied Science,
University of Regina,
e-mail: du225@uregina.ca

Fanhua Zeng

Faculty of Engineering and Applied Science,
University of Regina,
e-mail: fanhua.zeng@uregina.ca

Christine Chan

Faculty of Engineering and Applied Science,
University of Regina,
e-mail: christine.chan@uregina.ca

Contributed by the Petroleum Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received May 9, 2014; final manuscript received March 4, 2015; published online March 25, 2015. Editor: Hameed Metghalchi.

J. Energy Resour. Technol 137(4), 042901 (Jul 01, 2015) (15 pages) Paper No: JERT-14-1150; doi: 10.1115/1.4029972 History: Received May 09, 2014; Revised March 04, 2015; Online March 25, 2015

## Abstract

Cold heavy oil production with sand (CHOPS) has been applied successfully in many oil fields in Canada. However, typically only 5–15% of the original oil in place (OOIP) is recovered during cold production. Therefore, effective follow-up techniques are of great importance. Cyclic solvent injection (CSI), as a post-CHOPS process, has greater potential than continuous solvent injection to enhance heavy oil recovery. Continuous solvent injection results in early breakthrough due to the existence of wormholes; while in CSI process, the existence of wormholes can increase the contact area of solvent and heavy oil and the wormholes also provide channels that allow diluted oil to flow back to the wellbore. In this study, the effects of wormhole and sandpack model properties on the performance of the CSI process are experimentally investigated using three different cylindrical sandpack models. The length and diameter of the base model are 30.48 cm and 3.81 cm, respectively. The other two models, one with a larger length (i.e., 60.96 cm) and the other with a larger diameter (i.e., 15.24 cm), are used for up-scaling study in the directions parallel and perpendicular to the wormhole, respectively. The porosity and permeability of these models are about 35% and 5.5 Darcy typically. A typical western Canadian oil sample with a viscosity of 4330 $mPa·s$ at 15 °C is used. And pure propane is selected as the solvent. The experimental results suggest that the existence of wormhole can significantly increase the oil production rate. The larger the wormhole coverage is, the better the CSI performance obtained. In terms of the effect of wormhole's location, a reservoir or well with wormholes developed at bottom is more favorable for post-CHOPS CSI process due to the gravity effect. The production of the CSI process can be divided into two phases: early time chamber rising and late time chamber spreading phases. The oil recovery factor in the chamber rising phase is almost independent of the sandpack model diameter; and the oil relative production rates (the oil production rate divided by the OOIP) in two models with different diameters are close during the chamber spreading phase due to similar solvent dispersion rate. It is also found that if the wormhole length is the same, the sandpack model length hardly affects the oil production rate in the earlier stage. In terms of the effects of the wormhole orientation, the well with a horizontal wormhole is inclined to get a good CSI performance. Through analyzing the experimental data, a relationship of oil production rate to drainage height is also obtained and verified.

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## Figures

Fig. 1

Sandpack models

Fig. 2

Schematic of the experimental setup

Fig. 7

Residual oil saturation pictures for different wormhole location

Fig. 8

Effect of wormhole location on the recovery factor

Fig. 9

Effect of wormhole location on the production rate

Fig. 3

Wormhole location of each test

Fig. 13

Effect of model length on the recovery factor for models 1 and 2

Fig. 4

Effect of wormhole length on the recovery factor under the model 2

Fig. 5

Effect of wormhole length on the production rate under the model 2

Fig. 6

Effect of wormhole length on the average production rate in phase 1

Fig. 12

Effect of model diameter relative production rate for models 3 and 1

Fig. 14

Effect of model length on the relative production rate for models 1 and 2

Fig. 10

Comparison of residual oil saturation pictures

Fig. 11

Effect of model diameter on the recovery factor for models 3 and 1

Fig. 15

Effect of model orientation on the recovery factor for model 3

Fig. 16

Effect of model orientation on the production rate for model 3

Fig. 17

The relationship of recovery factor with relative coverage of wormhole

Fig. 18

The cumulative mass transfer during soaking period for test 6

Fig. 19

The cumulative mass transfer during soaking period for test 7

Fig. 21

The correlation between the recovery factor and time during the chamber rising phase for tests 4 and 5

Fig. 22

The correlation between the chamber height and time during the chamber rising phase for tests 4, 5, and 6

Fig. 23

The correlation between the recovery factor and time during the chamber spreading phase for tests 4, 5, and 6

Fig. 24

The correlation between the recovery factor and time verified by test 7

Fig. 25

The correlation between the chamber height and time verified by test 7

Fig. 20

The cumulative mass transfer during soaking period for test 8

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