N2-foam-assisted CO2 huff-n-puff process for enhanced oil recovery in a heterogeneous edge-water reservoir: experiments and pilot tests.

Hongda Hao,Handong Huang,Jirui Hou,Huaizhu Liu,Fenglan Zhao

doi:10.1039/d0ra09448j

Hongda Hao, Handong Huang + Show 3 more

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https://doi.org/10.1039/d0ra09448j

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Abstract

The CO2 huff-n-puff process is an effective method to enhance oil recovery; however, its utilization is limited in heterogenous edge-water reservoirs due to the severe water channeling. Accordingly, herein, a stable N2 foam is proposed to assist CO2 huff-n-puff process for enhanced oil recovery. Sodium dodecyl sulfate (SDS) and polyacrylamide (HPAM) were used as the surfactant and stabilizer, respectively, and 0.3 wt% of SDS + 0.3 wt% of HPAM were screened in the laboratory to generate a foam with good foamability and long foam stability. Subsequently, dynamic foam tests using 1D sand packs were conducted at 65 °C and 15 MPa, and a gas/liquid ratio (GLR) of 1 : 1 was optimized to form a strong barrier in high permeable porous media to treat water and gas channeling. 3D heterogeneous models were established in the laboratory, and N2-foam-assisted CO2 huff-n-puff experiments were conducted after edge-water driving. The results showed that an oil recovery of 13.69% was obtained with four cycles of N2-foam-assisted CO2 injection, which is twice that obtained by the CO2 huff-n-puff process. The stable N2 foam could temporarily delay the water and gas channeling, and subsequently, CO2 fully extracted the remaining oil in the low permeable zones around the production well. Pilot tests were conducted in 8 horizontal wells, and a total oil production of 1784 tons with a net price value (NPV) of $240 416.26 was obtained using the N2-foam-assisted CO2 huff-n-puff process, which is a profitable method for enhanced oil recovery in heterogenous reservoirs with edge water.

Highlights

Edge-water-driving reservoirs are widely distributed in China, which account for important proportions of geological reserves of crude oil.[1,2,3,4] The existence of edge water has both advantages and disadvantages for the development of oil elds
The foam volume increased rapidly when the sodium dodecyl sulfate (SDS) concentration increased from 0.1 wt% to 0.3 wt%, which indicates that a high concentration of surfactant is bene cial for foamability
When the foam volume increased slightly when the SDS concentration was higher than 0.3 wt%, the foam volume remained at a high value, and excessive surfactant had little in uence on the foamability

Summary

Introduction

Edge-water-driving reservoirs are widely distributed in China, which account for important proportions of geological reserves of crude oil.[1,2,3,4] The existence of edge water has both advantages and disadvantages for the development of oil elds. The invasion of edge water can cause a quick increase in the water cut and a low oil recovery efficiency.[5,6] North Gaoqian Block, located in the north of Bohai Bay, China, is a heavy oil reservoir with a sufficient edge-water aquifer. The permeability of this reservoir is in the range from 118 Â 10À3 mm[2] to 12 392 Â 10À3 mm[2], which indicates that serious heterogeneity exists in this reservoir. E-mail: haohongda90@126. com; Tel: +86 17601007653 bDrilling & Production Technology Research Institute, Jidong Oil eld Company, CNPC, Tangshan, Hebei, 063000, China conducted to enhance the oil recovery (EOR) in this heterogeneous reservoir

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