Open Access

ARTICLE

The Influence of ASP Flooding on Reservoir Formation Sensitivity

Duan Xiang-gang^1,2,3, Hou Ji-rui^1,2,3, Liu Hui^1,2,3, Yin Zhong-min⁴, Tang Yong-qiang^1,2,3, Su Wei^1,2,3

1 EOR institute of China university of petroleum Beijing 102249.
2 Key laboratory of Enhanced Oil Recovery, CNPC Beijing 102249.
3 Key Laboratory of petroleum Engineering, Ministry of Education, Beijing, 102249.
4 No. 2 Oil Production Site, Daqing Oilfields Co. Ltd.

Structural Longevity 2013, 9(2), 131-142. https://doi.org/10.3970/sl.2013.009.131

Abstract

As an enhance oil recovery method, Alkali, surfactant and polymer (ASP) flooding has been already widely used in Daqing oilfield. However, there are many challenges to reservoir formation by using the ASP flooding, such as the reaction between alkali and clay mineral, adsorption of surfactant and retention of polymer, which may cause damage to oil and gas formation. In order to evaluate the formation damage, reservoir sensitivity is researched.
Through the core flow testing, the sensitivity of velocity, water, alkali and acid of core sample has been studied. The core samples are taken from the formation in Daqing oilfield with or without ASP flooding. Moreover, the reason for the change of reservoir sensitivity also has been studied by using scanning electron microscope and X-ray diffraction method.
The experimental formation has the weak velocity sensitivity, strong to medium water, acid sensitivity and weak to medium alkali sensitivity before ASP flooding. However, when comparing the result with the reservoir sensitivity after ASP flooding, it is found that the velocity sensitivity disappears because of the decreasing water sensitive minerals kaolinite, which has been corroded by alkali mostly. The water sensitivity becomes more serious due to the increasing illite/smectite layer, which has strong expansion ratio and cation exchange capacity, and can absorb a large amount of polar water molecules. After the long time reaction between the alkaline fluids and rocks after ASP flooding, both the acid and the alkali sensitivity reduce relatively.
According to analyzing results, the components of reservoir stratum and clay mineral have been changed after the ASP flooding. Due to the Erosion of alkali on formation Minerals, the content of kaolinite reduces, and some minerals increase, such as illite/smectite layer, chlorite and plagioclase. In conclusion, alkali corrosion and scale-forming is considered to be the main reason for reservoir sensitivity changing.

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Keywords

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