Abstract
Alkali-surfactant-polymer (ASP) flooding is very promising chemical enhanced oil recovery (EOR) technology which can make an incremental oil recovery factor (IORF) of 30% original oil in place (OOIP). How to choose alkali in ASP flooding remains a question for a long time. As the world’s only and largest ASP flooding application place, Daqing Oilfield has always adhered to the strategy of parallel development of strong alkali ASP flooding (SASP) and weak alkali ASP flooding (WASP), but SASP is in a dominant position, indicated by more investments and more project numbers. This leaves an impression that SASP is better than WASP. However, WASP is drawing more interest than SASP recently. Moreover, as the ASP flooding in Daqing went from field tests to commercial applications since 2014, how to comprehensively consider the benefit and cost of ASP flooding has become a new focus at low oil prices. This paper compares two typical large-scale field tests (B-1-D SASP and B-2-X WASP) completed in Daqing Oilfield and analyzes and discusses the causes of this difference. The injection viscosity and interfacial tension (IFT) for the two field test areas are substantially equivalent under the conditions of Daqing Oilfield, and WASP is better than SASP when reservoir geological conditions are considered. WASP exhibits the same IORF of 30% as SASP while having a much better economic performance. For the SASP field test, the injected strong alkali NaOH makes the test behave unlike a typical strong ASP flooding due to the presence of CO2 in the formation fluid, which well explains why IORF is much higher than all the other SASPs but scaling is less severe than others. This paper confirms that under Daqing Oilfield reservoir conditions, it is the alkali difference that caused the performance difference of these two tests, although some minor uncertainties exist. WASP is better than the SASP providing the same conditions . In addition, the detailed information of the two ASP field tests provided can give reference for the implementation of ASP flooding in other oilfields. After all, the study of ASP flooding enhanced oil recovery technology under low oil prices requires great foresight and determination.
Highlights
Surfactants are important surface-active chemicals with a hydrophobic tail and a hydrophilic head [1, 2]
It should be noted that some of China’s new ASP flooding projects are not included in the literature [24], like one in high reservoir temperature started in 2011 in Henan Oilfield (81°C) [36] and the first weak ASP demonstration block started in 2013 in Daqing Oilfield [37]. e incremental oil recovery factor (IORF) of ASP flooding can be as high as 33% original oil in place (OOIP) and the average IORF is 21.8% [24]
Both strong ASP flooding (SASP) and weak ASP flooding (WASP) have been developed in Daqing Oilfield and huge amount of money has been invested to this enhanced oil recovery (EOR) technology, the number of SASP completed in Daqing Oilfield is much more than WASP according to a previous summary [24]
Summary
Surfactants are important surface-active chemicals with a hydrophobic tail and a hydrophilic head [1, 2]. Alkali-surfactantpolymer (ASP) flooding is an important chemical flooding enhanced recovery technology [21, 22] with wide range of applications [23, 24] It can be used in sandstone reservoirs [23, 25, 26], fault block reservoirs [27,28,29], conglomerate reservoir [30], and carbonate reservoir [31]. ASP flooding oil production in Daqing is 3.5 million tons, accounting for 9% total oilfield production, covering 22 blocks and 7273 wells [37]. The technical and economic differences between the SASP and WASP field tests completed in Daqing Oilfield are analyzed and compared. 2. Comparison of Test Blocks e two ASP flooding field tests compared in this paper are both industrial tests in Daqing Oilfield.
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