Lessons Learned From Alkali/Surfactant/Polymer-Flooding Field Tests in China

Abstract

Summary Although the alkali/surfactant/polymer (ASP) flooding technique used for enhanced oil recovery (EOR) was put forward many years ago, it was not until 2014 that it was first put into practice in industrial applications with hundreds of injectors and producers in the Daqing Oil Field in China. In this study, 30 ASP-flooding field tests in China were reviewed to promote the better use of this promising technology. Up to the present, ASP flooding in the Daqing Oil Field deserves the most attention. Alkali type does affect the ASP-flooding effect. Strong alkali [using sodium hydroxide (NaOH)] ASP flooding (SASP) was given more emphasis than weak alkali [using sodium carbonate (Na2CO3)] ASP flooding (WASP) for a long time in the Daqing Oil Field because of the lower interfacial tension (IFT) of the surfactant and the higher recovery associated with NaOH than with Na2CO3. Other ASP-flooding field tests completed in China all used Na2CO3. With progress in surfactant production, a recent large-scale WASP field test in the Daqing Oil Field produced an incremental oil recovery nearly 30% higher than most previous SASP recoveries and close to the value of the most-successful SASP test. However, the most-successful SASP test was partly attributed to the weak alkali factor. Recent studies have shown that the WASP incremental oil recovery factor could be as good as that of SASP but with much-better economic benefits. Screening of surfactant by IFT test is very important in the ASP-flooding practice in China. Whether dynamic or equilibrium IFT should be selected as criteria in surfactant screening is still in dispute. Many believe the equilibrium IFT is more important than the dynamic IFT in terms of the displacement efficiency; thus, it is better to choose a lower dynamic IFT when the equilibrium IFT meets the 10−3 order-of-magnitude requirement. However, it is impossible for many surfactants to form ultralow equilibrium IFT. Because of the low acid value of the Daqing crude oil, the asphaltene and resin components play a very important role in reducing the oil/water IFT and asphaltene is believed to be more influential, although more work is required to resolve this controversial issue. Whether polymer viscoelasticity can reduce the residual oil saturation is still a matter of debate. Advances in surfactant production and in the overcoming of scaling and produced-fluid-handling challenges form the foundation of the industrial application of ASP flooding. Further work is advised on the emulsification effect of ASP flooding. According to one field test, the EOR routine should be selected depending on consideration of the residual oil type to decide whether to increase the sweep volume and/or displacement efficiency. The micellar flooding failure in one ASP field test in China has led all subsequent field tests in China to choose the “low concentration, large slug” technical route instead of the “high concentration, small slug” one. ASP flooding can increase oil recovery by 30% at a cost of less than USD 30/bbl; thus, this technique can be used in response to low-oil-price challenges.

Polymer Flooding in Heterogeneous Heavy Oil Reservoirs: Experimental and Simulation Studies

“…The simulation results indicated that polymer degradation, polymer solution shear thinning, and heavy oil TPG all exerted a negative impact on PF performance. To reduce their negative effects, several approaches such as the application of more stable polymers with better performance and TPG reduction methods have been proposed [ 51 , 52 , 53 , 54 , 55 , 56 ]. In the near future, we will pay closer attention to these methods and attempt to study PF in heterogeneous heavy oil reservoirs based on a microscopic perspective, in order to enrich and deepen our research [ 57 , 58 ].…”

Dialkyl Sulfobetaine Surfactants Derived from Guerbet Alcohol Polyoxypropylene–Polyoxyethylene Ethers for SP Flooding of High Temperature and High Salinity Reservoirs

“…Chemical enhanced oil recovery (EOR) techniques, especially the alkali‐surfactant‐polymer (ASP) flooding, have been extensively investigated in the past decades, as they can effectively improve the overall oil recovery of an oilfield in the late stage of development (Guo et al, 2019; Hirasaki et al, 2011; Olajire, 2014; Sheng, 2011; Zhu et al, 2013). As the most important part of EOR chemicals, surfactants are able to reduce the crude oil/connate water interfacial tension (IFT) to ultralow (<1.0 × 10 −2 mN m −1 ), allowing the crude oils trapped in small pore throats by capillary force to be displaced out (Sheng, 2013).…”

Alkali Effect on Alkali-Surfactant-Polymer (ASP) Flooding Enhanced Oil Recovery Performance: Two Large-Scale Field Tests’ Evidence

“…e incremental oil recovery factor (IORF) of ASP flooding can be as high as 33% OOIP and the average IORF is 21.8% [24]. Most of ASP flooding in China is conducted in Daqing Oilfield, which is summarized in our previous publication [38]. ASP flooding has been put into commercial use in 2014 in Daqing [39].…”