Comparison of Strong Alkali and Weak Alkali ASP Flooding Pilot Tests in Daqing Oilfield

Abstract

ASP flooding is one of the most promising EOR technologies. Lots of laboratory studies and pilot tests have been finished in Daqing oilfield which is the largest oilfield in China. Comparison of two typical strong alkali ASP (WASP) and weak alkali ASP (SASP) pilots are presented with detained information. ASP flooding could not only remarkably improve displacement efficiency but also improve sweep efficiency due to the low interfacial tension effect and mobility control technique with help of viscosity enhancement and emulsification effects. The incremental recovery of two ASP was near, while in peak oil production period after the injection took effects, WASP had high oil production rate than SASP. The emulsification effects in weak alkali ASP was weaker than strong one. The chromatographic separation was different in two pilot tests, in which weak alkali ASP had alleviated chromatographic separation. The constitution production sequence was both polymer first, then alkali and finally surfactant. The time gap between surfactant and polymer was about 0.0606 PV for strong alkali ASP, while a respective value of 0.1281PV for weak alkali ASP. Scaling was different and thus anti-scale technique adopted in two pilot tests were a little different. The overall input-output ratio for two tests was different and weak alkali ASP performed much better. Comparison was first made between strong alkali and weak alkali based ASP flooding from field tests perspective. Weak alkali based ASP is proven the development trend.

ASP Flooding: Theory and Practice Progress in China

“…Surfactants used in Daqing are domestic and their cost is much lower than those imported abroad. This large scale strong alkali ASP flooding in Daqing was reported as the highest incremental oil recovery (28%) in China up to present [62]. However, the economics performance of this field tests is not highest because of scaling and antiscale measures taken.…”

“…The progress in surfactant production makes it possible to produce large amount and cheap surfactant used for weak alkali ASP flooding. Comparison between two finished large scale ASP flooding field tests performances was finished in 2016 [62] and it is obvious that weak alkali is better choice. Mechanism between NaOH and Na 2 CO 3 ASP flooding in laboratory is thus interesting to many engineers and researchers.…”

“…Alkali corrosion restricted the application of ASP flooding, while the universal concern is focused on how to prevent or weaken corrosion. Corrosion and scaling in strong alkali ASP flooding are worse than that in weak alkali ASP flooding [62]. The scaling mechanism and scaling type of strong alkali and weak alkali were briefly compared [62].…”

“…Corrosion and scaling in strong alkali ASP flooding are worse than that in weak alkali ASP flooding [62]. The scaling mechanism and scaling type of strong alkali and weak alkali were briefly compared [62]. In weak alkali ASP flooding, scaling samples are mainly carbonate scale, while scale in strong alkali ASP flooding is carbonate scale and silica scale.…”

“…The ASP fluid demulsification is difficult. Emulsion from weak alkali ASP flooding is much easier to break and dehydrate than that from strong alkali ASP flooding [62]. Bituminous and gelatin content increase the difficulty of dehydration of oil emulsification and the influence of asphalt is greater than the colloid [67].…”