Influence of Hydrolyzed Polyacrylamide (HPAM) Molecular Weight on the Cross-Linking Reaction of the HPAM/Cr³⁺ System and Transportation of the HPAM/Cr³⁺ System in Microfractures

Abstract

The influence of the molecular weight (M w ) of hydrolyzed polyacrylamide (HPAM) on the cross-linking reaction of HPAM/Cr 3+ and the transportation of HPAM/Cr 3+ in microfractures is systematically studied using viscometry, ultraviolet− visible absorption spectrophotometry, and displacement experiment with a visual microfractured model. The results show that a high-M w HPAM is advantageous to the intramolecular cross-linking reaction of the HPAM/Cr 3+ system but disadvantageous to the transportation of the HPAM/Cr 3+ system in microfractures. At the intramolecular cross-linking stage, the injection pressure of the HPAM/Cr 3+ system in microfractures is almost equal to that of the HPAM solution, which undergoes no change with the degree of the cross-linking reaction. The higher the HPAM M w , the earlier the intramolecular cross-linking ends (thus, the intermolecular cross-linking reaction of HPAM/Cr 3+ occurs earlier, which leads to an earlier increase in the injection pressure of the HPAM/Cr 3+ system). Moreover, there is a matching relationship between the fracture aperture and the HPAM/Cr 3+ system to minimize the chromatographic separation when the HPAM/Cr 3+ system transports in the microfracture. For the conformance control of a fractured tight oil reservoir, we conclude that an HPAM/Cr 3+ system with a low-M w HPAM can more easily enter the deep reservoir to expand the swept volume on a larger scale. However, the system with a high-M w HPAM can form a gel with a higher viscosity to produce a higher plugging strength.

Influence of salinity on the properties of the different HPAM/Al3+systems

“…Intermolecular cross-linking can both allow the viscosity and the absorbance to be increased. This conclusion has been verified in Zhang et al's article [42,47]. We can conclude that the process of the cross-linking reactions of the three is the same and the difference is only that the reaction time corresponding to each stage is different.…”

A New Method of Plugging the Fracture to Enhance Oil Production for Fractured Oil Reservoir using Gel Particles and the HPAM/Cr3+ System

“…A series of the particle sizes of the gel particles were screened out by the sieves with the different pore sizes. The HPAM/Cr 3+ system consisted of partially hydrolyzed polyacrylamide (HPAM) and chromium acetate, which has been studied extensively and reported in detail [29,30]. HPAM with a molecular weight of 12 million g/mol and a hydrolysis degrees of 25% was obtained from Beijing Hengju Chemical Co., Ltd. in Beijing, China.…”

Reducing the Magnesium Content from Seawater to Improve Tailing Flocculation: Description by Population Balance Models

“…The conventional flocculant used in copper mining is hydrolyzed polyacrylamide (HPAM) with a high molecular weight, which gives high settling rates, low densities, and proper rheological properties of concentrated underflows at relatively low doses and low cost [9,10]. Several efforts have been made in the study of HPAM behaviour in the solution [11,12] and high-saline conditions [13][14][15]. These studies provide enough proof that bridging flocculation may benefit from a saline medium because ions can act as a bridge between the anionic solid particles and anionic flocculants, commonly known as ion binding.…”