Copolymer MCJS as a retarder of the acid–rock reaction speed for the stimulation of deep carbonate reservoirs

Abstract

The fast reaction rate between hydrochloric acid and carbonates causes the most acid consumption near the wells, and the acid cannot penetrate the deeper places of the carbonate reservoir; this limits the application of acidizing modifications for the reservoir. In this study, we chose acrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), allyl alcohol polyoxyethylene ether (APEG), and N-dimethyl-N-vinyl nonadecan-1-aminium chloride (DMAAC-18) to synthesize a quadripolymer (MCJS) that could reduce the reaction rate mentioned previously. The molecular structure of MCJS was characterized by Fourier transform infrared and 1 H-NMR spectroscopy. The molecular weight and molecular weight distribution of MCJS was determined by gel permeation chromatography. Carbonate rock was analyzed by X-ray diffraction and energy-dispersive X-ray spectroscopy. The retarding properties of the acid mixed with MCJS (MCJS acid) were investigated, and the resulting reaction rate between the acid and carbonate decreased obviously, even at a low viscosity. Scanning electron microscopy and core flood experiments showed that the MCJS could be adsorbed on the carbonate rock surface and form a hydrated film that delayed the reaction.

Adsorption of new hydrophobic polyacrylamide on the calcite surface

“…However, HPAM has some negative effects when it is injected into the reservoir: the molecular chain is adsorbed to block the hole in the rocks. This leads reductions in the permeability of the formation and reservoir productivity …”

Adsorption–desorption behavior of the hydrophobically associating copolymer AM/APEG/C-18/SSS

“…The CO 2 gas produced by the reaction of the polymer acid solution and the calcium carbonate rocks was collected using a CO 2 gas-collecting device. 10 The acid-rock reaction rate was calculated using the volume of the collected CO 2 . [27][28][29] The formula used is as follows:…”

“…6 and the other is to separate the acid solution from the rock by forming a lm on the rock surface, thus reducing the reaction rate between the acid and the rock. 10 Recently, gelled acids have effectively improved the permeability of reservoirs as retarded acids have attracted the interest of many researchers. A gelled acid is usually composed of HCl as the base-acid and a polymer gelling agent as an addictive.…”

The effect of hydrophobic chains on retarding performance of retarding acids

“…However, the former has the shortcomings of large dosage and high price, the latter mainly reduces the acid-rock reaction through the method of adsorbed lm. Quan's [20][21][22] research group proposed that a retarding acid with low viscosity could be adsorbed on the surface of carbonate rock and form a hydrated lm that would delay the acid-rock reaction, but no published research has described a study of which factors could inuence the lm-forming properties.…”