Acid fracturing, mechanism

B. D. Sanford, C. R. Dacar, and S. M. Sears. Acid fracturing with new fluid-loss control mechanisms increases production. Little Knife field. North Dakota. In Proceedings Volume, pages 317-324. SPE Rocky Mountain Reg Mtg (Casper, WY, 5/18-5/21), 1992. 

Fracture mechanisms and microstructure as well as distribution of chemical elements along it were studied with scanning electron microscopy (SEM) and X-ray microanalysis (XRMA) using Superprobe-733, JEOL, Japan, after deep electrolytic etching with an etchant based on acetic acid. X-ray diffraction phase analysis was done with DRON diffractometer, Burevestnik, the Russian Federation. 

Fluang [246] investigated the SCC of AISI 321 stainless steel in acidic chloride solutions by the SSRT technique and fracture mechanics. It was found that the cleavage fracture characterizes the fracture surface. The active dissolution mechanism controls the SCC of AISI 321 stainless steel in acidic chloride solutions and can be inhibited by using KI. The inhibition effect of KI on the SCC is due to inhibition of the anodic reaction of the corrosion process. 

Fig. 35. Dependence of fracture energy on the modifier composition (CTBN 1300 X 9 = carboxyl-tenninated acrylonitrile, acrylic acid and butadiene rubber with 18% acrylonitrile and 2% acrylic acid contents CTBN 1300x 13 = carboxyl-terminated acrylonitrile, butadiene rubber with 26% acrylonitrile content) (Reprinted from Journal of Materials Science, 27, T.K. Chen, Y.H. Jan, Fracture mechanism of toughened epoxy resin with bimodal rubber-particle size distribution, 111-121, Copyright (1992), with kind permission from Chapman Hall, London, UK)...

Acid fracturing must be used only where good differential etching is probable. The rock strength and closure pressure must indicate that good conductivity will remain after fracture closure. Formation mechanical properties and their response to contact by different acid types and systems must always be evaluated as best as possible in advance of a treatment program. ... 

Abass, H. H., A. A. Al-Mulheim, M. S. Alqem, and K. R. Mirajuddin. 2006. Acid fracturing or proppant fracturing in carbonate formation A rock mechanic s view. Paper SPE 102590, presented at the 2006 SPE Annual Technical Conference and Exhibition, San Antonio. 

Hydroxyacetic Acid Condensates. A condensation product of hydroxyacetic acid can be used as a fluid loss material in a fracturing fluid in which another hydrolyzable aqueous gel is used [313-315,317]. The hydroxyacetic acid condensation product degrades at formation conditions to set free hydroxyacetic acid, which breaks the aqueous gel. This mechanism may be used for delayed gel breaking. Here permeability is restored without the need for separate addition of a gel breaker, and the condensation product acts a fluid loss additive. 

---