Investigating the Effects of Core Length on Pore Volume to Breakthrough (PVBT) Behavior in Carbonate Core Samples during Matrix Acidizing with Hydrochloric Acid
Abstract
Most literature contains Hydrochloric acid (HCl) carbonate acidizing
experiments performed on short (2 - 6 inch) cores. These cores do not accurately
represent reservoir conditions, as spent acid is not propagated for any appreciable
distance along the length of the sample. In this work, HCl injection experiments are
performed on both short (6 inch) and long (20 inch) calcite cores to investigate the pore
volume to breakthrough (PVBT) behavior.
PVBT is defined as the volume of acid necessary to propagate the wormhole
network from the inlet to the outlet of the core sample, divided by the pore volume of the
core. HCl (5 and 15 percent by weight) injection core flood experiments were performed
on 6 inch and 20 inch calcite (Indiana Limestone) cores. The cores were CAT scanned
before and after acid injection to observe wormhole propagation. Core outlet effluent
samples were collected and their calcium concentration was measured using Inductively-
Coupled Plasma.
Results from core flood experiments show an increased PVBT for 20 inch cores
compared to the 6 inch samples. Results from CAT scan experiments show enlarged
worm-holing and face dissolution on the 20 inch cores compared to the 6 inch cores, due
to increased acid spending at the same acid concentration, flow rate, and injection
temperature. Results from experiments performed at various flowrates indicate the
existence of an optimum injection rate for 20 inch cores, just as in 6 inch cores. This
study summarizes and explains the results obtained from the aforementioned
experiments.
Citation
Nour, Mohamed (2014). Investigating the Effects of Core Length on Pore Volume to Breakthrough (PVBT) Behavior in Carbonate Core Samples during Matrix Acidizing with Hydrochloric Acid. Master's thesis, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /152518.