Gas Assisted Acidizing of Carbonate Formations
Academic Article
Overview
Overview
abstract
A series of experiments were conducted to examine the effect of nitrogen injection ahead of the acid on the wormhole structures created, and, hence, on the efficiency of the acidizing process. Gas injection prior to acid injection significantly reduced the volume of acid required to propagate wormholes through cores. Compared with a sample that is initially water saturated, the gas injection reduced the acid volume by a factor of 1.5 to 3 times. When gas was injected, the wormholes were narrower and less branched than those formed under equivalent conditions without gas injection. The presence of oil saturation at residual water saturation in the core had a similar beneficial effect on wormhole propagation to gas injection. Oil present at its residual saturation had little effect on the acidizing process. All of these results confirmed the strong influence that fluid loss from a propagating wormhole had on the efficiency of the acidizing process.
