Experimental Investigation for the Effects of the Core Geometry on the Optimum Acid Flux in Carbonate Acidizing
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Previous matrix acidizing experimental research showed that there exists an optimum acid interstitial velocity (Vi-opt) that results in the minimum volume of acid used while providing the best stimulation results. There are already several upscaling models that translate experimental results into field conditions. By finding the optimum core geometry to use for matrix acidizing experiments, a great amount of time and money will be saved in selecting the correct size core for future experimental work. Laboratory experiments have already indicated that the optimum acid interstitial velocity can be independent of the core length when the core length is long enough. In this thesis, further core flood experiments were done using four inches diameter cores that varied in length. The lengths of the cores are 4 inches, 6 inches, and 8 inches long. The acid concentration used for these experiments was 15 wt% HCl. A pressure drop plot was created as the acid penetrates through the core sample. By looking at the pressure drop plot, the start of acid penetration, the early stages of wormhole competition, the later stages of a dominant wormhole forming, and the time when the acid breaks through the core can all be recorded. Theoretical works were done to correlate experimental results with previously published work. It can be concluded that when the core reaches a certain length, the optimum interstitial velocity becomes independent of the core length due to the dominant wormhole being formed. Also, when the core length reaches a certain value, the optimum acid injection rate is independent of the core radius given that the core radius is large enough to comprise the early effects of wormhole competition. One inch diameter cores should never be used because it only shows the dominant wormhole being formed.