Success of acid fracturing treatment depends greatly on the created conductivityunder closure stress. In order to have sufficient conductivity, the fracture face must benon-uniformly etched while the fracture strength maintained to withstand the closurestress. While there have been several experimental studies conducted on acid fracturing,most of these have not scaled experiments to field conditions and did not account for theeffect of rock weakening and etching pattern. Hence, acid fracture conductivitypredictions based on the above works have not been able to match actual results.In order to develop a more appropriate and accurate prediction of acid fracturingtreatment outcome, a laboratory facility was developed that is properly scaled to fieldconditions and enables analysis of etching pattern and rock strength. A systematicexperimental study that covered a variety of formations, acid types, and acid contacttimes was conducted. An acid fracture conductivity correlation was developed based onetched volume, etched pattern, and fracture strength under closure stress.Results suggested that there is an optimal time of acid exposure resulting inmaximum fracture conductivity. There were large differences in the conductivity created with the different acid systems tested due to different etching patterns and degree of rockstrength weakening. There was an optimal acid system depending on formation type,contact time and overburden stress. The acid fracture conductivities measured did notagree with the predictions of the Nierode-Kruk correlation. The newly developedcorrelation predicts conductivity much closer as it includes the effect of rock strengthand surface etching pattern on resulting conductivity.
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