Successful acid-fracturing treatment requires the creation of etched channels of sufficient width and length. This paper shows how the channel shape can be calculated using knowledge of the acid/rock reaction process, in-situ temperature and hydraulic profile. A simulator has been developed for this purpose, on the basis of an implicit finite-difference scheme permitting rigorous treatment of all relevant processes, such as the cooling of the rock adjacent to the fracture and the heat transfer between fracture and wall during and after pumping, is employed. Detailed knowledge of the temperatures of both the fracture fluid and the rock face allows quantitative description of the progress of the acid/rock reaction. Model calculations show that the channels etched in calcitic rock may be very wide near the wellbore because of turbulence effects. On the other hand, the etched channels may be too narrow in dolomitic rock, or rock with a low fracture toughness. This will impair well productivity, and should be avoided by modifying the pumping scheme. Two field examples of treatment design and evaluation using the new simulator are discussed.

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