or radial flow at least two temperature sensors 34 should be installed sufficiently far away from each other such that they capture temperature differences due to radial acid flow in particular embodiments the minimum distance between two temperature sensors 34 is greater than the radial diameter of the wormholes thus it is preferred that the sensors 34 are spaced apart from each other on the tool body 22 by a distance that is greater than the diameter of the wormholes 24 theoretical calculations show that the minimum distance between two temperature sensors 34 should be between 4 and 20 meters 13 66 feet depending upon the reservoir properties porosity permeability wormhole size and shape geothermal gradient thermal conductivity etc and well details shape dimensions completion type etc the method could be refined by adding temperature sensors between the two end sensors adding more temperature sensors in between increases the accuracy of temperature variation measurement in addition to the temperature sensors other sensor types could be used for instance pressure sensors could also be installed both temperature and pressure measurements are useful in accurately evaluating the matrix acidizing performance when they are coupled with a mathematical model that solves the classical energy flow equation inside the well where u03c1 is acid density t and z are time and the curvilinear coordinated along the well path v is acid velocity u c p t u2212 t ref and h u p u03c1 are the specific internal energy and enthalpy respectively c p is the specific heat defined at reference temperature t ref and t and p are acid temperature and pressure note also that q is the term that includes all other heat exchange effects such.