ABSTRACT Conventional oil reserves are coming to an end, then, some unconventional sources, such as heavy oil, are being the aim of oil companies. Most of heavy oils, drilling fluids and fracturing fluids behave as non-Newtonian and these fluids are erroneously approximated by Newtonian fluid flow models. Currently, there are no mathematical expressions for the application of the straight-line conventional analysis method for the interpretation of pressure tests in heterogeneous or naturally-fractured occurring formations (dual porosity) which are saturated by a non-Newtonian pseudoplastic fluid. The literature includes an analytical solution for predicting the behavior of the pressure in dual porosity reservoirs containing a non-Newtonian fluid; this solution was subsequently used to interpret the well-pressure data using the pressure and pressure derivative log-log plot without employing type-curve matching. None commercial software includes up to date such analytical solution. Several expressions to complement the conventional straight-line method are presented in this work so pressure tests in naturally fractured reservoirs with a non-Newtonian power-law fluid can be interpreted. This is accomplished mainly by estimating the interporosity flow parameter and dimensionless storage coefficient. The developed equations were successfully tested using well pressure tests reported in the literature. Very good results were obtained from the worked examples when compared to the reference values. Keywords: Non-newtonian fluids, Naturally-fractured reservoirs, Conventional technique. Analisis convencional de pruebas de presion para yacimientos naturalmente fracturados con fluidos pseudoplasticos no newtonianos RESUMEN Las reservas convencionales de petroleo estan llegando a su fin, por tanto, las companias petroleras le estan apuntando a algunas fuentes no convencionales como los crudos pesados. La mayoria de los crudos pesados, fluidos de perforacion y fracturamiento se comportan en forma no Newtoniana y son erroneamente aproximados por los modelos de flujo de fluidos Newtonianos. Actualmente, no existen expresiones matematicas para la aplicacion del metodo convencional de la linea recta para interpretar pruebas de presion en yacimientos heterogeneos o naturalmente fracturados (doble porosidad) saturados con un fluido no Newtoniano pseudoplastico. La literatura incluye unicamente una solucion analitica para predecir el comportamiento de la presion en yacimientos de doble porosidad con fluidos no newtonianos; solucion que fue mas tarde usada para interpretar datos de presion usando la presion y derivada de presion sin emplear curvas tipo. Ningun programa comercial incluye a la fecha dicha solucion analitica. En este trabajo se presentan varias expresiones para complementar el metodo convencional de la linea recta para caracterizar yacimientos naturalmente fracturados cuando un fluido no Newtoniano pseudoplastico fluye a traves del medio poroso. El principal proposito es la estimacion del parametro de flujo interporoso y el coeficiente de almacenamiento adimensional. Las expresiones desarrolladas se verificaron satisfactoriamente con pruebas de presion reportadas en la literatura, encontrandose muy buenos ajustes con los valores de referencia. Palabras Clave: Fluidos no newtonianos, Yacimientos naturalmente fracturados, Tecnica convencional