Models for Oil Recovery from Naturally Fractured Reservoirs, Considering Multiple Block Size, Capillarity and Gravity Effects

Rafael Rodriguez-Nieto, School of Engineering, Earth Science Engineering Division, National Autonomus University of Mexico, 2a Cerrada de Pablo de la Llave #35, Casa 10, Colonia Bosques de Tetlameya, Mexico, 04730, Mexico, phone: (5255)56-06-42-32, fax: (5255)55-50-00-40, rafaelrn10@hotmail.com and Mario Alberto Vasquez-Cruz, Naturally Fractured Reservoir Program, Mexican Petroleum Institute, Cruz del Sur #73-1, Colonia Prado Churubusco, Mexico, 04230, Mexico.

Variable block size models are presented to study naturally fractured reservoirs under waterflooding, taking into account discrete or continuous block size distributions, imbibition, and gravity segregation mechanisms.

First of all, the corresponding theory is developed to obtain the total oil flow rate for a certain time (for instance, at the beginning of the process). The starting point considers only one block of a given size and then equations are derived for any number of block sizes (NBS). Afterwards, the continuous case equations are obtained, presenting illustrating examples for each one of the involved models.

Based on this theory, models are developed for calculating oil recovery behavior as a function of time, considering capillarity and gravity effects. Thus, any field history is readily taken into account to adjust the variable block size models, in order to use them adequately in the prediction phase. Finally, synthetic examples are included to illustrate the usefulness of the models.

Exploring and Producing Fractured Reservoirs
2004 AAPG International Conference and Exhibition Technical Program