Rock Typing for a Fractured Carbonate Reservoir with Low Resistivity in Middle East

The T reservoir is a fractured carbonate reservoir located in Middle East with low resistivity and high total porosity. Fractures of various scales and dip-azimuth are well developed. The storage space for matrix consists of intragranular pores and microfractures. Effective porosity interpretation suggests that less than 20 percent porous volume in total porosity is effective. FMI log interpretation of more than 120 wells show that fractures are well developed with various apertures, dip and strikes. Three types of the reservoir rock were distinguished according to the combination of range of effective porosity and scale of fractures. Rock Type 1 is the fractured limestone in lower part of reservoir characterized by development of large scale fractures. The effective porosity is less than 5% with total porosity over 20%. Rock Type 2 is the fracture-matrix mixed limestone in middle part of reservoir characterized by smaller scale fractures and pores connected to fractures. Rock Type 3 is the matrix limestone in upper part of reservoir with higher effective porosity (over 20%). Dynamic data show that the major productivity is contributed by Rock Type 1 and Rock Type 2, which are distributed in lower and middle intervals of T reservoir.