In this work one of the Iranian fractured carbonate reservoirs has been studied. This reservoir is located in south west of Iran with 40 km long and 4 km wide and consists of two culminations with crest depths of 3780 and 3749 mss respectively. Eastern part is smaller and productive compared to the western part which is larger but with high water saturation causing no production from this part. Two parts are separated by a saddle like region. Economic production from this reservoir has been started in 1977 and the cumulative production has reached 12.064 MMSTB in 2004.
The main ambiguity of this reservoir is whether two parts are sealed or not. Geologists couldn't answer this question because of the lack of data. This question has been addressed in this study from reservoir engineering point of view. Therefore, after data gathering and calculating reservoir engineering parameters, oil in place and reserve are estimated in two parts. Then the reservoir is analyzed by material balance calculations, after which the reservoir has been simulated. By evaluating the results, the problem of communication between two parts is resolved in 7 sections: core description and analysis, core experiments and rock type, fluid characterization and PVT analysis, pressure analysis, water-oil contacts, production history and petrophysical evaluations. Finally considering all aspects of evaluations, it is concluded that there is no communication between two parts of the reservoir.
This field is located in southern Iran with 40 km long and 4 km wide and has two culminations. Eastern part is smaller but productive and western part is larger but with high water saturation that until yet there is no production from it. Between two parts of the reservoir it is a saddle and depth of crest of eastern part is 3780 mss and western part in 3749 mss. There are 6 wells drilled and only 2 of them in the eastern part are productive.
The field is on production since 1977. The reservoir is under saturated but the current pressure is near saturation pressure.
The reservoir is divided to 4 zones. Zone 1&2 are productive zones and mainly carbonate. Zone 3 has thin beds of sand and shale and zone 4 is composed of different types of layers such as carbonate, shale, marn, dolomite… There is no fault or folding but from mud loss information it seems that the reservoir has hairline fractures.
To evaluate original oil in place and reserve, UGC map is used to calculate the area of top zones. Then by using the thickness, area of the bottom layers is calculated. After that by using petrophysical properties, oil formation volume factor and water oil contacts, rock volume, net rock volume, pore space volume and hydrocarbon volume in matrix and fracture is calculated. Uncertainty analysis is done by Monte Carlo method. The results are in Tables (2).
The volumetric balance equation more commonly known as Schilthuis material balance equation was introduced by Schilthuis in 1936. It is well accepted tool to predict reservoir performance.
