This paper presents the application of high-resolution static and dynamic modelling in complex faulted fluviatile sandstone reservoirs. It is based on results of an integrated study of one of AFPC's fields in the Euphrates Graben, Syria, with the Cretaceous Lower Rutbah and Triassic Mulussa F1 & F2 forming the three main reservoir units. It describes the modelling challenges and the advantages of high-resolution models in reproducing the dynamic reservoir processes as observed from well data. It also shows how a dynamic process-based modelling workflow resulted in history match improvements and higher reliability of predictions. Subsequent field implementation of the project recommendations provided the ultimate validation of the modelling approach and demonstrated the predictive value of the models.

The paper also highlights the added value of 3-phase streamline simulation in full field history matching and improving the understanding of flow paths in the reservoir as a result of the interplay of fluvial channel sands and numerous fault juxtapositions. It compares streamline simulation with the traditional finite difference simulation results and describes the strengths and weaknesses of streamline simulation applied during history matching.

The Reservoirs

The investigated field has three main reservoir formations, which are the Lower Rutbah (RUL), Mulussa F1 (MUF1) and Mulussa F2 (MUF2), shown in a schematic cross section in Figure 1.

The Mulussa F sequence (MUF) is dominated by fluvial sandstone bodies alternating with flood plain fines and soil horizons. The reservoir quality of sands is good (average net porosity of some 16%, permeabilities ranging from 30 to 1000 mD, average oil saturation of 83%). The Triassic Mulussa is separated from the overlying Cretaceous Lower Rutbah formation by the regional BKL unconformity, which resulted in partial erosion of the formation within the field area, in particular in the western part. Hence the MUF1 varies greatly in thickness over the field, whereas the MUF2 has a layer-cake architecture (at the level of major stratigraphic units). Another key difference between the MUF1 and the MUF2 formations is the N/G ratio, which is high in the MUF2 (50–70%) and low in the MUF1, where it only attains 30%.

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