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The Taq Taq Field is located within an anticline in the gently folded zone of the Zagros mountains, northeastern Iraq, approximately 50 km ESE of Erbil. The main reservoirs are fractured limestones and dolomites of Late Cretaceous age, with an oil column exceeding 500 m in thickness. Eocene limestones and dolomites at shallow depth form a subsidiary reservoir. The structure is a gentle thrust-related fold which has also been affected by dextral transpression. A pervasive fracture system is present within the reservoirs, giving good connectivity and deliverability. Initial discovery and appraisal was made in 1978 when three wells were drilled. The recent appraisal programme started in 2005 and by the end of 2008 two seismic surveys had been acquired and eight additional wells had been drilled. Mapping has incorporated a seismic principal component analysis for horizon and lithology identification. Modelling of the fractures has utilized a comprehensive data set derived from core and image logs. Special core analysis has been directed towards the understanding of the pore system and its interaction with the fractures. Synthesis of all these elements is performed in a dual-media dynamic model which is currently in use for development planning.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Meren oil field is located offshore Nigeria, about 110 miles south-east of Lagos. The reservoir consists of interstratified sandstones and shales, mostly representing shoreface to shelf deposition. The E-01/MR-05 reservoir, one of the most prolific intervals in the Niger Delta, was placed on production in 1968. The field was shut-in in 1985 due to declining pressure and production, and was brought back on production in 1989. In 1991, a waterflood was initiated. Although the waterflood was successful on an overall basis, limited response was observed in some of the reservoir units due to preferential movement of the water bank. To improve the waterflood conformance and thus the recovery, an integrated study of the E-01/MR-05 reservoir was proposed.This study involved building a highly detailed earth model to accurately define the geologic framework, and a scaled-up simulation model to study the in-situ fluid dynamics accompanying production. The stratigraphy of the reservoir was defined using sequence stratigraphic analysis and facies modeling. Preliminary geological analysis indicated probable pressure communication with the Malu gas field to the northwest and this area was incorporated into the earth model. Two adjacent Meren blocks to the south-east were also included to increase the well and geologic control. The complexity of the simulation of the Meren E-01/MR-05 sandstone is due to two principal unknowns in the field: • The largest uncertainty is the magnitude of crosscommunication between each of the sandstone units that constitute the reservoir. This cross-communication occurs due to the patchy shale distribution.the history-matching hurdles-the water breakthrough times and the post-injection pressure histories of the individual wells-are also discussed in the paper.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Meren oil field is located offshore Nigeria, about 110 miles south-east of Lagos. The reservoir consists of interstratified sandstones and shales, mostly representing shoreface to shelf deposition. The E-01/MR-05 reservoir, one of the most prolific intervals in the Niger Delta, was placed on production in 1968. The field was shut-in in 1985 due to declining pressure and production, and was brought back on production in 1989. In 1991, a waterflood was initiated. Although the waterflood was successful on an overall basis, limited response was observed in some of the reservoir units due to preferential movement of the water bank. To improve the waterflood conformance and thus the recovery, an integrated study of the E-01/MR-05 reservoir was proposed.This study involved building a highly detailed earth model to accurately define the geologic framework, and a scaled-up simulation model to study the in-situ fluid dynamics accompanying production. The stratigraphy of the reservoir was defined using sequence stratigraphic analysis and facies modeling. Preliminary geological analysis indicated probable pressure communication with the Malu gas field to the northwest and this area was incorporated into the earth model. Two adjacent Meren blocks to the south-east were also included to increase the well and geologic control. The complexity of the simulation of the Meren E-01/MR-05 sandstone is due to two principal unknowns in the field: • The largest uncertainty is the magnitude of crosscommunication between each of the sandstone units that constitute the reservoir. This cross-communication occurs due to the patchy shale distribution.the history-matching hurdles-the water breakthrough times and the post-injection pressure histories of the individual wells-are also discussed in the paper.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA key difficulty associated with modeling faulted reservoirs is honoring both the structure and stratigraphy while simultaneously generating models that are acceptable in terms of practical simulation run times. In this paper, we describe our approach for designing finely gridded, faulted simulation models which we then scale up using a flow based nonuniform coarsening technique that takes into account the impact of the faults. Two field examples of faulted reservoirs are presented to demonstrate the new grid design and upscaling tools and, also, to investigate the impact of faults on flow behavior.An important characteristic of our work process to generate faulted simulation models is that all of the tasks, from horizon and fault mapping to geostatistical reservoir characterization to scale up, are performed within an integrated earth modeling environment. Our grid design and scale up calculations accommodate complex fault networks and non-vertical faults (including reverse faults), although in the current implementation we allow only "logically-vertical" faults; i.e., faults with slip along the w or nominally vertical coordinate in a u, v, w stratigraphic grid. The rationale for specifying logically vertical faults is that they represent a compromise between accurately modeling fault geometry while maintaining computational efficiency when simulating flow in faulted reservoirs.Although fault geometry, which we capture with our grid design and upscaling tools, is an important component of fault transmissibility, it is not the only one. Consequently, we present a technique for modifying fault transmissibility by introducing transmissibility multipliers at fault locations in the grid. We use this technique to generate sealing faults. We then compare reservoir performance predictions based on sealing, partially communicating, and no-fault formulations. Plots of individual well performance from the field examples reveal significant differences between the three formulations.