TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper summarizes the findings of a compositional simulation study of a gas injection pilot in a transition zone reservoir onshore Abu Dhabi. The field covers an area of more than 600 sq. km straddling land, islands, shallow and deep marine environments. A multi-disciplinary team including reservoir, petroleum, planning, conceptual design engineers and geoscientists, geologists, geophysicists and petrophysicists, was formed to examine different development options for the field. The team is faced with a number of technical and economic challenges to design an optimum field development scheme, maximizing ultimate oil recovery and minimizing development cost while maintaining high level of environmental protection through the whole life cycle of the field.

Horizontal drilling was under consideration for the development of the poorer reservoir quality northern area of a large onshore oil field in Abu Dhabi. This paper presents the case history of two horizontal holes drilled in a pilot well to help evaluate horizontal well performance for development planning purposes. Geological and petrophysical data are described. The reservoir consists of layered limestone with porous layers alternating with continuous, thin, dense, stylolitic intervals. An existing vertical well, with production test history from two completion intervals, was re-entered. The short radius technique was used to drill two horizontal holes into two porous layers, separated by several intervening dense and porous intervals. Production test results, before and after horizontal drilling, are presented. For both horizontal holes, productivity was higher than the previous vertical completions. Vertical interference testing was also carried out, by monitoring the pressure in the lower hole while producing from the upper hole. Well test interpretation is discussed. Results of analysis, assuming a single homogenous layer, are described. The layered nature of the reservoir appears to affect transient pressure behavior. Numerical simulation, with local grid refinement around the horizontal holes, was also used to match the test results, including the vertical interference test observed pressures.

Gas reservoirs in the Nile Delta of Egypt are characterized vertically by its thin beds of sands and shale and laterally by severe variations in facies. These challenges in the static modeling have a strong impact in the dynamic modeling which can be summarized in the following points. First, the vertical sequence of sands and shale leads to the difficulty in detecting a single gas-water contact in the field. Second, the vertical heterogeneity leads to the use of fine gridding especially in the vertical direction to accurately simulate the fluid flow in the reservoir. Third, the lateral variation in facies forces to use different saturation functions at different parts of the reservoir. The dynamic behavior of pressure and production performance from few wells (total seven wells) producing from this field show severe vertical discrepancy in pressure, gas and water production. This adds another challenge in the dynamic modeling and leads to dividing the field into three main reservoirs that are completely isolated with each has different reservoir and production characters. Due to these challenges, we developed an unconventional approach to model this field and estimate its gas in place that honors both static and dynamic data. First, we used the concept of initialization by enumeration instead of the conventional approach of initialization by equilibration that requires accurate detection of gas-water contact. The initial pressures are obtained from MDT (Modular Dynamic Tester) data and the water saturation are obtained from the petrophysical analysis in initial wells and populated in the reservoir to honor the seismic and the production data. Second, we used low vertical permeability to simulate the vertical variations in sand-shale sequence. This also helps in reducing the severity of the phases being not in equilibrium due to the initialization by enumeration. Third, we used fine gridding to capture the heterogeneous variation in property. To reduce the CPU time for running one single fine grid model, we divided it into three different models each represent one reservoir with running each model separately. Both production and pressure data confirms that these reservoirs are completely isolated and no wells are producing commingled from these reservoirs thus separating them will not have any effect on its performance. This work summarizes the workflow we developed in the dynamic modeling of this field, the history match approach we used to calibrate the model and finally the suggested optimum development plan to increase its reserves. Introduction South El-Manzala field is one of the fields in the Delta of Egypt. It is located to the North of Cairo and it is about 64.6 Km2. Figs. 1a and b show the location of South El-Manzala (SEM) field. South El-Manzala field is dissected by ENE striking low angle dip-slip fault that was active since Early Pliocene up to Pleistocene. It dies on the top of the Messinian rocks, and divided the field into two blocks; the northern downthrown block enclosing the main production area of the field.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAlthough computer power has significantly increased in recent years, the need for upscaling is still mandatory to save run time for many reservoir-modeling studies. In this paper we demonstrate the results of reservoir upscaling using nine different algorithms. A comprehensive evaluation for these upscaling methods was performed using several models with increasing complexities and heterogeneity.Several simulation models were constructed to investigate the effect of the upscaling technique on the quality of the simulation results (including history matching). A very fine model, closest to the geological model, was constructed as a benchmark. Simulation models were then upscaled using nine different upscaling techniques for both natural depletion and water injection driving mechanisms. The models were run for a period of time and the results were compared with those of the fine model. The results were treated statistically to quantify the resultant deviation (errors) from the benchmark results. It was found that some of the upscaling techniques gave better results than others.In this paper, we also suggest a road map to follow when upscaling geological models and discuss the upscaling for different levels of refinement. The suggested procedures can be applied to many modeling problems and is expected to save time in simulation studies.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper summarizes the findings of a compositional simulation study of a gas injection pilot in a transition zone reservoir onshore Abu Dhabi. The field covers an area of more than 600 sq. km straddling land, islands, shallow and deep marine environments. A multi-disciplinary team including reservoir, petroleum, planning, conceptual design engineers and geoscientists, geologists, geophysicists and petrophysicists, was formed to examine different development options for the field. The team is faced with a number of technical and economic challenges to design an optimum field development scheme, maximizing ultimate oil recovery and minimizing development cost while maintaining high level of environmental protection through the whole life cycle of the field.