Mechanistic Modeling for Well Configuration Screening in EOR Pilot

摘要

Pilot objectives are usually predetermined before pilot field implementation. In order to study different pilot performance predictions, dynamic reservoir simulation is used as screening tool to ensure pilot designs meet pilot objectives. A Mechanistic "box” model is a limited size simulation model used to compare different pilot configuration performances on an equal basis and so saves both CPUs and simulation time. A 1 km × 1 km mechanistic model was constructed with refined grid of 25m × 25m. The reservoir properties, attributes and layering used are similar to the geological "static" model to avoid upscaling issues. Transmissibility multipliers were used at the boundaries of the mechanistic model and production or injection rates of the edge wells were constrained to mimic full pattern performance. Several pilot scenarios were studied in terms of well configurations, well spacing, well type (vertical or horizontal), well completion (reservoir sub-zone), injection/production rates, injected fluid (water, gas), injection continuity (continuous injection, WAG) and WAG cycles. All of these prediction cases were run under reservoir voidage replacement. Certain criteria were selected to screen these cases such as recovery factor at breakthrough, ultimate recovery factor, sweep efficiency, injection rates and breakthrough time. More than fifty cases were run and screened using mechanistic models. A number of these cases, those which meet the pilot objectives, were selected to be run using larger sector model for comparison with the mechanistic models. Results show good agreement between the mechanistic model and sector model results. The mechanistic model is a good tool to quickly screen many pilot scenarios rather than running much larger compositional models. The prediction results of the pilot performance can be used to create Tornado charts to determine the impact of key uncertainty parameters on oil recovery, sweep efficiency and breakthrough time. These charts will dictate the pilot design and pilot monitoring requirements.