Confirm Water Sweep Dimensions and Extent to Guide Injection, UAE

Published: 01/01/2009

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Insufficient resolution and coverage for monitoring

Uneven sweep (water override) was occurring in a prolific UAE field operated by Abu Dhabi Company for Onshore Oil Operations (ADCO). But lateral coverage with conventional logs and the vertical resolution of subsurface seismic surveys were insufficient for monitoring interwell fluid flow. What was missing was measurement of the flood movement in the areas between wells. The limited dataset in turn impeded prediction of the water front dimensions and extent generated using stochastic flow simulation.

Graphic: Confirm Water Sweep Dimensions and Extent to Guide Injection, UAE
DeepLook-EM service’s transmitter and receiver tools were run in pairs of observer wells to monitor water injection.

Reservoir-scale resistivity images

Instead of logging just the near-well environment, DeepLook-EM crosswell electromagnetic imaging service provides reservoir-scale resistivity images between boreholes up to 1,000 m [3,280 ft] apart. The extent and direction of injected fluid flow is revealed by DeepLook-EM service's time-lapse surveys, imaging fluid displacement across the reservoir to guide injector placement and operation and infill drilling.

Graphic: Confirm Water Sweep Dimensions and Extent to Guide Injection, UAE
Time-lapse surveys by DeepLook-EM crosswell electromagnetic imaging service at a 6-month interval show a large water sweep preferentially from east to west between Wells 1 and 3.

Insight from accurate images of fluid flow

DeepLook-EM service's surveys of well pairs were acquired for a set of three observer wells, with baseline acquisition conducted preinjection. The data were fit into a model constructed from conventional wireline resistivity measurements made in the observer wells. Survey images from 6 months after the baseline indicate successful water flooding from the injector well to observer Wells 1 and 3, with a large volume of water swept through a preferential east–west flow direction. The flow preference was confirmed by RST reservoir saturation tool logs.

At the time of the 6-month survey, water had not migrated to the pair of observer Wells 2 and 3. Further DeepLook-EM service surveys at 6-month intervals will verify the direction and coverage of water movement, enabling fine-tuning of injection management to avoid both water override and ineffective sweep for more complete recovery than usual.

United Arab Emirates, Asia, Onshore

Challenge: Determine waterflood movement on a reservoir scale to avoid override.

Solution: Monitor fluid displacement using reservoir-scale resistivity images from DeepLook-EM crosswell electromagnetic imaging service.

Results: Used time-lapse survey results to correct flow simulation model for accurately projecting sweep movement and guiding injection strategy.

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