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Case Study: Well Section Placed Precisely in Thin, Heavy Oil Reservoir



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Cross sections of offset wells indicated a target sand TVD of approximately 20 ft.


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PeriScope bed boundary mapping provided the real-time understanding of reservoir geometry needed to place the 1,690-ft horizontal section entirely within the thin target sand.


The 1,690-ft horizontal section was placed entirely within the thin target sand, using PeriScope mapping and a PowerDrive RSS.

First horizontal well drilled in Colombia’s Girasol field geosteered successfully with PeriScope bed boundary mapping


Challenge

Place 1,600-ft horizontal well section within 20-ft-TVD reservoir sand without exiting target zone.

Solution

Use PeriScope bed boundary mapper to guide proactive geosteering of PowerDrive rotary steerable system.

Results

Placed 1,690-ft horizontal section—90 ft longer than originally planned—entirely within target zone.

Understanding reservoir geometry key to success

The operator of Girasol field, located in Colombia’s Middle Magdalena Valley basin, wanted to maximize production of the field’s heavy oil, which was being recovered mainly by steam injection. To acquire information needed to define field development strategy, the operator planned to place a 1,600-ft horizontal well section within a reservoir sand that had a TVD of approximately 20 ft.

Offset well data indicated that placement in the thin sand would be challenging, due to the possible presence of geological discontinuities, such as subseismic faults and lateral or vertical facies variation, and shale layers. This uncertainty made understanding reservoir geometry in real time a key factor for success.

Geosteering optimizes well placement

The operator successfully determined reservoir geometry in real time, using the unique PeriScope bed boundary mapper to acquire deep, directional electromagnetic measurements and images. A fully rotating PowerDrive rotary steerable system (RSS) provided precise steering control, as well as real-time continuous surveys and gamma ray measurements near the bit.

During drilling of the long horizontal section, Schlumberger well placement engineers and directional drillers and the operator’s geoscientists and reservoir and drilling engineers worked together to optimize well placement. This multidisciplinary team used RTGS Real-Time GeoSteering and Petrel seismic-to-simulation software for real time data processing, geosteering modeling, and interpretation. Interaction of the team and remote monitoring were enabled by two Web-based applications—WebEx and InterACT real-time monitoring and data delivery.

Precise well placement maximizes results

The real-time data provided by the PeriScope bed boundary mapper and the PowerDrive RSS enabled the multidisciplinary team to make proactive geosteering decisions and execute them precisely, resulting in successful placement of the first horizontal well section drilled in Girasol field. Total length of the section was 1,690 ft—90 ft more than planned and it was placed entirely within a target that was only about 18 ft thick.


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