Advances in drilling technology continue to reduce the cost and risk of multi-lateral well construction. Multi-lateral wells improve reservoir production by maximizing drainage and sweep efficiency with only incremental increases in drilling and completion costs. Multi-lateral wells also solve the problem of reaching structurally isolated zones in spite of limited slots in offshore platforms.
Working together, geologists, well planners, and reservoir and drilling engineers continue to evolve multi-lateral well geometries to reach isolated reserves. Relative depths and lateral extents of production targets determine the multi-lateral geometry. In the decades since multi-laterals were pioneered, the industry has developed a formal classification—Technology Advancement of Multilaterals (TAML). The six classes are based on the type of junction that joins the lateral to the main wellbore. Vertical, horizontal, or deviated laterals drilled from the main borehole can economically reach attic oil, layered, faulted, fractured, and compartment structures in complex geology.
Stacked laterals, opposed laterals, and herringbone are other variations of geometries developed to reach target zones.
Visualizing Subsurface Conditions
Effective multi-lateral well planning begins with a detailed understanding of subsurface conditions.Geological and petrophysical models, seismic surveys, well logs, production histories, and other relevant reservoir information each separately characterize a subset of subsurface conditions. When these data are combined and visualized in 3D, their value increases considerably.
With access to combined data, all disciplines involved in the well-planning process can collaboratively evaluate various options, identifying potential risks as well as opportunities more quickly and easily. Visualization enables well planners to more accurately determine the optimal multi-lateral well geometries for a particular reservoir.
Visualization enables well planners to more accurately determine the optimal multi-lateral well geometries for a particular reservoir.
Multi-lateral Well Planning: Visualizing the Options
WellArchitect from Dynamic Graphics, Inc. is an advanced well planning, directional drilling, survey management tool, designed for collaborative viewing and planning of multi-lateral wellpaths, sidetracks, and re-entry drilling. It easily combines relevant reservoir datasets and visualizes the data in 3D to evaluate subsurface conditions and develop multi-lateral well plans that optimize recovery while reducing risk. WellArchitect addresses those needs by:
- visualizing and modeling potential wellpaths in context of geologic data, cellular models, earth models, offset wells, and targets
- automatically monitoring the proximity of faults and horizons while planning
- calculating the target size (i.e., the “driller’s target”) based on positional uncertainty, and visualizing it while planning
- depicting minimum allowable separation distances in 3D between a reference wellpath and its offset wellpaths while planning and drilling
- showing collision-avoidance symbols along a wellpath while planning to indicate available space (including length and direction) for steering away from nearby wells; symbols are based on industry-recommended and user-defined anti-collision rules
- running automated clearance calculations ahead of the bit while drilling to give advance warning of collision risk with existing wells and avoid replanning proposed wells by not encroaching on their drainage area
- identifying possible magnetic blind spots while planning and drilling to avoid magnetic tool interference on-the-fly
Quickly Identifying Risks and Opportunities
With the visualization and automated calculation capabilities, well planners can easily explore and evaluate multi-lateral options to quickly recognize and accommodate potential risks such as collisions, as well as take advantage of opportunities that maximizing drainage and sweep efficiency.
- drainage of nearby laterals
- areas of potential borehole instability
- problematic drill bit angles when intersecting faults
- dogleg severity that increases the probability of stuck pipe
- optimal number of laterals determined by reservoir characteristics
- lateral trajectory from the target back to the main borehole, based on rock stress, permeability, and stress anisotropy
- optimized location and length of lateral in the pay zone to maximize recovery
- junction designs (TAML) that balance cost against long-term recovery potential
With 3D visualization, subsurface structures can be sliced, shaded, colored, queried, made transparent, and annotated to provide a more detailed understanding of spatial relationships. Slicing 3D models along a wellpath provides a cross-sectional view of the stratigraphic or property model, further enhancing the spatial understanding.
WellArchitect Enables Multi-lateral Planning in Complex Subsurface Environments
Well planning becomes increasingly challenging as more infill wells are drilled. WellArchitect gives geoscientists and well planners enhanced ability to understand and quickly evaluate the complexity by combining and visualizing a wide range of relevant subsurface data to plan the design and location of multi-lateral wells that maximize recovery while minimizing risk.
Image courtesy Katty Astra