Doglegs are a fact of life in most/many well planning and drilling operations. Properly planned and drilled, doglegs are part of an optimized wellpath, avoiding problematic formations and maintaining the right drilling angle to reach the pay zone. Many factors influence whether the dogleg location and curvature are appropriate or undesirable. The more accurate and complete the subsurface data that well planners have, the better prepared they are to plan well trajectories that minimize dogleg severity drilling risks.
Unexpected doglegs, however, can wreak havoc later on, causing issues during drilling as well as during production. Evaluating dogleg severity throughout the well planning process can avoid problematic situations such as:
- difficulty placing casing strings due to dogleg severity
- keyseats created by repeated drill string abrasion risk bottom hole assembly components getting stuck
- cemented casing wearing quickly due to excessive contact between the drill string and casing inner diameter
- navigation problems for stiff bottom hole assemblies
- drill string friction created by multiple doglegs increasing the likelihood of getting stuck and failing to reach the planned total depth
While most of these problems can be managed during the drilling process, the mitigation efforts to correct dogleg severity drilling problems delay completion and add to operational costs. The best strategy is to plan wellpaths with the goal of minimizing dogleg severity that compromises drilling operations.
Planning the Wellpath
Dogleg severity drilling problems can be anticipated and minimized with the use of well planning software that integrates relevant subsurface datasets to provide a 3D visualization of subsurface conditions. With a detailed understanding of complex geological formations and established (and planned) wellbores, well planners can then evaluate the pros and cons of different wellpath trajectories.
WellArchitect is an advanced software solution for integrated planning and drilling of directional wellpaths with or without earth models. WellArchitect is designed to manage single and multi-well sites from start to finish: single/multi-well planning, survey calculations, collision risk-analysis, and data management. WellArchitect allows a planner to design any number of potential wellpaths, comparing the advantages and disadvantages of each in context of relevant geological formations and existing wells. WellArchitect offers users the ability to:
- Build complex wellpaths from simple building blocks using a spreadsheet-like application.
- Plan multiple wellpath versions for a wellbore to facilitate the comparison of alternate path compositions, collision risks, and survey programs.
- Avoid collisions as symbols along a wellpath are displayed 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.
- Run 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.
WellArchitect’s 3D visualization capabilities are particularly powerful in helping planners to carefully evaluate subsurface conditions and identify factors that help minimize drilling costs. With WellArchitect, planners can:
- Incorporate data from earth models, logs, and reservoir grids to view wellpaths in combination with targets, offsets, positional uncertainty ellipsoids, and collision-avoidance data.
- Select coordinates interactively in 3D to use in the well design.
- Visualize wellpath relationships in a 3D space as well as on a traveling cylinder plane to optimize wellbore placement and minimize collision risk.
- Slice, shade, color, query, make transparent, and annotate 3D views to better understand spatial arrangement.
- Slice 3D models along a wellpath to provide a cross-sectional view of a stratigraphic or property model to aid geosteering.
- Query wellpath intersections at faults or horizons to better evaluate potential wellbore hazards.
With the ability to integrate and visualize a wide range of geologic data and a powerful pallet of tools and algorithms, well planners spend less time in the planning process to achieve desired wellpath designs. Efficient design considers many different factors. Managing dogleg severity is one of the more critical factors.
Minimizing Dogleg Severity Drilling Risk
WellArchitect offers functionality specific to managing dogleg severity. Planners can establish a default limit (dogleg constraint) when designing a well, yet override that limit in wellpath segments when needed.
Dogleg severity (DLS) units are set to either degrees per 30 feet or 100 feet or degrees per 10 meters, 30 meters, or 100 meters, with the WellArchitect default is 15.0 degrees per 100 feet. As the planner designs the wellpath, the DLS for each segment is calculated or based on the curvature between design points.
Based on the specifications, WellArchitect creates a curve between the two well design points. DLS is monitored from design point to design point along the wellpath. If the DLS either entered by the planner or calculated is greater than the value specified by the dogleg constraint, a warning is issued. A planner then confirms the warning (accepting the out-of-range DLS value) or enters a DLS within range.
Monitor Wellbore Progress While Drilling
WellArchitect provides additional benefit during the drilling process, comparing drillbit progress against the planned wellpath. By incorporating near-real-time data obtained from directional surveys, WellArchitect depicts the actual wellpath in 3D. WellArchitect monitors proximity to faults and horizons while drilling and alerts to potential collision problems ahead-of-the-bit using industry-standard tool models and anti-collision rules. These capabilities give drilling engineers time to correct bit direction, avoid problematic doglegs, and put the wellpath back on track to reach the target.
WellArchitect provides additional benefit during the drilling process, comparing drillbit progress against the planned wellpath.
WellArchitect: Planning and Monitoring Dogleg Severity
WellArchitect offers the ability to visualize layers, horizons, and faults during the well planning process and carefully evaluate dogleg severity along the entire wellpath. Planners can easily factor in drilling methods, casing points, cementing, pump rods, and other concerns impacted by dogleg designs. With relevant information integrated into a powerful visualization and planning environment gives planners greater confidence in designing wellpaths that minimize risk and lower development costs.