Innovations in multilateral well drilling and completion technologies continue to reduce the cost of well construction and enable secondary and tertiary recovery. With minimal increase in drilling and completion costs, multilaterals improve reservoir production by increasing the contact area of a wellbore in a formation or reaching multiple production zones from a single pad. Multilateral well design has also helped to significantly reduce the environmental impact of surface operations.
The Use of Visualization and Well Planning Software
To fully realize the benefits of multilateral wells, reservoir and drilling engineers need to plan multilateral well designs that optimize wellbore exposure within the formation, avoid geologic risks, and prevent collisions with nearby producing wells. Visualization software that provides detailed understanding of subsurface conditions (accurate geologic models) and well planning software that incorporates the geologic model are essential tools for guiding multilateral well design for new fields. For developed fields, the same visualization and well planning software can help well planners navigate the complexity of the myriad of existing wells and laterals, avoiding collisions and “thief zones,” and locating new laterals to reduce drilling cost and risk while optimizing recovery.
The Value of Accurate 3D Geologic Models
When the relevant geological, geophysical, and petrophysical data can be integrated into a single model that accurately characterizes a reservoir and depicts the subsurface environment, well planners gain the detailed insight needed to begin multilateral well design. With the ability to visualize the model in 3D, reservoir engineers can readily explore and analyze horizons, faults, and targets, and develop multilateral well plans to avoid risk and maximize opportunities. Specific analysis and visualization capabilities that facilitate in-depth exploration of the geologic model include:
- Comparison, validation, and refinement of fault and horizon interpretations
- Assessment of normal and reverse faults, major fault gaps, anticlines and synclines, fault-wedges, salt diapirs, and similar complex geologic structures
- Evaluation of geologic attributes using contour maps, isochore maps, cross-sections, base maps, and fence displays
- Display of three-dimensional property distributions within fault blocks
With as accurate as possible understanding of the subsurface environment, well planners can begin the process of determining the optimum kickoff point, the number of laterals to drain the reservoir, appropriate lateral distancing, and most importantly, the wellbore paths for each of the laterals.
Design Multilateral Wells in the Context of 3D Geologic Models
Accurate 3D geological models enhance the entire well planning process. Well planners who develop multilateral well designs based on 3D geological models achieve better results due to the informational detail provided in the models. With the ability to visualize a proposed wellbore in context of the geological and petrophysical conditions local to the wellbore, planners can:
- Readily identify geological factors that increase drilling risk and cost and explore multiple mitigation strategies.
- Optimize the wellbore curve from pad to target to minimize problems associated with torque and drag, hole cleaning, premature bit wear, tool limitations, and cementing.
- Recommend the appropriate casing and tubing design to accommodate the loads throughout the life of the well.
- Work with drilling engineers to design the BHA to handle the formation.
- Work with completion engineers to design the completion system for the frack stage of the production zone, selecting components appropriate for the downhole environment.
The wealth of integrated subsurface data allows well planners to explore and evaluate the geology and geophysical characteristics of a reservoir in detail, leading to greater confidence in understanding the challenges and developing multilateral wells designed to economically exploit reserves.
Collision Avoidance in Established Fields
Tubes displayed around each offset well show minimum allowable separation distance (MASD) from the reference wellpath.
In the case of established fields, where not all planned laterals have been established or new reservoir data indicates the opportunity for additional laterals, multilateral well design has to factor in collision risks that could jeopardize production. Here, the ability to visualize the current subsurface environment—geology as well as existing welbore locations—gives well planners greater assurance in placing additional laterals.
Here, the ability to visualize the current subsurface environment—geology as well as existing welbore locations—gives well planners greater assurance in placing additional laterals.
Collision-avoidance visualization in 3D allows well planners to easily identify areas of concern that might otherwise be overlooked using traditional reports/plots, adding a new level of safety awareness. The minimum allowable separation distance (MASD) results from anti-collision scans (using rules established by the operator or industry) are depicted as tubes displayed around offset wells. Color-coded collision-avoidance symbols indicate the available space relative to nearby wells, with the colors and shapes indicating proximity and local convergence/divergence, respectively.
Three-dimensional visualization and collision avoidance features also aid the drilling phase. Comparing the new wellpath as it is being drilled against the original plan and earth model facilitates increased understanding of the geology and proactive mitigation of unanticipated problems.
Comprehensive Software Tools for Multilateral Well Design
To meet the needs of multilateral well design Dynamic Graphics, Inc. offers a comprehensive set of geologic modeling and well design tools. EarthVision integrates diverse two-dimensional and three-dimensional data types to optimize data verification and interpretation of 3D geologic models. Using the 3D geologic models and a wide range of planning tools available in WellArchitect, well planners can develop the multilateral well design for optimal wellbore placement within a reservoir to cost-effectively achieve recovery objectives.
