Multilateral well drilling technologies have evolved significantly since being pioneered in the Bashkiria fields in Russia in 1953. Today, the diversity of drill string and bottom hole assembly designs combined with the ever-increasing volumes of subsurface data allow operators to more accurately understand geological conditions, identify risks, and plan and drill multilateral wells to maximize recovery.
Multilateral drilling innovations have facilitated greater flexibility in reservoir development. In this blog, we review the complementary ways that data and multilateral well drilling technologies are allowing operators to achieve those goals.
Geology and Geophysics Guide Drilling Technology
Data integration and visualization software, such as CoViz 4D, by Dynamic Graphics, Inc., designed for the petroleum industry provides well planners and drilling engineers with detailed 3D models of the subsurface environment. When used in conjunction with advanced directional drilling packages, such as WellArchitect, also by Dynamic Graphics, 3D models allow drilling teams to assess the reservoir at the macro level, showing formations, faults, horizons, salt domes, and share layers. The 3D models also allow teams to explore properties such as lithology, porosity, permeability, and saturation along proposed multilateral well paths.
In developed fields, 3D models can depict existing nearby wells and well data to help well planners avoid encroachment and gain a better understanding of local geologic and geophysical properties. A detailed 3D model of the geologic and geophysical characteristics of a reservoir gives well planners relevant information to:
- Accurately identify targets.
- Identify geologic risks such as faults or salt domes, or thin sand zones and thin layer formations that demand accurate entry and placement of laterals.
- Plan the preliminary distribution of the laterals through the reservoir—multi-branched, forked, stacked, dual-opposing, or variations of each.
- Locate wellbore and laterals within the geology to maximize reservoir coverage and exposure to fractures.
Well planners can also create 3D cross-sections “on-the-fly” to explore any specific area in detail. A detailed understanding of geologic and geophysical characteristics sets the initial stage for determining drilling methods, lateral drilling sequence, casing and completion strategy, and frac stages.
Plan Well Trajectories in Context of the Geology
Well planning software that incorporates a detailed 3D model of the subsurface environment is an essential component of today’s multilateral well drilling technology. The ability to visualize the geology, including existing or planned offset wells, significantly enhances a well planner’s ability to interactively design multilateral wells that minimize risk and drilling costs. Leading well-design software that incorporates geologic models into the process makes it easier for well planners to:
- Identify and avoid geologic features that may compromise borehole stability.
- Plan multilateral well trajectories from KOPs to targets, selecting specific points in the geologic model, allowing software to calculate curves.
- Be alerted when a planned trajectory intersects a horizon or fault at an angle that could deflect the BHA.
- Determine minimum allowable separation distance (MASD) from a reference wellpath, using collision avoidance rules.
- Examine and compare several multilateral trajectory design options to determine the preferred design with respect to drilling costs and risks.
- Review geology, plans, drilling logs, production data, etc. of nearby multilaterals and apply insights to current multilateral design.
Powerful visualization capabilities that incorporate a wide range of subsurface data sources are critical in helping well planners carefully evaluate risks and develop multilateral well designs that can be drilled safely and cost-effectively.
Geology Also Determines Multilateral Well Drilling Technology
The wealth of subsurface information also guides drilling engineers in determining the appropriate methods and technologies to achieve those goals. Given the preliminary well plan, a drilling engineer can review the details, collaborate with the well planner to resolve any questions, then plan the specifics of the drilling process—from surface to target. With 3D visualization, drilling engineers can evaluate geologic and geophysical characteristics along the entire proposed multilateral well paths, and use this information to:
- Determine the sequence for drilling laterals.
- Specify bit and BHA configuration for the main wellbore and laterals.
- Decide the appropriate Technology Advancement of Multilaterals (TAML) junctions to provide required hydraulic integrity.
- Specify the window milling techniques and components (whipstock, milling assembly, or pre-milled window casings) for each lateral branch.
- Plan frac stages in adjacent multilaterals using a “wine rack” view.
As the drilling engineer specifies the multilateral drilling technology, annotations can be added anywhere along a planned wellbore or lateral to call attention to conditions, provide explanatory notes regarding a specific technique, or link to additional information.
The Added Value of WITSML Technology
Drilling engineers can further improve their understanding while drilling wellbores and laterals by incorporating near-real-time drilling data obtained from WITSML servers. Obtaining positional data (MD, AZI, INC) generated by BHA components, as well as periodic survey data that indicates drill bit location allows drilling engineers to:
- Show lateral and current bottom hole location and automatically use ahead-of-bit calculations to avoid collisions and ensure the trajectory remains on-target relative to zones.
- Visualize as well as analyze lateral drilling progress in the context of nearby wells to ensure the lateral does not encroach on offset wells.
- Monitor drilling performance—rotational speed, vibration, torque, downhole temperature, and mudflow—to ensure BHA components are operating within their technical limits.
During the drilling process, engineers can also update the drilling plan, annotating the 3D wellbore and laterals at specific depths to describe or explain problems encountered and solutions devised. The added information can be useful in avoiding similar problems that might impede drilling productivity in future laterals.
Data Drives Multilateral Well Drilling Technology
The disciplines involved in multilateral well development benefit from an integrated approach that uses data and visualization to guide well planning and the selection of multilateral well drilling technology. Well planning cycles are reduced when geologists, well planners, and drilling engineers share detailed 3D models with drilling plans. Wellbores and laterals are designed to avoid geologic and drilling risks. Multilateral well drilling technology is closely matched to the strata and subsurface conditions for optimized drilling productivity. At the end of the process, a detailed 3D model of the reservoir, including accurate locations of the recently-drilled laterals, provides the reservoir team with a reliable foundation for future reservoir development or production improvements.