Offshore well development brings added complexity and costs that vary depending on sea floor depth and distance from onshore resources. Offshore rig time is expensive, ranging anywhere from USD $250K-$300K per day in 2020. Anything that can be done to reduce rig time positively impacts costs. Consequently, every phase of an offshore development project demands a higher level of scrutiny in evaluating conditions and making plans to minimize risks and costs.
In this blog, we focus on the subsea well completion phase. We’ll explain how access to relevant subsea data sources that are integrated and visualized in a 3D environment for analysis by reservoir engineering teams facilitates cost and time savings in planning and executing subsea well completions.
Understanding Subsea Geological Attributes
Subsea seismic surveys, reservoir and geologic models can be combined with well logs from exploratory or producing wells and visualized in a 3D environment for analysis by geologists and drilling engineers to evaluate well trajectory options. With a shared view of geological and geophysical data, teams can more efficiently identify conditions that could impact drilling and subsea well completions and determine the best strategies to reduce drilling time without compromising safety.
A collaborative, shared 3D visualization environment makes it easier for geologists, well planners, and drilling engineers to:
- Select the pay zone that presents the best opportunity for hydrocarbon recovery.
- Identify faults that could threaten wellbore stability.
- Evaluate different well trajectory proposals, comparing estimated drilling time and costs.
- Determine the maximum feasible length for an extended reach lateral and the feasibility of the wellbore angle.
- Recommend drilling equipment and methods to successfully navigate the geology as well as tolerate extreme subsea conditions.
- Decide casing requirements—surface, and intermediate—that will withstand subsea environments throughout the life of the well.
- Select cementing methods based on temperature, pressure, rheology, density, compressive strength attributes.
Offshore rig time is expensive, ranging anywhere from $250K-$300K per day. When drilling and completion engineers are able to obtain as accurate as possible analysis of reservoir conditions they are better prepared to collaborate and make decisions that reduce drilling time and expense.
Downhole Environment Guides Subsea Well Completion Strategy
Just as geologic and petrophysical analysis in a 3D visualization environment can guide drilling strategy, it has equal value in guiding subsea well completion strategy. Careful analysis of the immediate environment surrounding a proposed subsea wellbore in the pay zone enables completion engineers to more confidently reach decisions regarding:
- Type of downhole materials, typically high-alloys (tolerate heat, pressure, and possible reservoir souring) to ensure performance over the life of the well
- Location and spacing of perforated sections to direct hydrocarbons into the production casing
- Casing designs to isolate fluid migration along the length of the borehole—adjacent to productive formations with packers and tubing to direct flow to the surface
- Sand-control requirements (gravel-packed screens, upper and lower packers) for poorly-consolidated subsea formations likely to produce fines during production
- Inflow control devices and monitors if unwanted water or other fluid invasion is anticipated
CoViz 4D: Detailed Insight for Subsea Well Completions
Geologists, geophysicists, well planners, and drilling and completion engineers are using the data integration, 3D visualization, and analytic capabilities of CoViz 4D to reduce time and costs associated with well planning, drilling, and completions. CoViz 4D integrates a wide range of subsurface data sources, transforming the data into highly-detailed 3D models that give reservoir teams unparalleled abilities to:
- Explore relationships among subsurface data to gain a more accurate understanding of reservoir characteristics and more confidently determine development strategies.
- Design well trajectories and drilling strategies with the goal of reducing drilling costs, difficulty, and time.
- Determine subsea well completion strategies based on the analysis of downhole conditions.
With CoViz 4D, well planners and drilling and completion engineers can develop and collaborate detailed plans for well trajectories and completions. This allows for accuracy in specifying well tops, seeing the angle that a trajectory intersects a stratum, and depicting detailed fluid flow models within a reservoir. Along the length of a wellbore annotations can be included to specify types of casing and cementing, locations and types of perforations, locations of packers, and proposed staging sequence, and treatments applied.
As drilling progresses, near-real-time data from WITSML servers can update the reservoir models to show the actual wellbore location in comparison to the planned trajectory. Microseismic surveys can also be integrated into the model to show the progression and extent of fracturing as each interval is completed, allowing completion engineers to refine subsequent fracking treatments if needed.
CoViz 4D enables completion engineers to visualize and analyze how previous completion strategies have affected production in nearby wells or wells with similar geologic and geophysical attributes.
CoViz 4D enables completion engineers to visualize and analyze how previous completion strategies have affected production in nearby wells or wells with similar geologic and geophysical attributes. Using time-step data, CoViz 4D can display the completion process to see what treatments were employed, how it progressed, and most importantly, the well production data to help show the efficacy of the completion strategy.
Effective Subsea Well Completion
Effective subsea well completion requires an in-depth understanding of a reservoir’s geological and geophysical characteristics and the use of technologies suited to extreme pressure, temperature, and potentially corrosive conditions. Significantly higher costs and time factors across all phases of subsea well development place added pressure on reservoir engineering teams to find ways to be as efficient as possible in drilling and completions. Shared access to all relevant subsea data and the ability to visualize and analyze it in 3D and 4D give engineers the understanding they need to confidently develop the strategy and methods that help minimize time and costs associated with subsea well completions.
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