Well spacing is one of the most critical factors affecting onshore well production. Reservoir teams striving to optimize well spacing can utilize the wealth of data that describe subsurface environments to achieve that goal. In particular, geologists, well planners, and drilling and completion engineers can benefit from 3D visualizations of geologic and petrophysical data, existing well trajectories, microseismic and tracer data, and production data to continually improve well spacing optimization strategies. Here we discuss how.
Begin With Geology and Petrophysical Properties
Seismic data and petrophysical property models are transformed into discrete fracture networks (DFN) to depict rock fractures—faults, joints, veins, bedding planes—that portray the complexity of subsurface environments. Drilling engineers can exploit the presence of natural fractures and heterogeneous stress fields identified in the DFN to guide the initial decisions regarding well trajectory planning, oil well spacing, and completion designs.
With an integrated, 3D visualization of the relevant subsurface data that influence well locations, trajectories, and completions, geologists, geophysicists, well planners, and drilling and completion engineers are far better informed regarding subsurface complexities. When additional information such as existing wells, the extent of existing frac networks, and production data can be incorporated into the analysis, petroleum professionals can collaboratively evaluate conditions, challenge assumptions, and reach well-informed conclusions regarding well spacing optimization and completion strategies.
Learn From the Results of Producing Wells
Completion engineers can benefit from the wealth of data available from existing wells. Historical data regarding drilling and completion methods and production data provide insight into the efficacy of previous development decisions. Reviewing historical data can reveal:
- well interference that caused a pressure drop among wells and negatively impacted production when a new well was brought online (Additional data may also be available regarding successful mitigation strategies.)
- well spacing with offset completion intervals that maximized production rates, yet avoided draining adjacent wells
- wells with similar geology where fracture length, size, and density optimized recovery (Fracture fluids and proppants used to achieve these results are also valuable in guiding future completions strategies.)
Well spacing optimization can also be guided by production data. As new wells are completed in proximity to existing wells, production data can provide the first indication of wells spaced too closely or confirm that a new well has been successfully drilled and completed. An unexpected drop in a well’s production is a likely indicator that a newly-completed well is interfering.
Monitor Well Completions in Near-Real-Time
Microseismic surveys can be used to refine the oil well completion process and provide insight to guide future well spacing. Microseismic data acquired during the course of a well completion process and visualized in near-real-time can:
- Depict microseismic events to show the development and extent of fractures size, density, and orientation) and their drainage areas.
- Determine if modifications should be made to subsequent frac stages to avoid incursions into nearby wells or extend the reach to achieve better drainage.
- Compare the effectiveness of different fracture treatments to correlate the results with wellbore geologic and petrophysical properties.
With near-real-time microseismic monitoring, completion engineers can quickly determine the effectiveness of the chosen stimulation method, gain a better understanding of stress directions, and modify subsequent stages to optimize coverage and drainage.
Use Tracers to Confirm Problems With Well Spacing
Even with the wealth of data, the ability to visualize it, and collaborative decision making by reservoir teams, the uncertainty inherent in reservoir development can lead to well spacing and completions that jeopardize production. In those situations, where connections between wells are suspected, tracer data can be used to:
- Detect connections between wells to identify thief zones that undermine well performance or detect how much flows back to the source well which is an indication of the frac job quality.
- Show fluid pathways between wells to allow completion engineers to isolate those problems and implement mitigation strategies that restore pressure and production.
- Provide a more detailed understanding of a well’s fracture pattern through the injection of natural gas with tracers into a central well and measuring tracer diffusion over time.
The use of tracer data can help provide a greater degree of confidence in determining the extent of a fracture network or suspected connectivity between wells. Based on the outcomes of the analysis, geologists, well planners, and completion engineers can apply that knowledge to improve well spacing and completion methods.
CoViz 4D: Well Spacing Optimization Using Integrated Data and Visualization
Well spacing optimization is a delicate balance. Place wells too close together and you’ll negatively impact production. Place wells too far apart and you’ll leave oil in the ground. Determining the optimum well spacing is easier when reservoir teams have software tools like CoViz 4D that integrate and visualize relevant subsurface data acquired throughout the life of an oil field. When reservoir teams can collaboratively evaluate how previous development strategies regarding well spacing and completions have impacted production, they can apply that insight to refine well spacing optimization strategies to maximize recovery.
Well spacing optimization is a delicate balance.