Accurate characterization of the geology of oil and gas fields is an essential aspect of successful field development. Identifying and avoiding or mitigating risks as early as possible reduces development costs. With the wealth of geologic and other subsurface data and efficient analytic software tools, geoscientists can be better informed than ever before regarding the geology of oil and gas fields and its influence on field development. In this blog, we focus primarily on identifying and mitigating geologic risks.
Proactively Identify and Mitigate Geologic Risks
Of particular concern in any geologic analysis is the identification of formations that present immediate or long-term development risks. A few examples help illustrate how geological information influences field development:
- Over time, active faults and salt domes can threaten wellbore stability, shear casings, and bring production to a halt. Is the problem local, or is it characteristic of the entire field? Should the well be abandoned or is sidetracking a feasible alternative? Once an active fault is identified, future wells can be planned to avoid the active fault.
- Shallow wells pose the threat of subsidence. At what point in field development might subsidence become a problem? How extensive would it be? What mitigation strategies would be most effective, based on knowledge of fields with similar formations?
- Fissures, fractures, and cavities can induce lost circulation during drilling. What well planning strategies would minimize the risk of lost circulation during drilling or cementing?
Preliminary analysis of the geology of oil and gas fields doesn’t always reveal all potential risks—particularly in fields characterized by active geology. Additional data gathered during fIeld development increases the geologic understanding. In one instance before commencing drilling, an initial wellbore stability study was done. However, after encountering severe instability problems in the first well, a more detailed geological analysis ensued. The results of the analysis indicated greater stability with wells oriented in a North-West to South-East plane. Subsequent horizontal wells planned with this orientation showed greater stability.
Although geoscientists may have significant volumes of geological and geophysical data, realizing the maximum benefit from the data is often hindered by the inability to combine and analyze the data in context. Software tools with strong data integration and visualization capabilities help overcome those problems.
Integrate and Visualize Data to Understand the Geology Of Oil and Gas Fields
Analysis of the geology of oil and gas fields is more conclusive when all relevant subsurface datasets can be integrated and rendered in a 3D space and evaluated by members of the reservoir team. EarthVision, from Dynamic Graphics, Inc., is an integrated software package that combines a wide range of geologic and geophysical data such as seismic surveys, well logs, cores, and fluid samples. It enables geoscientists to transform geologic data into 3D models, contour maps, isochore maps, and cross-sections. Visualization facilitates a more detailed understanding of major fault gaps, normal and reverse faults, fault-wedge contours, overthrusts, salt diapirs, stratigraphic discontinuities, and other complex tectonic structures.
EarthVision supports modeling of complex geologic formations with capabilities to:
- Integrate seismic interpretations with depth models via geo-model-driven velocity and time-to-depth conversion algorithms.
- Create intermediate horizons using true vertical thickness (TVT) or true stratigraphic thickness (TST).
- Employ geometric reconstructive techniques to represent strata depositional history in faulted reservoirs.
- Show any or all wellbore and outcrop data used in generating a faulted 3D geologic model.
Powerful 3D visualization capabilities then allow geoscientists to collaboratively evaluate geologic risks and guide development strategy by:
- Comparing and validating various fault and horizon interpretations.
- Displaying individual fault blocks to explore fault structure in greater detail.
- Determining which geologic model layers to display (or hide) so that fault offsets of particular areas can be analyzed.
- Creating cross-sections (perpendicular to the x, y, or z axes) through 3D models and seismic volumes.
- Annotating cross-sections with data from geophysical logs and property distributions within fault blocks.
As additional geologic data are acquired when new wells are drilled or additional seismic surveys are taken, the geological models and 3D visualizations are easily and quickly updated, allowing geoscientists to monitor the evolving geology of oil and gas fields.
Visualization facilitates a more detailed understanding of major fault gaps, normal and reverse faults, fault-wedge contours, overthrusts, salt diapirs, stratigraphic discontinuities, and other complex tectonic structures.
Visualize Changing Geology of Oil and Gas Fields Over Time
Geoscientists can obtain an even greater understanding of the changing geology of oil and gas fields throughout the evolution of a field using CoViz 4D which excels in integrating geological models, geophysical data (developed with EarthVision), and many other relevant subsurface datasets. Using reservoir simulation models and seismic data acquired at various intervals during a field’s development and integrating it with data from well completions, well logs, production, and microseismic, CoViz 4D can animate the data to depict the changing geologic response.
Temporal analysis of geological changes gives geoscientists, well planners, and drilling and production engineers a far more accurate understanding of field dynamics. Better understating of geology and its influence on field development and performance leads to proactive identification of geological risks in support of well-informed planning and operational decision making.