Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Observations of anisotropy in fractured carbonate reservoirs can yield important information such as the orientation of aligned crack systems and crack density. A new generation of borehole acoustic tools provides the data necessary to observe anisotropy around the borehole. The flexural waves, excited by two dipole sources operating perpendicularly to each other in these tools, are recorded in two perpendicular directions, resulting in fourcomponent flexural wave recordings, Superposition of sources and rotation of receivers are the basic elements for the inversion of the waveforms to determine fast or slow mode orientations. Since the two sources are not necessarily of the same strength, a reciprocitybased source equalization is carried out as part of the inversion. We have inverted fourcomponent borehole flexural waves, recorded in a vertical well, penetrating three lithologic units of a fractured carbonate reservoir in northern Oman. For the lower unit, a northeastsouthwest azimuth of flexural wave anisotropy is well resolved, which is parallel to the strike of open fractures observed in the borehole, preferential flow directions, and to the regional presentday insitu maximum horizontal stress. Furthermore, the northeastsouthwest direction corresponds with polarization directions of the fast shear wave observed in a multicomponent surface seismic survey over the reservoir. The middle unit is most likely isotropic, except for a depth interval of low gamma readings, where a northeastsouthwest orientation is found for the fast mode. For the upper unit, a northsouth fast mode orientation is found, which does not correspond to the expected northeastsouthwest direction. Borehole geometry data indicate that the shape of the hole is circular for the middle unit but elongated for the upper and lower unit. Caliper orientations track the flexural wave anisotropy azimuths in these two units. Because of the elongation of the borehole, the observed flexural mode orientations, as well as the magnitude of flexural wave anisotropy, cannot be related to formation anisotropy directly, which obscures the determination of fracture orientation and fracture density from fourcomponent borehole flexural waves.
- North America > United States (0.94)
- Asia > Middle East > Oman (0.36)
- Geology > Rock Type (0.89)
- Geology > Petroleum Play Type > Unconventional Play > Fractured Carbonate Reservoir Play (0.80)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
- North America > United States > South Dakota > Williston Basin (0.99)
- North America > United States > North Dakota > Williston Basin (0.99)
- North America > United States > Montana > Williston Basin (0.99)
- Asia > Middle East > Oman > Ad Dhahirah Governorate > Fahud Salt Basin > Natih Field (0.99)
Abstract Fault-controlled karst carbonate reservoirs are one of the most important reservoir types in the Tahe oilfield of the Tarim Basin. These reservoirs have a large oil reserve and belong to a strongly reconstructed reservoir type with a highly heterogeneous distribution of pores and fractures. This study characterizes a fault-controlled karst reservoir by using integrated methods, including outcrops, well logging, structure interpretation, seismic inversion, and statistical geomodeling. We have established a fault-/fracture-controlling karstic geologic model and classified the internal architectural elements so that we adopted an origin-controlled hierarchical geomodeling strategy based on the fault-controlling characteristics. The results determined that large strike-slip faults provide an important tectonic framework and that its derived fractures act as important channels and spaces for dissolution. Flower structure fault zones and the associated fractures are the main range of karst development, within which a high stress is concentrated during the strike-slip shear process with a high-density fracture development. This is the highly developed karst reservoir, which mainly is concentrated along large faults. The coexistence of fractures and karst dissolution has resulted in a complicated reservoir architecture (karst architecture), which can be classified into four types: (1)ย large caverns, (2)ย small caverns and vugs, (3)ย fractured zones, and (4)ย matrix (tight limestone). Controlled by the degree of dissolution, the karst architecture is quite different from the sedimentary facies. Large caverns are formed under the strongest degree of dissolution and are the most favorable reservoir type. Small caves and vugs are created under relatively strong dissolution; they are distributed outside large caves and also can act as favorable reservoirs. The fractured zones are not necessarily affected by strong dissolution but have high conductivity and act as important channels for fluid movement. The carbonate matrix is less reconstructed. The architecture development model of the fault-controlled karst carbonate reservoir presented a tree system, within which the karst reservoir caves are connected by the fractures and faults similar to fruits and trunks. The new geomodeling method revealed the constraining characteristics of faults, seismic attributes, and hierarchical architectural elements. Furthermore, we also have built a 3D model of the Tuoputai unit in the Tahe oilfield to show the robustness of this workflow. This research enables us to better understand the structure of fault-controlled karst reservoirs, and it could provide a specified characterization approach that is considered to be theoretically and practically useful.
- Asia > China > Xinjiang Uyghur Autonomous Region (1.00)
- North America > United States > Texas (0.93)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Surface Seismic Acquisition (0.69)
- Geophysics > Seismic Surveying > Seismic Interpretation (0.66)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (27 more...)
Reducing Water Saturation Uncertainties in a Low Resistivity Pay Carbonate Reservoir
Bankole, I. O. (ADNOC Onshore, Abu Dhabi, UAE) | Nachiappan, R. (ADNOC Onshore, Abu Dhabi, UAE) | Pramudyo, Y. B. (ADNOC Onshore, Abu Dhabi, UAE) | Reddy, R. (ADNOC Onshore, Abu Dhabi, UAE) | Al Marzouqi, K. I. (ADNOC Onshore, Abu Dhabi, UAE) | Alsalami, M. (ADNOC Onshore, Abu Dhabi, UAE) | Alzeyoudi, M. (ADNOC Onshore, Abu Dhabi, UAE) | Ojha, A. (ADNOC Onshore, Abu Dhabi, UAE) | Fathalla, M.F (ADNOC Onshore, Abu Dhabi, UAE) | Baslaib, M. A. (ADNOC Onshore, Abu Dhabi, UAE) | Amer, M. (ADNOC Onshore, Abu Dhabi, UAE)
Abstract Water saturation is a key input in the determination of hydrocarbon resource estimations among many other uses. Evaluating water saturation is a huge challenge in heterogenous carbonate because of its diverse pore types. In order to find suitable evaluation techniques, a proper identification of the source and the characterization of these reservoirs is essentially required. There are several known causes of the low resistivity pay phenomenon namely: micro-porosity, fractures, paramagnetic minerals, and deep conductive borehole mud invasion. In Carbonates main cause is the presence of micritic pores or microporosity which strongly suppress or mask resistivity log response making water saturation evaluated from this type of reservoir rock inaccurate or over-estimated using the Archie equation. To compute a more accurate and realistic water saturation from such reservoir requires, an alternative resistivity independent approach is required to reduce the uncertainty in water saturation estimations. This paper demonstrated a simple alternative and pragmatic approach in evaluation of water saturation in complex carbonate reservoir with varying presence of micro porosity formed from micritization. The approach an integrated workflow based on geological(lithofacies/diagenesis) and petrophysical rock typing with other petrophysical methods to build a realistic saturation model in this challenging environment. The integration of various subsurface and dynamic data has contributed significantly to identification of the source of LRP, the distribution and the impact on the water saturation in oil and gas zones of the reservoir. Thus, reducing uncertainty, improving the reservoir characterization and HCIIP significantly most especially in the oil zone where LRP effect is more pronounced.
- North America > United States > Texas (0.47)
- Asia > Middle East > UAE > Abu Dhabi Emirate > Abu Dhabi (0.16)
- Geology > Sedimentary Geology (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.68)
- North America > United States > Texas > East Texas Salt Basin (0.99)
- North America > United States > Louisiana > East Texas Salt Basin (0.99)
- Asia > Middle East > UAE > Rub' al Khali Basin (0.99)
- (4 more...)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Sedimentology (0.95)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (0.86)
ABSTRACT Joint modeling and inversion of frequency-dependent dielectric constant and electrical resistivity well-log measurements has been addressed in literature in recent years. However, this problem is not studied for dual-porosity carbonate formations. Besides, the salinity and matrix dielectric constant are presumed to be known in previous studies. We have combined a model for brine dielectric constant and two laboratory-supported models for the electrical resistivity and dielectric constant of dual-porosity carbonates. Using this methodology, we replicate electrical resistivity and dielectric well-log measurements. Using a stochastic global optimization algorithm, we formulate a joint inversion workflow to estimate petrophysical properties of interest. For a constructed dual-porosity carbonate reservoir, we determine that the inversion workflow matches the forward-modeled data for the oil column, water column, and transition zone. We also found that our inversion workflow is capable to retrieve local model parameters (water-filled intergranular porosity and water-filled vuggy porosity) and global model parameters (matrix dielectric constant, lithology exponents for intergranular and vuggy pores, and salinity) with reasonable accuracy.
Abstract Using a variety of recent public-domain data sets comprising porosity, velocity (P- and S-waves), and, in most cases, mineralogy and petrographic data, I created an extensive global data set and evaluated the importance of mineralogy and pore type on the elastic properties behavior of carbonate core plugs. Results from this investigation clearly illuminated the potential for overinterpreting elastic properties behavior as a function of pore type(s) when mineralogy was not explicitly included in the analysis. Rock-physics analysis using a combination of heuristic and theoretical models illustrated that mineralogy exerted a significant additional variation on velocity at a given porosity. Failure to account for mineralogy exacerbated inferences about the effect of pore type(s) made using a comparison of P-wave velocity to an inappropriate empirical model (Wyllie) that did not account for pore shape(s). In this analysis, extreme variability in carbonate velocity was observed in only portions of two data sets, when mineralogy was explicitly considered and robust models that accounted for inclusion (pore) shape were used. Results from this analysis resulted in a recommended workflow, including a rock-physics template and dry-rock modulus diagnostics, for the evaluation of lab-based carbonate rock-physics data. The workflow was amenable to further integration with well-based data and other core-based petrophysical measurements (e.g., electrical properties).
- Asia (1.00)
- Europe (0.68)
- North America > United States > Texas (0.28)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (1.00)
- Geology > Geological Subdiscipline > Mineralogy (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation (0.67)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.47)
- Geophysics > Seismic Surveying > Seismic Processing (0.46)
- Asia > Philippines > Palawan > South China Sea > West Philippine Sea > Northwest Palawan Basin > Block SC 38 > Malampaya Field (0.99)
- Asia > Philippines > Palawan > South China Sea > Quezon > Northwest Palawan Basin > Block SC 38 > Malampaya Field (0.99)
- Asia > Philippines > Palawan > Palawan > West Philippine Sea > Northwest Palawan Basin > Block SC 38 > Malampaya Field (0.99)
- (6 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- (2 more...)