%{search_type} search results

7 catalog results

RSS feed for this result
Collection
The Stanford Shale Smear Project
Entrainment of shale along faults or shale smear represents a significant mechanism providing fault seal in hydrocarbon reservoirs. This ongoing project is designed to asses the combined structural and diagenetic effects on permeability reduction of shale smear with the objective of establishing predictive tools for fault seal behavior as a function of the depositional, structural, and diagenetic evolution of petroliferous basins. For a shale smear exposed in an underground mine, preliminary mercury injection analyses indicate a reduction in shale smear permeability by 1-2 orders of magnitude compared to reference samples of undeformed shale taken 2 m away from the fault. Permeability reduction in shale smear correlates with a distinct fabric reorganization which is attributed to the combination of mechanical clay-particle reorientation and possible diagenetic clay neoformation. An observed reduction in smectite content and a corresponding increase in kaolinite component of shale smear is indicative of interaction of organic-rich shale with infiltrated meteoric fluids and suggests that water-mineral reactions are an integral component of shale smear formation. Continued investigations are proposed to refine sampling at this underground site for a quantitative assessment of compositional and rock physical heterogeneity and to extend sampling to faults in different depositional and burial diagenetic environments.
Collection
The Stanford Shale Smear Project
Fault segmentation along strike is commonly observed in outcrop and subsurface but is less common along dip, particularly using seismic data. We document outcrop and core examples of fault segmentation in the dip direction and compare findings to seismic faults. In all cases, segmented faults formed an echelon array consistently stepping perpendicular to fault strike, towards either the hanging wall or the footwall. Faults step at contacts of competent and incompetent layers (e.g., sandstone and shale). Larger steps correspond with thicker incompetent layers, especially in the case of footwall steps. Continued slip on fault segments produces a coalesced single fault strand. During fault coalescence, the step deformation can produce two distinct fault rock types depending on step type. In the hanging wall steps, deformation is dominated by shale smearing which involves the rotation of the incompetent layers until they are smeared parallel to the fault. Further slip may case the incompetent layers to thin out and disconnect. In contrast, deformation along footwall steps forces the shale out of the step, and eventually becomes dominated by brecciation of hanging and footwall rocks. The hydraulic properties and sealing capacity of a fault may then depend on the fault step type and associated fault rock material (smearing or brecciation). moreover, higher ratios of competent to incompetent layers force footwall steps to become more laterally distributed, and hence, when coalesced, they will tend to form shallower fault dip angles than hanging wall steps. Examples from seismic data illustrate that along-dig segmentation may be mapped when seismic data is adequate.
Collection
The Stanford Shale Smear Project
This report covers the results from the fourth year of the Shale Smear Project. It includes the final results from the Gulf of Suez, Egypt and the Niger Delta. We have just initiated a new study in Black Diamond Mine Regional Park. A progress report from this study will be presented. Table of Contents: "Progress Report on shale smear study at Black Diamond Mine, California." Atilla Aydin. "3D Fault segmentation: implications for entrapment and compartmentalisation." Thierry Rives and Antonio Benedicto. "Normal fault segmentation along dip direction and its impact on fault sealing." Poster 1. Amgad Younes and Atilla Aydin. "A new, process-based methodology for the analysis of faults and their sealing potential in the Niger Delta." Poster 2. Bashir Koledoye, Atilla Aydin, and Eric May. "Segmented faults: dynamic behavior in well test simulations." Poster 3. Eric Caput, Thierry Rives, and Yann Lagelaye.
Collection
The Stanford Shale Smear Project
3D seismic and well log data from the producing Okan field in the Niger Delta and a working conceptual model derived from field observations and theoretical considerations were used to map the three dimensional geometry of a representative normal fault with shale smear. Seismic data show clear fault segmentation in the dip direction with extensional relays occupied by smeared shales. Log data help to identify lithologic horizons throughout the field and in some cases, where the wellbores crossed the fault, to quantitatively determine the amount of smeared shale within the fault zone. Conceptual models provide means to interpret crucial details of the fault geometry and the distribution of fault rock beyond the conventional resolution of a 3D seismic data set. Combining these three approaches, we have developed a procedure to determine the fault geometry and to asses the nature of the smeared shales and their evolving configurations as a function of fault throw and the thickness of corresponding shale units. The result is a new and improved technique to visualize fault architecture and to interpret fault rock, both of which lead to constructing structurally realistic juxtaposition diagrams and physically sound fault seal analyses in reservoirs.
Collection
The Stanford Shale Smear Project
We measured the thickness of fault rock material and fault offset along normal faults in interbedded shales and sandstones and delineated their architecture. Fault zones and the associated shale smear involving multi-shale units are much more complex than those involving single-shale units. the complexity arises from the fact that the faults in multi-shale and sandstone sequences are segmented across each shale unit in the sequence, resulting in a highly variable fault and fault-rock geometry as a function of fault offset and shale thickness. In spite of these complexities, it appears that the shale smear factors for multi-shale cases follow a similar trend to that for single-shale cases, if appropriate thickness for the mechanically coherent shale units is chosen.
Collection
The Stanford Shale Smear Project
We have used a smeared crack model to stimulate faults in brittle/viscous layers for the ultimate purpose of analyzing faults in shale/sandstone (or limestone) sequences. The preliminary results are encouraging. Future work is being planned to address the role of layer thickness and rheology as well as large strain on the process.
Collection
The Stanford Shale Smear Project
Guidebook of a field trip to the Eastern Gulf of Suez to examine normal faults with shale smear