Identification and Prediction of the High Heterogeneous Channel Sand in Southern Turgay Basin
With the development of high quality 3D seismic exploration in Southern Turgay Basin, the exploration targets are being shifted from the structural traps to stratigraphic traps. As for one of the most important reservoir, the identification and prediction of the high heterogeneous channel-sands is the key to enhance drilling success rate and reduce the investment risk. The multi-geophysical methods and integrated studies of geology and geophysics have been applied to determine the distributed area of the channel-sands in Southern Turgay Basin of Kazakhstan. The channel-sands are widely distributed from Upper Jurassic to Cretaceous. The channel-sands in the mature explored Cretaceous strata are meandering or braided river bars. On well-logging, the SP curve of the channel sand presents the block - shape and positive cycle with bell – shape with high porosity and permeability, and lower self-potential, gamma ray and density; Whereas in seismic profiles, channel sands presented the „bright spot‟ with the low frequency, high amplitude and short reflection. No obvious rules of „bright spot‟ can be found in the seismic profiles. The multi-geophysical methods, such as strata slice, 3D visualization and spectral decomposition, etc., have been applied to identify more than 50 pieces of channel-sands with the cutting and overlying each other vertically and horizontally. As for the relatively lower explored Upper Jurassic strata, the channel-sands developed in submerged distributary channel, branching mouth bars of deltaic system or fan deltaic system. On well-logging, channel sand presents the middle porosity and permeability, and lower selfpotential, gamma ray and density; Low-frequency and varied amplitude presents in seismic profiles. The area distribution of the deltaic or fan deltaic can be determined by sequence stratigraphy and the distribution of the channel-sands in different cycles vertically can be identified by chronostratigraphic interpretation in wheeler domain. Several cases suggested that the integration of strata slice, chronostratigraphic interpretation in wheeler domain, 3D visualization and spectral decomposition is an effective method to identify the high heterogeneous channel-sand, which has been confirmed by drilling results.
Stratal Slice Method and Delineation of Thin Sand Geometry in Cambay Basin, India
Zero-phase wavelets are deemed superior in seismic interpretation as its many advantages, including wavelet symmetry and best resolution, described by Wood (1982) and Brown (1991). However, zero-phase wavelets, designed for optimal mapping of single interfaces, become archaic to detect Kalol reservoir geometry, as most reservoir facies in Kalol Formation are inter-bedded and small in vertical dimension and many are below seismic resolution.
On the use of the Hardening Soil Small Strain model in geotechnical practice
This article highlights the importance of using advanced constitutive soil models in numerical modelling as daily geotechnical practice. In this context, the Hardening Soil (HS) model is presented as the most advanced soil model implemented in the ZSoil finite element code. The article recalls the basic features of the HS model and it explains their role in numerical simulations. The role of pre-failure non-linear behaviour of soils is also discussed. An application of the HS model is illustrated on typical geotechnical problems such as retaining wall excavation, tunnel excavation and undrained loading followed by consolidation.