Inversion of Shear Wave Anisotropic Parameters in Strongly Anisotropic Formations

Deepwater reservoirs use highly deviated wells to reduce cost and enhance hydrocarbon recovery. Due to the strong anisotropic nature of many of the marine sediments, anisotropic seismic imaging and interpretation can improve reservoir characterization. Sonic logs acquired in these wells are strongly dependent on well deviations. Cross-dipole sonic logging provides apparent shear wave anisotropy in deviated wells, which can be far from the truth. Although anisotropic parameters have been successfully obtained using data from wells of several deviations or using single well data based on weak anisotropy approximation, estimation of strong shear wave anisotropy from single well data remains a challenge. Using sensitivity analysis, we find Stoneley wave velocity has good sensitivity to qSV and SH wave velocities in deviated wells. We create a linear inversion scheme to estimate shear wave anisotropy using SH, SV, and Stoneley wave velocities logged in one well. We first apply the method to laboratory measurements from boreholes of various deviations relative to the symmetry axis of an anisotropic material. We then apply the method to a field data set acquired in a deviated well. We also compute the vertical and horizontal shear wave velocity logs in this well using the inverted elastic shear wave constants.Massachusetts Institute of Technology. Earth Resources Laborator

A software tool to display message sequence charts

Message Sequence Charts (MSC) is a trace language. It is widely used to show sequences of messages interchanged between system components and their environment. It is gaining popularity in software engineering methods for concurrent and real-time systems. MSC has been standardized by the ITU-T (International Telecommunication Union, Telecommunication Standardization Sector of ITU) in Recommendation Z. 120 since 1992. A new revised standard Z.120 (MSC96) was approved by ITU-T in 1996. MSC includes two syntactical forms, MSC/PR as a pure textual and MSC/GR as a graphical representation. An MSC in MSC/GR representation can be transformed automatically into a corresponding MSC/PR representation. However, the reverse way is difficult since MSC/PR does not include graphical information such as height, width of symbols and texts. This report presents a software tool to convert a textual description into an internal representation, then to display the graphical representation. The object structure built in this software can be used in the further studying or analyzing of MSC96

Acoustic logging in fractured and porous formations

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1990.Includes bibliographical references (leaves 202-210).by Xiaoming Tang.Sc.D

Robust arbitrary view gait recognition based on parametric 3D human body reconstruction and virtual posture synthesis

This paper proposes an arbitrary view gait recognition method where the gait recognition is performed in 3-dimensional (3D) to be robust to variation in speed, inclined plane and clothing, and in the presence of a carried item. 3D parametric gait models in a gait period are reconstructed by an optimized 3D human pose, shape and simulated clothes estimation method using multiview gait silhouettes. The gait estimation involves morphing a new subject with constant semantic constraints using silhouette cost function as observations. Using a clothes-independent 3D parametric gait model reconstruction method, gait models of different subjects with various postures in a cycle are obtained and used as galleries to construct 3D gait dictionary. Using a carrying-items posture synthesized model, virtual gait models with different carrying-items postures are synthesized to further construct an over-complete 3D gait dictionary. A self-occlusion optimized simultaneous sparse representation model is also introduced to achieve high robustness in limited gait frames. Experimental analyses on CASIA B dataset and CMU MoBo dataset show a significant performance gain in terms of accuracy and robustness

Dynamic Fluid Flow In Heterogeneous Porous Media And Through A Single Fracture With Rough Surfaces

This study investigates the frequency-dependence of fluid flow in heterogeneous porous media using the theory of dynamic permeability and a finite-difference method. Given a permeability distribution, the dynamic permeability is applied locally to calculate the frequency-dependence of fluid flow at each local point. An iterative Alternating Direction Implicit finite-difference technique is applied to calculate the flow field in the frequency domain. We compare the flow through a 2-D heterogeneous porous medium and that through an equivalent homogeneous medium and find that the two media do not behave equivalently as a function of frequency. At very low-frequencies, the heterogeneous medium is less conductive than the homogeneous medium, However, in the transition region from quasi-static to dynamic regimes, the former medium becomes more conductive than the latter medium, with the ratio of the former flow over the latter flow reaching a maximum in this region. The larger the scale, or the higher the degree of the heterogeneity, the higher this maximum is. This finding is important for studying the interaction of a borehole stoneley wave with a heterogeneous porous formation. The finite-difference technique is also applied to simulate frequency-dependent flow through a single fracture with rough surfaces. It is shown that the flow exhibits strong frequency-dependence even for small fractures with contacting surfaces. The amount of flow through the fracture is reduced by the surface roughness .Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumUnited States. Dept. of Energy (Grant DE-FG02-86ERI3636

Borehole Stoneley Wave Propagation Across Permeable Structures: Comparison Between Theory And Experiment

The attenuation of borehole Stoneley waves across a permeable structure (e.g., fractures or fracture zone) is correlated with the permeability of the structure. Using a simplified Biot theory, the structure can be modelled as a permeable porous layer intersecting the borehole. In order to study the effect of such a structure on Stoneley waves and to evaluate the theoretical model, we performed laboratory experiments using ultrasonic borehole models. The porous layer model is made of fine-grained sands with high permeability and porosity. The experiments are carried out with three saturant fluids: water, alcohol, and glycerol. The iso-offset Stoneley waveforms are recorded by moving the source and receiver across the porous layer. In this way, robust estimates of Stoneley wave transmission coefficients are obtained. The experimental transmission coefficients are compared with the theoretical coefficients calculated using the borehole and permeable zone parameters. There is good agreement between theoretical results and experimental results. For low viscosity fluid water and ethyl alcohol, the agreement is very good. For high viscosity fluid, glycerol, the agreement is fair with the experimental Stoneley attenuation higher than the theoretical value.Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumUnited States. Dept. of Energy (Grant DE-FG02-86ER13636

Laboratory study of acoustic velocity in different types of rocks at seismic frequency band

In order to understand the characteristics of acoustic wave propagation in rocks within seismic frequency band (<100 Hz), the velocities of longitudinal and transverse waves of four different types of rocks were tested using low-frequency stress-strain method by means of the physical testing system of rock at low frequency and the experimental data of acoustic velocities of four different types of rocks at this frequency band were obtained. The experimental results showed that the acoustic velocities of four different types of rocks increased with the increase of temperature and pressure within the temperature and pressure ranges set by the experiment. The acoustic velocity of fine sandstone at 50% water saturation was smaller than that of dry sample. The acoustic velocities of four different types of rocks were different and the velocities of longitudinal waves of gritstone, fine sandstone, argillaceous siltstone and mudstone increased in turn under similar conditions and were smaller than those at ultrasonic frequency. Few of existing studies focus on the acoustic velocity at seismic frequency band, thus, further understanding of the acoustic characteristics at this seismic frequency band still requires more experimental data