Comparison Of Scattered Energy Using Point Scatterers Versus Full 3D Finite Difference Modeling

We present results of 3D numerical modeling using a series of simple point scatterers to create synthetic seismic shot records collected over regular, discrete, vertical fracture systems. The background medium is taken to be constant velocity. The model contains a series of point scatterers delineating the top tip and bottom tip of each vertical fracture. We use these results to gain an understanding of some of the features seen in full 3D elastic modeling of vertical fractures. We compare our results to those of Willis et al (2003) and Willis et al (2004) for their 5 layer model with 50m spacing between discrete, vertical fractures. Our modeling shows that a series of back scattered events with both positive and negative moveouts are observed when the shot record is oriented normal to the direction of fracturing. When the shot record is both located in the middle of the fractured zone and is oriented normal to the direction of fracturing, a complicated series of beating is observed in the back scattered energy. When the shot record is oriented parallel to the fracturing, ringing wavetrains are observed which moveouts similar to reflections from many horizontal layers. The point scattering models are, in general, very consistent with the full 3D elastic modeling results.Eni S.p.A. (Firm)United States. Dept. of Energy (Grant number DE-FC26-02NT15346)Massachusetts Institute of Technology. Earth Resources Laborator

Fractured Reservoir Characterization using Azimuthal AVO

Ordinary least squares is used to investigate the ability to detect changes in physical properties using Amplitude Versus Offset (AVO) information collected from seismic data. In order to characterize vertically aligned fractures within a reservoir, this method is extended to Azimuthal AVO (AVOA) analysis. Azimuthal AVO has the potential not only to detect fractured zones, but to spatially describe the fracture strike orientation and changes in fracture or fluid properties. Depending on the data acquisition geometry, signal-to-noise ratio, and extent of fracturing, AVOA analysis can be marginally successful. A study of the robustness and limitations of AVOA analysis is therefore first classified with synthetic data. These methods are then applied to seismic data collected during an Ocean Bottom Cable (OBC) survey over a known fractured reservoir.Massachusetts Institute of Technology. Earth Resources LaboratoryUnited States. Dept. of Energy (Grant DE-FC26-02NT15346)Eni S.p.A. (Firm

Interferometric correlogram-space analysis

Seismic interferometry is a method of obtaining a virtual shot gather from a collection of actual shot gathers. The set of traces corresponding to multiple actual shots recorded at two receivers is used to synthesize a virtual shot located at one of the receivers and a virtual receiver at the other. An estimate of a Green’s function between these two receivers is obtained by first cross-correlating pairs of traces from each of the common shots and then stacking the resulting cross-correlograms. In this paper, we study the structure of cross-correlograms obtained from a VSP acquisition geometry using a surface source reflected by flat or dipping layers and/or diffracted by point inclusions. The model is purely acoustic. The shape of events in the cross-correlogram space can be used to infer the location and geometry of a subsurface structure. A pilot wavelet created by a curvilinear stacking process is used as a detector of predicted events in the cross-correlogram. Results of a semblance-based velocity scan of the cross-correlograms using curvilinear stacks can be used to improve the quality of the virtual gather.Massachusetts Institute of Technology. Earth Resources Laborator

Theory and Laboratory Experiments of Elastic Wave Scattering by Dry Planar Fractures

Remote sensing of fractures with elastic waves is important in fields ranging from seismology to nondestructive testing. In many geophysical applications, fractures control the flow of fluids such as water, hydrocarbons or magma. While previous analytic descriptions of scattering mostly deal with very large or very small fractures (compared to the dominant wavelength), we present an analytic solution for the scattering of elastic waves from a fracture of arbitrary size. Based on the linear slip model for a dry fracture, we derive the scattering amplitude in the frequency domain under the Born approximation for all combinations of incident and scattered wave modes. Our analytic results match laser-based ultrasonic laboratory measurements of a single fracture in clear plastic, allowing us to quantify the compliance of a fracture

Conditional Lot Splitting to Avoid Setups While Reducing Flow Time

Previous research has clearly and consistently shown that flow time advantages accrue from splitting production lots into smaller transfer batches or sub-lots. Less extensively discussed, and certainly undesired, is the fact that lot splitting may dramatically increase the number of setups required, making it impractical in some settings. This paper describes and demonstrates a primary cause of these “extra” setups. It then proposes and evaluates decision rules which selectively invoke lot splitting in an attempt to avoid extra setups. For the closed job shop environment tested, our results indicate that conditional logic can achieve a substantial portion of lot splitting’s flow time improvement while avoiding the vast majority of the additional setups which would be caused by previously tested lot splitting schemes

Fracture Characterization from Scattered Energy: A Case Study

We use 3D surface seismic data to determine the presence and the preferred orientation of fracture corridors in a field. The Scattering Index method is proving to be a robust tool for detecting and mapping fracture corridors. Fracture corridors largely control permeability and fluid flow in some fractured reservoirs. To apply the Scattering Index method, we compute the scattering transfer functions from the reservoir interval using prestack migrated data collected in four azimuth sectors. By measuring the azimuthal differences in the amount of scattering, we obtain maps of density of fracture corridors and their orientation across the survey area. We use geostatistical filtering to improve the spatial correlation of scattering index maps. The distribution and orientation of the final fracture corridors are interpreted considering the structure, fault network, and stress information. In the field, we observe several regions of high fracturing near the anticline’s crest and on its steepest slopes, on the southwest flank. Around well locations, fractures are oriented to the NW and NNW, which agrees with estimates of maximum stress direction from well data.Massachusetts Institute of Technology. Earth Resources Laborator

Signaling from mTOR to eIF2α mediates cell migration in response to the chemotherapeutic doxorubicin.

After exposure to cytotoxic chemotherapeutics, tumor cells alter their translatome to promote cell survival programs through the regulation of eukaryotic initiation factor 4F (eIF4F) and ternary complex. Compounds that block mTOR signaling and eIF4F complex formation, such as rapamycin and its analogs, have been used in combination therapies to enhance cell killing, although their success has been limited. This is likely because the cross-talk between signaling pathways that coordinate eIF4F regulation with ternary complex formation after treatment with genotoxic therapeutics has not been fully explored. Here, we described a regulatory pathway downstream of p53 in which inhibition of mTOR after DNA damage promoted cross-talk signaling and led to eIF2α phosphorylation. We showed that eIF2α phosphorylation did not inhibit protein synthesis but was instead required for cell migration and that pharmacologically blocking this pathway with either ISRIB or trazodone limited cell migration. These results support the notion that therapeutic targeting of eIF2α signaling could restrict tumor cell metastasis and invasion and could be beneficial to subsets of patients with cancer.R.F.H. was supported by MRC studentship and Wellcome Trust (grant number 110071/Z/15/Z). A.E.W., T.A.A.P., and M.S. were supported by MRC Programme funding (MC_UP_A600_1023

Analysis of Scattered Signal to Estimate Reservoir Fracture Parameters

We detect fracture corridors and determine their orientation and average spacing based on an analysis of seismic coda in the frequency-wave number (f-k ) domain. Fracture corridors have dimensions similar to seismic wavelengths which causes scattering. The distribution of energy in shot records in the f-k domain depends upon the orientation of the records relative to the fracture strike. In the direction normal to fractures, scattered waves propagate with slower apparent velocities than waves propagating along the fracture channels. The associated f-k spectral differences allow the identification of the preferred fracture orientation and spacing. We apply our technique to a fractured reservoir in the Lynx field, in the Canadian foothills. The estimated preferential fracture orientation is about N40 E, which agrees with regional stress measurements. The average fracture spacing is 75 m on the West side of the survey, while fractures are more sparse on the East side. We also apply the Scattering Index methodology (Willis et al., 2006) to the same data, post-stack and pre-stack. This technique has higher resolution to map fracture distribution, intensity and orientation, and therefore complements the spectral method in providing an integrated description of reservoir fractures.United States. Dept. of Energy (award number DE-FC26-06NT42956)Massachusetts Institute of Technology. Earth Resources Laborator