On the theory of solitons of fluid pressure and solute density in geologic porous media, with applications to shale, clay and sandstone

In this paper we propose the application of a new model of transients of pore pressure p and solute density \r{ho} in geologic porous media. This model is rooted in the non-linear waves theory, the focus of which is advection and effect of large pressure jumps on strain (due to large p in a non-linear version of the Hooke law). It strictly relates p and \r{ho} evolving under the effect of a strong external stress. As a result, the presence of quick and sharp transients in low permeability rocks is unveiled, i.e. the non-linear Burgers solitons. We therefore propose that the actual transport process in porous rocks for large signals is not the linear diffusion, but could be governed by solitons. A test of an eventual presence of solitons in a rock is here proposed, and then applied to Pierre Shale, Bearpaw Shale, Boom Clay and Oznam-Mugu silt and clay. A quick analysis showing the presence of solitons for nuclear waste disposal and salty water intrusions is also analyzed. Finally, in a kind of "theoretical experiment" we show that solitons could also be present in Jordan and St. Peter sandstones, thus suggesting the occurrence of osmosis in these rocks

Elastic pre-stack seismic inversion through Discrete Cosine Transform reparameterization and Convolutional Neural Networks

We develop a pre-stack inversion algorithm that combines a Discrete Cosine Transform (DCT) reparameterization of data and model spaces with a Convolutional Neural Network (CNN). The CNN is trained to predict the mapping between the DCT-transformed seismic data and the DCT-transformed 2-D elastic model. A convolutional forward modeling based on the full Zoeppritz equations constitutes the link between the elastic properties and the seismic data. The direct sequential co-simulation algorithm with joint probability distribution is used to generate the training and validation datasets under the assumption of a stationary non-parametric prior and a Gaussian variogram model for the elastic properties. The DCT is an orthogonal transformation that is here used as an additional feature extraction technique that reduces the number of unknown parameters in the inversion and the dimensionality of the input and output of the network. The DCT reparameterization also acts as a regularization operator in the model space and allows for the preservation of the lateral and vertical continuity of the elastic properties in the recovered solution. We also implement a Monte Carlo simulation strategy that propagates onto the estimated elastic model the uncertainties related to both noise contamination and network approximation. We focus on synthetic inversions on a realistic subsurface model that mimics a real gas-saturated reservoir hosted in a turbiditic sequence. We compare the outcomes of the implemented algorithm with those provided by a popular linear inversion approach and we also assess the robustness of the CNN inversion to errors in the estimated source wavelet and to erroneous assumptions about the noise statistic. Our tests confirm the applicability of the proposed approach, opening the possibility to estimate the subsurface elastic parameters and the associated uncertainties in near real-time while satisfactorily preserving the assumed spatial variability and the statistical properties of the elastic parameters

The Cures Act: How can we alleviate patient confusion and provider workload?

This project aimed to develop a better understanding of patient and provider needs at all UVMMC family medicine and urgent care offices in regards to the new Cures Act. Data was gathered via a 8 question multiple choice survey and we had 24 provider responses. Most providers have found that they are receiving more phone calls from patients with questions in regards to their medical notes or results since the enactment of the Cures Act. Providers mentioned common patient questions are about imaging results, CBC, and electrolytes. Nearly half of providers noted they have changed the way in which they write notes since the Cures Act and all providers felt that a handout with tips to interpret lab results would be helpful.https://scholarworks.uvm.edu/fmclerk/1773/thumbnail.jp

A data-driven transdimensional approach to include lateral constraints on 2D target-oriented AVA inversion

Seismic inversion aims to infer subsurface properties from processed seismic data; since these are often ill-conditioned procedures, numerous strategies can be investigated. To date currently adopted procedures assume an a priori structural knowledge of the investigated area and impose such constraints to the recovered solution. To overcome this downside we apply a transdimensional reversible jump-Markov chain Monte Carlo (Rj-McMC) algorithm to solve the interval-oriented amplitude versus angle (AVA) inversion on 2D synthetic seismic data. This approach considers the model parametrization as an unknown, together with the elastic properties of the investigated area. The algorithm samples models discretized in Voronoi cells characterized by similar AVA responses. The elastic values associated with each Voronoi cell are obtained taking the average of the elastic properties of the CDPs falling within it. This data-driven approach does, therefore, need no external assumption over the investigated area and ensures an automatically inferred strategy to include lateral variability of data inside the inversion kernel. We compare results obtained to a standard Bayesian approach for different SNR, showing how the increase of random noise contaminating the data strongly affects the linear approach, while the Rj-McMC generates model predictions in accordance with the true model, producing more reliable results

Towards a Non-linear Theory for Induced Seismicity in Shales

Abstract We analyze the pore transmission of fluid pressure p and solute density ρ in porous rocks. To investigate shale deformation, fundamental for deep oil drilling and for gas extraction ("fracking"), a non-linear model of mechanic and chemo-poroelastic interactions among fluid, solute and the solid matrix is discussed. The solutions of the model are quick non-linear Burger's solitary waves, potentially destructive for deep operations. Following Civan [2], diffusive and shock waves are applied to fine particles filtration. Then the delaying effects of fine particles filtration is compared with fractional model time delay and the fractional order parameter can be realistically estimate

Towards a Theory of Solitary Shock Waves of Fluid Pressure and Solute Density in Geologic Porous Media

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On the propagation of nonlinear transients of temperature and pore pressure in a thin porous boundary layer between two rocks.

The dynamics of transients of fluid-rock temperature, pore pressure, pollutants in porous rocks are of vivid interest for fundamental problems in hydrological, volcanic, hydrocarbon systems, deep oil drilling. This can concern rapid landslides or the fault weakening during coseismic slips and also a new field of research about stability of classical buildings. Here we analyze the transient evolution of temperature and pressure in a thin boundary layer between two adjacent homogeneous media for various types of rocks. In previous models, this boundary was often assumed to be a sharp mathematical plane. Here we consider a non-sharp, physical boundary between two adjacent rocks, where also local steady pore pressure and/or temperature fields are present. To obtain a more reliable model we also investigate the role of nonlinear effects as convection and fluid-rock “frictions”, often disregarded in early models: these nonlinear effects in some cases can give remarkable quick and sharp transients. All of this implies a novel model, whose solutions describe large, sharp and quick fronts. We also rapidly describe transients moving through a particularly irregular boundary layer

The evolution of density currents and nepheloid bottom layers in the Ross Sea (Antarctica)

In this study we have analyzed the thermohaline, light transmission and particulate matter data, obtained in the western sector of the Ross Sea during the X Italian Expedition, for the purpose of investigating the evolution of the High Salinity Shelf Water in this area. In particular CTD data were used to estimate the baroclinic velocity field. Light transmission and total particulate matter data (from Niskin bottles mounted on a Carousel water sampler) were used to analyze the nepheloid layers and the evolution of the suspended sediments. This basin is characterized by a northward flow of very dense High Salinity Shelf Water (θ ∼ −1.95°C, S ∼ 34.90), much colder than the incoming Circumpolar Deep Water (θ ∼ 1.20°C, S ∼ 34.70). We obtained a scenario in which the High Salinity Shelf Water interacts with the Circumpolar Deep Water along the Antarctic Slope Front, and deviates from its geostrophic equilibrium. Interestingly, this cold dense water mixes with Circumpolar Deep Water at the shelf break and flows downward until it seems to disappear. Below this cold flow, a thin turbulent current has been observed, again moving northward with a high velocity ∼ 0.2–1.0 m s−1. This thin flow also contains high concentration of suspended matter produced by the interaction of the dense water and the bottom sediments. The various elementary mechanisms ruling the dynamics of such down-flows, namely the effects of topographic irregularities, bottom friction, Ekman benthic boundary layers or the effect of the variability of the Antarctic Circumpolar Current, which can push offshore the dense water, are discussed in this paper