3-D Geostatistical Seismic Inversion With Well Log Constraints

Information about reservoir properties usually comes from two sources: seismic data and well logs. The former provide an indirect, low resolution image of rock velocity and density. The latter provide direct, high resolution (but laterally sparse) sampling of these and other rock parameters. An important problem in reservoir characterization is how best to combine these data sets, allowing the well information to constrain the seismic inversion and, conversely, using the seismic data to spatially interpolate and extrapolate the well logs. We develop a seismic/well log inversion method that combines geostatistical techniques for well log interpolation (i.e., kriging) with a Monte Carlo search method for seismic inversion. We cast our inversion procedure in the form of a Bayesian maximum a posteriori (MAP) estimation in which the prior is iteratively modified so that the algorithm converges to the model that maximizes the likelihood function. We follow the approach used by Haas and Dubrule (1994) in their sequential inversion algorithm. Kriging is applied to the well data to obtain velocity estimates and their covariances for use as a priori constraints in the seismic inversion. Inversion of a complete 3-D seismic section is performed one trace at a time. The velocity profiles derived from previous seismic traces are incorporated as "pseudo well logs" in subsequent applications of kriging. Our version of this algorithm employs a more efficient Monte Carlo search method in the seismic inversion, and moves sequentially away from the wells so as to minimize the kriging variance at each step away from the inverted wells. Numerical experiments with synthetic data demonstrate the viability of our seismic/ well data inversion scheme. Inversion is then performed on a real 3-D data set provided by Texaco.Texas CompanyMassachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumMassachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation Consortiu

Simultaneous least squares deconvolution and kriging using conjugate gradients

Least squares deconvolution is a method used to sharpen tomographic images of the earth by undoing the bandlimiting effects imposed by a seismic wavelet. Kriging is a method used by geoscientists to extrapolate and interpolate sparse data sets. These two methodologies have traditionally been kept separate and viewed as unrelated fields of research. We demonstrate the connection between these methods by deriving them both as examples of linear inversion. By posing the methods in this way we can define a joint inverse problem in which observed values of reflectivity in wells are used to improve deconvolution, and, conversely, seismic data is used to help extrapolate well data. Solving this joint problem involves the solution of large sparse sets of linear equations. Due to the structure of the problem, the conjugate gradients method is ideal to perform the solution. Preliminary results show that convergence to a solution for a 3-D problem is fast and accurate, requiring only a few iterations. This methodology can be of great use to interpreters by sharpening the post stack image as well as helping to tie seismic data to wells

Geostatistical Seismic Inversion Using Well Log Constraints

Information about reservoir properties usually comes from two sources: seismic data and well logs. The former provide an indirect, low resolution image of rock velocity and density. The latter provide direct, high resolution (but laterally sparse) sampling of these and other rock parameters. An important problem in reservoir characterization is how best to combine these data sets, allowing the well information to constrain the seismic inversion and, conversely, using the seismic data to spatially interpolate and extrapolate the well logs. We have developed a seismic/well log inversion method that combines geostatistical methods for well log interpolation (i.e., kriging) with a Monte Carlo search technique for seismic inversion. Our method follows the approach used by Haas and Dubrule (1994) in their sequential inversion algorithm. Kriging is applied to the well data to obtain velocity estimates and their variances for use as a priori constraints in the seismic inversion. Further, inversion of a complete 2-D seismic section is performed one trace at a time. The velocity profiles derived from previous seismic traces are incorporated as "pseudo well logs" in subsequent applications of kriging. Our version of this algorithm employs a more efficient Monte Carlo search algorithm in the seismic inversion step, and moves progressively away from the wells so as to minimize the kriging variance at each step. Numerical experiments with synthetic data demonstrate the viability of our seismic/well data inversion scheme.Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumMassachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation Consortiu

Geostatistically Constrained Seismic Deconvolution

We present a method for combining seismic deconvolution and geostatistical interpolation. Both problems are posed as a single joint inverse problem in the maximum likelihood framework. Joint inversion allows for well data to improve the deconvolution results and, conversely, allows the seismic data to improve the interpolation of well data. Traditional interpolation and trace-by-trace deconvolution are special cases of the joint inverse problem. Inversion is performed on 2-D and 3-D field data sets.Massachusetts Institute of Technology. Earth Resources Laborator

The Treatment and Outcome of Patients With Soft Tissue Sarcomas and Synchronous Metastases

Introduction: There is a strong association between poor overall survival and a short disease-free interval for patients with soft tissue sarcomas (STS) and metastatic disease. Patients with STS and synchronous metastases should have a very dismal prognosis.The role of surgery in this subgroup of patients with STS has not been defined

Practice patterns and outcomes of equivocal bone scans for patients with castration-resistant prostate cancer: Results from SEARCH.

ObjectiveTo review follow-up imaging after equivocal bone scans in men with castration resistant prostate cancer (CRPC) and examine the characteristics of equivocal bone scans that are associated with positive follow-up imaging.MethodsWe identified 639 men from five Veterans Affairs Hospitals with a technetium-99m bone scan after CRPC diagnosis, of whom 99 (15%) had equivocal scans. Men with equivocal scans were segregated into "high-risk" and "low-risk" subcategories based upon wording in the bone scan report. All follow-up imaging (bone scans, computed tomography [CT], magnetic resonance imaging [MRI], and X-rays) in the 3 months after the equivocal scan were reviewed. Variables were compared between patients with a positive vs. negative follow-up imaging after an equivocal bone scan.ResultsOf 99 men with an equivocal bone scan, 43 (43%) received at least one follow-up imaging test, including 32/82 (39%) with low-risk scans and 11/17 (65%) with high-risk scans (p = 0.052). Of follow-up tests, 67% were negative, 14% were equivocal, and 19% were positive. Among those who underwent follow-up imaging, 3/32 (9%) low-risk men had metastases vs. 5/11 (45%) high-risk men (p = 0.015).ConclusionWhile 19% of all men who received follow-up imaging had positive follow-up imaging, only 9% of those with a low-risk equivocal bone scan had metastases versus 45% of those with high-risk. These preliminary findings, if confirmed in larger studies, suggest follow-up imaging tests for low-risk equivocal scans can be delayed while high-risk equivocal scans should receive follow-up imaging

Integrase-deficient lentiviral vectors mediate efficient gene transfer to human vascular smooth muscle cells with minimal genotoxic risk

We have previously shown that injury-induced neointima formation was rescued by adenoviral-Nogo-B gene delivery. Integrase-competent lentiviral vectors (ICLV) are efficient at gene delivery to vascular cells but present a risk of insertional mutagenesis. Conversely, integrase-deficient lentiviral vectors (IDLV) offer additional benefits through reduced mutagenesis risk, but this has not been evaluated in the context of vascular gene transfer. Here, we have investigated the performance and genetic safety of both counterparts in primary human vascular smooth muscle cells (VSMC) and compared gene transfer efficiency and assessed the genotoxic potential of ICLVs and IDLVs based on their integration frequency and insertional profile in the human genome. Expression of enhanced green fluorescent protein (eGFP) mediated by IDLVs (IDLV-eGFP) demonstrated efficient transgene expression in VSMCs. IDLV gene transfer of Nogo-B mediated efficient overexpression of Nogo-B in VSMCs, leading to phenotypic effects on VSMC migration and proliferation, similar to its ICLV version and unlike its eGFP control and uninfected VSMCs. Large-scale integration site analyses in VSMCs indicated that IDLV-mediated gene transfer gave rise to a very low frequency of genomic integration compared to ICLVs, revealing a close-to-random genomic distribution in VSMCs. This study demonstrates for the first time the potential of IDLVs for safe and efficient vascular gene transfer

Luttinger Parameter g for Metallic Carbon Nanotubes and Related Systems

The random phase approximation (RPA) theory is used to derive the Luttinger parameter g for metallic carbon nanotubes. The results are consistent with the Tomonaga-Luttinger models. All metallic carbon nanotubes, regardless if they are armchair tubes, zigzag tubes, or chiral tubes, should have the same Luttinger parameter g. However, a (10,10) carbon peapod should have a smaller g value than a (10,10) carbon nanotube. Changing the Fermi level by applying a gate voltage has only a second order effect on the g value. RPA theory is a valid approach to calculate plasmon energy in carbon nanotube systems, regardless if the ground state is a Luttinger liquid or Fermi liquid. (This paper was published in PRB 66, 193405 (2002). However, Eqs. (6), (9), and (19) were misprinted there.)Comment: 2 figure

Essays on Western History in Honor of Elwyn B. Robinson

This book was published on the occasion of the retirement of Dr. Elwyn B. Robinson from the Department of History at the University of North Dakota. It features articles by several different historians regarding various subjects in the history of the American West.https://commons.und.edu/und-books/1021/thumbnail.jp