Dispersive Wave Analysis – Method and Applications

A technique for estimating the dispersion characteristics of propagating waves as measured by an array is detailed. The technique consists of bandpass filtering the data through a filterbank and then processing the filtered waveforms non-dispersively. The results can show the dispersion of the entire time series or be parsed in time to analyze the dispersion characteristics of any section of the time series. Processing LWD field data shows that this method can extract dispersion characteristics over a broadband of frequencies and with low amplitude signals. Both the field data and laboratory scale data show that multiple modes present over the same frequency band can be identified.Halliburton CompanyMassachusetts Institute of Technology. Earth Resources LaboratoryMassachusetts Institute of Technology. Borehole Acoustics and Logging Consortiu

PHARMACOKINETIC DRUG INTERACTIONS OF GLICLAZIDE AND ITOPRIDE IN NORMAL AND DIABETIC RATS

Objective: The present study was aimed to investigate the safety, reliability of Gliclazide and possible drug interaction with Itopride when they were administered as combination treatment.Methods: Studies were conducted in normal and streptozotocin induced diabetic rats with oral administration of selected doses of gliclazide, itopride and their combination. Blood samples were collected from rats by retro orbital/marginal ear vein puncture at regular intervals of time. All the blood samples were analyzed for pharmacokinetic parameters by HPLC method.Results: There was no significant difference in pharmacokinetic parameters of both Gliclazide alone and combination with itopride in healthy and diabetic rats on day 1 and day 8.Conclusion: Based on the results it can be concluded that the concurrent administration of these two drugs have potential benefit without any drug interactions in the effective management of diabetes and gastroparesis.Â

Geomechanical Modeling of In-Situ Stresses Around a Borehole

In this paper, we present a modelling of the in-situ stress state associated with the severe hole enlargement of a wellbore. Geomechanical information is relevant to assure wellbore stability, i.e., to prevent damages in the formation and later on, the casing. Many of the drilling parameters, as mud weight or the optimal orientation of the borehole, require some knowledge of the mechanical behaviour of the rock. The lack of these kind of data in exploratory areas, where there are usually insufficient constraints for the geological model, increases even more the risk, hence the costs. The present model uses the concepts of poroelasticity theory to compute the stationary 2D, brittle response of the formation around a borehole that is submitted to effective compressive horizontal stresses. The numerical solution is obtained using a finite element approximation. The initial stress state at the far field was estimated combining a frictional-failure theory with the observations of dipmeter caliper in a particular borehole that presents elongations in a preferential direction. The direction and relative extension of the observed breakouts at a particular depth are modelled successfully using formation realistic parameters and dimensions, although the exact shape of the borehole (at all angles) was unknown. For the particular case study, the orientation of the breakout is NE-SW, at about 82 degrees azimuth. Therefore, the maximum horizontal stress lies at approximately 350 degrees azimuth. The ratios of horizontal principal stresses to vertical stress that best honor the observations are SHmax = 2.3Sv and Shmin = 1.7Sv. The compressive strength necessary for the rock to fail, as indicated by the caliper data under this stress field, is about 140 MPa.Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumMassachusetts Institute of Technology. Earth Resources Laborator

Effects of source mismatch on multipole Logging

The effects of mismatched multipole sources were investigated. Multipole sources considered here are those that they are constructed of monopoles with appropriate sign combination. To simulate mismatched dipole and quadrupole sources, we made the amplitude of one of monopoles smaller than those of the other monopoles. The dipole and quadrupole component were obtained with four monopole receiver array system by subtracting or adding appropriate responses. Mismatched dipole source excites nondipole modes in addition to the flexural mode. The strongest of these is the Stoneley mode, whose amplitude increases with increasing mismatch. Similarly, mismatched quadrupole sources produce nonquadrupole modes such as the Stoneley mode in addition to the screw mode. The amplitude of the Stoneley mode increases with mismatch. However, we can obtain the flexural mode by A-C and the screw mode by A-B+C-D processing, respectively. The Stoneley mode, which has the same amplitude at the same radial position from the borehole axis, is cancelled out by A-C and A-B+C-D processing as long as the tool is placed at the center of the borehole.Massachusetts Institute of Technology. Earth Resources LaboratoryMassachusetts Institute of Technology. Borehole Acoustics and Logging Consortiu

Simultaneous Inversion of cross-dipole acoustic waveforms in anisotropic media for azimuthal angle and dispersion of fast and slow shear waves

A method to jointly invert for azimuthal angle and dispersion relations from cross-dipole data is presented. Dispersion curves from the joint inversion are compared to both Prony’s method and a simple back propagation schema and an agrrement is found. The azimuthal angle estimate is shown to differ from a frequency domain rotaion that takes no account of dispersion within the waveforms indicating the importance of joint inversion.Massachusetts Institute of Technology. Earth Resources LaboratoryMassachusetts Institute of Technology. Borehole Acoustics and Logging Consortiu

Measured radiation patterns of the scale model dipole tool

The sound field of finite dipole acoustic transducers in a steel tool was investigated and their horizontal by measuring their vertical radiation patterns in water at two different frequencies. Measurements were also made with the tool in scale models representative of sonic logging conditions in the field. A Lucite borehole model was used to represent a soft formation and an Austin Chalk borehole model was used to represent a hard formation. The presence of the tool as a finite baffle for the transducer, introduces differences between the vertical and horizontal radiation patterns. In contrast to the vertical pattern, the horizontal radiation pattern has a narrower main lobe with relatively larger side lobes. The angular location of the side lobes as seen in the water measurements, do not change much in the borehole.Massachusetts Institute of Technology. Earth Resources LaboratoryMassachusetts Institute of Technology. Borehole Acoustics and Logging Consortiu

Simultaneous inversion for fast azimuth and dispersion of borehole flexural waves using cross-dipole data

This paper presents an inversion algorithm for obtaining azimuthal angle and borehole flexural wave dispersion in an anisotropic formation. The technique constructs an objective function that can be minimized using standard non-linear inversion methods, which is sensitive to both dispersion and rotation. The method is tested on both synthetic and real borehole data and gives good agreement with traditional processing.Massachusetts Institute of Technology. Borehole Acoustics and Logging Consortiu

Millimetric Wave Seeker for Third Generation Antitank Guided Missiles

For the third generation antitank guided missiles (ATGMs) with fire-and-forget and top attack capabilities, a noncoherent millimetric wave (MMW) active radar seeker has been configured with all weather capabilities. To meet the stringent dimensional and weight constraints and beamwidth requirements of ATGM, a W-band system has been designed with trans-twist antenna with a compact comparator. The paper covers the system description and critical design issues, and presents the performance results achieved so far. Areas for improvements, especially for achieving a higher range, have also been pointed out

Acoustic Logging While Drilling (LWD): Experimental Studies with Anisotropic Models

A model LWD tool (0.16" ID, 0.4" OD) was built to investigate its operation in an anisotropic formation. The tool consists of a dipole source and six dipole receivers capable of operating at several hundred kHz. The formation was a block of delabole slate with a borehole of 1.27 cm diameter. In an anisotropic °uid-¯lled borehole with a dipole source and dipole receiver ori- ented along the principal directions, dipole (°exural) modes are mainly observed. Weak compression and shear refracted arrivals are also discernable when they were not ob- scured by stronger arrivals. Further, modes corresponding to fast shear direction are evident in the slow shear direction measurement. With a model LWD tool in the °uid-¯lled borehole, and oriented in the fast and slow directions, the main arrivals were the corresponding °exural modes. Modes cor- responding to the fast shear direction are no longer evident in the slow shear direction measurments. These preliminary experiments suggest that, with an LWD tool in an anisotropic formation, arrivals sensitive to formation properties can be discerned.United States. Dept. of Energy (Grant DE-FG02-00ER15041)Massachusetts Institute of Technology. Borehole Acoustics and Logging Consortiu

HYDROGEL: RESPONSIVE STRUCTURES FOR DRUG DELIVERY

Hydrogels are water-swollen 3D networks made of polymers, proteins, small molecules, or colloids. They are porous in structure and entrap/encapsulate large amounts of therapeutic agents and biopharmaceuticals. Their unique properties like biocompatibility, biodegradability, sensitivity to various stimuli, and the ability to be easily conjugated with hydrophilic and hydrophobic drugs with a controlled-release profile make hydrogels a smart drug delivery system. Smart hydrogel systems with various chemically and structurally responsive moieties exhibit responsiveness to external stimuli including temperature, pH, ionic concentration, light, magnetic fields, electrical fields, and chemical and biological stimuli with selected triggers includes polymers with multiple responsive properties have also been developed elegantly combining two or more stimuli-responsive mechanisms. This article emphasized the types, features, and various stimuli systems that produce responsive delivery of drugs