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A measurement system capable of in situ measurements of formation permeability is described. The measurement method relies upon imaging the distribution of magnetic permeability fluid injected into a wellbore system through mutual inductance measurements between pairs of coils and relating the change in distribution of this fluid over time to a direct measurement of formation phase permeability. Analysis of the mutual inductance measurement method shows a unique response to distributions of magnetic permeability for various coil spacings and insensitivity to other confounding electrical parameters. The lower bound of measurement variance for this system is modeled for a continuum of coil spacings and radii of investigation for a perturbation in magnetic permeability. [ABSTRACT FROM AUTHOR]

Texas two-step is a novel framework for addressing the nonblind multiple-input single-output deconvolution (MISO-D) problems. The effectiveness of the framework in solving the MISO-D problems is described.

We present the design and test of a magnetic actuator that is used to hold and release a ballast and switch buoyancy of a miniaturized autonomous well-logging tool from negative to positive. The actuator makes use of a low coercivity aluminum-nickel-cobalt (AlNiCo) magnet paired with a high coercivity neodymium-iron-boron (NIB) magnet to create and cancel a magnetic pull force on a steel plate by changing the polarization direction of the former magnet. Brief current pulses sent through a solenoid wrapped around the AlNiCo magnet by charging and discharging a capacitor. The resulting resistor-inductor-capacitor (RLC) circuit is analyzed to understand the polarization process of the AlNiCo magnet and state change of the actuator's pull force. Our numerical solution using a nonlinear inductor model and test results showed that the repolarization can be achieved in steps using a relatively small 0.1 mF capacitor thanks to stored remnant field at each step. This made it possible to save space and energy for the miniaturized autonomous logging tool. Effects of NIB and steel weight piece on the AlNiCo polarization are experimentally analyzed. Magnetic circuit geometry is optimized using finite element analysis to maximize the pull force on the weight. The actuator occupies less than 2 cm3 and provides more than 2 kg-f to carry a ballast that weighs about 60 grams. [ABSTRACT FROM AUTHOR]

It has long been a goal of neuroethologists to record continuous neural activity from electrodes integrated into the nervous system of an unrestrained, naturally behaving animal. Recent studies have produced [...]

During well-logging operations, the depth of a logging tool is usually obtained by measuring the length of the wireline cable that suspends the tool in the well. In some cases, a secondary depth reference is obtained with a casing collar locator (CCL) that detects the collars along the steel casing lining the well. The thicker steel at these collars is detected by measuring the perturbations it causes to the field of a permanent magnet in the CCL logging tool. Due to its simplicity and efficiency, the CCL tool has not seen many changes throughout the years. However, for small, untethered sensor platforms, neither of the above methods is practical. This paper describes the theory, design, construction, and testing of an inductive sensor that detects the gap on the inside of the casing where two pipe joints mate together within a collar. Two identical cylindrical coils along a common axis are connected in a bridge configuration and driven by an ac signal. When one coil is near the gap, its inductance is slightly larger than that of the other, misbalancing the bridge. The sensor was implemented in a wireline tool and tested in a well. The field data show a clear double pulse of ac signal across the bridge each time the tool passes a collar. This sensor is smaller and lighter than CCLs that use permanent magnets, making it suitable for small, untethered sensor platforms. [ABSTRACT FROM PUBLISHER]

The measurement of fluid and rock properties within oil and gas wells is critical to efficient hydrocarbon production. These data are generally acquired by wireline logging, where sensors are lowered into the well at the end of a long cable. The handling of this cable adds significant cost to downhole data acquisition. In this paper, a proof of concept demonstration of an untethered sensor platform for logging vertical wells is presented. The platform is the size of a golf ball and works based on buoyancy change. The buoyant sensor housing and electronics initially holds a weight such that it sinks in the well. It releases the weight when it reaches a programmed depth and floats back up to the surface, logging data during the whole operation. The data are downloaded after retrieving the sensor. This miniaturized, tetherless platform can reduce the cost of logging operations and pave the way for semipermanent downhole sensors. [ABSTRACT FROM PUBLISHER]

Real-time monitoring of wellbore fluids is of crucial importance for oil recovery. During various operations such as drilling, production, stimulation, and intervention, the characteristics of the fluids being produced or injected into the well needs to be monitored to ensure safe operation or to optimize production. However, measuring their physical properties, such as viscosity and density, can still pose a great challenge when the fluids are part of a multiphase flow or are complex inhomogeneous fluids whose properties can vary largely with external parameters such as temperature, pressure, and flow rates. While commercial instruments that make comparable measurements can be found in other industries, a solution tailored to these oilfield challenges does not exist at the moment. In this paper, we demonstrate two examples of viscosity/density systems using tuning fork-based mechanical oscillators tailored to different measurement scenarios in the oilfield. In the first example, we use a miniature piezoelectric tuning fork which can be integrated in small-scale measurement platforms for downhole deployment. By using the tuning fork as the frequency-defining element of an oscillator circuit, fast measurements of viscosity and density are possible. This feature allows us to use this device in fast changing multiphase flows, such as those found in live producing wells. In the second example, we demonstrate a ruggedized tuning fork device for in-line measurements of viscosity and density of non-Newtonian fluids. This instrument is a robust permanent tool for surface installation with applications in quality assessment of drilling mud and other wellbore fluids. We discuss some initial studies in a water-based drilling fluid. [ABSTRACT FROM PUBLISHER]

The high cost of simulating densely sampled seismic forward modeling data arises from activating sources one at a time in sequence. To increase efficiency, one could leverage recent innovations in seismic field-data acquisition and activate several (e.g., 2-6) sources simultaneously during modeling. However, such approaches would suffer from degraded data quality because of the interference between the model's responses to the simultaneous sources. Two new efficient simultaneous-source modeling approaches are proposed that rely on the novel tandem use of randomness and sparsity to construct almost noise-free model response to individual sources. In each approach, the first step is to measure the model's cumulative response with all sources activated simultaneously using randomly scaled band-limited impulses or continuous band-limited random-noise waveforms. In the second step, the model response to each individual source is estimated from the cumulative receiver measurement by exploiting knowledge of the random source waveforms and the sparsity of the model response to individual sources in a known transform domain (e.g., curvelet domain). The efficiency achievable by the approaches is primarily governed by the sparsity of the model response. By invoking results from the field of compressive sensing, theoretical bounds are provided that assert that the approaches would need less modeling time for sparser (i.e.. simpler or more structured) model responses. A simulated modeling example is illustrated that shows that data collected with as many as 8192 sources activated simultaneously can be separated into the 8192 individual source gathers with data quality comparable to that obtained when the sources were activated sequentially. The proposed approaches could also dramatically improve seismic field-data acquisition efficiency if the source signatures actually probing the earth can be measured accurately. [ABSTRACT FROM AUTHOR]

A computational method for time-domain multi-physics simulation of wave propagation in a poroelastic medium is presented. The medium is composed of an elastic matrix saturated with a Newtonian fluid, and the method operates on a digital representation of the medium where a distinct material phase and properties are specified at each volume cell. The dynamic response to an acoustic excitation is modeled mathematically with a coupled system of equations: elastic wave equation in the solid matrix and linearized Navier–Stokes equation in the fluid. Implementation of the solution is simplified by introducing a common numerical form for both solid and fluid cells and using a rotated-staggered-grid which allows stable solutions without explicitly handling the fluid-solid boundary conditions. A stability analysis is presented which can be used to select gridding and time step size as a function of material properties. The numerical results are shown to agree with the analytical solution for an idealized porous medium of periodically alternating solid and fluid layers. [ABSTRACT FROM AUTHOR]

Inductive neural telemetry was used to record from microwire electrodes chronically implanted into the anterior lateral line nerve of the oyster toadfish, Opsanus tau (L./. The lateral lines of free-ranging toadfish were stimulated by the swimming movements of a prey fish (Fundulus heteroclitus), and the corresponding neural activity was quantified. Both spontaneously active and silent afferent fibers experienced an increase in neural firing as the prey approached the lateral line. Activity was evoked when the prey fish approached to within 8–12 cm of the neuromast, with increases in nerve firing rates directly correlated with diminishing distance. Thus, adult toadfish 128 cm standard length; 33 cm total length) were only able to detect mobile prey that approached within approximately 40% of their body length. Both spontaneously active and silent afferent fibers also experienced a dramatic increase in firing during predatory strikes, indicating that the fibers were not inhibited during rapid body movement. This study investigates, for the first time, the neural response of the anterior lateral line to prey stimuli in free-ranging fish. [ABSTRACT FROM AUTHOR]

Presents information on a study which reported the development of an acoustic telemetry tag used to monitor electromyograms remotely from free-swimming marine fish. Information on the device; Studies concerning measurements of muscle contraction; Materials and methods; Discussion on the results.

Highlights • We realized a quartz-enhanced photoacoustic (QEPAS) sensor for methane, ethane and propane detection using a single intercascade laser source. • We achieved for ethane a QEPAS record sensitivity of 7 ppb in 1-second integration time. • Detection of propane with QEPAS technique is reported for the first time. • We demonstrated methane, ethane and propane detection at atmospheric pressure avoiding the use of pump and pressure controller systems. Abstract Hydrocarbon detection in the gas phase represents a powerful tool to guide oil exploration and production operations for the oil & gas industry. This application requires highly sensitive, selective and robust spectroscopic techniques. In this work, a quartz-enhanced photoacoustic sensor system designed to detect methane (C1), ethane (C2) and propane (C3), employing a single interband cascade laser emitting in the spectral range 3.342–3.349 μm, is reported. Detection levels in the part-per billion concentration range for C1 and C2 and a few parts per million for C3 were achieved. Measurements at both low and atmospheric pressures were carried out for mixtures simulating typical downhole hydrocarbon concentrations. [ABSTRACT FROM AUTHOR]

A computational method for time-domain multi-physics simulation of wave propagation in a poroelastic medium is presented. The medium is composed of an elastic matrix saturated with a Newtonian fluid, and the method operates on a digital representation of the medium where a distinct material phase and properties are specified at each volume cell. The dynamic response to an acoustic excitation is modeled mathematically with a coupled system of equations: elastic wave equation in the solid matrix and linearized Navier-Stokes equation in the fluid. Implementation of the solution is simplified by introducing a common numerical form for both solid and fluid cells and using a rotated-staggered-grid which allows stable solutions without explicitly handling the fluid-solid boundary conditions. A stability analysis is presented which can be used to select gridding and time step size as a function of material properties. The numerical results are shown to agree with the analytical solution for an idealized porous medium of periodically alternating solid and fluid layers.