Acoustic Logging Research Articles

Petrophysical and geomechanical characterization of the Late Cretaceous limestone reservoirs from the Southeastern Constantine Basin, Algeria

We have characterized the petrophysical and geomechanical properties of the Late Cretaceous Turonian and Cenomanian carbonate reservoirs from the southeast Constantine Basin, northern Algeria. In general, Turonian carbonates exhibit a wide range of porosities (2%–15%) and permeabilities (0.001–10 mD), whereas the Cenomanian reservoir appears to be very tight (<6% porosity and <0.1 mD permeability). Based on their storage and hydraulic flow characteristics, these carbonates were classified into two distinct reservoir rock types (RRT): RRT-I is hosted by nano- to microporosities that displays poor reservoir qualities compared to the RRT-II, consisting of mesoporous Turonian intervals (>10% porosity and 0.5–10 mD permeability). The reservoir pore-pressure gradient is interpreted to be a little above the hydrostatic (0.51 psi/ft), whereas the minimum horizontal stress ([Formula: see text]) has a 0.72 psi/ft gradient. In situ stress analysis establishes a dominant strike-slip tectonic stress field in the basin. Shale intercalations associated with the carbonate facies are characterized by comparatively high failure pressure that can lead to wellbore failures, which may be avoided considering the recommended minimum drilling mud weight as obtained from the rock failure criterion. Extensive wellbore breakouts (C-quality) were observed in the acoustic image logs recorded in the studied reservoir intervals, inferring a mean maximum horizontal stress azimuth of 350°N. We recommend that deviated wells in the direction of the interpreted [Formula: see text] orientation (approximately east–west) using hydraulic fracturing can be useful to attain optimum wellbore stability and effective permeability enhancement. Our findings have significant implications for enhanced production within the tight carbonate reservoirs situated in a strike-slip domain.

Research of actual information on well casing using machine learning and neural networks

In domestic and world practice, despite the measures applied and developed to improve the quality of well casing, there is a problem of leaky structures in almost 50 % of completed wells. The study of actual data using classical methods of statistical analysis (regression and variance analyses) doesn't allow us to model the process with sufficient accuracy that requires the development of a new approach to the study of the attachment process. It is proposed to use the methods of machine learning and neural network modeling to identify the most important parameters and their synergistic impact on the target variables that affect the quality of well casing. The formulas necessary for translating the numerical values of the results of acoustic and gamma-gamma cementometry into categorical variables to improve the quality of probabilistic models are determined. A database consisting of 93 parameters for 934 wells of fields located in Western Siberia has been formed. The analysis of fastening of production columns of horizontal wells of four stratigraphic arches is carried out, the most weighty variables and regularities of their influence on target indicators are established. Recommendations are formulated to improve the quality of well casing by correcting the effects of acoustic and gamma-gamma logging on the results.

Vibration and horizontal directivity analysis of transmitting transducer for acoustic logging while drilling

Abstract Radially polarized open-cylindrical piezoelectric transducers are widely used in the field of acoustic logging while drilling (LWD). Unlike the wireline logging transducer, the structure of the acoustic LWD transducer is an open structure; in this case, its radial vibration is accompanied by apparent circumferential vibration. In this paper, based on the two-dimensional wave equations and electrostatic charge equation, according to the free boundary conditions of the transducer, the resonance frequency equation of radial-circumferential coupled vibration for the acoustic LWD transducer is obtained. The vibration modal and resonance frequency for transducers of several typical sizes are simulated using COMSOL software. The results show that when the geometrical size of the transducer satisfies certain conditions, the theoretical calculation and the numerical analysis are in good agreement and the relative error is controlled below 3%. Meanwhile, the horizontal directivity of the LWD transducer after actual installation is discussed, and it is found that adding appropriate coupling materials can improve the monopole sound field radiation. So, it is expected that this work can serve as a reference for the acoustic LWD transducer design and install.

Uncertainty in the real-time estimation of ship speed through water

The ship speed through water (STW) is a critical variable for evaluation of ship performance. With a cubic relation to the expected shaft power, even small inaccuracies in measured STW amplifies to more considerable inaccuracies in the expected shaft power. STW is traditionally measured using a speed log, more specifically by the Doppler acoustic speed log principle. The stability and precision of this technique is however questionable, particularly when ships are exposed to waves. For ships equipped with sensors and instrumentation for measuring propulsion related data, the STW can be estimated from in-service measurements on the propeller shaft. An accuracy of this STW estimate similar to the speed log will increase the overall confidence in the ship performance evaluation. In this paper we study the uncertainty in the estimated STW using propeller loading measurements, and identify the most critical components of ship instrumentation in order to achieve an estimate of STW with sufficient accuracy. The uncertainty analysis includes a fixed pitch and controllable pitch propeller, influence from including a thrust sensor and influence from waves on the expected uncertainty in estimated STW. The uncertainty in estimated STW is found to be similar to the uncertainty provided by manufacturers of Doppler speed logs. The propeller pitch angle is found to have a significant contribution to the total uncertainty in STW. Including thrust measurements decreases the uncertainty in STW by 34%, and the uncertainty is found to be not very much affected by the presence of waves.

Estimation of transversely isotropic formation parameters using flexural and quadrupole dispersion data in the fast formation

Borehole acoustic logging plays an important role in inverting the five Thomsen parameters of many formations characterized as a transversely isotropic medium with a vertical axis of symmetry (VTI). In general, these parameters are obtained under certain assumptions, and the formation type defined by the relation of Thomsen parameters is not taken into consideration. We have developed a method to determine the Thomsen parameters of all kinds of fast VTI formations from the first-order flexural and first-order quadrupole dispersion data by dividing the Thomsen parameters inversion process into two parts: low-frequency asymptotic slowness inversion of the flexural or quadrupole dispersion and Thomsen anisotropy parameter inversion by a constrained evolutionary optimization algorithm. Compared with traditional approaches, the new method is not only independent of any assumed correlation among the Thomsen anisotropy parameters but it also provides a more accurate result than the inversion of either of them alone for both kinds of fast VTI formations. The inversion results obtained from either the flexural or quadrupole dispersion data alone are incorrect if the formation type is incorrectly identified, such as misidentifying an isotropic formation as a special VTI formation. The new method can not only identify the type of fast VTI formation, but it also obtains the shear slowness in a special VTI formation, which cannot be obtained by existing methods. Accordingly, the application to synthetic examples validates the significance and necessity of the proposed joint method in inversion of the Thomsen parameters.

Acoustic field simulation of phased array in borehole in layered formation

Horizontal stratified strata is a common geological model, and it needs to be simulated numerically in order to get the propagation law of sound waves in it, usually using the finite-difference time-domain method. However, for hundreds of meters underground well section, how to improve the calculation efficiency is a question that we need consider. In this paper, a dynamic method is proposed to obtain the computational domain, which can minimize the computational domain when the simulation results are reliable. When the transmitter is located below the receiver and the nearest delamination boundary is more than 2.0 m below the instrument, all delamination media below the instrument can be ignored in the calculation. A similar strategy is used for the layered boundary located above the array receiver. In this paper, the method is used to simulate the response of phased array acoustic logging in multi-layer media.

Design of a New Acoustic Logging While Drilling Tool.

To obtain qualified logging while drilling (LWD) data, a new acoustic LWD tool was designed. Its overall design is introduced here, including the physical construction, electronic structure, and operation flowchart. Thereafter, core technologies adopted in this tool are presented, such as dominant exciting wave bands of dipole source, a sine wave pulse excitation circuit, broadband impedance matching, and an intellectualized active reception transducer. Lastly, we tested this tool in the azimuthal anisotropy module well, calibration well, and normal well, working in the model of the cable, sliding eye, and logging while drilling. Experiments showed that the core technologies achieved ideal results and that the LWD tool obtained qualified data.

Prediction of velocity, gas content from neural network modeling and estimation of coal bed permeability from image log in coal bed methane reservoirs: Case study of South Karanpura Coalfield, India

P-wave velocity and gas content of major coal seams are predicted from three wells from the South Karanpura coalfield, India. Multilayered feed-forward neural network (MLFN) model is developed for prediction P-wave velocity from two wells using three input log parameters: gamma ray, resistivity and bulk density. The model is tested on coal seams: Sayal, Balkudra, Banasgarah and Argada of three wells namely; A, B and C with satisfactory goodness of fit (R2 = 0.77). The ratio of P-wave and S-wave velocities (Vp/Vs) ranges from 1.68 to 3.10 in the coal seams of this field. Cleat density using image log is obtained from four major coal seams namely; Balkudra, Kurse, Hathidari, Banasgarah varying from 1/m to 11/m. Ash content varies from 15 to 51% whereas gas content of major coal seams varies from 2.30 to 4.4 10−3 kg/m3. There is a good correlation between ash content and Vp/Vs of coal seams under the study area. MLFN model for prediction of gas content of the above-mentioned coal seams from two well is trained with input parameters such as: Vp/Vs, bulk density, cleat density and ash content. The model estimates gas content of other coal seams: Argada from well A, Hathidari from well B and Balkudra, Kurse, Banasgarah from well C with satisfactory R2 = 0.77. Maximum horizontal stress orientation is observed from azimuthal shear wave anisotropy from cross multipole array acoustic (XMAC) log for a well A. It varies from N110° to N115° in these coal seams. Permeability of coal seams are computed from X-tended Range Microresistivity Imager (XRMI) tool from a well C. Permeability of coal is varying from 0.5 md in Saunda seam to 17.29 md in Banasgarah seam. The estimated permeability matches well with the pre-fracture permeability of these seams. It is observed that increase in cleat density enhances coal seam fracture permeability in coal seam.

Application of Acoustic Variable Density Logging Technology in Petroleum Energy Development

Energy is an important factor restricting the development of national economy, and petroleum energy is the main supplier in the current world energy environment, which promotes the development of agriculture, and various industrial sectors are closely related to petrochemical products. However, with the long-term development of the oilfield, it has experienced the stages of flowing production, water injection development and three times of chemical agent injection development, the production and explorable new reserves have decreased significantly, especially after the oilfield entered the well pattern three times of infilling adjustment, because of the exploitation of thin, poor and off surface reservoirs mixed between the main oil layers. Due to the requirements of oilfield development, not only the channeling between the adjusted thin and poor layers should be prevented, but also the channeling between the adjusted thin and thick layers should be prevented. Therefore, the requirements for cementing quality are higher and higher, and the requirements for testing and evaluation standards of cementing quality are more and more accurate. In this paper, through the application of acoustic variable density logging technology in petroleum energy development, combined with the examples of acoustic amplitude and acoustic variable density logging curve, the cementing accuracy of the first, second and interface of cement sheath after cementing is further improved, so as to meet the new requirements of correctly evaluating the cementing quality in the later stage of oilfield development.

Technology and specificity of surface seismic in the Upper Kama Potash Salt Deposit

Exploration surveys at the Upper Kama Potash Salt Deposit widely use the surface seismic method by the common reflection point at depth. Based on the implemented research, a technology is developed for shallow seismic using an explosion source of elastic vibrations for the purposes of geological exploration. The research involved the comparative analysis of the main elastic wave sources used in the shallow seismic. It is highlighted that it is important to consider carefully the near-surface section structure and the surface relief. The accuracy of the velocity analysis procedure in the high-velocity section of salt strata is analyzed. The specificity of acquisition in the shallow seismic with an explosion source is discussed. The actual test data show a considerable increment in the energy of reflections from the roof and floor of the salt strata, which, in the absence of a priori geological information and geophysical logging data (acoustic logging and vertical seismic profiling), affects the velocity analysis precision and, as a consequence, the accuracy of reflection identification at depth. It is found that the explosion source has a much higher signal/noise ratio as against a pulse cartridge, which greatly improves neutrality of interpretation results. The use of a pulse cartridge in the surveys in the depth interval of 200–400 m is only justified when the surface conditions are perfect and the low velocity layer is not thick.

Drilling Data-Based Approach to Build a Continuous Static Elastic Moduli Profile Utilizing Artificial Intelligence Techniques

Abstract Young's modulus is a principle geomechanical property that reflects the material stiffness. Good knowledge about rock mechanical properties significantly facilitates fracturing design and in-situ stresses estimation. Conventionally, rock elastic properties are estimated either experimentally or using well log data, known as static and dynamic respectively. Conducting experiments on core samples is costly, time-consuming and does not provide continuous information. While dynamic Young's modulus provides a complete profile, however, it needs the availability of acoustic logs and its estimations differ from the static values. The objective of this paper is to create a continuous profile of Young's modulus using the drilling rig sensors records. The presented approach relies on the fact that the drilling data such as drill pipe torque, weight on bit and rate of penetration are available at an early stage without additional cost. Three machine-learning algorithms were used to correlate the drilling data with Young's modulus: random forest, adaptive neuro-fuzzy inference system and functional network. Two different datasets were used in this study, one construct and test the model, while the other was hidden from the algorithms and used later to validate the built models. The two datasets contain over 3900 data points and cover different types of rocks. Two out of the three methods utilized yielded a remarkable match between the given and predicted values. The correlation coefficients ranged between 0.92 and 0.99 average absolute percentage errors were less than 13%. Supported by these results, the utilization of drilling data and artificial intelligence techniques to predict the elastic moduli is promising. This approach could be investigated for other geomechanical properties, besides, the performance of other machine-learning methods for the same purpose.

Анализ зависимости между акустическими и физико-механическими свойствами горных пород терригенных отложений

During the entire development of an oil and gas field, it is necessary to carry out a complex of various studies aimed at identifying the parameters of the productive layer. One of such studies is the analysis of core material, as a result of which the following parameters of the rock are determined: porosity, permeability, Young's modulus and others. The listed characteristics must be taken into account when building a geological and hydrodynamic model of a field. In addition to these parameters, the strength properties of the rock should be determined, since they are necessary in the design of the wellbore. Such characteristics can be obtained by conducting research in specialized laboratories. This is not always possible due to various reasons. A number of studies confirm the fact of the relationship between the acoustic properties of a rock (the velocity of the longitudinal and transverse waves) and the strength characteristics. The acoustic properties of the rock must be taken into account when interpreting the acoustic logs of the wells, which allows to reveal the distribution of rocks along the wellbore. Based on the velocities of ultrasonic waves propagation, it is possible to calculate the elasticity dynamic modulus, which let assess the tendency of the rock skeleton to compaction as a result of the effective stress action. Therefore, the determination of the rock acoustic properties is necessary when planning the development of a field and its implementation. The results of laboratory studies aimed at establishing the relationship between the strength and acoustic properties of rocks are presented. During the experiment, the dynamic Young's modulus was also determined and its relationship with the speed of ultrasonic waves propagation was revealed. As a result of laboratory studies, empirical dependences of the ultimate strength in volumetric compression (σс), elasticity dynamic modulus (E ) and the velocity of transmission of longitudinal (vp) and transverse waves (vp) were obtained. An assessment of the obtained values was given over the entire measurement range.

The theoretical-empirical technique of hydrocarbons prediction in wells sections. New aspects

We present the developed theoretical-empirical technique for predicting of rocks’ oil-and-gas bearing in wells sections according to acoustic logging (AL) and core research (CR) and its variants by using data of other loggings and also the results of testing them on wells sections data in the Western oil and gas bearing region of Ukraine (WOGR). The mathematical apparatus of the created technique is based on a mathematical model of solid porous rock, empirical relationships between elastic and reservoir characteristics of rocks and acoustic logging data for specific studied wells. The key parameter in the calculations is the rock compressibility. Determination of the porosity of rocks and prediction of the type of pore filler (water, oil, gas) is implemented by comparing the results of calculating the velocities using theoretical and constructed empirical relationships with the actual data of the AL, by the parameter of compressibility of rocks, by the density of the pore filler fluid. Additional versions of the technique have been developed based on correlation dependences and data from other logging methods — gamma-ray logging (GL), electric logging (EL/SP), offset method and seismic logging (SL). They are used in case of absence of AL data for the studied wells or for the intervals of their sections, and also for improving the reliability of prediction the oil and gas content of these sections. The software for the implementation of the technique was developed in Fortran, C# and Excel software environments. The technique was tested on the data of wells of a number of structures of the WOGR of Ukraine (Lishchyns’ka, Buchats’ka, Ludyns’ka, Zaluzhans’ka, Zarichnyans’ka and Nyklovyts’ka).The technique ensures reliable prediction of petrophysical characteristics, porosity and oil-gas-water saturation of rock layers of different thicknesses (including thin layers — from 0.1—0.2 m) in well sections. For this, in addition to the data of the general parametric base of the WOGR reservoir rocks, the specially constructed refined empirical relations for various specific types and subtypes of the WOGR reservoir rocks are used, they are based on the results of analysis of petrophysical characteristics of those rocks.

Evaluation of Coal Body Structures and Their Distributions by Geophysical Logging Methods: Case Study in the Laochang Block, Eastern Yunnan, China

The coal body structure is one of the key parameters in the exploration and exploitation of coalbed methane (CBM). Accurate identification of the structure of a coal seam is important for CBM exploration and development. In the present study, we collected coal seam logging data and drilling data from six CBM wells in the Laochang block in eastern Yunnan, China. Four logging curves, including gamma-ray logging (GR), density logging (DEN), acoustic travel time logging (DT) and compensated neutron logging (CNL), were selected. Principal component analysis was used to establish a geophysical identification approach for the coal body structures in the Laochang block. The geophysical identification results for the coal body structures were in good agreement with the actual coring data. We found that if the coal body structures score (F value) was less than 12, the coal seam belongs to Type I coal; otherwise, it is Type II coal. With increasing coal seam thickness, the proportion of Type I coal showed a decreasing power function trend. When coal seam thickness exceeded 1 m, it was dominated by Type II coal. The coal seams near well YW-04 had the highest degree of overall damage, followed by wells YW-02, YW-03 and YW-01. The coal seam in well YW-04 was affected by the superimposed regional and local tectonic tensile stress fields; the coal seam in well YW-02 was subject to the regional tensile stress field and the goaf, and the coal seams in wells YW-01 and YW-03 were subject to the joint effects of the regional tensile and local compressive tectonic stress fields. The distributions of the coal body structures in the Laochang block were the result of the combined effects of the coal thickness, goaf, tectonic type and tectonic stress field. These results may provide guidelines for the exploration and development of CBM in the Laochang block in eastern Yunnan. Furthermore, the scientific and quantitative evaluation method developed in this research can be applied to the identification of coal body structures in other CBM blocks worldwide.

Multi-parameter logging evaluation of tight sandstone reservoir based on petrophysical experiment

Acoustic, resistivity and nuclear magnetic resonance (NMR) logging are important means of reservoir evaluation. In this paper, the information of pore structure, such as the aspect ratio and the shape, is obtained by rock physical experiments like constant velocity mercury injection and casting thin section. Taking pore structure information as a link, the theoretical relations among acoustic-NMR, acoustic-resistivity and resistivity-NMR of rocks are studied, respectively, based on the differential equivalent model and fractal theory, and the theoretical derivation results are verified by AE acoustic emission experiment, rock resistivity experiment and NMR experiment. It is found that there is a power function relationship between the P/S wave velocity and the geometric mean value of NMR T2. Moreover, there are also power function relationships between the slowness of P/S wave and resistivity, and between the value of NMR T2 and the increase rate of resistance. Based on the above relationship, the gas reservoir can be identified by acoustic-resistivity-NMR multi-parameters in well G of the study area. Compared with the conventional P/S velocity ratio and P-wave slowness intersection method, the separation effect of gas and water is more obvious.

Geothermal Resources Recognition and Characterization on the Basis of Well Logging and Petrophysical Laboratory Data, Polish Case Studies

Examples from the Polish clastic and carbonate reservoirs from the Central Polish Anticlinorium, Carpathians and Carpathian Foredeep are presented to illustrate possibilities of using well logging to geothermal resources recognition and characterization. Firstly, there was presented a short description of selected well logs and methodology of determination of petrophysical parameters useful in geothermal investigations: porosity, permeability, fracturing, mineral composition, elasticity of orogeny and mineralization of formation water from well logs. Special attention was allotted to spectral gamma-ray and temperature logs to show their usefulness to radiogenic heat calculation and heat flux modelling. Electric imaging and advanced acoustic logs provided with continuous information on natural and induced fracturing of formation and improved lithology recognition. Wireline and production logging were discussed to present the wealth of methods that could be used. A separate matter was thermal conductivity provided from the laboratory experiments or calculated from the results of the comprehensive interpretation of well logs, i.e., volume or mass of minerals composing the rocks. It was proven that, in geothermal investigations and hydrocarbon prospection, the same petrophysical parameters are considered, and well-logging acquisition equipment and advanced methods of processing and interpretation, developed and improved for almost one hundred years, can be successfully used in the detection and characterization of the potential geothermal reservoirs. It was shown that the newest (current investment)—as well as the old type (archive)—logs provide useful information.

Acoustic fields for monopole logging while drilling with an eccentric collar

The acoustic problem of an eccentric drill collar in a fluid-filled borehole has been of interest in the field of acoustic logging while drilling (ALWD) in recent years. To reduce the effects of tool eccentricity on ALWD measurements, studies on acoustic responses under such conditions are essential. This study therefore has developed an analytical method to investigate borehole wavefields with an off-center monopole ALWD tool in fast and slow formations. By evaluating the contributions of compressional and shear branch points, the effects of the tool eccentricity on individual formation primary and shear head waves are investigated. Results illustrate that tool eccentricity only affects the excitation properties and has almost no effect on the extracted velocities. The joint analysis of synthetic full waveforms and dispersion diagrams with varying eccentricity degrees indicates that multipole modes are excited when the tool is off center, and their excitation amplitudes gradually increase with the increasing eccentricity, especially in the direction of tool movement. Moreover, the dispersion analysis reveals that the two modes with intersections in the centered case are coupled when the tool becomes eccentric. In particular, the coupling performance between the Stoneley and flexural modes is the most prominent. Furthermore, the effects of tool eccentricity on the monopole acquisition method, that is, the sum of waveforms received at four orthogonal azimuths, are evaluated. Results show that the above summation method can effectively reduce the effects of slight or moderate eccentricity. However, for large or extreme eccentricity, reducing or eliminating the effects of eccentricity on the Stoneley wave is a challenge for this method. Based on the above analyses, measurements may not be reliable for formation evaluation in the case of extreme eccentricity, especially for Stoneley wave applications.

Centralizing devices to complement acoustic logging tools

One of the cornerstones to high-precision acoustic logging equipment is high reliability and maneuverability of tools in a sophisticated well. The paper outlines the requirements for centralizing devices (CD), experimental and theoretical rationale for different configurations, and the need for appropriate calculations. The outputs involve a series of updated centralizing devices, the classification of centralizing devices and a crossplot that all allow for an optimal centralizing configuration to be selected depending on the equipment available and a well examined.

Modeling In-situ tectonic stress state and maximum horizontal stress azimuth in the Central Algerian Sahara – A geomechanical study from El Agreb, El Gassi and Hassi Messaoud fields

Central Algerian Sahara hosts many prolific hydrocarbon accumulations in the Paleozoic successions. In this work a contemporary stress field of the Saharan platform has been evaluated using the dataset from recently drilled wells in El Agreb, El Gassi and Hassi Messaoud fields. A pore fluid pressure gradient of 0.56 PSI/feet is interpreted from the in-situ measurements in the Paleozoic reservoir units. Vertical stress (Sv) modeled from the bulk-density data indicates an average of 1.02 PSI/feet gradient. Rock elastic property-based approach is employed to model the magnitudes of minimum (Shmin) and maximum horizontal stress (SHmax) components, which were calibrated with leak off test/minifrac and breakout widths, respectively. Paleozoic stress profiles reveal Shmin/Sv range of 0.74–0.84, while SHmax/Sv varies between 1.1 and 1.33. Subsurface stress distribution indicates that the present-day stress field in the Saharan platform is principally strike-slip faulting (SHmax > Sv > Shmin). A cumulative 1490 m of B-D quality wellbore breakouts, inferred from the acoustic image logs, suggest a NW-SE/WNW-ESE SHmax orientation, which is parallel to the absolute African plate motion and Africa-Eurasia plate convergence direction, implying ridge push force to be the dominant contributor to the tectonic stress field. Mean SHmax orientation shows slightly anticlockwise rotation (126°N to 144°N) from south (El Agreb) to north (Hassi Messaoud field). Inferences are discussed regarding the fault slip potential and hydrocarbon reservoir development.

Revealing Hidden Information: High-Resolution Logging-While-Drilling Slowness Measurements and Imaging Using Advanced Dual Ultrasonic Technology

A new logging-while-drilling (LWD) acoustic tool has been developed with novel ultrasonic pitch-catch and pulse-echo technologies. The tool enables both high-resolution slowness and reflectivity images, which cannot be addressed with conventional acoustic logging. Measuring formation elastic-wave properties in complex, finely layered formations is routinely attempted with sonic tools that measure slowness over a receiver array with a length of 2 ft or more depending upon the tool design. These apertures lead to processing results with similar vertical resolutions, obscuring the true slowness of any layering occurring at a finer scale. If any of these layers present significantly different elastic-wave properties than the surrounding rock, then they can play a major role in both wellbore stability and hydraulic fracturing but can be absent from geomechanical models built on routine sonic measurements. Conventional sonic tools operate in the 0.1- to 20-kHz frequency range and can deliver slowness information with approximately 1 ft or more depth of investigation. This is sufficient to investigate the far-field slowness values but makes it very challenging to evaluate the near-wellbore region where tectonic stress redistribution causes pronounced azimuthal slowness variation. This stress-induced slowness variation is important because it is also a key driver of wellbore geomechanics. Moreover, in the presence of highly laminated formations, there can be a significant azimuthal variation of slowness due to layering that is often beyond the resolution of conventional sonic tools due to their operating frequency. Finally, in horizontal wells, multiple layer slownesses are being measured simultaneously because of the depth of investigation of conventional sonic tools. This can cause significant interpretational challenges. To address these challenges, an entirely new design approach was needed. The novel pitch-catch technology operates over a wide frequency range centered at 250 kHz and contains an array of receivers having a 2-in. receiver aperture. The use of dual ultrasonic technology allows the measurement of high-resolution slowness data azimuthally as well as reflectivity and caliper images. The new LWD tool was run in both vertical and horizontal wells and directly compared with both wireline sonic and imaging tools. The inch-scale slownesses obtained show characteristic features that clearly correlate to the formation lithology and structure indicated by the images. These features are completely absent from the conventional sonic data due to its comparatively lower vertical resolution. Slowness images from the tool reflect the formation elastic-wave properties at a fine scale and show dips and lithological variations that are complementary to the data from the pulse-echo images. The physics of the measurement are discussed, along with its ability to measure near-wellbore slowness, elastic-wave properties, and stress variations. Additionally, the effect of the stress-induced, near-wellbore features seen in the slowness images and the pulse-echo images is discussed with the wireline dipole shear anisotropy processing.