LATERAL VELOCITY VARIATIONS NEAR BOREHOLES

Geophysics ◽  
1959 ◽  
Vol 24 (3) ◽  
pp. 451-461 ◽  
Author(s):  
Warren G. Hicks
Keyword(s):  
Field Data ◽  
Radial Distance ◽  
Stress Relief ◽  
Deep Penetration ◽  
Sound Waves ◽  
Drilling Mud ◽  
Lateral Velocity ◽  
Mechanical Stress Relief ◽  
Swelling Studies ◽  
Clay Type

Difficulties occur in obtaining accurate two‐receiver velocity logs in formations sensitive either to damage by exposure to drilling mud or to mechanical stress relief. Some shales are so altered by the drilling operation that their elastic properties are modified. Vertical velocity measured immediately adjacent the boreface is lower than if it were measured at a greater radial distance from the bore. These damaged shales require relatively deep penetration by the acoustic signal; consequently, the transmitter‐to‐first‐receiver spacing in a two‐receiver velocity logging system should be long enough to refract the sound waves through virgin formation. Experiments in one predominantly shaly section show a difference of almost 10 percent between times measured using transmitter‐to‐first‐receiver spacing of 4.3 ft compared to 8.8 ft. A limited amount of field data suggest that sodium montmorillonite is the clay type most sensitive to hydration and swelling. Studies of areal prevalence of the shale damage problem are incomplete.

Numerical Modeling of Mud Invasion Profile Based on the Well Logging with the Shallow Depth of Investigation

2012 ◽  
Vol 524-527 ◽  
pp. 148-151
Author(s):  
Yuan Zhong Zhang ◽  
Xiu Ying Miao
Keyword(s):  
Numerical Modeling ◽  
Dynamic Process ◽  
Water Saturation ◽  
Radial Distance ◽  
Well Logging ◽  
Shallow Depth ◽  
Borehole Wall ◽  
Drilling Mud ◽  
Invasion Depth ◽  
Depth Of Investigation

The drilling mud invasion is a dynamic process varying with time and reveal the permeability or the relatively permeability of the formation saturated with fluid. The mud invasion profile denotes the water saturation change with the radial distance from the borehole wall. The logging with the shallow depth of investigation (DOI), such as density logging, neutron logging and shallow electrical logging, often detects the information of the flushed zone. We chose DOI logging to model the slope invasion profile with the hyperbolic secant function, and the calculated logging reading comparing from the real logging reading to optimize the invasion profile. The results show that the mud invasion profile and the invasion depth are strongly affected by porosity, where the invasion depth reduces with porosity adding.

scholarly journals Mechanical stress relief in porous silicon free standing membranes

2015 ◽  
Vol 5 (10) ◽  
pp. 2128 ◽  
Author(s):  
Romain Guider ◽  
Cristina Traversa ◽  
Paolo Bettotti
Keyword(s):  
Porous Silicon ◽  
Mechanical Stress ◽  
Stress Relief ◽  
Free Standing ◽  
Mechanical Stress Relief

scholarly journals Calculation of Pressure Loss of Two Drilling Muds in Noor Oil Field

2020 ◽  
Vol 26 (2) ◽  
pp. 57-69
Author(s):  
Hassan Abdul Ameer ◽  
Hassan Abdul Hadi
Keyword(s):  
Pressure Loss ◽  
Field Data ◽  
Drill String ◽  
Oil Field ◽  
Flow Data ◽  
Drilling Mud ◽  
Pressure Losses ◽  
The Difference ◽  
Drilling Site ◽  
Drilling Muds

    In this work, calculation of pressure losses in circulating system for two drilling muds is evaluated in Noor oil field. Two types of drilling muds that were used for drilling section 12 1/4" and 8 3/4" which are Salt saturated mud and Ferro Chrome Lignosulfonate-Chrome Lignite mud. These calculations are based on field data that were gathered from the drilling site of well Noor-15, which are included, rheological data, flow data and specification of drill string. Based on the obtained results, the best rheological model that fit their data is the Herschel-Bulkley model according to correlation coefficient value for their two drilling mud. Also, the difference between the calculated pressure loss by Herschel-Bulkley model and standpipe pressure value are very convergence.

Reply to Dr. Kaarsberg

Geophysics ◽  
1959 ◽  
Vol 24 (3) ◽  
pp. 463-464
Author(s):  
Warren G. Hicks
Keyword(s):  
Mechanical Stress ◽  
Elastic Moduli ◽  
Stress Relief ◽  
Low Velocity ◽  
Mechanical Stress Relief

Paragraph II: Kaarsberg states that mechanical stress relief should not be ruled out as an explanation of low velocity adjacent the borehole. If the volume of the material stressed increases, the elastic moduli decrease. Therefore, velocity immediately adjacent the bore decreases. This is indeed a powerful point and properly should have been discussed more fully.

Wellbore Stability Research to the Direction Well in the Salt Layer

2011 ◽  
Vol 250-253 ◽  
pp. 4042-4045
Author(s):  
Hui Mei Wu ◽  
Yi Shan Lou ◽  
Zhong Hui Li ◽  
Liang Zhu ◽  
Wan Long Huang
Keyword(s):  
Creep Rate ◽  
Field Data ◽  
Creep Property ◽  
Wellbore Stability ◽  
Drilling Mud ◽  
Deviation Angle ◽  
Overburden Pressure ◽  
Salt Layer ◽  
Major Principal Stress ◽  
Creep Constitutive Model

The creep of salt layer often leads to tight hole and pipe sticking, while the deviation angle has an important impact on creep rate when drilling directional wells in salt layer. This paper firstly built the creep constitutive model according to the creep property of salt layers, and defined the creep parameters by field data and log data; then built geomechanics model and applied FLAC3Dsoftware to simulate the creep of salt layer, so the safe mud density window drilling the salt layers smoothly is obtained. at the same time, at last analyzed the effect of the deviation angle to the drilling in the salt layer, The conclusion is that when the overburden pressure is major principal stress, drilling mud density is certain, the creep rate increases with the increasing of the deviation angle, the safe mud density also increased, the high deviation angle directional well in salt layers is much more risky. The conclude makes great contribution to the optimizing deviation angle, designing well track and reducing the drilling troubles when drilling directional wells in the salt layer.

Improved subsalt images with least-squares reverse time migration

2017 ◽  
Vol 5 (3) ◽  
pp. SN25-SN32 ◽  
Author(s):  
Ping Wang ◽  
Shouting Huang ◽  
Ming Wang
Keyword(s):  
Least Squares ◽  
Field Data ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Lateral Velocity ◽  
Image Domain ◽  
Time Migration ◽  
Iterative Inversion ◽  
Velocity Variations ◽  
Subsalt Imaging

Complex overburdens often distort reservoir images in terms of structural positioning, stratigraphic resolution, and amplitude fidelity. One prime example of a complex overburden is in the deepwater Gulf of Mexico, where thick and irregular layers of remobilized (i.e., allochthonous) salt are situated above prospective reservoir intervals. The highly variant salt layers create large lateral velocity variations that distort wave propagation and the illumination of deeper reservoir targets. In subsalt imaging, tools such as reflection tomography, full-waveform inversion, and detailed salt interpretation are needed to derive a high-resolution velocity model that captures the lateral velocity variations. Once a velocity field is obtained, reverse time migration (RTM) can be applied to restore structural positioning of events below and around the salt. However, RTM by nature is unable to fully recover the reflectivity for desired amplitudes and resolution. This shortcoming is well-recognized by the imaging community, and it has propelled the emergence of least-squares RTM (LSRTM) in recent years. We have investigated how current LSRTM methods perform on subsalt images. First, we compared the formulation of data-domain versus image-domain least-squares migration, as well as methods using single-iteration approximation versus iterative inversion. Then, we examined the resulting subsalt images of several LSRTM methods applied on the synthetic and field data. Among our tests, we found that image-domain single-iteration LSRTM methods, including an extension of an approximate inverse Hessian method in the curvelet domain, not only compensated for amplitude loss due to poor illumination caused by complex salt bodies, but it also produced subsalt images with fewer migration artifacts in the field data. In contrast, an iterative inversion method showed its potential for broadening the bandwidth in the subsalt, but it was less effective in reducing migration artifacts and noise. Based on our understanding, we evaluated the current state of LSRTM for subsalt imaging.

New Analytical Model for Predicting the Unstable Zone Around the Borehole

SPE Journal ◽  
2014 ◽  
Vol 19 (06) ◽  
pp. 1177-1183 ◽  
Author(s):  
Mohamad Heidarian ◽  
Hossein Jalalifar ◽  
Mahin Schaffie ◽  
Saeed Jafari
Keyword(s):  
Numerical Methods ◽  
Plastic Zone ◽  
Numerical Solution ◽  
Analytical Model ◽  
Failure Criterion ◽  
Field Data ◽  
Drilling Mud ◽  
Underbalanced Drilling ◽  
Coulomb Failure ◽  
Coulomb Failure Criterion

Summary In this study, a new analytical model, which is computationally lower in cost than current numerical methods, is presented to calculate the radius of the plastic zone around the borehole in underbalanced drilling (UBD) to prevent borehole instability. With this model, it is also possible to analytically calculate the optimal drilling-mud weight, which is the amount of mud weight with no plastic zone. The presented model is based on the Mouhr-Coulomb failure criterion. The model can be used in both vertical and inclined wells and in poroelastic formations with anisotropic horizontal stresses. Predictions from the model provide a reasonable match to the field data and numerical solution results.

Application of Ultrasonic Anemometer Array to Field Measurements of the Downwash Flow of an Agricultural Unmanned Helicopter

2019 ◽  
Vol 62 (5) ◽  
pp. 1219-1230 ◽  
Author(s):  
Qing Tang ◽  
Ruirui Zhang ◽  
Chenchen Ding ◽  
Liping Chen ◽  
Min Xu ◽  
...  
Keyword(s):  
Velocity Field ◽  
Flow Velocity ◽  
Field Data ◽  
Radial Distance ◽  
High Accuracy ◽  
Unmanned Helicopter ◽  
Differential Gps ◽  
Forward Flight ◽  
Flow Velocity Field ◽  
Ultrasonic Anemometer

Abstract. Unmanned helicopters are widely used in agricultural spray applications; however, there is a lack of high-accuracy field data on the complex downwash flows caused by such helicopters to support efficient spraying. Therefore, we aimed to collect high-accuracy reference data by developing an ultrasonic anemometer array and related software to measure the downwash flow velocity field of a common agricultural unmanned helicopter (Copterworks AF-25B) during outdoor hovering and forward flight. Differential GPS and image scaling were used to determine the exact position and velocity of the helicopter to ensure repeatability of the tests. When the hovering height of the rotor above the ground plane was y/R = 2.5 (where y is the height above ground level and R is the radius of the rotor), the maximum downwash velocity reached 7 m s-1 at x/R = 0.5 (where x is the radial distance from the axis of the rotor). In addition, we obtained the spatial distribution of the turbulence kinetic energy. The attached flow velocity in the near-ground boundary layer increased radially and reached a maximum of 3 m s-1 at x = 3.6 m, after which it decreased. Comparatively, the maximum downwash velocity during forward flight occurred between x/R = 0.5 and 1.5 and was only about 3 m s-1, which was less than half the maximum downwash velocity while hovering. In addition, the circulation flow below the rotor tips had a velocity of 1.5 m s-1. The downwash flow lasted more than 1 s as the helicopter passed over a given point on the ground, the downwash velocity decreased from 3 m s-1 to 1.5 to 2.5 m s-1, and the symmetry of the flow field was not maintained. This study is the first application of an ultrasonic anemometer array to measure the airflow around an unmanned helicopter and provides high-accuracy field data that can be used as a reference for future indoor and simulation studies. Keywords: Agricultural unmanned helicopter, Downwash flow velocity field, Forward flight, Hovering, Ultrasonic anemometer.

3D velocity-independent elliptically anisotropic moveout correction

Geophysics ◽  
2009 ◽  
Vol 74 (5) ◽  
pp. WB129-WB136 ◽  
Author(s):  
William Burnett ◽  
Sergey Fomel
Keyword(s):  
Field Data ◽  
Azimuthal Anisotropy ◽  
Three Dimensions ◽  
Velocity Analysis ◽  
Lateral Velocity ◽  
Analysis Techniques ◽  
West Texas ◽  
Imaging Approach ◽  
Velocity Variations ◽  
Seismic Images

Azimuthal anisotropy or lateral velocity variations cause azimuthal variations in moveout velocity, which can degrade seismic images if handled improperly. In cases in which apparent azimuthally anisotropic moveout is present, a single picked velocity is inadequate to flatten an event on a 3D CMP gather. Conventional velocity-analysis techniques require a significant amount of time and effort, especially in areas where apparent anisotropy is observed. We propose a velocity-independent imaging approach to perform an elliptically anisotropic moveout correction in three dimensions. The velocity-independent approach relies on volumetric local traveltime slopes rather than aggregate velocities and therefore provides an azimuthally flexible description of traveltime geometries throughout the gather. We derive theoretical expressions for extracting the moveout slowness matrix and the angle between the symmetry and acquisition axes as volumetric local attributes. A practical inversion scheme to extract the same parameters is also developed. These parameters are used to solve for moveout slowness as a function of azimuth. Tests on a synthetic common-midpoint (CMP) gather show accurate results for the automatic moveout correction and the inversion scheme. A field data example from west Texas illustrates the application of the automatic moveout correction as a residual moveout.

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