Separation of azimuthal effects for new-generation resistivity logging tools — Part 2

Geophysics ◽  
2011 ◽  
Vol 76 (3) ◽  
pp. F185-F202 ◽  
Author(s):  
Sofia Davydycheva
Keyword(s):  
Numerical Modeling ◽  
Visual Interpretation ◽  
Resistivity Measurements ◽  
Eccentricity Effect ◽  
Drilling Tools ◽  
Water Based ◽  
Rotation Technique ◽  
Logging While Drilling ◽  
Resistivity Logging ◽  
New Generation

Symmetrization/antisymmetrization of tensor resistivity measurements and data rotation technique enable separation of the formation response from the tool eccentricity effect in the borehole. Similar principles of data processing can be applied to tensor measurements acquired by both wireline and logging-while-drilling tools of the new generation. I show how to directly determine the bed boundary positions and the formation anisotropy azimuth and how to perform visual interpretation of raw tool data in the presence of the tool eccentricity. I study the tool behavior in conductive water-based mud boreholes — the situation that requires much more complicated numerical modeling than the case of resistive oil-based mud boreholes. I show when and how the tool eccentricity effect can be separated from the formation response. The separation technique can accelerate and improve existing methods of formation interpretation.

Separation of azimuthal effects for new-generation resistivity logging tools — Part I

Geophysics ◽  
2010 ◽  
Vol 75 (1) ◽  
pp. E31-E40 ◽  
Author(s):  
Sofia Davydycheva
Keyword(s):  
High Efficiency ◽  
Visual Interpretation ◽  
Eccentricity Effect ◽  
Induction Logging ◽  
Resistivity Anisotropy ◽  
Logging While Drilling ◽  
Resistivity Logging ◽  
New Generation ◽  
Lwd Resistivity ◽  
Further Development

A symmetrization approach used in new-generation logging-while-drilling (LWD) resistivity tools separates the dipping anisotropy and dipping boundary effects. It deals with couplings between axial transmitters and tilted or transverse receivers. I have investigated the performance of two symmetrization schemes in full 3D scenarios for LWD and rigorously extended them to triaxial induction logging, including couplings between transverse transmitters and transverse receivers. Thus, I apply similar principles of data processing to new-generation wireline and LWD tools. The method enables separation of the formation response from the borehole eccentricity effect, which cannot be ignored for triaxial induction. The technique can accelerate and improve existing methods of formation interpretation by directly determining bed boundary positions, formation anisotropy azimuth, and tool eccentricity direction and by improving visual interpretation of raw tool data. The second objective of my investigation was a brief review of previously published work on a 3D finite-difference (FD) modeling approach, its latest development and its ability to simulate responses of new-generation resistivity tools in general 3D formations. This approach, based on the Lebedev staggered FD grid, handles arbitrary resistivity anisotropy effectively. Its high efficiency encourages its routine use for modeling. In addition, the method enables simultaneous multispacing and multifrequency computing at no cost. It makes the detailed investigation and further development of the separation technique possible.

Development of a directional resistivity logging-while-drilling tool using a joint-coil antenna and its geosteering applications

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. D165-D171
Author(s):  
Zhong Wang ◽  
Huaping Wang ◽  
Treston Davis ◽  
Jing Li ◽  
Suming Wu ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Gas Production ◽  
Voltage Response ◽  
Drilling Tool ◽  
Detection Depth ◽  
Logging While Drilling ◽  
Resistivity Logging ◽  
Coil Antenna ◽  
Production Zone ◽  
Distance To The Boundary

Geosteering is a key technique to increase oil- and gas-production rates, especially within a thin reservoir layer. The purpose of geosteering in the production zone is to keep the drilling path in oil- and gas-bearing reservoirs. To keep the drilling system inside the production zone, downhole sensors must be able to detect bed boundaries, which include identifying the boundary location with respect to the sensor and the boundary distance from the sensor. We have developed a directional resistivity logging-while-drilling (LWD) tool for geosteering applications. The directional LWD tool is equipped with a joint-coil antenna composed of an axially polarized coil Rz connected in series with two transversely polarized coils Rx. During a revolution around the axis of the tool, the voltage of the axial coil VRz, voltage of the transverse coils VRx, and tool face angle [Formula: see text], which indicates the boundary direction, can be extracted through curve fitting the total voltage response of the joint-coil antenna. The distance to the boundary can be derived from a 1D inversion. The LWD tool has been tested in several reservoirs in China, and it has a demonstrated capability to provide reliable and accurate estimations of the boundary direction and distance. Field data indicate that the boundary detection depth can reach 2.1 and 1.7 m when the tool is in a sand and shale formation. Using wireline-logging data from surrounding wells as reference, deviations between the reference and the measured distance to the boundary are within 0.2 m.

A New Generation Environment Friendly Water-Based Drilling Fluid and Field Applications

2018 ◽  
Author(s):  
Qi Zhu ◽  
Yong Wang ◽  
Yongqing Zhang ◽  
Zhihe Sun ◽  
Yinghui Wei ◽  
...  
Keyword(s):  
Drilling Fluid ◽  
Environment Friendly ◽  
Water Based ◽  
New Generation

SOME EFFECTS OF FORMATION ANISOTROPY ON RESISTIVITY MEASUREMENTS IN BOREHOLES

Geophysics ◽  
1958 ◽  
Vol 23 (4) ◽  
pp. 770-794 ◽  
Author(s):  
K. S. Kunz ◽  
J. H. Moran
Keyword(s):  
Anisotropic Medium ◽  
Wide Class ◽  
Anisotropic Media ◽  
Resistivity Measurements ◽  
Potential Problems ◽  
Isotropic Media ◽  
Equivalent Problems ◽  
Resistivity Logging

It is shown that a wide class of potential problems involving anisotropic media can be transformed into equivalent problems involving only isotropic media. By means of such transformations it is possible, in a large number of cases, to determine the apparent resistivities which would be observed in anisotropic formations, using electrode‐type resistivity logging devices. Discussion is given of an infinite, anisotropic medium with and without borehole, of two semi‐infinite anisotropic beds (without borehole), and of a thin isotropic bed bounded by anisotropic adjacent formations (without borehole). An interpretation chart for the normal device is presented for thick, non‐invaded, anisotropic beds penetrated by a borehole.

Quantitative comparison of processes of oil- and water-based mud-filtrate invasion and corresponding effects on borehole resistivity measurements

Geophysics ◽  
2009 ◽  
Vol 74 (1) ◽  
pp. E57-E73 ◽  
Author(s):  
Jesús M. Salazar ◽  
Carlos Torres-Verdín
Keyword(s):  
Electrical Resistivity ◽  
Flow Rate ◽  
Water Saturation ◽  
Base Case ◽  
Petrophysical Properties ◽  
Resistivity Measurements ◽  
Fluid Saturation ◽  
Mud Cake ◽  
Water Based ◽  
Mud Filtrate

Some laboratory and qualitative studies have documented the influence of water-based mud(WBM)-filtrate invasion on borehole resistivity measurements. Negligible work, however, has been devoted to studying the effects of oil-based mud(OBM)-filtrate invasion on well logs and the corresponding impact on the estimation of petrophysical properties. We quantitatively compare the effects of WBM- and OBM-filtrate invasion on borehole resistivity measurements. We simulate the process of mud-filtrate invasion into a porous and permeable rock formation assuming 1D radial distributions of fluid saturation and fluid properties while other petrophysical properties remain constant. To simulate the process of mud-filtrate invasion, we calculate a time-dependent flow rate of OBM-filtrate invasion by adapting the available formulation of the physics of WBM-filtrate invasion. This approach includes the dynamically coupled effects of mud-cake growth and multiphase filtrate invasion. Simulations are performed with a commercial adaptive-implicit compositional formulation that enables the quantification of effects caused by additional components of mud-filtrate and native fluids. The formation under analysis is 100% water saturated (base case) andis invaded with a single-component OBM. Subsequently, we perform simulations of WBM filtrate invading the same formation assuming that it is hydrocarbon bearing, and compare the results to those obtained in the presence of OBM. At the end of this process, we invoke Archie’s equation to calculate the radial distribution of electrical resistivity from the simulated radial distributions of water saturation and salt concentration and compare the effects of invasion on borehole resistivity measurements acquired in the presence of OBM and WBM. Simulations confirm that the flow rate of OBM-filtrate invasion remains controlled by the initial mud-cake permeability and formation petrophysical properties, specifically capillary pressure and relative permeability. Moreover, WBM causes radial lengths of invasion 15%–40% larger than those associated with OBM as observed on the radial distributions of electrical resistivity. It is found also that, in general, flow rates of WBM-filtrate invasion are higher than those of OBM-filtrate invasion caused by viscosity contrasts between OBM filtrate and native fluids, which slow down the process of invasion. Such a conclusion is validated by the marginal variability of array-induction resistivity measurements observed in simulations of OBM invasion compared with those of WBM invasion.

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