Browsing by Author "Liu, Richard C."
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Item Complex Image Theory and Applications in Boundary Detection in Geo-Steering Using Data from a Directional Resistivity LWD Tool(2014-05) Wang, Jing; Liu, Richard C.; Wilton, Donald R.; Jackson, David R.; Holley, Thomas K.; Malki, Heidar A.Geo-steering is the process of controlling and adjusting the direction of the drilling bit in a horizontal or deviated well, in real time to keep the drilling in the desired zone. One of the most challenging steps of Geo-steering is the boundary detection, which is to calculate the distance from the bit to upper or lower boundary based on the measured data from an LWD tool. Generally, calculating the distance from bit to boundary is an inversion problem. To speed up the inversion process, a fast forward modeling algorithm is critical. In this study, the Complex Image Theory applied in finite conductivity layered media is derived to speed up the forward modeling of the geo-steering system. Two approximation results are shown in detail in dealing with the two general cases of dipole radiation. The first one is when the dipole is placed in the relative high resistive layer. The second one is when the dipole is placed in the relative high conductive layer. The algorithm is tested in both two-layer and three-layer cases and in high deviated well. Compared with the results from the full solution (the result from INDTRI), the Complex Image Theory has satisfactory accuracy and when the number of logging points is 600,000, it is 160 times faster. Error only exists in area two ft. or three ft. away from boundary. By considering the power of real source, the possibility of real application is investigated. The tolerance in different frequencies, spacing and conductivity combinations is discussed too. The simulation results show that the Complex Image Theory works in most geo-steering situations. The proposed method reduces the simulation time and improves the real-time performance of the control system. The distance inversion is developed for two-layer formation. The inversion results show that the algorithm works well even at the position 10 ft. away from the boundary. The anti-noise capacity of the propose method is measured by further involving random white noise in the simulation scenario. The relative error of simulation is as low as 5% in the area six ft. away from the boundary. With higher conductivity contrast formation, the proposed method is even more robust.Item Simulation of Triaxial Induction Tool Response in Biaxial Anisotropic Formation(2014-12) Zhou, Mengsu; Liu, Richard C.; Wolfe, John C.; Malki, Heidar A.; Davydycheva, SofiaA fast 1D electromagnetic method for simulating triaxial induction tool responses is used to model the field distribution in fractured anisotropic formations. Fractures are a specific feature of geological formations. Using the bucking coil technique, we interpreted the simulation results as apparent conductivity of the formation and modeled the practical wireline induction tool response. The method is validated versus other independent modeling software. Multiple examples are presented to compare the apparent conductivity of transversely isotropic and biaxial anisotropic formations. Sensitivity to anisotropic conductivity, bed boundaries, dip angle and layer thickness were observed, which proves that the failure to consider the biaxial anisotropy would have great impact on the interpretation of triaxial induction tool responses. We discuss particular features which enable visual log interpretation for the presence of possible fractures.Item Study of Dielectric Constant Logging Tools(2012-08) Lin, Chang-Ming; Liu, Richard C.; Wilton, Donald R.; Malki, Heidar A.One of the important issues of well logging is to determine the water saturation from the oil bearing formation. The induction resistivity tool may finish the job if the water is fairly saline. In fresh water, the induction tool is difficult to figure out the exact water saturation and oil/gas contents. Therefore, it is crucial that there be a method to determine water saturation that is less dependent upon the knowledge of water salinity thus making it of great use in fresh water zones. Dielectric constant logging tools offer an attractive new method of formation evaluation, which is relatively independent of water salinity. In this thesis, a dipole model is developed in that it consists of three infinitesimal dipoles: one for the transmitter and the other two for the receivers. The model, then, is used to simulate the dielectric constant tool responses by measuring the amplitude ratios and phase shifts in both homogeneous and inhomogeneous layered formation. The results show a good agreement with the experimental data and theoretical results published in previous studies. Moreover, the numerical results portray that the dipole model accurately provides a decent estimation of the formation dielectric properties compared to other models.Item Study of Dielectric Tools and Dielectric Property of Rocks(2014-12) Zhang, Yinxi; Liu, Richard C.; Wilton, Donald R.; Jackson, David R.; Holley, Thomas K.; Malki, Heidar A.Dielectric tools have mainly been used for identifying freshwater zones in oil- or gas-bearing formations. New-generation dielectric tools are also used for detecting shale reservoirs, heavy oil, and residue oil in invasion zones. However, currently commercialized tools either lack information on frequency dispersive behavior or offer redundant logging curves. This dissertation investigates both the design and simulation of novel array dielectric tools; meanwhile, it throws light on the dielectric properties of rocks through lab measurements. A multi-component, multi-spacing array dielectric tool working at 5 different frequencies in the range of 10 MHz to 1 GHz was studied. It covered the frequency gap between propagation tools and conventional dielectric tools. Tool sensitivity was carefully investigated to demonstrate tool capability in exploring formation properties, including permittivity, conductivity, dipping, and anisotropy. Meanwhile, tool simulations with COMSOL provided comprehensive evaluations of tool performance. From the simulation results, it was found that the size of the tool pad has an influence on tool response, especially when lower frequency channels are fired. However, the impact from borehole mud can be negligible since the tool is pushed against the borehole wall. Moreover, the existence of mud cakes and invasions affect the measurements and depth of investigation of the tool as well. In addition, vertical resolution was studied for different formation conditions. The designed tool was proven to be able to detect thin conductive beds or beds with high dielectric constants. In the past few decades, dielectric dispersion has been observed from core data. Practical core measurements for dielectric constant and conductivity were also conducted in this dissertation to study the dielectric properties of sediment rocks. A parallel plate system was used for the study. The relative dielectric constant and conductivity were measured in a frequency range from 10 KHz to 1GHz. Measured data agreed well with the resistivity log inversion results, and large dielectric enhancement at the induction frequencies was observed. Dielectric and conductivity corrections were applied to the original log to correct the errors caused by dielectric dispersions. The results lead to the conclusion that dielectric correction should be added to the resistivity inversion routine to avoid misinterpretation.Item Study of Downhole Electromagnetic Boundary-Detection Methods Using Numerical Simulations(2014-05) Gong, Bo; Liu, Richard C.; Wilton, Donald R.; Jackson, David R.; Holley, Thomas K.; Malki, Heidar A.Logging-while-drilling (LWD) technology has been used as a real-time aid in directional drilling. In this dissertation, a full investigation is conducted on the use of LWD resistivity tools in geosteering, especially the application in detecting remote bed boundaries. By looking into the electromagnetic field of multiple tool configurations using numerical simulations, an independent evaluation is provided on the downhole boundary detection capability of different resistivity logging tools, as well as their applicability in various drilling environments. In order to explore the potential of predicting formation properties in front of the drill bit, tool responses are first modeled with different downhole electromagnetic transmitters in homogeneous formation, where ahead-of-the-bit field distribution is investigated. Field attenuation rates are compared among different tools, and the influence of borehole conductivity is studied. Next, tool responses are modeled in two-layer formation models to evaluate their boundary detection capabilities. Look-ahead capabilities are compared between tools with axially symmetrical antennas when boundaries are perpendicular to the tool axis. Also, the feasibility of using cross-component measurements to detect horizontal boundaries is studied for tools using orthogonal antennas. After that, the deep-looking capability of a new directional resistivity tool using ultra-long spacings and low frequencies is explored. Tool responses for different configuration parameters and drilling environments are calculated and discussed. At last, an inversion algorithm based on the Gauss-Newton method is developed to recover the boundary distance from the tool response. This dissertation presents a comprehensive summary for the first time on the use of LWD resistivity tools in predicting formation anomalies ahead of or around the drill bit. It is found that the conventional resistivity logging tools using axially symmetrical antennas can only penetrate the formation ahead of the bit by a limited range, which is restricted by the borehole dimension and power supplies, but a deep-looking capability can be acquired by using cross-component measurements in high angle and horizontal wells. The detailed comparisons between tools of different types establish a missing link in the research of deep resistivity logging tools, and provide a natural guide for the future development of downhole boundary detection methods.Item Study of Time Domain Logging Tools Using Finte Difference Time Domain Method(2013-05) Yu, Boyuan 1985-; Liu, Richard C.; Vipulanandan, Cumaraswamy; Wilton, Donald R.; Charlson, Earl J.; Malki, Heidar A.In the well logging industry, before designing any kind of logging tools, the tool response needs to be simulated and analyzed in different circumstances. Those kinds of logging tools can be generally categorized into two main genres: frequency domain tools and time domain tools. This dissertation presents a numerical way to simulate the time domain tool response. The 3-D finite difference time method is employed in this dissertation. In this dissertation I used 3D FDTD method to simulate the logging tools response in complicated logging circumstance to see how the response will appear with different formation. A few examples were included in this dissertation and shown very decent results. As it is known that the frequency is set relatively low so the tool can detect further when dealing with well logging problems. In order to improve the efficiency of the entire simulation process, two main techniques are introduced in this dissertation: perfectly matched layer boundary conditions and artificially high dielectric constant. With those techniques combined together, the specific tool (Look-Ahead time do main logging tool) response is studied such as the distance to bed boundary response, sea-bed logging tool response, and reservoir effect. With those cases study in detail, the response patterns are investigated while the formation parameters are varied. One thing that needs to be pointed out is that the source excited in all the examples through this dissertation is a Differential Gaussian wave with different maximum operating frequency chosen based on different needs and different examples.