Experimental Researches On The Characterizations Of Anisotropy And Kerogen Content In Organic-rich Shale

The primary focus of this dissertation is to improve the characterization of anisotropy and study the effects of kerogen content in organic-rich shale through multiple techniques,such as ultasonic measurements,rock physics model,microscopic methods,signal processing approaches and physical modeling.Shales compose a large part of the clastic fill in sedimentary basins and can be cap rocks of hydrocarbon bearing reservoirs.As unconventional reservoirs are increasingly targeted,organic-rich shales are realized as reservoir rock and contain a colossal energy resource.Shale normally exhibits strong seismic anisotropy,which often cause significant influences in the accuracies of time-to-depth conversion of seismic data,subsurface structure delineation by seismic imaging or tomography,amplitude variation with offset?AVO?analysis,and estimation of the in-situ stress or stress changes resulting from production.Besides many other factors influencing the properties of shale gas,kerogen is of particularly importance not only because it is indicative of gas-production potential,but also because of its unique velocity,density,and resistivity characteristics.The development of detailed physical relationships between kerogen content and elastic properites are key to improving unconventional exploration procedures and reservoir predictions.The main achievements can be summarized as follows.?1?In this dissertation,a total-angle ultrasonic test system was designed,which can measure the P-wave and S-wave velocities in the direction of any angle to the bedding plane easily and fast.Based on the comparisons and error analysis between the observations and theoretical curves,the Berryman's approximations were demonstrated to be most feasible to characterize the strong anisotropy of shale,and the range of application would be that both?and?exceed 25%.?2?Transducers-based and laser-based testing methods were conducted on to measure the group velocities of organic rich shale in all directons to the bedding plane.The observations proved the former one would be more applicable under normal conditions,thereby for higher accuracy of inverted Thomsen parameter?.Relative system error between the systems tend to be 2.76%.With the Berryman's approximated equations and boundary of?combination as well as the optimally measured observations,the accuracy of invertied?would be enhanced greatly.?3?In order to take full advantage of the laser ultrasonic measurements and avoid the SNR problem,I propose novel and effective approach?SOSVMF?for attenuating the strong erratic noise existing in the waveform data recorded from LUT measurement.Both synthetic and real waveform examples are used to show the superior performance using the proposed approach over the traditional median filtering approach.The anisotropic parameter?and elastic parameter C₁₃ that are estimated from the denoised waveforms by SOSVMF are demonstrated to be more accurate.?4?Practical workflows and pioneering experimental methodologies were proposed to construct the artificial organic-rich shale,which was based on a novelly presented hot-pressing technique.These samples compared well against a natural organic rich shale in terms of wave speed anisotropy and microscopic textures of both mineral grains and organic material.This good comparison suggests that the articifial shales do mimic well many of the characteristics of some natural shales.Subsequently,a set of 12 artificial shale blocks were manufactured in which only the proportion of organic material was varied from about 1%to 15%by weight.Laboratory measurement showed V_P/Vs ratio may be a practical tool to predicted kerogen content.