In the continuous search for Hydrocarbon and Geothermal resources in the earth, wells are drilled for various purposes. Wildcat, Appraisal, Production and Injection wells are drilled for proper field development and operation. Based on the purpose and plan for the wells, trajectory and targets are defined. During drilling, continuous monitoring of trajectory, rock and fluid characteristics are required to achieve defined objectives. Measurement while Drilling (MWD) and Logging while Drilling (MWD) systems are included as part of the Bottom Hole Assembly (BHA) to perform continuous measurement and transmission of downhole data to the surface. Measured data are converted to binary form and transferred to the surface for further processing and interpretation. Several methods of data transfer are possible albeit with various pros and cons. Currently, the most widely used method of transfer still remains the Mud Pulse Telemetry (MPT) system which makes use of the mud (drilling fluid) within the system for transmission of data. The major focus of this research was to further expand the envelope in the research towards increasing data transmission rates using the mud siren, a form of mud pulse telemetry. This research includes practical investigations which was conducted within the unique Flow Loop Laboratory at the Institute of Drilling and Fluid Mining, TU Bergakademie Freiberg. Within the research, minor adjustments were made to the flow loop facility to align with realities expected on the Rig. Effects of the changes made were evaluated and presented. The pulser section of the flow loop was also redesigned and new mud sirens manufactured to allow for the practical investigation in series and parallel. The major concept for increasing data transmission rate investigated in this research is the Multifrequency Mud Siren transmission in series and parallel. Following up with previous research, simulation of the flop loop scenario using ANSYS CFX was done to allow for numerical evaluation of the multifrequency transmission concept. Simulation runs were performed with various scenarios both in series and parallel, results evaluated and analyzed thereafter. A little mention on the amplification theory was also investigated and results shown. For the practical experiments, the pulser section was redesigned to allow investigations both into the series and parallel conditions for multifrequency transmission. Various experimental flow runs were successfully performed, observations recorded, data analyzed using MATLAB and results discussed. In closing, a conceptual design that contributes towards the possible field application of the Multifrequency transmission concept was developed. The Compact Double Multifrequency Siren concept was designed to aid easier adaptation of the Multifrequency transmission concept both in series and parallel.:Table of Contents Declaration ii Abstract iii Acknowledgements v List of Abbreviations vi List of Symbols viii Table of Contents x 1. Introduction 1 2. Literature Review and Fundamentals 5 2.1. Historical perspective 5 2.1.1. Introduction 5 2.1.2. Mud Pulse Telemetry 6 2.1.3. Telemetry drill pipe 7 2.1.4. Electromagnetic telemetry 7 2.1.5. Acoustic Telemetry 8 2.2. Mud Pulse Telemetry devices 9 2.2.1. Positive Pulser 9 2.2.2. Negative Pulser 10 2.2.3. Mud Siren 11 2.2.4. Oscillating Shear Valve 12 2.3. Modulation Techniques for Data Transmission 13 2.3.1. Baseband Transmission 13 2.3.2. Passband Transmission 15 2.4. Signal Transformation and Processing 16 2.4.1. Fourier Transformation 17 2.4.2. Short time Fourier Transformation 17 2.4.3. Continuous Wavelet Transformation 18 2.5. Summary of Previous Research Work on the Flowloop 19 3. Flowloop setup and current changes 21 3.1. Description of Flowloop 21 3.1.1. General overview of Flowloop 21 3.1.2. Pulser Prototypes 25 3.2. Improvement in Flow Loop Set-Up 28 3.2.1. Pump Change Justification 28 3.2.2. Pump replacement 35 3.2.3. Analysis of Pump Replacement 36 4. ANSYS Modelling and Simulation of the Multi Frequency Mud Siren in Series and Parallel 47 4.1. Basics of Numerical simulation with ANSYS CFX 48 4.2. Mesh Generation and Quality 51 4.3. Modelling 53 4.4. CFX-Pre Set-up and Post view 54 4.5. Flow Simulation Results in Series and Parallel 57 5. Laboratory Investigation on the Multi-Frequency Mud Siren Concept 64 5.1. Experiment Background and setup 64 5.2. Laboratory Practical Results and Analysis 68 5.2.1. Series Transmission Test 1: Single Siren vs Double Siren, Same Frequency 69 5.2.2. Series Transmission Test 2: Double Siren, Multi Frequency 72 5.2.3. Series Transmission Test 3: Double Siren, Multi Frequency Data String Transmission 75 5.2.4. Parallel Transmission Test 1: Single Siren vs Double Siren, Same Frequency 79 5.2.5. Parallel transmission test 2: Double siren, multi frequency 82 5.2.6. Parallel transmission test 3: Double siren, multi frequency Data String Transmission 84 6. Discussion on the Multi-Frequency Mud Siren Simulation and Practical Results 89 6.1. Result Discussion 89 6.2. Challenges and Sources of Errors 93 7. Outlook 100 7.1 Future Work (Compact Multifrequency Mud Siren) 100 7.2 Recommendations 106 8. Conclusion 107 9. References 111 10. List of Figures 114 11. List of Tables 120 12. Appendix 121