Numerical Simulation and Modeling of a Laboratory MWD Mud Siren Pressure Pulse Propagation in Fluid Filled Pipe By M. A. NAMUQ, M. REICH and A. AL-ZOUBI* Abstract This article presents modeling and numeri- cal simulations of a laboratory mud siren pressure pulse propagation in a water filled pipeline. The unsteady flow behavior is sim- ulated and modeled with ANSYS CFX11 (Computational Fluid Dynamics (CFD) commercial code). Time domain simulations were performed for three different carrier frequencies of the mud siren, and the results were also analyzed in frequency using a Fast Fourier Transformation code in MATLAB. The estimated results from the model are compared with real experimental data in both time and frequency domain in order to validate the model. A pretty good agreement is obtained between the predicated and mea- sured pressure pulses at different locations along the pipeline for all experimental runs. 1 Introduction Modern bottom hole assemblies are equipped with various sensors, which mea- sure the geological and directional informa- tion of the borehole while drilling. It is very crucial to get the measured downhole infor- mation to the surface in order to be able to monitor, steer, and optimize the drilling pro- cess while drilling. The transmission of the information to the surface is most com- monly carried out by coded pressure waves (pulses), which propagate through the drill- ing mud inside the drill string toward the sur- face. The telemetry system, which uses pres- sure waves (mud pulses) for carrying downhole information, is called a mud pulse telemetry system. The mud pulse telemetry is available in three varieties positive, nega- tive and mud siren. The information is trans- mitted by the mud siren using waves with specific frequencies (carrier frequencies), which are not overlapping with the dominant noise frequencies in the mud channel. The development of a reliable method, which can simulate dynamic pressure pulse transmis- sion behavior in fluid filled pipe, would lead to considerable improvement of the perfor- mance of the existing mud pulse telemetry systems and the development of an innova- tive pulse telemetry system in the future. In this article, the numerical simulation and modeling results of a laboratory mud siren signal propagation with various carrier frequencies in water filled pipeline are presented. A brief description of the experimental setup was published in a previous article [1]. 2 Experimental Setup The flow loop which is schematically shown in Figure 1 was built up to study the effects of pressure wave propagation in drill strings in the laboratory. The pulser section (length 0.6 m) and a connection pipe of 4.6 m length ahead of the pulser are made of a slightly larger pipe diameter than the rest of the flow loop, which has an ID of 57 mm. The pipe used for the setup is made of PVC (Polyvinyl Chloride), its maximum operating pressure is 10 bars. The mud siren pulser is connected to the flow loop at a distance of 38.86 m from the pump. The pressure in the pipe is measured at four different locations by using pressure sensors (called P1, P2, P3, and P4) which are attached to the pipe at 4.5, 19.5, 38.51, and 39.89 m distance from the pump’s discharge respectively. 2.1 Mud siren pulser The mud siren pulser consists of a stator plate and a rotor plate, each having 4 lobes, as illustrated in Figure 2. The total length of the mud siren pulser is 269.5 mm. It is placed inside a double trans- parent pipe. The distance between the stator and rotor plates is fixed to 1 mm to avoid friction. The rotor plate is connected to an electrical motor shaft. Continuous positive pressure pulses are produced as the rotor closes and opens the open spaces in the stator. The maximum pressure in the flow loop is reached each time the massive rotor fingers completely close the open spaces of the stator. In contrast, the pressure will be at its minimum value when the open spaces of the rotor are in line with the open spaces of the stator. 2.2 Wave speed measurement To determine the speed of pressure waves under the laboratory conditions, the flow loop was equipped with a positive pulser, which consists of a double acting pneumatic cylinder with a continuous piston rod (Fig. 3). A maximum air pressure of 9 bars is used to move the moving part of the pulser by 5 mm into the restriction ring as shown in Figure 3B and back to its original position as shown in Figure 3A. With each restriction of OIL GAS European Magazine 3/2012 OG 125 DRILLING 0179-3187/12/III © 2012 URBAN-VERLAG Hamburg/Wien GmbH * Mohammed A. Namuq, Matthias Reich, Institute of Dril- ling Engineering and Fluid Mining, TU Bergakademie Frei- berg; Ahmad Al-Zoubi, Institute of Fluid Dynamics, Helm- holtz-Zentrum Dresden-Rossendorf e. V., Dresden, Germa- ny (E-mail: Mohammed-Ali.Namuq@student.tu-freiberg.de). Fig. 1 Scheme of the laboratory flow loop [1]