Optimal Energy Transfer Pipe Arrangement for Acoustic Drill String Telemetry
Drill string acoustic telemetry is an effective transmission method to retrieve downhole data. Finite-difference simulations produce the comb-filter-like channel response (patterns of pass bands and stop bands) due to the presence of coupling joints in the metallic drill string. Practical pipes used for drilling deep wells have slight variation in length. The selection and arrangement of downhole pipes is important for improving the transmission efficiency of extensional waves transmitted through the drill string. Downhole drill string channel is studied using the transmission coefficients calculated from the transmission matrix method, and the resultant transfer function produces identical results similar to the finite-difference simulations. Reciprocity of the drill string structure is proved by comparing the pass band responses using the ascend-only (AO) and descend-only pipe arrangements. Transferred energies calculated up to 180 pipes of random length at the end of the drill strings using transmission coefficients for the three different pipe arrangements, namely, AO, descend-then-ascend, and ascend-then-descend (ATD), are compared to find the optimal pipe arrangement for single measurement. For the situations when pipes are distributed in sets, multiple measurements are required. In this paper, two sets of AO and two sets of ATD arrangements are analyzed for multiple measurements. ATD and nxATD arrangements are proposed as optimal pipe arrangements to produce the best possible telemetry performance in terms of optimal acoustic energy transfer via one- and two-way acoustic communication for single and multiple measurements, respectively.
Using Transfer Matrix Method to Study the Acoustic Property of Drill Strings
Using the drill string to transfer the telemetry data is a focus in the fields of logging while drilling (LWD) and measurement while drilling (MWD). The acoustic property of the drill string is the foundation for improvement the transmission rate. In this paper, we study the filtering property of the drill string using the transfer matrix (TM) method. Compared with the classical finite difference (FD) method, the TM method need not deduce the partial difference equation (PDE) and thus can be extended to the cases of torsional and flexural waves easily. Numerical experiments show that the TM method can give more precise results than the FD method, which indicates its potential for further applications
Exopolysaccharide biosynthesis and related enzyme activities of the medicinal fungus, Ganoderma lucidum, grown on lactose in a bioreactor
Exopolysaccharide (EPS) production and biosynthesis were studied in Ganoderma lucidum, a fungus used in traditional Chinese medicine, grown with lactose in a bioreactor. β-Galactosidase activity, which implies the existence of a lactose permease system, was induced by lactose. Lactose feeding also increased α-phosphoglucomutase activity and EPS accumulation but decreased phosphoglucose isomerase activity and lactate concentration in the culture broth. A maximum cell density of 22 g l−1 and EPS at 1.25 g l−1 were obtained in fed-batch bioreactor culture.