Transfer function modelling, which is a statistical technique used to relate a dependent or output variable to one or more independent or input variables when there may be time lags between inputs and output, is used in this study to examine the dynamic relationships between the turbidity of the surface water of Lake Eppalock with the inflows from its tributary streams and rainfall. The formulation of transfer function models is considered first, then single-input and finally double-input models are given. Single-input models are identified using the sample cross-correlation function. The problems caused by correlated input series are overcome by identifying the double-input models with a biased regression technique. Akaike's Information Criterion is used to choose between competing models. The results indicate that the turbidity of the lake is mostly explained by the inflow from the Coliban River and the rainfall in the vicinity of the dam. We conclude that the catchment of the Coliban River and the foreshore of the lake are the most important regions affecting the turbidity of its surface waters.
This paper was prepared for the Second Annual European Meeting of the Society of Petroleum Engineers of AIME, to be held in London, England, April 2–3, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract A new test system for floating vessels uses annulus pressure control to operate down-hole valves. A nitrogen-charged test valve senses the change in annulus pressure to provide positive well control at all times. A correction system is included to provide reliable operations over a wide range of pressures and temperatures. A sampling chamber is available with a complete set of accessory tools for safe testing. The results of field testing are included. Introduction A drill stem testing system for floating vessels has been introduced in the rough conditions of the North Sea and has given satisfactory results in this environment. The system uses a Pressure controlled Test Valve known as Pressure controlled Test Valve known as the PCT valve. When pressure is applied to the annulus (in excess of the hydrostatic pressure), the test valve opens. The valve recloses when the pressure is released. This allows the operator to conduct a test with the minimum of pipe manipulation. This avoids the problems of trying to position down-hole tools accurately while the vessel is moving up and down due to wave action. The system includes a complete line of accessory equipment to provide positive well control through redundancy of all valve functions, to ensure that the reservoir can be adequately tested in complete safety. EQUIPMENT AND OPERATION Tool System The heart of the system is the Pressure controlled test (PCT) valve. Pressure controlled test (PCT) valve.
Intervention analysis is a rigorous statistical modelling technique used to measure the effect of a shift in the mean level of a time series, caused by an intervention. A general formulation of an intervention model is applied to water-quality data for two streams in north-eastern Victoria, measuring the effect of drought on the electrical conductivity of one stream, and the effect of bushfires on the flow and turbidity of the other. The nature of the intervention is revealed using exploratory data-analysis techniques, such as smoothing and boxplots, on the time-series data. Intervention analysis is then used to confirm the identified changes and estimate their magnitude. The increased level of electrical conductivity due to drought is determined by three techniques of estimation and the results compared. The best of these techniques is then used to model changes in stream flow and turbidity following bushfires in the catchment.
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