Advances in the hydraulic interpretation of water wells using flowmeter logs

[摘要] This paper reports on the methodology developed for a newhydraulic interpretation of flowmeter logs, allowing a bettercharacterization of continental hydrological basins. In the course of aflowmeter log, different flow stretches are established, mostly corresponding to permeable layers (aquifers), among which there are other stretches mainlycorresponding to less permeable layers (aquitards). In such hydrologicalbasins of sufficient thickness, these flow stretches may not have the samehydraulic head. This fact brings about the need for a new hydraulicinterpretation that provides the actual distribution of horizontalpermeability throughout the aquifer at depth. The modified hydraulicinterpretation developed in this study focuses on the differences of theeffective pressure gradient (considered the difference between the hydraulic head in the well and the hydraulic head of each stretch)experienced by the different flow stretches along the well, due to theexistence of different hydraulic heads. The methodology has been developedstarting from a water well located in a multilayered aquifer within theso-called Madrid basin (the north-western part of the continental basin of the Tagus River), located in the centre of the Iberian Peninsula. In this well, a step-drawdown pumping test was conducted, in which the pumping rate versusdrawdown and the specific capacity versus drawdown showed discrepancies withDarcian behaviour and an exponent of the Jacob equation of less than 1.Flowmeter logs were then recorded for different discharge rates and pumpdepths; the resulting water input from deeper permeable layers did notappear to show the expected relation with respect to drawdown. With theproposed methodology the results comply with the expected linearity and thecited discrepancies are solved.

[学科分类] 妇产科学