کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6409316 1629911 2016 16 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Research papersDepth-discrete specific storage in fractured sedimentary rock using steady-state and transient single-hole hydraulic tests
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
Research papersDepth-discrete specific storage in fractured sedimentary rock using steady-state and transient single-hole hydraulic tests
چکیده انگلیسی


- Literature values for specific storage include large values for all types of rock.
- Accurate T values are essential for determining S from single-hole hydraulic tests.
- Leakage can cause error in S derived from a hydraulic test.
- Ss from 32 different hydraulic tests in sandstone range from 2.9 × 10−7 to 7.9 × 10−5 m−1.

A method is presented for obtaining depth-discrete values of specific storage (Ss) from single-hole hydraulic tests in fractured rock boreholes using straddle packers (1.5-17 m test intervals). Low flow constant head (CH) step tests analyzed using the Thiem method provide transmissivity (T) values free from non-Darcian error. Short-term, constant-rate pumping tests (0.5-2 h) analyzed using the Cooper-Jacob approximation of the Theis method provide S from the hydraulic diffusivity using the Darcian T value from the CH step test. This synergistic use of two types of hydraulic tests avoids the common source of error when pumping tests (injection or withdrawal) are conducted at higher flow rates and thereby induce non-Darcian flow resulting in the underestimation of T. Other errors, such as well bore storage and leakage, can also substantially influence S by causing a shift in the time axis of the Cooper-Jacob semi-log plot. In this approach, the Darcian T values from the CH step tests are used in the analysis of the transient pumping test data for calculating S throughout the pumping test using the Cooper-Jacob approximation to minimize all of the aforementioned errors, resulting in more representative S values. The effect of these non-idealities on the measured drawdown is illustrated using the Theis equation with the Darcian T and S values to calculate drawdown for comparison to measured data. The Ss values for tests in sandstone obtained from this approach are more consistent with confined aquifer conditions than values derived from the traditional Cooper-Jacob method, and are within the range of field and lab values presented from a compilation of literature values for fractured sandstone. (10−7-10−5 m−1) This method for obtaining Ss values from short-interval, straddle packer tests improves the estimation of both K and Ss and provides opportunity to study their spatial distribution in fractured rock.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Hydrology - Volume 542, November 2016, Pages 756-771
نویسندگان
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