Comparative analyses of pumping tests conducted in layered rhyolitic volcanic formations

- Multilayer formation models with linear cross flow are applied.
- The vertical and radial formation heterogeneities are elaborated.
- Drawdown induced flow in observation borehole is simulated.

SummaryThe rhyolitic volcanic formations are modeled as multilayer flow systems composed of high permeability fractured zones separated by less permeable depth intervals referred to as matrix zones. The multilayer or linear cross flow model is applied which considers lateral flow in all units. The vertical cross flow between the model layers is calculated as the product of the head difference and the vertical inter-layer conductance. The axi-symmetrical well flow simulation software WT (i) applies either analytical or numerical drawdown simulators in the formation, (ii) assumes uniform well bore drawdown conditions in the pumping wells, and (iii) considers drawdown driven induced flow in the observation well. The interpretation of the pumping-recovery test in the well Megyaszó K-9 (Hungary) includes 7 low permeability and 6 screened water yielding zones and applies analytical method to compute the formation response. The benchmark Drill Hole Wash pumping test (Nevada) with pumped and monitoring open boreholes involves 5 fracture and 8 matrix zones. The radial formation heterogeneity is approximated by the bi-zonal flow domain and numerical method is used for drawdown simulation in the formation. Appropriate agreement with the measured drawdown data (both tests) and flow logging data (Drill Hole Wash) is achieved. Computer aided calibration is used for the parameter estimation. The results of the presented evaluations are compared with outputs of independent analyses.