Hydrogeologic Factors Influencing Well Yields in Folded and Faulted Carbonate Rocks in Central Pennsylvania

Hydrogeologic factors influencing well yields in folded and faulted Cambro‐Ordovician carbonate rocks and shales were investigated in central Pennsylvania. Productivity values (in gallons per minute per foot of drawdown per foot of saturated thickness) were obtained from 80 wells, the geometric mean value being 19.00, and were grouped into various categories according to well location. Productivities for the various categories were ranked and plotted against the percentage of wells on logarithmic probability paper. Parametric and nonparametric statistical tests were applied; the results of the nonparametric tests are presented. Fracture trace wells were more productive than nonfracture trace wells. Accidentally located fracture trace wells were as productive as intentionally located fracture trace wells because the accidentally located wells were clustered in more productive rocks. The success ratio of accidentally locating a fracture trace well is 4:6. Wells in sandy dolomite and coarse‐grained dolomites were the best producers; wells in valley bottoms were more productive than those in valley walls and uplands; anticlinal wells were better producers than synclina wells; and wells in beds dipping at less than 15° had higher yields than others. The Upper Sandy dolomite member and the Nittany dolomite have similar aquifer characteristics, which are significantly different from those of Bellefonte dolomite, limestones, and shales.