WorldWide Drilling Resource

44 JULY 2018 WorldWide Drilling Resource ® Frequently-Used Geological Terms Part 72 Glossary Adapted from the Dictionary of Geological Terms P Producing Zone - The rock stratum of an oil field which will produce petroleum or gas when pen- etrated by a well. Often incorrectly referred to as producing horizon. Profile Section - A diagram or drawing showing along a given line, the configuration or slope of the surface of the ground as it would appear if intersected by a vertical plane. The vertical scale is often exaggerated. Propylite - An andesitic rock resembling greenstone and consisting of such minerals as calcite, chlorite, epidote, serpentine, quartz, pyrite, and iron oxides. It results from hydrothermal alteration. Proration - Restriction of gas and oil production by a regulatory commission, usually in anticipation of market demand. Prospect - An area which is a potential site of mineral deposits, based on preliminary exploration. This term is also used to describe an area which has been explored in a preliminary way, but has not given evidence of economic value. A prospect is distinct from a mine in that it is nonproducing. Prospecting - Searching for economically valuable deposits of fuel or minerals. Prospect Pit - Any hole, pit, shaft, or tunnel made for the purpose of prospecting mineral-bearing ground. Protoclastic - Said of igneous rocks in which the earlier formed crystals have been broken or deformed due to differential flow of the magma before complete solidification. Said of an igneous rock containing deformed xenocrysts (crystals in an igneous rock not derived from the original magma). Protodolomite - A crystalline calcium-magnesium carbonate with a disordered structure, in which the metallic ions occur in the same crystallographic layers instead of in alternate layers as in the mineral dolomite. Proved Reserves - Reserves of metallic and nonmetallic minerals, as well as gas and oil, for which reliable quantity and quality estimates have been made. Proven Reserves - Oil which has been discovered and determined to be recoverable, but is still in the ground. Proximal - An ore deposit formed adjacent to a volcanic feature to which it is genetically related and from which its constituents have been derived. Also said of a sedimentary deposit consisting of coarse clastics, formed nearest the source area. Look for more terms next month! A pyroclastic flow can sometimes contain large pieces of pumice. WWDR photo of pumice from Hess Pumice in Malad City, Idaho. G&O