Shhh, you are in the library ... no talking allowed. Nevertherless, from the Encyclodpedia Britannica, we read "anhydrite, an important rock-forming mineral, anhydrous calcium sulfate (CaSO4). It differs chemically from gypsum (to which it alters in humid conditions) by having no water of crystallization. Anhydrite occurs most often with salt deposits in association with gypsum, as in the cap rock of the Texas-Louisiana salt domes. Anhydrite is one of the major minerals in evaporite deposits; it also is present in dolomites and limestones, and as a gangue mineral in ore veins. It is used in plasters and cement as a drying agent. Anhydrite crystals possess orthorhombic symmetry"
This is the caprock mineral in most of the Belizean oilfields. In nature it occurs when large saline playas or reef protected benches slowly evaporate in the sun... one of the "facies" or environments producing a variety of minerals at any point in time as you draw a line across a beach inspecting the rocks nature is forming over time. These environents shift back and forth over one another, time and again, creating columns of carbonate or silicate sands, capped with anhydrite, which eventually trap the oil we are looking for. When the coastal geology subsequently deforms the hydrocarbons percolate through the porous sand and reef rock to produce little concentrations or hydrocarbons, hopefully up and down that old beach front, which in this case streches from the ancient sedimentary deposits of the Maya Mountains far out to sea. Pray for two or three layers of anhydrite in the litholgy we drill through near Monkey River (or wherever it is we first spud-in). And that is your geology lesson for the day. Class dismissed. Good Luck and Good Driling Treaty ... though today is hopefully a "new day" for our operations in Texas. Goooooo Texas.
