Dealer tank wagon (DTW) sales Wholesale sales of gasoline priced on a delivered basis to a retail outlet. Decatherm Ten therms or 1,000,000 Btu. Decommissioning / Abandonment Removal of production equipment from depleted oil fields. Dedicated reserves The volume of recoverable, salable gas reserves committed to, controlled by, or possessed by the reporting pipeline company and used for acts and services for which both the seller and the company have received certificate authorization from the Federal Energy Regulatory Commission (FERC). Reserves include both company-owned reserves (including owned gas in underground storage), reserves under contract from independent producers, and short-term and emergency supplies from the intrastate market. Gas volumes under contract from other interstate pipelines are not included as reserves, but may constitute part or all of a company's gas supply. Deferred fuel costs An expenditure for fuel that is not recognized for bookkeeping practices as a cost in the operating period incurred, but carried forward to be written off in future periods. Deliverability Represents the number of future years during which a pipeline company can meet its annual requirements for its presently certificated delivery capacity from presently committed sources of supply. The availability of gas from these sources of supply shall be governed by the physical capabilities of these sources to deliver gas by the terms of existing gas-purchase contracts, and by limitations imposed by State or Federal regulatory agencies. Delivered (gas) The physical transfer of natural, synthetic, and/or supplemental gas from facilities operated by the responding company to facilities operated by others or to consumers. Demurrage The charge paid to the vessel owner or operator for detention of a vessel at the port(s) beyond the time allowed, usually 72 hours, for loading and unloading. Depleted storage field A sub-surface natural geological reservoir, usually a depleted gas or oil field, used for storing natural gas. Depth of deepest production The depth of the deepest production is the length of the well bore measured (in feet) from the surface reference point to the bottom of the open hole or the deepest perforation in the casing of a producing well. Derv Diesel Engined Road Vehicles. As Derv Fuel usually referred to as Diesel. Development Well Well drilled in order to produce oil and gas after an appraisal well has proved the reserves sufficiently large for exploitation. Diesel #1 and Diesel #2 Diesel #1 is also called kerosene and is not generally used as a fuel oil in diesel vehicles. Diesel #1 has a lower viscosity (it is thinner) than Diesel #2. Diesel #2 is the typical diesel vehicle fuel. Biodiesel replaces Diesel #2 or a percentage. Diesel engine/span> Named for the German engineer Rudolph Diesel, this internal-combustion, compression-ignition engine works by heating fuels and causing them to ignite. It can use either petroleum or bio-derived fuel. Diesel fuel A distillate of fuel oil that has been historically derived from petroleum for use in internal combustion engines. Can also be derived from plant and animal sources. Diesel, Rudolph German inventor famed for fashioning the diesel engine, which made its debut at the 1900 World's Fair. He initially intended for his machine to run on vegetable-derived fuels, with the hope that farmers would be able to grow their own fuel sources. Direct-injection engine A diesel engine in which fuel is injected directly into the cylinder. Directional Drilling Also known as deviated drilling; technique used in production drilling whereby wells are drilled at an angle from a central point so that a number of development wells can be drilled from a single drilling facility. Dirty Ballast Term applied to the sea water used for ballast when it is contaminated with the remnants or residue left in cargo tanks that previously carried crude oil or heavy persistent refined oils. Dirty products Refers to heavy oils such as crude oil or refined oil products such as fuel oil or bunker oil. Dogleg A deliberate or accidental sharp bend in a well. Downstream Usually refining and the marketing and distribution operations that occur after refining as opposed to Upstream. Downtime The time during which offshore operations cannot be continued owing to adverse weather conditions or other factors. Drill-bit The cutting head attached to the drill-pipe. Drill-Ship Free-floating, offshore drilling unit shaped like a ship, positioned by anchors of dynamic positioning. Drilling Muds or Fluid Fluid, containing barytes, which is pumped through the drill-string to the bottom of the well, whence it rises to the surface through the space between drill-string and bore-hole wall. It acts as a lubricant and is used to control flow. Dry hole Any exploratory or development well that does not find commercial quantities of hydrocarbons.