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Odorant: (1) A substance, such as a mercaptan, that is added to odorless natural gas and natural gas liquids; gives them a characteristic smell and thus enables them to be detected. (2) Substance (e.g., mercaptan) added to odorless natural gas or NGLs to enable detection. Odorizing: A process whereby an additive is injected to natural gas to provide a readily perceptible odor at a very low concentration in air as a warning indication of the presence of natural gas. Also called “stenching.” OEG: See Oil equivalent gas. OEMs: See Original equipment manufacturers. Off-Load (Shipping): Discharge of cargo from a ship. Off-Pattern Well: A well outside the normal drilling/production pattern. Off-Peak Gas: Natural gas supplied during periods of relatively low system demands. Offset Well: (1) A well drilled on the next location to the original well. The distance from the rst well to the offset well depends upon spacing regulations and whether the original well produces oil or gas. (2) A well drilled on one tract of land to prevent the drainage of oil or gas to an adjoining tract where a well is being drilled or is already producing. (3) A well drilled next to another. Sometimes refers to neighboring wells of different operators. Offshore Oil Loading Nomenclature: Single buoy mooring (SBM), singlepoint mooring (SPM), exposed location single buoy mooring (ELSBM). Offshore Platform: A xed, moored, or dynamically positioned platform for hydrocarbon production or handling operations offshore. Offshore Reserves and Production: Unless otherwise indicated, reserves and production that are in either state or Federal domains, located seaward of the coastline. Offshore Well: A well that has its wellhead location offshore, either on a platform or on the sea ¤oor as a subsea well. Off-System Supply: Natural gas supply purchased from an entity other than the delivering pipeline or local distribution company. Offtake Point: The point in a natural gas distribution system where natural gas is taken by supply pipe to a major customer. Ofgem: The UK regulatory body that oversees electricity and gas trade, pipelines, and the power grid. Located in London. Combines the former Offer and Ofgas regulators. OFOs: See Operational Žow orders. OFP: Open ¤ow potential. OGIP or OGP: See Original gas in place. OGLV: See Operating gas lift valve. OGP: International Association of Oil and Gas Producers. OH: See Open hole. OHFP: Open-hole frac pack. Frac packing in an open hole. OHGP: Open-hole gravel pack. Ohm: (1) Electric unit of resistance. One ohm is the resistance through which a potential of one volt will maintain a current of one ampere. (2) The unit of

measurement of electric resistance. One ohm of resistance will allow one ampere of current to ¤ow through a pressure of one volt. Ohm’s Law: E = IR, I = E/R, or R = E/I; the current “I” in a circuit is directly proportional to the voltage “E” and inversely proportional to the resistance “R.” Oil: (1) A mixture of liquid hydrocarbons of different molecular weights. (2) A liquid hydrocarbon. See Crude oil. Oil and Gas Leases: A contract between an oil operator and a landowner that gives the operator the right to drill for oil and gas on his property for a consideration. It is simply a “ticket to hunt.” Oil-Based Mud: A mud in which the external, liquid phase is oil. Oil behind the Pipe: Refers to oil and gas sands or formations knowingly passed through, never produced. Such formations usually were of low permeability (tight formations) that, say, 20 years ago, were uneconomical to produce when oil was around $5 or less a barrel. Other times, formations would be purposely ignored because the operator was going deeper for bigger game, so the less-spectacular, plain-Jane sands were cased off. When the price of crude oil reached $30 per barrel, the bypassed formations looked pretty good and were opened up and produced. Oil Column: Vertical thickness of an oil accumulation above an oil/water contact. Oil-Cut Mud: Drilling mud with which crude oil has been unintentionally mixed. This may occur when drilling into or through an oil-bearing formation whose pressure is sufcient to overcome the pressure or weight of the column of mud in the hole. Oil also may become mixed with the drilling mud when a drill-stem test is taken. Oil Emulsion: A mixture of oil and water in which the oil is permanently suspended in the water in the form of very small droplets or vice versa. Oil Emulsion Mud: A predominately oil phase drilling mud with trace water (<10%) as an additive or a contaminant. Oil as the continuous or external phase. Note: Special cleanup and dispersants are needed before displacing with brine or treating with acids. Oil Equivalent Gas: See Barrel of oil equivalent. Oil Field: A geographic area under which an oil reservoir lies. Oil Field Services: The support services involved in constructing, stimulating, producing, and repairing a well. Oil Gravity: The most widely used indicator of a crude oil’s worth to the producer is its API gravity. Normally, the price that a producer receives for his oil depends on its gravity, the less dense oils (higher API gravity) being the most valuable. This price schedule is based on the premise that the lighter oil contains higher percentages of the more valuable products such as gasoline. API gravity (degrees) = (141.5/sp. gr.) − 131.5. Oil in Place: (1) Estimation of real amount of oil in a reservoir. Higher value than recoverable reserves of reservoir. (2) Crude oil estimated to exist in a eld or a reservoir; oil in the formation not yet produced. (3) An estimated measure of the total amount of oil contained in a reservoir and, as such, a

higher gure than the estimated recoverable reserves of oil. (4) The oil in place at any time in the reservoir. Oil-in-Water Emulsion: A common oil eld emulsion where oil droplets (the internal phase) are suspended and surrounded by the water (the continuous or external phase). Oil Jar: A jarring tool, capable of very large impacts that is cocked and then triggered by oil moving through an orice. Oil Pool: A porous rock reservoir that contains oil. Oil Run: The oil production or transfer during a specic time period. Oil Sand: (1) Payzone, usually produces oil in economic quantities. (2) A deposit of sand saturated with bitumen. Oil Saturation (Reservoir): The fraction of the porosity of a zone occupied by oil. Oil Saver: A seal arrangement on top of a wire line lubricator that prevents the loss of oil or gas to the atmosphere. Oil Shale: A mudrock or mudstone, composed of a large amount of kerogen or similar deposit, which will yield oil only when rened. Oil/Water Contact: Local boundary between the oil and the bottom water. OW contact may vary in the eld depending on individual drawdowns and local variations in vertical permeability. Oil Well (Casinghead) Gas: Associated and dissolved gas produced along with crude oil from oil completions. Oil Wet Rock: Rock coated with an oil in direct with the rock and attracted by natural surfactant properties. Oil Zone: A formation from which oil might be produced. OIM: Operations installation manager. OIP: See Oil in place. OIW: Oil in water. OJ: See Oil jar. OJT: On the job training. Oleate Ion: The oleate ion is one of the most common soaps, being derived from triolein, a component of olive oil.