Updip. In an upward direction in a tilting formation.

Downdip. The direction going down the tilt angle of the formation.

Underground formations usually are not parallel to the surface of the ground. The term "dip" denotes the incline or slope of the formation. Updip therefore means located up the slope, and downdip is the antonym denoting the downward location. When a well is drilled, a dipmeter measures the tilt of the formation that is penetrated. From an observer's perspective, a specific point in the formation is said to be updip if it is higher and downdip if it is lower than the observer's reference point. This is relevant to hydrocarbon recovery because oil and gas tend to move higher in the formation, especially if there is water in the formation because oil floats on water.

In a conventional reservoir, a place that is higher in the formation (updip) is likely to have a greater accumulation of oil or gas and one lower in the formation (downdip) is likely to have less or none. In hydrocarbon reservoirs with oil, gas, and water, the gas is updip, the gas-oil contact is downdip from the gas, and the oil-water contact is even farther downdip. In non-conventional formations, the rock is tight and the hydrocarbons do not migrate at all or migrate slowly so whether you are updip or downdip is not as important.