COMMON TERMS USED IN E&P INDUSTRY

There few terms associated with reservoir. These terms are often perplexing. Let’s try to decode them today-

a) GOR- Gas Oil Ratio-It is a volumetric ratio of gas produced at STP to that of oil produced at STP.

b) API gravity- Oil gravity is defined by API gravity.

API= 141.5/DENSITY-131.5

API for water is 10. API for heave curde oil is <25

API for a good crude oil is between 35-45

c) Consider following diagram to understand Dew point and bubble point

d) Wet Gas-Wet gas is a gas which is accompanied by larger fraction of hydrocarbon i.e. C2-C6. These higher hydrocarbons sell at premium price. Remember we gas does not mean accompanied by water.

e) Gas Condensate-

Gas condensates are valuable commodity and there is an incentive to extract them while producing gas. Thus reservoir pressure is so maintained in order to keep these condensates above dew point. Once all the condensates have been produced, gas is produced.

f)    Wobbe Index-It is a measurement of the quality of gas. It is defined as-

Energy Density/(Relative density of the gas)^0.5

WI has advantage over calorific value as heating per unit varies with density. All the contracts of gas are done in terms of WI.

g) Solution Gas- The gas dissolved in the oil is called solution gas. The ratio of volume of gas dissolved per volume of oil is GOR.

h) Dip- The earth’s sub surface is not purely horizontal in layers. The angle sub surface layers make with horizontal is called dip.

i)     Permeability-  It is the way in which pores of rocks are connected  to each other. Better the permeability better the oil and gas reservoir since extraction will be easier.

j)     Porosity- It is the carrying capacity of the rock or in other words how much liquid or gas a reservoir can hold. More the porosity  better is the reservoir.

k)  Isochore- a line connecting areas which are formed at the same time.

l)     Isopach- a line connection areas of same thickness.

m)                 PVT analysis- Once the field has been producing, the pressure and temperature changes which drastically change the fluid properties of the reservoir. Thus, a thorough knowledge of reservoir condition id required to effectively produce from the reservoir. So a study of Pressure, Volume and Temperature (PVT) of the reservoir fluids have to be done in order to make field development plan.

Skimming – It is separation of water from oil.

Stripping-Removal of heavy hydrocarbons from oil and gas via separators mainly