MODELS FORRESERVOIR ESTIMATION

METHODSBy

Suhaib Mahmood SiddiqueTo

Engineer Hassan Abbas

HYDROCARBONS RESERVES ESTIMATION

• IGIP, Amount of gas present in reservoir we cannot recover 100% gas or oil from reservoir. Oil recovery is typically less than gas, synonym of IGIP for oil is IOIP.

• The recoverable amount is called reserves

TYPES

• Volumetric Reserves Estimation• Material Balance• Decline Curve Method• Reservoir Simulation

VOLUMETRIC RESERVES ESTIMATION

• Estimation of volume that would be recovered• IGIP / IOIP is estimated with the help of Eg / Bg. Total volume would be

obtained at surface conditions• Economics Estimated• If exploration is not being done on the formation before an analogous well

data from the same formation is assumed

ADVANTAGES AND LIMITATIONS

• Does not require production history• Static modeling of reservoir• Only method of reserves estimation

at exploration phase • In development phase, this method

provides checks on other HCs reserves estimations

• If there are some cracks or seepage, that permits the inflow into the reservoir , this method will not able to express it and the reservoir reserves would just be estimated

MATERIAL BALANCE METHOD

• Dynamic modeling• Depend purely on pressure , dynamic properties • This method require production history• Its results are valid after 10% decline of initial reservoir pressure• Also find reservoir drive mechanism • If drive mechanism of the reservoir is water drive then aquifer modeling

become necessary

DECLINE CURVE METHOD

• Require production data• Choke size must remain un changed • Producing mechanism must not alter• Three types of decline curves1. Exponential Decline 2. Hyperbolic Decline3. Harmonic Decline

Exponential Decline• Flow rate vs Time ( semi-log )• Flow rate vs Cumulative Production ( log-

log)

Hyperbolic Decline• Flow rate vs Cumulative Production ( semi-log)

Harmonic Decline• Does not show straight line on any log

RESERVOIR SIMULATION

• A complete model that resembles sub surface reservoir , physically with all properties and with all dynamics

• Can be done on exploratory well but better to do it with production history