Characterizing Average Permeability in Oil and Gas Formations

Abstract

Permeab~i!y in.a f?~tio~ fr~~ently follows a unim~ p~obability distribution. In many formations, particularly sedimentary ones, the permeabIhty dIstrIbutIOn IS sImIlar to the log-normal dIstnbution. Theoretical considerations field cases and a reservoir simulation example s~~w t~at ~e ~ed~an, rather ~an the arithmetic mean, is tlte appropriate measure of ~entral tend~ncy or average ~alue of tlt~ pe~eablh~ dIstrIbutIon In a formatIOn. Use of tlte correct estimate of average permeability is of particular importance In the claSSIficatIOn of tIght gas formations under statutes in tlte 1978 Natural Gas Policy Act (NGPA).

Effects of Flow Measurement Errors on Oil and Gas Production Forecasts

“…Some of the parameters used in the simulators to build the reservoir model are the measured characteristics of reservoir fluids and rocks, and these are normally determined by taking samples from the wells. However, since reservoirs are inexorably heterogeneous in their characteristics, the characteristics of the fluid and core samples taken in a limited number of wells are not representative of the average characteristics of the reservoir [13]. Consequently, reservoir engineers assess the precision of the simulation results against the measured production data of the reservoir to make sure if the simulated model represents the actual reservoir properly.…”