Tight Gas Reservoirs

Low Permeability Reservoirs

The main contributor of unconventional gas in the US

By definition any reservoir with a permeability of.1 md or less is a tight gas reservoir.

Defined by the NGPA of 1978

This is matrix permeability

Most have much less perm, .01 or less

Not all tight gas reservoir act the same

Very low matrix perm w/ natural fractures

low matrix perm wo/ natural fractures

Gas shales used to be listed as tight gas

By Definition Tight-Gas Reservoirs are Anisotropic.

.1 md Permeability will not produce economically.

Formation must be Naturally Fracturedand/or

Hydraulically Fractured

Which gives them directional Permeability.

Kmax

Kmin

Drainage in an Anisotropic Reservoir

Traditional Methods for finding Anisotropy

Oriented CoresBest method to find direction of anisotropy

Multi-well Interference TestsCan find values for Kmax and Kmin Also the direction

The low perm makes these test very hard to run unless the spacing is very tight

Alternative Methods for finding Anisotropy

Find Keff & Kmin

Then use

minmaxKKKeff

Methods to optimize production in Tight-Gas Reservoirs

Horizontal Drilling Regional Fractures Multi staged Frac Jobs

Infill Drilling All Reservoirs with large spacing

From a presentation 11 years ago

Within the next 10 yearsgas demand in the United States will increase from 21 tcf to 30 tcf of gas annuallyToday the U. S. Produces 18 tcf of gas annually