Sweet spot is an informal expression for a target location that represents the best probable production enable wellbores to be placed in the most productive areas of the reservoir. 

How do we select our best places to drill?

We need to explain the whole system; we need to go beyond finding high-quality reservoir. Commerciality of gas is generally associated with areas of enhanced reservoir quality, known as ‘sweet spots’.

These are areas of enhanced porosity and permeability thought to be controlled by:

1)                  Depositional trends of enhanced porosity and permeability; 

2)                  Enhanced natural fracturing, hence increased permeability; or 

3)                  Over pressuring and improved reservoir properties in a pressure compartment. 

Identification and mapping of sweet spots can be facilitated by advanced 3D seismic mapping techniques and detailed reservoir characterization.

For accurate sweet spots identification the following key risk factors are needed to be calculated

Key Geological Factors

TOC & Maturity

Thickness & Areal extent

Lithological heterogeneity, porosity

Fractures

Gas content (free + adsorbed)

Key Engineering Factors

Permeability

Reservoir Pressure

Gas composition & Geomechanics

Stimulation effectiveness

Well performance

Key Economic Factors

Gas Price

Access to gas market

CAPEX & OPEX

Environmental factors

Tax incentives & lease terms 

The following are examples for sweet spots in fractured basement and carbonate reservoirs