It is known that around the world there remain thousands of trillions of cubic feet of natural gas that could be produced to supplement the world's energy supplies. However, these particular gas resources are contained in low permeability (1mD to 1ěD) and are very difficult to develop. Well stimulation techniques are required in order to achieve economic production rates. The high costs involved in offshore operations make the development of these resources particularly challenging in the UKCS. Thus the permeability range for developable ‘Tight gas’ reservoirs differs significantly between the UK and US.
There is a considerable volume of literature addressing long-term gas forecasting of tight gas reservoirs by analytical techniques. These primarily take the form of decline curves and/or diagnostic plots as illustrated in SPE Papers 25909 and 26178.
Recent published analytical techniques have commonly been developed on the basis of reservoir homogeneity and ‘tank’ material balance behaviour. The SPE Paper 25909 provides full details of such an approach. The validity of the material balance equation in Tight gas reservoirs has been questioned in the literature (References).
If a Tight gas reservoir performance is such that it;
then the validity of assuming ‘tank’ material balance behaviour warrants investigation.