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Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Hydraulic Fracture and Natural Interface Interaction in Tight Gas Sweet Spots
(1) Petroleum Engineering, Curtin University of Technology, Perth, WA, Australia.
Tight formations are considered as those with low porosity and permeability. Large volume of hydrocarbons is proven in the tight formations in the US and also tight gases largely exist in such formations in Australia. Producing hydrocarbon from tight formations are not economical using conventional methods. Hydraulically induced fractures are known as one of the most effective method of stimulation in tight formations. However, fracturing operation in tight formation needs special care comparing to conventional formation: this is due to the different mechanical properties of tight formations.
In this paper, firstly, the influencing parameters in initiation and propagation of a hydraulic fracture including formation and fluid properties and in-situ stresses are introduced and a sensitivity analysis are performed to determine the impact of each parameter on fracturing process. To do this, analytical formulae developed based on elastic and poro-elastic approaches were used. The sensitivity analysis was repeated again this time considering tight formation properties in the formulae. This allowed the most effective parameters in fracturing into a tight formation to be identified and the interaction between different parameters to be studied. Also, the transition of a fracture once it passes a tight to another formation was studied.
In the second part of this work, the above analyses were carried out numerically using HFRANC3D software. The software allows studying the effect of changing formation and fluid properties as well as in-situ stresses. In general, the results are in agreement with those obtained from analytical solutions however, in some instances the numerical approach appears to provide more accurate results than analytical solution.
The results of this study indicated that fracture toughness and stress ratios are the two important parameters to be considered in fracturing tight formations.