Proppant Free Fracturing Technique for Production Optimization in Tight Gas Reservoirs — An Overview
Chaturvedi, Kanupriya *1
(1) Applied Petroleum Engineering, University of Petroleum and Energy Studies, Dehradun, India.
Tight gas refers to natural gas reservoirs locked in extraordinarily impermeable, hard rock, making the underground formation extremely "tight. “and its permeability below or equal to 0.01md.It is a promising resource because of its inherent association with conventional hydrocarbon systems.
The challenges are
1. When Very Low Permeability Matrix and Limited Fracture Penetration is encountered.
2. Formation Damage is very high
3. Limited Productivity
4. When water saturation is very high no mobile water phase is observed.
5. It becomes difficult to obtain dynamic reservoir properties and to characterize the gas reserves.
Situation becomes more complicated when heavy minerals like pyrite and siderite are present
The noticeable perspectives in India appear to be the Bhuvanagiri Formation (permeability of 0.033mD) and Mandapeta sandstone(permeability of 0.01mD) in the Cauvery and Krishna-Godavari basins respectively.
The Albian Andimadam sandstone (Cauvery Basin), The Mukta and Bassen formations(Mumbai offshore basin) have been considered as tight reservoirs also in India
Applying proppant free fracturing technique to stimulate tight gas reservoirs is the newest technology. It has been recognized as shear dilation induced by elevated fluid pressure. This paper discusses the mechanism of proppant free fracturing technique, advantages, limitations and candidates for proppant free technique.
During fluid injection, the pressure is elevated inside a natural fracture, and thus the stress distribution around the fracture changes. Beyond a threshold pressure, rock material around the fracture fails by sliding instead of opening the sliding of two rough fracture surfaces (shear slippage) dilates an aperture normal to the fracture surface. There exists a threshold stimulation fluid pressure above which permeability of stimulated fractures increases rapidly with increase in fluid pressure. The overall reservoir permeability is the combined effect of numerous dilated fractures Thus; creation of a large volume of reservoir by relatively low stimulation pressure could make the proppant free stimulation a viable alternative to conventional massive hydraulic stimulation from both technical and economical stand point.
AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain