Development of Unconventional Gas Resources: Stimulation Perspective

Abstract

Abstract Natural gas is an important global energy resource. In the last few years its consumption has increased significantly and being a cleaner fuel it is certain that in future it will play an ever increasing role in satisfying the increasing energy demand across the world. In order to meet the growing energy demand, exploration and production has increased across the world. However, due to the higher depletion rates of oil & gas reserves as compared to their discoveries, today the international energy sector is seriously thinking of developing unconventional energy resources, especially gas, so that the future energy needs can be met not only from an economic but also from reduced environmental impact point of view. Three such Unconventional gas resources are tight gas reservoirs, coalbed methane and shale gas. These resources hold great potential as a source of natural gas (e.g. USA has the potential of recoverable gas of about 350, 100 & 45 Tcf from tight gas resources, CBM and shale gas respectively) and at the moment extensive work is being done for the development of these resources across the world. But, to produce these resources (gases) economically and efficiently well stimulation plays a major role in achieving the optimal target production from these reservoirs. Unconventional gas reservoirs require the formation to be fractured by hydraulic means to improve the formation productivity by providing a conductive path and joining the existing fractures and cleats in the reservoir. The purpose of this paper is to discuss the role and effectiveness of different stimulation techniques in the development of unconventional gas resources. The improved stimulation has made a positive impact on the development of these resources which were considered uneconomical to produce due to lack of properly developed stimulation methods. Due to improved stimulation treatments, recovery from these resources has been enhanced greatly and producing gas from these unconventional gas reservoirs is far more economical and feasible than it was in the past. This paper presents a complete overview of the current scenario of unconventional gas resources and focuses on the fracturing stimulation techniques for the development of Unconventional gas resources. 1. Introduction Unconventional resources are one of the hot topics of debate in the international energy sector at the moment. At present, the rapidly growing energy demand worldwide and the higher depletion rates of existing reserves as compared to their discoveries are a major causes of gap between supply and demand. This situation of increasing gap between demand and supply has prompted the world to explore and develop unconventional resources of gas. However, the technological advancements, long-term potential, environmental benefits and attractive gas prices bring unconventional gas resources more rather than oil into the forefront of our energy future. At the moment the world is witnessing an increasing demand of gas and thus unconventional gas resources development has the focus of increased attention. In future, a significant percentage of the world's energy demands (especially North America) will be satisfied by the natural gas. Gas consumption will increase and it will be a key factor in the future economic performance and strategic stability of a nation. Furthermore, some experts believe that the consumption of gas will exceed that of oil by about 2025, this may also be confirmed by the reviewing the current gas consumption when put in consistent units of barrels of oil equivalent per day (BOE/D) 3 as shown in figure 1.