Formation Damage in Tight Gas Reservoirs

Abstract The increased demand for more sources of clean energy such as natural gas from unconventional reservoirs has forced the industry to explore the more challenging tight gas reservoirs. Tight gas reservoirs constitute a significant proportion of the world's natural gas resource and offer great potential for future reserve growth and production. However, to meet future global energy demand, access to tight gas reservoirs requires innovative and cost effective technical solutions. Yet, tight gas reservoirs are often characterized by complex geological and petrophysical systems as well as heterogeneities at all scales. Exploring and developing tight gas accumulations are both technically and commercially challenging due to the large subsurface uncertainty and low expected ultimate recovery per well. In addition, formation damage is an undesirable operational and economic dilemma that may occur during any phase of gas recovery from tight gas reservoirs. Tight gas reservoirs normally show significant damage during well drilling, completion, stimulation and production. Therefore, they may not flow gas at optimum rates without advanced production improvement techniques. The main damage mechanisms and the factors that have significant influence on well productivity in tight gas reservoirs include mechanical damage to formation rock, plugging of natural fractures by mud solid particles invasion, relative permeability reduction around wellbore as a result of filtrate invasion, liquid leak-off into the formation during fracturing operations, water blocking, damage due to wellbore breakouts, compression damage and the damage associated with perforation. Drilling and fracturing fluids invasion mostly occur through natural fractures and may also lead to serious permeability reduction in the rock matrix that surrounds the natural or hydraulic fractures. Prevention, control and remediation of formation damage are among the most important issues to be resolved for efficient exploitation of tight gas reservoirs. Designing certain chemicals and/or treatment procedures for damage control and remediation is not an easy scientific and engineering task. Good understanding of the formation damage mechanisms would allow operators to make informed decision as to the best practices to drill, complete and produce tight gas wells. In this paper, a review of commonly practiced methods and tools available for prevention, control and remediation of formation damage will be discussed and presented.