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Abstract
In acidizing long intervals in heterogeneous formations, almost all the injected acid will flow into high permeability streaks. As a result, low permeability zones or zones of high skin factor will not be stimulated. Several diverting systems were developed over the last few years. In-situ gelled acid is one of these systems, which is used in carbonate reservoirs. In-situ gelled acids consist of an acid soluble-polymer, cross linker, buffering agent, breaker and corrosion inhibitor. This acid has a viscosity of 20-30 mPa.s. when injected in the well, its viscosity increases to 1,000 m.Pa.s and when the acid reacts with the carbonate its pH reaches value of 2. Previous studies showed that this works in the field. However, recent laboratory results indicated that there are short comings for this acid, an extreme care should be taken when using this acid. The objective of this study is to have better understanding of this acid system and its limitations. This study aims to study the rheology of the in-situ gelled acid, investigate the effect of hydrogen sulfide and other contaminants, and also examine the in-situ gelled acid performance with the corrosion inhibitor and finally study the effect of different cross linker on the gel performance.
In acidizing long intervals in heterogeneous formations, almost all the injected acid will flow into high permeability streaks. As a result, low permeability zones or zones of high skin factor will not be stimulated. Several diverting systems were developed over the last few years. In-situ gelled acid is one of these systems, which is used in carbonate reservoirs. In-situ gelled acids consist of an acid soluble-polymer, cross linker, buffering agent, breaker and corrosion inhibitor. This acid has a viscosity of 20-30 mPa.s. when injected in the well, its viscosity increases to 1,000 m.Pa.s and when the acid reacts with the carbonate its pH reaches value of 2. Previous studies showed that this works in the field. However, recent laboratory results indicated that there are short comings for this acid, an extreme care should be taken when using this acid. The objective of this study is to have better understanding of this acid system and its limitations. This study aims to study the rheology of the in-situ gelled acid, investigate the effect of hydrogen sulfide and other contaminants, and also examine the in-situ gelled acid performance with the corrosion inhibitor and finally study the effect of different cross linker on the gel performance.
In acidizing long intervals in heterogeneous formations, almost all the injected acid will flow into high permeability streaks. As a result, low permeability zones or zones of high skin factor will not be stimulated. Several diverting systems were developed over the last few years. In-situ gelled acid is one of these systems, which is used in carbonate reservoirs. In-situ gelled acids consist of an acid soluble-polymer, cross linker, buffering agent, breaker and corrosion inhibitor. This acid has a viscosity of 20-30 mPa.s. when injected in the well, its viscosity increases to 1,000 m.Pa.s and when the acid reacts with the carbonate its pH reaches value of 2. Previous studies showed that this works in the field. However, recent laboratory results indicated that there are short comings for this acid, an extreme care should be taken when using this acid. The objective of this study is to have better understanding of this acid system and its limitations. This study aims to study the rheology of the in-situ gelled acid, investigate the effect of hydrogen sulfide and other contaminants, and also examine the in-situ gelled acid performance with the corrosion inhibitor and finally study the effect of different cross linker on the gel performance.