TY - THES

T1 - Evaluation of acid stimulations

AU - Janiczek, Peter

N1 - embargoed until null

PY - 2008

Y1 - 2008

N2 - The objective of this thesis was to identify critical parameters which influence acid stimulations and formation damage. This master thesis is based on the work of Chavez [1]. The first part of this thesis deals with technical analyses and economical considerations. It was tried to work out a heterogeneity index using gamma ray data and spontaneous potential logs. A simple approach to describe this value was developed by introducing the standard deviation. Fluid losses, productivity indices and the production scenarios with a description of the workovers and pertinent information were plotted versus time in order to trace the origin of the formation damage and determine factors controlling the success of acid stimulations. In several cases, increasing the gross rate also resulted in an increase of sand production. In other cases high fluid losses during the workover caused a rising water cut. It was found out that in some wells the treatment pressures may have exceeded the fracture gradient of the formation. It was further noted that the documentation and nomenclature for the workover database is not standardized. Additional stimulations, which were monitored online, were analyzed. The method for calculating the bottomhole pressure derived by Chavez [1] could be verified. The correlation could be improved by accounting for friction pressure losses in the surface line by using the equivalent length concept. An economical evaluation of the stimulation treatments was performed by calculating the pay out time. About half of the analyzed wells were economic successes. The laboratory work comprises two series of experiments: The first one demonstrated that two polymeric mud components were equivalent in terms of formation damage. The other showed that acidizing plugs from a shaly sandstone with 15 % hydrochloric acid resulted in most cases in a reduction of permeability or even in collapse of the plugs.

AB - The objective of this thesis was to identify critical parameters which influence acid stimulations and formation damage. This master thesis is based on the work of Chavez [1]. The first part of this thesis deals with technical analyses and economical considerations. It was tried to work out a heterogeneity index using gamma ray data and spontaneous potential logs. A simple approach to describe this value was developed by introducing the standard deviation. Fluid losses, productivity indices and the production scenarios with a description of the workovers and pertinent information were plotted versus time in order to trace the origin of the formation damage and determine factors controlling the success of acid stimulations. In several cases, increasing the gross rate also resulted in an increase of sand production. In other cases high fluid losses during the workover caused a rising water cut. It was found out that in some wells the treatment pressures may have exceeded the fracture gradient of the formation. It was further noted that the documentation and nomenclature for the workover database is not standardized. Additional stimulations, which were monitored online, were analyzed. The method for calculating the bottomhole pressure derived by Chavez [1] could be verified. The correlation could be improved by accounting for friction pressure losses in the surface line by using the equivalent length concept. An economical evaluation of the stimulation treatments was performed by calculating the pay out time. About half of the analyzed wells were economic successes. The laboratory work comprises two series of experiments: The first one demonstrated that two polymeric mud components were equivalent in terms of formation damage. The other showed that acidizing plugs from a shaly sandstone with 15 % hydrochloric acid resulted in most cases in a reduction of permeability or even in collapse of the plugs.

KW - Säurestimulation Formationsschädigung Laborversuche zu Säurestimulationen und Formationschädigung

KW - Acid Stimulation Formation Damage Laboratory Research for Acid Stimulation and Formation Damage

M3 - Master's Thesis

ER -