--> ABSTRACT: Application of Geochemical Modeling to Formation Damage with an Example from South Texas, by A. C. Riese, W. C. Riese, and J. P. Laplante; #91030 (2010)

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Application of Geochemical Modeling to Formation Damage with an Example from South Texas

A. C. Riese, W. C. Riese, J. P. Laplante

The tendency to form carbonate scale during production of fluids from a formation has traditionally been expressed with coefficients derived from the Stiff-Davis equation. The application of this index to descriptions of the higher temperature and pressure reservoirs being encountered today, however, is inappropriate and may lead to erroneous conclusions: the assumptions inherent in the calculation are not adequate in describing reservoirs much hotter than 100°F-150°F.

We have successfully applied more rigorous geochemical modeling techniques to the description of reservoirs in the 250°F to 350°F range. The thermodynamic basis to our calculations is an extended Debye-Huckel relationship and van't Hoff or Kirchhoff expressions; employment of these equations in the geochemical characterization of reservoirs yields a more accurate picture of scaling tendencies than can be accomplished through the Stiff-Davis or similar approaches. It also allows consideration of more than carbonates: silicates and sulfates may also form as scales and these are specifically addressed in our approach.

The relative merits of both approaches is illustrated by investigation of an example from the Texas Gulf Coast. The reservoir temperatures encountered were beyond the range in which Stiff-Davis should be applied and the geochemistry of the system more complex than could be addressed with that approach.

The results of our geochemical modeling yielded considerably different results and allowed a more effective well treatment to be chosen.

We recommend that this approach to reservoir description be pursued prior to completion in any high-temperature reservoir from which water may be produced. This may help predict the tendency to form irreparable scale damage and may eliminate the application of costly clean-up procedures where the geochemistry of the system will render them ineffective.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.