An Integrated Efficient Approach To Perform IPTT Interpretation

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractInterval Pressure Transient Testing (IPTT) with an advanced formation tester has been widely applied to measure vertical and horizontal permeabilities. The principles behind IPTT may appear straightforward. But the interpretation of IPTT in complex reservoirs, such as carbonates presents many challenges, most of which are related to uncertainties arising from the heterogeneous nature of such reservoirs.A novel, generally applicable approach is proposed for interpretation of IPPT tests. The approach is integrated and efficient, and ensures that the most probably valid and/or valuable information is used and revealed by IPTT. The approach standardizes the complete interpretation procedure of IPTT in a heterogeneous reservoir, using if available, modern wireline logs (such as NMR and Imaging), dynamic data from wireline formation testers and any other relevant information (such as geological description, core data and local knowledge) as constraints on the interpretation. IPTT is also a multi-layer testing technique. An iterative method to define layering is incorporated in the approach to determine the most probable layering. Many types of possible information that can be used to constrain layering definition are classified. Principles and guidelines on using different sources of information to define and refine the layering are recommended. An advanced regression technology is used to get optimized horizontal and vertical permeabilities of reservoir layers. The key is to find as much useful information as possible to guide the regression. To this end, different sources of permeability are classified and used as initial estimates, for input to the regression. Practical skills to perform IPTT regression are also summarized. In many cases, the operating sequences of the formation tester are primarily designed for downhole sampling rather than IPTT. The complicated downhole sampling sequences can make the pressure responses of gauges complicated and noisy. Hence, a Quality Check (QC) procedure is also included into this integrated approach.Examples from a carbonate reservoir are presented * Trademark of Schlumberger