Use of a New Rate-Integral Productivity Index in Interpretation of Underbalanced Drilling Data for Reservoir Characterization

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe prospect of dynamic reservoir characterization using flow and pressure data gathered during underbalanced drilling (UBD) is a powerful driver for implementation of UBD. The mathematical aspects of this complex, ill-posed, inverse problem have been the subject of research in the past decade. This paper focuses on practical, field implementation of UBD reservoir characterization, and the problems that consequently arise. Interpretation of data from UBD is made difficult by transducer errors, operational transients, and noise in data. It is therefore often very difficult to interpret the reservoir characteristics from the instantaneous productivity index (PI). In this paper, we introduce a parameter known as the Rate Integral Productivity Index (RIPI), which borrows from the theory of rate-transient analyses. The mathematical and physical basis of RIPI and its relationship to the instantaneous PI are presented. The behavior of RIPI and its implications for reservoir characterization are discussed. RIPI de-noises the data, and scales the problem such that the trends in data are more obvious, enabling robust interpretation of UBD data, and increasing the confidence in calls made regarding reservoir characteristics. Application of RIPI to field data is illustrated through several examples. Data acquisition, processing, and preparation for UBD reservoir characterization are discussed. In particular, the importance of filtering, de-noising, and identifying and excluding operationally induced transients is described. Limitations imposed by the data gathering methods are highlighted. It is shown that the ability of RIPI to reduce noise in raw PI data allows trends to be read more easily. The use of RIPI for static and dynamic characterization of supermatrix features (such as fractures, thief zones, etc.) is illustrated. The limitations of the approach and future trends are discussed.

Under-Balanced Drilling: A Game-Changing Technology for the Development Strategy of a Giant Carbonate Reservoir

“…It is this data that is used in the advanced analysis stage to construct the RIPI plot. Further details on the subject are noted in the references [4][5] . The application and results of this process from our field case will be provided in depth in the following section.…”

“…Several professionals investigated different methods to perform the analysis which are documented in the references [4][5][6] . The acquisition and interpretation of FWD data utilizing transient analysis techniques to estimate reservoir parameters play an integral role in enhancing the understanding of the dynamic nature of the reservoir.…”

“…This paper will explicitly describe the details of the last pilot drilled for well-X where Real-Time geosteering was actively used to account for changes in the reservoir architecture, as well as the successful application of "Real-Time Reservoir Characterization (RTRC)" process developed by Blade Energy Partners [4][5] . Description of the data analyses & results acquired will be presented, highlighting the significant value derived in terms of improving reservoir understanding and its impact on the projected field development strategy.…”

Coiled-Tubing Underbalanced Drilling Applications in the Lisburne Field, Alaska

“…The Rate-Integral Productivity Index (RIPI) approach described by Suryanarayana, et. Al 6 . was used to improve the ability to interpret UBD data.…”

Reservoir Characterization through Automatic History Matching of Underbalanced Drilling (UBD) Data in a Horizontal Well

“…Automatic history matching for surface oil rate is implemented to compute permeability by the use of a bottom-hole pressure as a constraint. Suryanarayana et al 11 developed a practical procedure for data gathering and interpretation of the UBD data using a rate-integral well productivity index.…”