Underbalanced Drilling Experience in PDO

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.

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“…al. 12 give examples of value of UBD data interpretation to well performance. Finally, Gauthier, et.…”

Section: Introductionmentioning

confidence: 99%

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

Suryanarayana

Kennedy²,

Vaidya³

et al. 2007

Proceedings of Production and Operations Symposium

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Determination of Water–Producing Zones While Underbalanced Drilling Horizontal Wells—Integration of Sigma Log and Real–Time Production Data

Gauthier¹,

Hussain²,

Bowling³

et al. 2007

SPE Middle East Oil and Gas Show and Conference

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe paper presents a novel logging approach used to identify water producing zones while under-balanced drilling (UBD) horizontal wells. This approach will work in mixed-wet reservoirs and is particularly attractive for mature reservoir undergoing waterflooding.The logging process consists of a standard logging-whiledrilling (LWD) data acquisition followed by a pulse neutron capture run (PNC). The PNC data is acquired after pumping the tool inside the drillpipe to total depth (TD). The LWDresistivity and PNC-sigma measurements are used to calculate completely independent oil saturation curves. This additional information is important for non-water-wet reservoirs because a separation between the resistivity and sigma-derived oil saturation will indicate a flushed zone. The separation is due to what is called resistivity hysteresis and is well documented in the literature and observed in the laboratory for this reservoir.The logging information is complemented with real-time production data which provides a pseudo-inflow log of water and oil inflow intervals along the horizontal wellbore. The pseudo-inflow log is used to validate if saturation differences correlate with water production.The approach is made possible because the wells are drilled under-balanced meaning that, during the drilling process, the reservoir pressure is always higher than the pressure in the wellbore. This pressure differential avoids drilling fluid invasion into the formation, which is necessary for shallow nuclear logging and allows the reservoir to flow for real-time production characterization.Results from eleven UBD wells show that a positive correlation exists between inflow of water and separation between the resistivity and sigma-derived oil saturation. This is in agreement with the resistivity hysteresis concept.This application can become important for projects developing mixed-wet reservoirs especially during the infill drilling or waterflood phases. The PNC logging operations takes between 6 and 12 hours and can be adapted with minimal incremental cost to most UBD operations.

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Underbalanced Drilling Experience in PDO

Abstract: TX 75083-3836, U.S.A., fax 01-972-952-9435.

Cited by 2 publications

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

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

Determination of Water–Producing Zones While Underbalanced Drilling Horizontal Wells—Integration of Sigma Log and Real–Time Production Data

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