Borehole Stability Assessment Using Quantitative Risk Analysis

Ottesen, Steinar; Zheng, Ronghui; McCann, Roger C.

doi:10.2118/52864-ms

Cited by 29 publications

(8 citation statements)

References 5 publications

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“…Borehole stability, hydraulics, and hole cleaning are therefore clearly coupled and, for this reason, cannot be studied individually or assessed in isolation. These challenges led to the development of a new approach that exploits detailed understanding of the physics of borehole dynamics during drilling and the power of quantitative-risk-analysis (QRA) technology (Ottesen et al 1999;Kline et al 2005). This borehole-quality QRA technology is used to optimize the well-design architecture and drilling parameters for each individual hole section.…”

Section: Real-time Near Missmentioning

confidence: 99%

Borehole-Quality Design and Practices To Maximize Drill-Rate Performance

Dupriest¹,

Elks²,

Ottesen³

et al. 2011

SPE Drilling &Amp; Completion

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In 2005, the operator implemented a workflow that ensured that drilling-performance limiters were identified, redesigned, and extended continuously. The use of mechanical-specific-energy (MSE) surveillance to address bit limiters and dysfunction has been published previously. The purpose of this paper is to discuss additional practices that have been developed to extend the nonbit performance limiters, particularly those related to borehole quality.There have been more than 40 nonbit performance limiters identified and redesigned globally. While these are diverse, those with the greatest global impact were found to be tied directly to borehole quality. Consequently, in 2008, the performance-management workflow was modified to increase awareness of borehole quality as a performance limiter. The result was that acceptable borehole quality became defined as that which would not limit footage per day. Quality is now redesigned to the "economic limit of performance" in the given interval. The economic limit of performance is a significantly higher standard than the common industry objective for borehole quality, which is to achieve low trouble time and to run casing successfully.The average drilling footage per day drilled by the 23 operations that have been active since the performance-management process was implemented has improved by approximately 63%. Instantaneous drill rates have typically increased 100-300%. Advances in bit and nonbit limiters appear to have contributed equally, and the majority of the gain in nonbit limiters has come from improved borehole quality. Other gains have come from related limiters, such as an increased understanding of the manner in which cuttings transport and tripping operations are controlled by borehole quality.The paper discusses the technical models that are used to understand the major borehole limiters, the engineering design, and the real-time practices that have been developed, as well as the field results.

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Section: Real-time Near Missmentioning

confidence: 99%

Borehole-Quality Design and Practices To Maximize Drill-Rate Performance

Dupriest¹,

Elks²,

Ottesen³

et al. 2011

SPE Drilling &Amp; Completion

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“…Based on the several QRA (quantitative risk analysis) analyses [19][20][21][22][23][24][25][26][27][28] and the pore pressure profile with probability information, the fracture and collapse pressure profile with credibility can also be established similar with the pore pressure.…”

Section: Fracture and Collapse Pressure Profile With Credibilitymentioning

confidence: 99%

A New Approach for Casing Program Design with Pressure Uncertainties of Deepwater Exploration Wells

Guan¹,

Ke²,

Lu³

2010

Proceedings of International Oil and Gas Conference and Exhibition in China

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In exploration wells, particularly in deepwater exploration wells, the information regarding formation pressure has many uncertainties because of the lack of seismic data, logging data and daily drilling report. The present casing program design methods based on the deterministic formation pressure data did not take these uncertainties into account and the results could not satisfy field engineering requirements. This paper describes a method based on probabilistic theory for determining the formation pressure profile with credibility, and a new approach for casing program design has been also introduced. As a result, the formation pressure is not a deterministic value but a range with probability information, as the same with the casing set points selection. And then we describe a quantitative risk analysis method for quantitatively analyzing the risk of the casing point selection design. The model includes four sub-models for determining the quantitative risk due to lost circulation, kicking, collapse and sticking. The results can provide valuable information for designers. In one case study, we illustrate how this approach allows us to compute formation pressure profile with credibility and casing set points for a deep well with formation uncertainties. The risk of several casing program of this well has also been discussed finally.

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“…QRA To Drill a Stable Borehole Through the SAF QRA allows us to incorporate uncertainty in the most expected value of the various parameters used in this study to give the probability of success using a particular mud weight (Moos et al 2003;Ottesen et al 1999). Analysis will be performed for a maximum breakout width of 60°.…”

Section: Mud-weight Prediction For Phasementioning

confidence: 99%

Wellbore-Stability Study for the SAFOD Borehole Through the San Andreas Fault

Paul

Zoback

2008

SPE Drilling &Amp; Completion

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This paper presents a wellbore-stability study of the San Andreas Fault Observatory at Depth (SAFOD) research borehole located near Parkfield, California, USA. In the summer of 2005, the SAFOD borehole was drilled successfully through the active trace of the San Andreas Fault (SAF) in an area characterized by fault creep and frequent microearthquakes. In this study, we report how the analysis of wellbore failures in the upper part of the hole, geophysical logs, and a model for stress gradients in the vicinity of the fault were used to estimate the mud weights required to drill through the fault successfully. Because logging-while-drilling (LWD) acoustic caliper data and real-time hole-volume calculations both showed that relatively little failure occurred while drilling through the SAF, the predicted mud weight was successful in drilling a stable borehole. However, a six-arm caliper log, run after drilling was completed, indicates that there was deterioration of the borehole with time, which appears to be caused by fluid penetration around the borehole. The LWD-resistivity measurements show that essentially no fluid penetration occurred as the hole was being drilled. Because of this, the mud weight used was capable of maintaining a stable wellbore. However, the resistivity data obtained after drilling show appreciable fluid penetration with time, thus negating the effectiveness of the mud weight and leading to time-dependent wellbore failure. Using finite-element modeling (FEM), we show that mud penetration into the fractured medium around the borehole causes failure with time.

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Borehole Stability Assessment Using Quantitative Risk Analysis

Abstract: This paper was prepared for presentation at the 1999 SPE/IADC Drilling Conference held in Amsterdam, Holland, 9-11 March 1999.

Cited by 29 publications

References 5 publications

Borehole-Quality Design and Practices To Maximize Drill-Rate Performance

Borehole-Quality Design and Practices To Maximize Drill-Rate Performance

A New Approach for Casing Program Design with Pressure Uncertainties of Deepwater Exploration Wells

Wellbore-Stability Study for the SAFOD Borehole Through the San Andreas Fault

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