A New Approach to Borehole Trajectory Optimisation for Increased Hole Stability

Abstract

A New Approach to Borehole Trajectory Optimisation for Increased Hole Stability M.R. Awal; M.R. Awal King Fahd University of Petroleum and Minerals Search for other works by this author on: This Site Google Scholar M.S. Khan; M.S. Khan King Fahd University of Petroleum and Minerals Search for other works by this author on: This Site Google Scholar M.A. Mohiuddin; M.A. Mohiuddin King Fahd University of Petroleum and Minerals Search for other works by this author on: This Site Google Scholar A. Abdulraheem; A. Abdulraheem King Fahd University of Petroleum and Minerals Search for other works by this author on: This Site Google Scholar M. Azeemuddin M. Azeemuddin King Fahd University of Petroleum and Minerals Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Middle East Oil Show, Manama, Bahrain, March 2001. Paper Number: SPE-68092-MS https://doi.org/10.2118/68092-MS Published: March 17 2001 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Awal, M.R., Khan, M.S., Mohiuddin, M.A., Abdulraheem, A., and M. Azeemuddin. "A New Approach to Borehole Trajectory Optimisation for Increased Hole Stability." Paper presented at the SPE Middle East Oil Show, Manama, Bahrain, March 2001. doi: https://doi.org/10.2118/68092-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Middle East Oil and Gas Show and Conference Search Advanced Search AbstractBorehole instability due to stuck pipe, hole pack-off, and lost hole during drilling has been a major problem, which causes the industry to lose millions of dollars.In the last two decades, various rock mechanics principles have been tried, and experience has been shared in the literature as to the efficacy of these principles to minimize the problem. The commercial software, rich in such analytical and numerical models, however, have not mitigated the problem.We have found that this failure is attributable to:lack of full utilization of the classical Kirsch equations that represent the state of stresses around a borehole;negligence/ignorance of the complete in-situ stress field and the Biot's constant; and improper calibration of the rock mechanics parameters; andlack of translating the findings of mathematical models in an appropriate form that can be readily used for field deployment.We have addressed these shortcomings by utilizing more relevant solutions to the Kirsch equations by incorporating poro-elastic behavior of rock. Further, we have utilized hitherto neglected aspects of the geomechanical stability equations, and presented graphical solutions that can be used by field engineers having a minimal knowledge of rock mechanics.One of the important findings of these computer generated, graphical solutions is that the optimized trajectory can be vertical, inclined, or horizontal. This depends on whether the region is tectonically quiet or active. It also depends on whether or not, the prevailing insitu stress regime is normal, overthrust/reverse, or strike-slip type. Thus, the principal insitu stresses, in both magnitude and directions, are a fundamental data set that is needed in designing the safe borehole trajectory. For the deviated hole, further optimization is obtained by determining the best azimuthal direction to reach the target zone. What is more interesting, the optimized trajectory requires a much less mud weight to drill a stable borehole, thereby reducing drilling cost significantly.We have applied our method in a case study in an offshore field, where frequent borehole collapse has been reported in drilling through shale/sand stringers. The successful application of the proposed method would not only save millions by preventing borehole instabilities, but also cut drilling cost significantly by replacing the expensive and environmentally unsafe oil-based mud.IntroductionReview of published literature in the last two decades (McLean & Addis, 1990; McLellan & Hawkes, 1998; Svennekjaer & Bratli, 1998; Guo et al., 2000; Onaisi, et al., 2000) shows that borehole instability due to stuck pipe, hole pack-off, and lost hole during drilling are still common, although various rock mechanics principles have been tried, and experience has been shared in order to minimize these major problems. Keywords: azimuth, isotropy, reservoir characterization, wellbore design, mud weight, critical mud weight, stress regime, drilling, upstream oil & gas, reservoir geomechanics Subjects: Wellbore Design, Reservoir Characterization, Wellbore integrity, Reservoir geomechanics This content is only available via PDF. 2001. Society of Petroleum Engineers You can access this article if you purchase or spend a download.