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Title: Simulation of wellbore construction in offshore unconsolidated methane hydrate-bearing formation

Abstract

The unconsolidated nature of offshore methane hydrate-bearing formation poses concerns for sustainable methane gas production as the weak formation is susceptible to disturbance during wellbore construction. Furthermore, this could contribute to loss of well integrity which could manifest as sand production and error in the interpretation of downhole tests such as mini-frac tests. In this study, a simulation methodology of wellbore construction process is proposed. A finite element model adopting this methodology is developed in order to assess the effect of wellbore construction process on the integrity of the unconsolidated methane hydrate-bearing formation in the Nankai Trough, Japan. The primary objectives are (i) to develop a modelling methodology of well construction process for numerical simulations, (ii) to assess the zone and magnitude of well construction-induced stress/strain disturbance in the formation and (iii) to evaluate relative impact of each well construction stage on the integrity of the formation. The results from this study show that the zone of horizontal stress disturbance from the geostatic state due to wellbore construction could extend to more than three times the radius of the wellbore. Following the wellbore construction, the deviator stress is concentrated in the hydrate reservoir sublayers with high hydrate saturation while plasticmore » deviatoric strain has accumulated in the sublayers with low hydrate saturation. The results also show that modelling of cement shrinkage process is crucial in predicting the concentration of deviator stress in the high hydrate saturation layers.« less

Authors:
ORCiD logo [1];  [2];  [3]
  1. Univ. of Cambridge (United Kingdom); Univ. of California, Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States)
  3. Qatar Univ., Doha (Qatar)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC); Japan Oil, Gas and Metals National Corporation (JOGMEC)
OSTI Identifier:
1567150
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Natural Gas Science and Engineering
Additional Journal Information:
Journal Volume: 60; Journal Issue: C; Journal ID: ISSN 1875-5100
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
03 NATURAL GAS; Methane hydrate; Well construction; Unconsolidated formation; Soil mechanics; Drilling; Cement shrinkage

Citation Formats

Sasaki, Tsubasa, Soga, Kenichi, and Elshafie, Mohammed Z. E. B. Simulation of wellbore construction in offshore unconsolidated methane hydrate-bearing formation. United States: N. p., 2018. Web. doi:10.1016/j.jngse.2018.10.019.
Sasaki, Tsubasa, Soga, Kenichi, & Elshafie, Mohammed Z. E. B. Simulation of wellbore construction in offshore unconsolidated methane hydrate-bearing formation. United States. doi:10.1016/j.jngse.2018.10.019.
Sasaki, Tsubasa, Soga, Kenichi, and Elshafie, Mohammed Z. E. B. Wed . "Simulation of wellbore construction in offshore unconsolidated methane hydrate-bearing formation". United States. doi:10.1016/j.jngse.2018.10.019. https://www.osti.gov/servlets/purl/1567150.
@article{osti_1567150,
title = {Simulation of wellbore construction in offshore unconsolidated methane hydrate-bearing formation},
author = {Sasaki, Tsubasa and Soga, Kenichi and Elshafie, Mohammed Z. E. B.},
abstractNote = {The unconsolidated nature of offshore methane hydrate-bearing formation poses concerns for sustainable methane gas production as the weak formation is susceptible to disturbance during wellbore construction. Furthermore, this could contribute to loss of well integrity which could manifest as sand production and error in the interpretation of downhole tests such as mini-frac tests. In this study, a simulation methodology of wellbore construction process is proposed. A finite element model adopting this methodology is developed in order to assess the effect of wellbore construction process on the integrity of the unconsolidated methane hydrate-bearing formation in the Nankai Trough, Japan. The primary objectives are (i) to develop a modelling methodology of well construction process for numerical simulations, (ii) to assess the zone and magnitude of well construction-induced stress/strain disturbance in the formation and (iii) to evaluate relative impact of each well construction stage on the integrity of the formation. The results from this study show that the zone of horizontal stress disturbance from the geostatic state due to wellbore construction could extend to more than three times the radius of the wellbore. Following the wellbore construction, the deviator stress is concentrated in the hydrate reservoir sublayers with high hydrate saturation while plastic deviatoric strain has accumulated in the sublayers with low hydrate saturation. The results also show that modelling of cement shrinkage process is crucial in predicting the concentration of deviator stress in the high hydrate saturation layers.},
doi = {10.1016/j.jngse.2018.10.019},
journal = {Journal of Natural Gas Science and Engineering},
number = C,
volume = 60,
place = {United States},
year = {2018},
month = {10}
}

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