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Title: Failure of cap-rock seals as determined from mechanical stratigraphy stress history and tensile-failure analysis of exhumed analogs.

Abstract

Abstract not provided.

Authors:
; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
Sponsor Funded
OSTI Identifier:
1183155
Report Number(s):
SAND2014-17837J
537608
DOE Contract Number:
AC04-94AL85000
Resource Type:
Journal Article
Resource Relation:
Journal Name: AAPG Bulletin
Country of Publication:
United States
Language:
English

Citation Formats

E.S. Petrie, W. State Colorado Univ.,, J. P. Evans, Utah State University, and Bauer, Stephen J.. Failure of cap-rock seals as determined from mechanical stratigraphy stress history and tensile-failure analysis of exhumed analogs.. United States: N. p., 2014. Web.
E.S. Petrie, W. State Colorado Univ.,, J. P. Evans, Utah State University, & Bauer, Stephen J.. Failure of cap-rock seals as determined from mechanical stratigraphy stress history and tensile-failure analysis of exhumed analogs.. United States.
E.S. Petrie, W. State Colorado Univ.,, J. P. Evans, Utah State University, and Bauer, Stephen J.. Mon . "Failure of cap-rock seals as determined from mechanical stratigraphy stress history and tensile-failure analysis of exhumed analogs.". United States. doi:.
@article{osti_1183155,
title = {Failure of cap-rock seals as determined from mechanical stratigraphy stress history and tensile-failure analysis of exhumed analogs.},
author = {E.S. Petrie, W. State Colorado Univ., and J. P. Evans, Utah State University and Bauer, Stephen J.},
abstractNote = {Abstract not provided.},
doi = {},
journal = {AAPG Bulletin},
number = ,
volume = ,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 2014},
month = {Mon Sep 01 00:00:00 EDT 2014}
}
  • In this study, the sedimentologic and tectonic histories of clastic cap rocks and their inherent mechanical properties control the nature of permeable fractures within them. The migration of fluid through mm- to cm-scale fracture networks can result in focused fluid flow allowing hydrocarbon production from unconventional reservoirs or compromising the seal integrity of fluid traps. To understand the nature and distribution of subsurface fluid-flow pathways through fracture networks in cap-rock seals we examine four exhumed Paleozoic and Mesozoic seal analogs in Utah. We combine these outcrop analyses with subsidence analysis, paleoloading histories, and rock-strength testing data in modified Mohr–Coulomb–Griffith analysesmore » to evaluate the effects of differential stress and rock type on fracture mode.« less
  • In this paper the authors investigate the occurrence of compressive and tensile failures of arbitrarily inclined well bores under a wide variety of stress conditions. The principal assumptions in this analysis are that the rock is isotropic and that it deforms elastically to the point of failure. As has been shown by previous investigators, for a given stress state and well bore orientation, it is straightforward to predict the orientation of the failures around the well bore as well as whether failure is likely to occur depending on such parameters as rock strength and borehole fluid pressure. However, as themore » stress state is almost never known in situ, the authors demonstrate how observations of compressive and tensile wall failures in inclined holes can be used to constrain in situ stress orientations and magnitudes if there are independent data on the magnitude of the least principal stress from either lead-off or microfrac tests and on the formation pore pressure. They further demonstrate how once the stress state is determined, it is possible to assess both an upper bound on the effective in situ rock strength and the degree to which increasing the borehole fluid pressure (or mud weight) can reduce the likelihood of borehole failure. Through application of this methodology to an inclined well bore in an area of complex faulting in the Gulf of Mexico, the authors illustrate how it is possible to utilize observations of borehole failures to determine the magnitude and orientation of the stress tensor in areas such as offshore sedimentary basins where drilling inclined well bores is quite common. 51 refs., 18 figs.« less
  • Four exhumed hydrocarbon traps crop out in the Traill 0 region of East Greenland, each at the footwall crest of a fault-block formed during Early Cretaceous rifting. Former oil accumulations are indicated by a pore fill or pore lining of solid bitumen within the Jurassic sandstone-dominated Vardekloft and Olympen formations. The Vardekloft Formation is divided into an undated fluvial-dominated lower unit (0-520 m) and a Bajocian-Callovian upper unit (65-1020 m) deposited in a shallow-marine environment. The Oxfordian Olympen Formation (0-250 m) contains shallow-marine and fluviodeltaic deposits. The sandstones are dominantly quartzarenites, and petrographic fabrics, such as dissolved feldspar, late quartzmore » cement, and stylolites, are consistent with burial depths in excess of 2.5 km. Porosities ranged from 7 to 27% (generally about 20%, about one-half of which was primary), and permeabilities ranged from 1 to 622 md, prior to the formation of solid bitumen. The distribution of solid bitumen in each trap can be mapped out, allowing sealing elements and original oil-water contacts to be defined. Three of the four exhumed traps (Mols Bjerge, Laplace Bjerg, and Bjornedal) were simple one-seal structural traps. Conformable Upper Jurassic mudstone, unconformable Albian-Cenomanian mudstone, and normal faults are the three top-sealing elements. The fourth (Svinhufvuds Bjerge) was a poly-seal trap with a combined top-seal and a low-side fault closure. Preliminary estimates of the volume of original oil in place within these structures range from 0.2-1.1 billion bbl for the Mols Bjerge trap to 5.3-11.9 billion bbl for the Bjornedal trap. These estimates are prone to large errors, due to uncertainties in estimating original trap geometry, hydrocarbon saturation, and net/gross ratio, and in the understanding of volume changes of hydrocarbon in each trap during thermal degradation of the oil.« less
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