Present-day stress and neotectonics of Brunei: Implications for petroleum exploration and production

Tingay, Mark; Hillis, Richard R.; Morley, C.K.; King, Robert G.; Swarbrick, Richard E.; Damit, Abdul Razak

doi:10.1306/08080808031

Cited by 111 publications

(62 citation statements)

References 69 publications

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“…[36] It is interesting to note that the stress direction variation between the fore-arc and the outer arc domains remarkably resembles that seen in the delta-deepwater fold-thrust belt systems. Tingay et al [2009] and King et al [2010] showed that the maximum horizontal stress direction in a Tertiary delta, offshore northwestern Borneo, rotates from margin-parallel in the outer shelf (corresponding to fore arc here) to margin-normal in the inner shelf (delta toe). They also interpreted the margin-parallel S Hmax in the outer shelf in terms of gravity-driven extension.…”

Section: Discussionmentioning

confidence: 99%

In situ stress state in the Nankai accretionary wedge estimated from borehole wall failures

Chang

McNeill

Moore

et al. 2010

Geochem Geophys Geosyst

124

213

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[1] We constrain the orientations and magnitudes of in situ stress tensors using borehole wall failures (borehole breakouts and drilling-induced tensile fractures) detected in four vertical boreholes (C0002, C0001, C0004, and C0006 from NW to SE) drilled in the Nankai accretionary wedge. The directions of the maximum horizontal principal stress (S Hmax ), indicated by the azimuths of borehole wall failures, are consistent in individual holes, but those in C0002 (margin-parallel S Hmax ) are nearly perpendicular to those in all other holes (margin-normal S Hmax ). Constrained stress magnitudes in C0001 and C0002, using logged breakout widths combined with empirical rock strength derived from sonic velocity, as well as the presence of the drilling-induced tensile fractures, suggest that the stress state in the shallow portion of the wedge (fore-arc basin and slope sediment formations) is predominantly in favor of normal faulting and that the stress state in the deeper accretionary prism is in favor of probable strike-slip faulting or possible reverse faulting. Thus, the stress regime appears to be divided with depth by the major geological boundaries such as unconformities or thrust faults. The margin-perpendicular tectonic stress components in the two adjacent sites, C0001 and C0002, are different, suggesting that tectonic force driven by the plate pushing of the Philippine Sea plate does not uniformly propagate. Rather, the stress field is inferred to be influenced by additional factors such as local deformation caused by gravitation-driven extension in the fore arc and thrusting and bending within individual geologic domains.

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Section: Discussionmentioning

confidence: 99%

In situ stress state in the Nankai accretionary wedge estimated from borehole wall failures

Chang

McNeill

Moore

et al. 2010

Geochem Geophys Geosyst

124

213

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“…Hydrostatic fluid pressures are observed in the Champion Deep well (Fig. 9A) above a fluid-retention depth of z FRD z 1.2e1.5 km where extensional stress states exist based on analysis of failure of deviated boreholes (Tingay et al, 2009b). The top of overpressures is at~1.7 km and is marked by a discontinuity in permeability, with a shale-rich section below.…”

Section: Brunei Delta North Borneomentioning

confidence: 98%

“…The best fitting pressure dependence is k e ¼ 0.45 (m ¼ 0.3). Deeper leakoff and minifrac pressures approximate the overburden pressure, suggesting s 3 may be vertical, which may represent loading within the deep Borneo compressional wedge from which the Brunei delta extensional system detaches (Tingay et al, 2009b;Morley et al, 2008;see Fig. 9B below~2900 m).…”

Section: Brunei Delta North Borneomentioning

confidence: 99%

Fluid overpressures and strength of the sedimentary upper crust

Suppe

2014

Journal of Structural Geology

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a b s t r a c tThe classic crustal strength-depth profile based on rock mechanics predicts a brittle strength s 1 À s 3 ¼ kðrgz À P f Þ that increases linearly with depth as a consequence of [1] the intrinsic brittle pressure dependence k plus [2] an assumption of hydrostatic pore-fluid pressure, P f ¼ r w gz. Many deep borehole stress data agree with a critical state of failure of this form. In contrast, fluid pressures greater than hydrostatic rgz > P f > r w gz are normally observed in clastic continental margins and shale-rich mountain belts. Therefore we explore the predicted shapes of strength-depth profiles using data from overpressured regions, especially those dominated by the widespread disequilibrium-compaction mechanism, in which fluid pressures are hydrostatic above the fluid-retention depth z FRD and overpressured below, increasing parallel to the lithostatic gradient rgz. Both brittle crustal strength and frictional fault strength below the z FRD must be constant with depth because effective stress ðrgz À P f Þ is constant, in contrast with the classic linearly increasing profile. Borehole stress and fluid-pressure measurements in several overpressured deforming continental margins agree with this constant-strength prediction, with the same pressure-dependence k as the overlying hydrostatic strata. The role of z FRD in critical-taper wedge mechanics and jointing is illustrated. The constant-strength approximation is more appropriate for overpressured crust than classic linearly increasing models.

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“…These techniques all require the pressure decay to be monitored for a long duration after the pumps are shut-in (generally >10 min; Enever et al, 1996;Jørgensen and Fejerskov, 1998;Raaen et al, 2006). Furthermore, FCP is also almost universally observed to be less than or equal to the LOP, as the leak-off pressure involves fracture initiation and thus must overcome both the minimum principal stress and the rock's tensile strength (Breckels and van Eekelen, 1982;Gaarenstroom et al, 1993;Tingay et al, 2009). However, in stark contrast to all industry conventions, Sawolo et al (2009) have selected their 'fracture closure pressure' as the pressure at which the leak-off test stabilized before the pumps were turned off and a value that is much greater than the 15.8 ppg (18.57 MPa/km) LOP.…”

Section: What Pressure Could the Well Tolerate?mentioning

confidence: 99%

Sawolo et al. (2009) the Lusi mud volcano controversy: Was it caused by drilling?

Davies

Manga

Tingay

et al. 2010

Marine and Petroleum Geology

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Present-day stress and neotectonics of Brunei: Implications for petroleum exploration and production

Cited by 111 publications

References 69 publications

In situ stress state in the Nankai accretionary wedge estimated from borehole wall failures

In situ stress state in the Nankai accretionary wedge estimated from borehole wall failures

Fluid overpressures and strength of the sedimentary upper crust

Sawolo et al. (2009) the Lusi mud volcano controversy: Was it caused by drilling?

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