Repeat Time Lapse 4D Seismic Monitoring as a Tool for South Arne Field Development

Vejbæk, Ole Valdemar; King, Andrew; Palmer, J.

doi:10.3997/2214-4609.20148255

Cited by 2 publications

(7 citation statements)

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“…Four-dimensional seismic analysis has demonstrated that petrophysical and geomechanical properties of the South Arne reservoirs respond rapidly to water injection and production (Herwanger et al 2010(Herwanger et al , 2013Vejbaek et al 2012Vejbaek et al , 2013. Previous research also suggests that seismic data with very high repeatability such as South Arne 4D (NRMS less than 10%: Herwanger et al 2010) might capture production effects along a fault network (Borgos et al 2009).…”

Section: D Analysis Of a Fault Networkmentioning

confidence: 95%

“…If true, it can have important implications for the connectivity of the fault network. Evidence of reactivated conductive fault zones has been found in South Arne (Vejbaek et al 2012).…”

Section: D Analysis Of a Fault Networkmentioning

confidence: 97%

“…The preproduction 4D baseline seismic survey was acquired with classic towed-streamer technology in 1995. Two monitor surveys were acquired in 2005 (Schiøtt & King 2006) and 2011 (Vejbaek et al 2012), after 6 and 12 years of production, respectively, using point-receiver towedstreamer technology (Martin et al 2000). The latest reprocessing effort, including data from the 3D survey acquired in 2011, took place while this study was conducted; therefore, the most recent seismic survey could not be included in the analysis.…”

Section: Overview Of South Arne Fieldmentioning

confidence: 99%

“…Clear evidence of conductive fault zones has been observed on normalized root-mean-square (NRMS) 4D differences (Vejbaek et al 2012). Moreover, recent results of 3D geomechanical modelling coupled with reservoir simulation indicate that the field responds very rapidly to production-induced local stresses.…”

mentioning

confidence: 95%

“…The two main goals of the study were: (i) to assess whether the two fracture sets identified in the wells, one presumed to have formed while the Chalk was semi-lithified and the other once lithified, could be separated on the 3D seismic data; and (ii) to verify whether a 4D seismic signature exists within the fault network after recent studies have reported evidence of reactivated conductive faults in the northern part of the field (Vejbaek et al 2012).…”

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confidence: 99%

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Mapping and time-lapse analysis of South Arne Chalk fault network using new developments in seismic dip computation

Astratti

Aarre

Vejbæk³

et al. 2014

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In a reservoir, faults at the limit of the seismic resolution can be crucial to explain production history and to optimize field development. However, in most cases the detail required to describe such subtle features depends on the assistance of seismic attributes and semi-automated interpretation techniques. We generated a detailed description of the fault network in the South Arne Chalk Group using a workflow based on a globally consistent computation of the seismic dip. This led to more accurate seismic edge attributes than gained with standard dip estimation techniques. We analysed each fault set and qualitatively assessed its control on fluid flow. Our investigation suggests that the two fracture sets that influence production developed along the same WNW-ESE structural trend and cannot be separated based on the seismic data alone. These faults were active both during and post Chalk deposition. We observe ENE -WSW lineaments that match the pattern of a time-lapse seismic amplitude anomaly associated with water injection. It remains to be verified whether these lineaments could be an extension of overburden faults, as well as whether the increased intensity of the fault network as seen on the 2005 v. the 1995 3D seismic survey was caused by production effects.

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Section: D Analysis Of a Fault Networkmentioning

confidence: 95%

“…If true, it can have important implications for the connectivity of the fault network. Evidence of reactivated conductive fault zones has been found in South Arne (Vejbaek et al 2012).…”

Section: D Analysis Of a Fault Networkmentioning

confidence: 97%

Section: Overview Of South Arne Fieldmentioning

confidence: 99%

mentioning

confidence: 95%

mentioning

confidence: 99%

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Mapping and time-lapse analysis of South Arne Chalk fault network using new developments in seismic dip computation

Astratti

Aarre

Vejbæk³

et al. 2014

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Influence of Tensile Strength and Production Effects on Hydraulic Fracturing in Low Porosity Carbonates: The South Arne Case

Vejbæk¹,

Jakobsen²,

Lamb³

et al. 2013

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Well planning in mature fields can be challenging as the more marginal reserves are targeted. Hydraulic fracture stimulation is a key technology to access multiple reservoir layers and thereby maximize recovery. However, fracture propagation in low porosity carbonates may be strongly confined because of high tensile strengths in bounding layers. The strong confinement can impede vertical fracture propagation and the ability to access reservoir units adjacent to the initiation interval. Understanding vertical hydraulic fracture growth through low porosity layers improves the hydraulic fracture design, enhances reservoir deliverability potential and enables the identification of infill well potential and intervention opportunities.The South Arne field is located in the northern part of the Danish sector of the North Sea. The Tor and Ekofisk formations are high porosity/low permeability chalks with low to moderate natural fracturing. Porosities may reach 45%, but a hard low porosity interval of 10% or less at the bottom of the Ekofisk formation separates and partially compartmentalizes (horizontally) the two formations. A series of indirect tensile strength measurements on South Arne cores were conducted. The measurements verified a suspected exponential increase in tensile strength at low porosities, essentially causing the tensile strength to exceed 1,500 psi in some cases.Recent 4D seismic surveys have enabled separate sweep patterns for each reservoir unit to be mapped and indicate that the sweep is much less efficient in the Ekofisk. This supports that the hydraulic fracture stimulation treatments initiated in the Tor formation are not accessing the upper units to the degree previously assumed and it appears that connection is occurring via pre-existing faults and/or natural fractures. The hydraulic fractures propagate nearly longitudinal to the wellbore, guided by regional stresses, with limited height growth. However, production effects, specifically compaction induced by draw down, may perturb the stress field sufficiently so that the preferred alignment is not achieved, further reducing sweep efficiency. This is indicated by 3D coupled geomechanical modeling and is corroborated by 4D seismic observations.

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Repeat Time Lapse 4D Seismic Monitoring as a Tool for South Arne Field Development

Cited by 2 publications

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Mapping and time-lapse analysis of South Arne Chalk fault network using new developments in seismic dip computation

Mapping and time-lapse analysis of South Arne Chalk fault network using new developments in seismic dip computation

Influence of Tensile Strength and Production Effects on Hydraulic Fracturing in Low Porosity Carbonates: The South Arne Case

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