Forward modeling of fracture‐induced sonic anisotropy using a combination of borehole image and sonic logs

Prioul, Romain; Donald, Adam; Koepsell, Randy; Bratton, Tom; Boyd, Austin; Signer, C.

doi:10.1190/1.2792391

Cited by 6 publications

(7 citation statements)

References 8 publications

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“…With the exception of the result from Worthington and Hudson (2000) that was discussed earlier, we are not aware of any field estimates of shear fracture compliance. Estimates can be and were obtained from image and sonic logs (Prioul et al 2007). However, these values are very dependent on assumptions that have to be made about the relationship between Z n and Z t (or B n and B t ) and the fracture spacing so that can be applied.…”

Section: Fracture Compliance: a Reviewmentioning

confidence: 99%

Field measurements of normal and shear fracture compliance

Hobday

Worthington

2011

Geophysical Prospecting

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Field estimates of the normal and shear compliance of water saturated fractures were obtained from a seismic experiment carried out on a wave‐cut platform of Upper Caithness Flagstone on the North coast of Scotland. The rocks are cut by two orthogonal sets of vertical fractures. Vertical geophones were glued to the rock surface and seismic waves were generated by striking the surface with a sledge hammer. First arrival traveltimes were obtained for source‐receiver distances up to 30 m. Differences of compressional velocity with direction across the platform were interpreted as resulting from the compliance of the fractures intersected by the transmitted waves. The average normal compliance for fractures at this site is 4.0 × 10−12± 1.0 × 10−12 m/Pa. There is much less certainty about the precise value of shear compliance. However, the normal/shear compliance ratio is determined to be ≤0.1.

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Section: Fracture Compliance: a Reviewmentioning

confidence: 99%

Field measurements of normal and shear fracture compliance

Hobday

Worthington

2011

Geophysical Prospecting

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“…44 F I G U R E 4 Crossplots of coremeasured permeability versus net confining pressures for Sample A and Sample B. 43,53,54 The drilling-induced fractures are open mode fractures and appear as vertical fracture oriented at 180° from each other. The SHmax is parallel to the induced fractures, and Shmin is parallel to the wellbore breakouts The FMI imaging tools offer oriented images with a vertical resolution of 5 mm, and a borehole coverage of 80% in an 8.5 inch borehole.…”

Section: Methodsmentioning

confidence: 99%

“…20,50,52 Stress-induced fractures are classified as drilling-induced (tensile-or shear-induced) fractures and wellbore breakouts. 43,53,54 The drilling-induced fractures are open mode fractures and appear as vertical fracture oriented at 180° from each other. 6,43 Breakouts (wellbore enlargements) are recognized as broad, parallel, dark bands separated by 180° on image logs.…”

Section: Methodsmentioning

confidence: 99%

In‐situ stress determination and fracture characterization using image logs: The Paleogene Dongying Formation in Nanpu Sag, Bohai Bay Basin, China

Niu

Liu

Lai

et al. 2019

Energy Science & Engineering

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Fracture detection and in‐situ stress determination via well logs are important for exploration and exploitation of subsurface hydrocarbons. Cores, thin sections, and image logs are used to describe and interpret the subsurface fractures and in‐situ stress in the Paleogene Dongying sandstones in Nanpu Sag, Bohai Bay Basin, China. The maximum horizontal stress (SHmax) indicates a nearly east‐west trend according to the borehole breakouts and drilling‐induced fractures. Natural fractures in the Dongying sandstones are classified into: (1) open fractures and (2) closed fractures. The cement‐filled (closed) fractures are commonly detected by image logs as bright discontinuous sinusoidal waves due to resistive filling materials, while the open fractures are evident on image logs appearing as dark sine waves. The open fractures are of dominantly high dip angles, and the rose diagrams confirm the presences of two sets of fractures: northwest‐southeast and northwest‐southeast orientation. Fractures with strikes approximately parallel to the SHmax have good connectedness, making a significant contribution in hydrocarbon production. In addition, the oil‐bearing layers are mainly associated with the intervals with open fractures. The presence of natural fractures provides important pore spaces and fluid flow conduits. Insights can be provided into the subsurface fracture (natural and induced) detection and characterization using image logs.

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“…3 can be used to estimate permeability ranges at various fracture density and aperture values. Veltman et al (2012) defines fracture anisotropy modeling as a method that integrates the response of the fractures (natural and induced) from the borehole image; this result is compared with the reservoir (acoustic) anisotropy mechanism response obtained from the dispersion analysis technique (Prioul et al 2007) that probes the formation at various depths of investigation around the borehole. 10 indicates that fracture permeability can be very high, even at a low density and small aperture.…”

Section: Apparent Fracture Lengthmentioning

confidence: 99%

Revealing the Uncertainty of Heterogeneities in Fractured Basement: A Case Study from the South Malay Basin Offshore Peninsular, Malaysia

Gaafar

Najm²,

2015

SPE/IATMI Asia Pacific Oil &Amp; Gas Conference and Exhibition

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Fractured basement reservoirs represent more than 20% of the world's oil and gas reserves. Because of their heterogeneity and complex, unconventional natures, the process of mapping the reservoir properties presents a monumental task. The identification of the high productivity zones in basement reservoirs presents a major challenge because of the drastic vertical and temporal variation in porosity and permeability.Reservoir characterization in terms of rock-forming minerals, multipore system analyses, hydrocarbon typing and quantification, and textural variations can be performed by combining quad-combo, elemental spectroscopy, and resistivity-imaging measurements, regardless of the conveyance technique, in an integrated workflow.Because fractures play a major role in hydrocarbon production, rapid reservoir decline, and undesirable fluids breakthrough, fracture description is crucial. Aside from conventional techniques to quantify matrix porosity and permeability, a workflow has been designed to provide additional unconventional techniques for multipore system analyses using high-resolution resistivity imaging. With one technique, the resistivity image is sculptured using an object-oriented filter that produces fracture density, aperture, and porosity. The other technique is based on a transformation of image conductivity to porosity that is classified into a matrix and secondary pores to estimate their contribution to permeability.The multipore system analysis is then used to determine the cementation exponent parameter needed for hydrocarbon quantification. Finally, critically stressed fractures are identified, using geomechanical analyses, to determine the production-contributing fractured zones.Although the technique/workflow used is relatively new and uncommon for data acquired while drilling, its results successfully met the objectives of the study with quality deliverables.This paper presents a basement reservoir characterization study with a discussion of the technologies used in the workflow, study results, conclusions, and recommendations for future work. Data used in this work were obtained from a well in Malacca, Malaysia.

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Forward modeling of fracture‐induced sonic anisotropy using a combination of borehole image and sonic logs

Cited by 6 publications

References 8 publications

Field measurements of normal and shear fracture compliance

Field measurements of normal and shear fracture compliance

In‐situ stress determination and fracture characterization using image logs: The Paleogene Dongying Formation in Nanpu Sag, Bohai Bay Basin, China

Revealing the Uncertainty of Heterogeneities in Fractured Basement: A Case Study from the South Malay Basin Offshore Peninsular, Malaysia

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