UTILIZING NEAR AND FAR FIELD BOREHOLE MEASUREMENTS FOR A COMPREHENSIVE CARBONATE FRACTURE CHARACTERIZATION

2021 ◽  
Author(s):  
Amr M. Serry ◽  
◽  
Sultan D. Al-Hassani ◽  
Shafiq N. Ahmed ◽  
Owais A. Khan ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Carbonate Reservoir ◽  
Small Scale ◽  
Stoneley Wave ◽  
Far Field ◽  
Fracture Density ◽  
Well Test ◽  
Fracture Intensity ◽  
Borehole Image ◽  
Depth Of Investigation

The lower cretaceous carbonate sequence, offshore Abu Dhabi is represented by the third to forth order sequences. Limestone is the dominant lithology for this group of ramp to intrashelf basin sediments. Fracture intensity and density vary vertically along the sequences, controlled by rock texture contrast. Dense layers are heavily fractured compared to the porous bodies throughout these Formations. Two dominant sets of fractures are observed throughout the field, NW-SE and NNE-SSW. Historical well test data indicate strong preferential flow in that same direction compared to less flow in the NW-SE trend (anisotropic drainage behavior). The objective of this study is to demonstrate the capabilities of simultaneously acquired near and far field borehole sonic reflection logging measurements to characterize the present fractures along a dedicated horizontal drain for data gathering. Borehole image log interpretation and other well logs are integrated. Understanding fracture systems using resistivity imaging solely could be challenging due to the limited depth of investigation of the measurement (at the well location). Well trajectory, (open) fracture density and orientation can cause uncertainties in the number of fractures that intersect the borehole. Primary fractures could be abundant away from the borehole but still contributing to flow and reservoir pressure behavior. With a unique extended depth of investigation as well as azimuthal sensitivity, dipole sonic imaging is able to reach tens of meters into the formation and provide fracture intensity and extension information in the far field. A new scale of data integration using near field measurements from monopole sonic imaging, Stoneley wave reflectivity analysis and borehole image interpretation for a comprehensive fractures characterization is accomplished. A set of structural incidents could be detected tens of feet away from the borehole, some seemed to be extending towards the borehole wall itself as seen by the Stoneley reflectivity and the sonic-resistivity borehole imagers. Open fractures are clearly characterized in terms of orientation and aperture, extension inside the reservoir could be recognized, small-scale fractures near the borehole could be discriminated, as well as the closed ones, in addition to the dense stylolite markers. Comparisons with offset cores, seismic and offset well data shows a range of coherence. Most of the fracture clusters were observed at the stylolite boundaries. The main orientation of these fractures are consistent with the present day in-situ stress orientation. The integration of data with respect to resistivity, sonic borehole image and Stoneley wave data from sonic monopole processing are in coherence. Far-field dipole shear sonic imaging adds valuable information to investigate the major carbonate reservoir structural incidents away from the borehole. The value is maximized by integration with the high-resolution borehole image that drew some conclusions on the presence of different sets of fractures distribution and their nature.

Open fractures in pre-salt silicified carbonate reservoirs in block BM-C-33, the Outer Campos Basin, offshore Brazil

2021 ◽  
pp. petgeo2020-125
Author(s):  
O.P. Wennberg ◽  
G. McQueen ◽  
P.H. Vieira de Luca ◽  
F. Lapponi ◽  
D. Hunt ◽  
...  
Keyword(s):  
Open Fractures ◽  
Fracture Density ◽  
Well Test ◽  
Stress Concentrations ◽  
High Fracture ◽  
Matrix Permeability ◽  
Campos Basin ◽  
The Matrix ◽  
Borehole Image ◽  
Borehole Image Logs

Natural open fractures are present in sidewall cores and in whole core samples from pre-salt reservoirs in the license BM-C-33 in the Campos Basin, Brazil. Open fractures are also observed in borehole image logs, and fracture densities are in general high. The highest density of open fractures is seen in the damage zones above and below larger cavities (Amalgamated Cavern Damage Zones - ACDZs). Outside the ACDZs the fracture density is high in silicified carbonates, where it tends to increase with decreasing porosity. Clean dolomites are less fractured than the silicified interval while the less brittle argillaceous dolomites have the lowest fracture density. Some fractures appear vuggy on borehole image logs and fracture densities are high close to vugs and larger cavities. The positive correlation between fractures and vugs is caused by flow of dissolving fluids through open fractures, and fracturing at stress concentrations around vugs, Two major fault zones have been interpreted from borehole image logs which have damage zones with very high fracture density. The well test permeability is much greater than the matrix permeability estimated from sidewall core and log measurements. This excess permeability is attributed to fractures, in combination with caverns and intervals with frequent vugs.

scholarly journals Evidence of Preferential Flow Activation in the Vadose Zone via Geophysical Monitoring

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1358
Author(s):  
Lorenzo De Carlo ◽  
Kimberlie Perkins ◽  
Maria Clementina Caputo
Keyword(s):  
Preferential Flow ◽  
Water Movement ◽  
Test Site ◽  
Water Dynamics ◽  
Small Scale ◽  
Strong Impact ◽  
Aquifer Recharge ◽  
Spatial Moments ◽  
Artificial Rainfall ◽  
Preferential Pathways

Preferential pathways allow rapid and non-uniform water movement in the subsurface due to strong heterogeneity of texture, composition, and hydraulic properties. Understanding the importance of preferential pathways is crucial, because they have strong impact on flow and transport hydrodynamics in the unsaturated zone. Particularly, improving knowledge of the water dynamics is essential for estimating travel time through soil to quantify hazards for groundwater, assess aquifer recharge rates, improve agricultural water management, and prevent surface stormflow and flooding hazards. Small scale field heterogeneities cannot be always captured by the limited number of point scale measurements collected. In order to overcome these limitations, noninvasive geophysical techniques have been widely used in the last decade to predict hydrodynamic processes, due to their capability to spatialize hydrogeophysical properties with high resolution. In the test site located in Bari, Southern Italy, the geophysical approach, based on electrical resistivity tomography (ERT) monitoring, has been implemented to detect preferential pathways triggered by an artificial rainfall event. ERT-derived soil moisture estimations were obtained in order to quantitatively predict the water storage (m3m−3), water velocity (ms−1), and spread (m2) through preferential pathways by using spatial moments analysis.

Geomechanical and Fracture Network Interpretation of a Devonian Outcrop

2021 ◽  
pp. 1-16
Author(s):  
Scott McKean ◽  
Simon Poirier ◽  
Henry Galvis-Portilla ◽  
Marco Venieri ◽  
Jeffrey A. Priest ◽  
...  
Keyword(s):  
Large Scale ◽  
Multiple Scales ◽  
Fracture Network ◽  
Natural Fracture ◽  
Small Scale ◽  
Nugget Effect ◽  
Schmidt Hammer ◽  
Unconventional Reservoir ◽  
Fracture Anisotropy ◽  
Fracture Intensity

Summary The Duvernay Formation is an unconventional reservoir characterized by induced seismicity and fluid migration, with natural fractures likely contributing to both cases. An alpine outcrop of the Perdrix and Flume formations, correlative with the subsurface Duvernay and Waterways formations, was investigated to characterize natural fracture networks. A semiautomated image-segmentation and fracture analysis was applied to orthomosaics generated from a photogrammetric survey to assess small- and large-scale fracture intensity and rock mass heterogeneity. The study also included manual scanlines, fracture windows, and Schmidt hammer measurements. The Perdrix section transitions from brittle fractures to en echelon fractures and shear-damage zones. Multiple scales of fractures were observed, including unconfined, bedbound fractures, and fold-relatedbed-parallel partings (BPPs). Variograms indicate a significant nugget effect along with fracture anisotropy. Schmidt hammer results lack correlation with fracture intensity. The Flume pavements exhibit a regionally extensive perpendicular joint set, tectonically driven fracturing, and multiple fault-damage zones with subvertical fractures dominating. Similar to the Perdrix, variograms show a significant nugget effect, highlighting fracture anisotropy. The results from this study suggest that small-scale fractures are inherently stochastic and that fractures observed at core scale should not be extrapolated to represent large-scale fracture systems; instead, the effects of small-scale fractures are best represented using an effective continuum approach. In contrast, large-scale fractures are more predictable according to structural setting and should be characterized robustly using geological principles. This study is especially applicable for operators and regulators in the Duvernay and similar formations where unconventional reservoir units abut carbonate formations.

Analyzing the Impacts of Meshing and Grid Alignment in Dual-Porosity Dual-Permeability Upscaling

2021 ◽  
pp. 1-20
Author(s):  
Ziming Xu ◽  
Juliana Y. Leung
Keyword(s):  
Fracture Network ◽  
Fracture Plane ◽  
Fracture Density ◽  
Shape Factors ◽  
Stimulated Reservoir Volume ◽  
Reservoir Volume ◽  
Multiple Length Scales ◽  
Fracture Intensity ◽  
Cumulative Production ◽  
The Difference

Summary The discrete fracture network (DFN) model is widely used to simulate and represent the complex fractures occurring over multiple length scales. However, computational constraints often necessitate that these DFN models be upscaled into a dual-porositydual-permeability (DPDK) model and discretized over a corner-point grid system, which is still commonly implemented in many commercial simulation packages. Many analytical upscaling techniques are applicable, provided that the fracture density is high, but this condition generally does not hold in most unconventional reservoir settings. A particular undesirable outcome is that connectivity between neighboring fracture cells could be erroneously removed if the fracture plane connecting the two cells is not aligned along the meshing direction. In this work, we propose a novel scheme to detect such misalignments and to adjust the DPDK fracture parameters locally, such that the proper fracture connectivity can be restored. A search subroutine is implemented to identify any diagonally adjacent cells of which the connectivity has been erroneously removed during the upscaling step. A correction scheme is implemented to facilitate a local adjustment to the shape factors in the vicinity of these two cells while ensuring the local fracture intensity remains unaffected. The results are assessed in terms of the stimulated reservoir volume calculations, and the sensitivity to fracture intensity is analyzed. The method is tested on a set of tight oil models constructed based on the Bakken Formation. Simulation results of the corrected, upscaled models are closer to those of DFN simulations. There is a noticeable improvement in the production after restoring the connectivity between those previously disconnected cells. The difference is most significant in cases with medium DFN density, where more fracture cells become disconnected after upscaling (this is also when most analytical upscaling techniques are no longer valid); in some 2D cases, up to a 22% difference in cumulative production is recorded. Ignoring the impacts of mesh discretization could result in an unintended reduction in the simulated fracture connectivity and a considerable underestimation of the cumulative production.

High-resolution stratigraphic characterization of natural fracture attributes in the Woodford Shale, Arbuckle Wilderness and US-77D Outcrops, Murray County, Oklahoma

2018 ◽  
Vol 6 (1) ◽  
pp. SC29-SC41 ◽  
Author(s):  
Sayantan Ghosh ◽  
John N. Hooker ◽  
Caleb P. Bontempi ◽  
Roger M. Slatt
Keyword(s):  
Natural Fracture ◽  
Fracture Aperture ◽  
Aperture Size ◽  
Fracture Density ◽  
Area Formula ◽  
Woodford Shale ◽  
Fracture Spacing ◽  
Spacing Ratio ◽  
Fracture Intensity ◽  
Bed Thickness

Natural fracture aperture-size, spacing, and stratigraphic variation in fracture density are factors determining the fluid-flow capacity of low-permeability formations. In this study, several facies were identified in a Woodford Shale complete section. The section was divided into four broad stratigraphic zones based on interbedding of similar facies. Average thicknesses and percentages of brittle and ductile beds in each stratigraphic foot were recorded. Also, five fracture sets were identified. These sets were split into two groups based on their trace exposures. Fracture linear intensity (number of fractures normalized to the scanline length [[Formula: see text]]) values were quantified for brittle and ductile beds. Individual fracture intensity-bed thickness linear equations were derived. These equations, along with the average bed thickness and percentage of brittle and ductile lithologies in each stratigraphic foot, were used to construct a fracture areal density (number of fracture traces normalized to the trace exposure area [[Formula: see text]]) profile. Finally, the fracture opening-displacement size variations, clustering tendencies, and fracture saturation were quantified. Fracture intensity-bed thickness equations predict approximately 1.5–3 times more fractures in the brittle beds compared with ductile beds at any given bed thickness. Parts of zone 2 and almost entire zone 3, located in the upper and middle Woodford, respectively, have high fracture densities and are situated within relatively organic-rich (high-GR) intervals. These intervals may be suitable horizontal well landing targets. All observed fracture cement exhibit a lack of crack-seal texture. Characteristic aperture-size distributions exist, with most apertures in the 0.05–1 mm (0.00016–0.0032 ft) range. In the chert beds, fracture cement is primarily bitumen or silica or both. Fractures in dolomite beds primarily have calcite cement. The average fracture spacing indices (i.e., bed thickness-fracture spacing ratio) in brittle and ductile beds were determined to be 2 and 1.2, respectively. Uniform fracture spacing was observed along all scanlines in the studied beds.

Carbonate reservoir simulation improvement on base of well-test data to increase forecast reliability

2008 ◽  
Author(s):  
Danila Gulyaev ◽  
Andrey Ivanovich Ipatov ◽  
Nataliya Chernoglazova ◽  
Maxim Fedoseev
Keyword(s):  
Test Data ◽  
Reservoir Simulation ◽  
Carbonate Reservoir ◽  
Well Test

Acoustic Design of a Local Scatterer in a Phase-Space

1995 ◽  
Author(s):  
John J. McCoy ◽  
Ben Zion Steinberg
Keyword(s):  
Mechanical Property ◽  
Phase Space ◽  
Mass Density ◽  
Sound Field ◽  
Design Strategy ◽  
Local Region ◽  
Small Scale ◽  
Far Field ◽  
Acoustic Design ◽  
Surrounding Fluid

Abstract A spatially local region of mechanical property heterogeneity is a source of scattering, by which a structure-borne mechanical wavefield is released as sound, to a surrounding fluid. We consider the case of a scatterer which is of the order of the size of the wavelength of a plate-wave field for a frequency which is below coincidence. A design strategy for reducing the strength of the scattered sound field in the fluid, at far-field distances from the scatterer, by adding a small-scale structure to the heterogenity, is presented. The design is accomplished in a wavelet-based phase-space. Emphasized is a significant distinction required of the added structure, depending on the heterogeneity applying to a measure of the local mass density or the local bending stiffness.

The Stratigraphy of Pre-Tertiary Economic Basement in South Jambi B Block, South Sumatra Basin

2021 ◽  
Keyword(s):  
Significant Contribution ◽  
Fracture Network ◽  
Natural Fracture ◽  
Fracture Density ◽  
The South ◽  
The North ◽  
Fracture Intensity ◽  
Parent Rocks ◽  
Major Fault ◽  
Essential Function

As one of the most promising plays, the Pre-Tertiary basement play holds a significant contribution to the latest success of exploration efforts in the South Sumatra Basin, which then includes the South Jambi B Block. Yet, the natures of the Pre-Tertiary unit in this block remains unsolved. Lithology variability, spatial irregularity, genetic ambiguity, and different reservoir characteristic are indeterminate subjects in the block are the main focus here. The ultimate goals of this study are to better characterize the unit and gain more understanding in calibrating the remaining potential. Based on this study, The Pre-Tertiary units are mainly originated from layered marine-deltaic sedimentary parent rocks with carbonate, intruded by spotty granite where the concentration of each parent rocks varies at the north, the middle, and southern part. Secondly, both lithology heterogeneity and natural fracture density create distinctive reservoir deliverability at each structure. The storage concept is an essential function of natural fracture intensity and diversity, supported by matrix porosity that varies across a different succession of lithology. Lastly, this study observes that major fault orientation is essential in constructing the fracture network. Evidence from several image logs across the study area concludes that most of the interpreted fractures are oriented subparallel to the major faults. The northern belt area is relatively affected by NW-SE Neogene structure, where the southern area is recognized to be affected by both Neogene compression and pre-existing Paleogene structure.

A GoldSim Modeling Approach to Safety Assessment of an LILW Repository System

2010 ◽  
Author(s):  
Youn Myoung Lee ◽  
Jongtae Jeong ◽  
Jongwon Choi
Keyword(s):  
Performance Evaluation ◽  
Safety Assessment ◽  
Preferential Flow ◽  
Far Field ◽  
Well Drilling ◽  
Sensitivity Studies ◽  
Nuclide Transport ◽  
And Performance ◽  
Parameter Values ◽  
Flow Pathway

A program for the safety assessment and performance evaluation of a low- and intermediate level waste (LILW) repository system has been developed by utilizing GoldSim [1]. By utilizing this nuclide transport in the near- and far-field of a repository as well as a transport through a biosphere under various natural and manmade disruptive events affecting a nuclide release are modeled and evaluated. To demonstrate its usability, some illustrative cases under the selected scenarios including the influence of degradation of manmade barriers, pumping well drilling, and the natural disruptive events such as a sudden formation of preferential flow pathway have been investigated and illustrated for a hypothetical LILW repository. Even though all the parameter values applied to a hypothetical repository are assumed without any real base, the illustrative cases could be informative especially when seeing the result of the probabilistic calculation or sensitivity studies with various scenarios that possibly happen for nuclide release and further transport.

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