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Faults and fracture characterization
Numerous surface-felt earthquakes have been spatiotemporally correlated with hydraulic fracturing operations. Because large deformations occur close to hydraulic fractures (HFs), any associated fault reactivation and resulting seismicity must be evaluated within the length scale of the fracture stages and based on precise fault location relative to the simulated rock volumes. To evaluate changes in Coulomb failure stress (CFS) with injection, we conducted fully coupled poroelastic finite-element simulations using a pore-pressure cohesive zone model for the fracture and fault core in combination with a fault-fracture intersection model. The simulations quantify the dependence of CFS and fault reactivation potential on host-rock and fault properties, spacing between fault and HF, and fracturing sequence. We find that fracturing in an anisotropic in-situ stress state does not lead to fault tensile opening but rather dominant shear reactivation through a poroelastic stress disturbance over the fault core ahead of the compressed central stabilized zone. In our simulations, poroelastic stress changes significantly affect fault reactivation in all simulated scenarios of fracturing 50-200 m away from an optimally oriented normal fault. Asymmetric HF growth due to the stress-shadowing effect of adjacent HFs leads to 1.) a larger reactivated fault zone following simultaneous and sequential fracturing of multiple clusters compared to single-cluster fracturing; and 2.) larger unstable area (CFSgt;0.1) over the fault core or higher potential of fault slip following sequential fracturing compared to simultaneous fracturing. The fault reactivation area is further increased for a fault with lower conductivity and with a higher opening-mode fracture toughness of the overlying layer. To reduce the risk of fault reactivation by hydraulic fracturing under reservoir characteristics of the Barnett Shale, the Fort Worth Basin, it is recommended to 1.) conduct simultaneous fracturing instead of sequential; and 2.) to maintain a minimum distance of ~ 200 m for HF operations from known faults.
- North America > Canada (1.00)
- North America > United States > Texas > Travis County > Austin (0.28)
- North America > United States > Texas > Tarrant County > Fort Worth (0.24)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (1.00)
- Geology > Structural Geology > Fault (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
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- South America > Argentina > Patagonia > Neuquén > Neuquen Basin > Vaca Muerta Shale Formation (0.99)
- North America > United States > Wyoming > Green River Basin > Jonah Field (0.99)
- North America > United States > West Virginia > Appalachian Basin (0.99)
- (51 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
Fault structure and hydrocarbon prospects of the Palawan basin on the southeastern margin of the South China Sea based on gravity, magnetic, and seismic data
Zhang, Chunguan (Xian Shiyou University, Xian Shiyou University, National Engineering Research Center of Offshore Oil and Gas Exploration) | Liu, Shixiang (CNOOC Research Institute) | Yuan, Bingqiang (Xian Shiyou University, Xian Shiyou University) | Zhang, Gongcheng (CNOOC Research Institute)
In order to study the structural features and hydrocarbon prospects of the Palawan basin in the South China Sea (SCS), the authors collected and collated the existing gravity and magnetic data, and obtained edge recognition information from potential. Combined with the seismic profile data, this paper analyzed the features of the gravity and magnetic anomalies and the edge recognition information of the potential fields, determined the fault system, and delineated favorable areas for oil and gas exploration in the Palawan basin. The results showed that four main groups of faults with NE, NW, near EW, and near SN trends developed in the Palawan basin and adjacent areas in the SCS. The NE-trending fault was the regional fault, while the NW-trending fault was the main fault. The NW-trending fault often terminated at the NE-trending fault, indicating that the NW-trending fault was formed later. This investigation has characterized two different types (Type I and Type II) of exploration favorable areas based on characteristics observed. The most notable characteristic of these exploration favorable areas was that they were located in the high value zones of the local anomaly of Bouguer gravity anomaly, and their development was obviously controlled by the faults. The amplitude of gravity anomalies was higher and the gradient of the gravity anomalies was steeper, and there were oil and gas wells and fields distributed in Type I favorable areas for exploration. Compared with Type I favorable areas, the amplitude of gravity anomalies was relatively small and the gradient of the gravity anomalies was relatively gentle corresponding to Type II favorable areas.
- Asia > China (1.00)
- Asia > Philippines > Palawan (0.28)
- Phanerozoic > Mesozoic (1.00)
- Phanerozoic > Cenozoic > Paleogene (0.46)
- Geology > Structural Geology > Tectonics > Plate Tectonics (1.00)
- Geology > Structural Geology > Fault (1.00)
- Geology > Rock Type (1.00)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (1.00)
- Geophysics > Magnetic Surveying (1.00)
- Geophysics > Gravity Surveying > Gravity Acquisition (0.67)
- South America > Venezuela > Caribbean Sea > Tobago Basin (0.99)
- Asia > Philippines > Palawan > South China Sea > Northwest Palawan Basin > West Linapacan Field (0.99)
- Asia > Philippines > Palawan Basin (0.99)
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- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management (1.00)
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"Faults and fractures are not necessarily good or bad, but it's important to really understand them." In this compelling episode, host Andrew Geary and Molly dive into the murky depths of the Earth to unravel the enigmatic nature of faults and fractures. Molly sheds light on the crucial role of imaging these hidden networks in understanding their impact on production, injection, and completions. With a clear message that faults and fractures are neither inherently good nor bad, this conversation challenges common misconceptions and emphasizes the importance of detailed imaging to gauge their significance. Molly offers her expertise in navigating the persistent hurdles in characterizing faults and fractures, especially ones below seismic resolution.
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
Quantitative prediction of the fracture scale based on frequency-dependent S-wave splitting
Yu, Peilin (Chengdu University of Technology) | Yang, Yuyong (Chengdu University of Technology, State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation) | Qi, Qiaomu (Chengdu University of Technology, State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation) | Zhou, Huailai (Chengdu University of Technology, State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation) | Wang, Yuanjun (Chengdu University of Technology, China West Normal University)
ABSTRACT The development of natural fractures has a significant impact on underground reservoirs and leads to seismic anisotropy. Furthermore, the scale of natural fractures directly affects oil and gas preservation, hydraulic fracture construction, and the production development of shale reservoirs. The S-wave anisotropy is a frequency-dependent parameter and the change in S-wave anisotropy with frequency is a function of the fracture scale. We develop an innovative method for predicting the fracture scale quantitatively using frequency-dependent S-wave anisotropy. The quantitative relationship between different fracture scales and the frequency-dependent response of the S-wave splitting (SWS) anisotropy can be obtained using a dynamic rock-physics model. The frequency-dependent S-wave anisotropy is calculated via SWS analysis in the frequency domain, after which this quantitative relationship and the calculated frequency-dependent response are used to establish an objective function for the inversion of the fracture scale at different depths using the least-squares algorithm. We synthesize data under ideal conditions, test our method, apply our method to field data, and find that the quantitative prediction method of the fracture scale yielded reasonable prediction results. The S-wave anisotropy is calculated based on the SWS analysis from the horizontal components of the upgoing wavefields of the field vertical seismic profile. We compare the fracture scale calculated from logging data using our method, and the results obtained indicate that this method can successfully predict the fracture scale quantitatively.
- Geology > Geological Subdiscipline > Geomechanics (0.88)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.34)
- North America > United States > California > San Joaquin Basin > Lost Hills Field (0.99)
- Asia > Middle East > Oman > Ad Dhahirah Governorate > Fahud Salt Basin > Natih Field (0.99)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin (0.99)
- (2 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
In this special section, we present a collection S-wave attribute. of papers that, in the absence of world-class outcrop exposures Salazar Florez and Bedle demonstrate the usefulness of geometric such as that shown on this issue's cover, utilize various data sets seismic attributes such as aberrancy for enhancing fault and geophysical processing techniques to illuminate fault and visualization, especially for subseismic faulting scenarios. They find that including aberrancy and carbon storage sites. The authors also show that integrating aberrancy with (WCSB) using simple geologic tools and approaches, without other geometric attributes improves results from multiattribute relying on seismic reflection data. The author's work reveals analysis and unsupervised machine learning techniques such as extensive strike-slip fault systems, detachment planes, and self-organizing maps and generative topographic mapping. This examples of fault locking and alternate fault activity -- important study makes a strong case for interpreters to incorporate aberrancy considerations for hydrocarbon exploration and production.
- North America > Canada (1.00)
- North America > United States > Texas > Travis County > Austin (0.16)
- North America > United States > Wyoming > Washakie Basin (0.99)
- North America > United States > Texas > Permian Basin > Midland Basin (0.99)
- North America > United States > Colorado > Washakie Basin (0.99)
- (5 more...)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
- Data Science & Engineering Analytics > Information Management and Systems > Artificial intelligence (1.00)
Abstract One of the most important applications of shear-wave (S-wave) seismic exploration has been in reservoir fracture characterization. While many advancements have been made over the past 30 years to compute and correct for the long-wavelength kinematics of S-wave splitting (SWS) (fast S-wave polarization directions and slow S-wave time delays), practically no progress has been made in imaging the short-wavelength reflectivity of fractures directly with Δγ. This property is the contrast in the SWS anisotropy parameter, γ, and represents the reflection amplitude at vertical incidence for changes in fracture density and orientation across an interface. In this article, we examine the Lupin nine-component survey in Midland Basin, Texas, for the technical reliability of imaging fractures in depth with converted P to S waves (PS waves) guided by pure-mode horizontal shear waves and vertical shear waves. Final Δγ amplitude maps for each mode show sensitivity to fractures, faults, and the maximum horizontal stress direction. These maps are computed from the difference between fast and slow S-wave stacks (after SWS analysis and correction) and P-wave amplitude variation with offset gradient stacks. The S-wave difference maps identify an east–west lineament, possibly a strike-slip fault or fracture corridor, that is not observed by P-wave depth slices. Pure-mode S waves and PS waves are orders of magnitude more sensitive to Δγ than P waves. We also review the development of Δγ and find that it has been relatively unexploited by the exploration industry. In addition, we demonstrate that Δγ can be obtained directly from the objective function of the transverse energy to correct for SWS, and show a four-component Alford rotation example from a previous PS-wave survey in the Washakie Basin, Wyoming.
- North America > United States > Texas (1.00)
- North America > United States > Wyoming (0.88)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Fault > Strike-Slip Fault (0.34)
- North America > United States > Wyoming > Washakie Basin (0.99)
- North America > United States > Wyoming > Sand Wash Basin (0.99)
- North America > United States > Wyoming > Green River Basin (0.99)
- (44 more...)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
Abstract The geology toolkit that is used to reveal faults and fractures is much wider than before. This is due to 3D and 4D views in exploratory statistics programs and to the availability of user-friendly GIS software. These tools allow us to visualize a multitude of parameters that will be briefly explored here. A review of many geologic and nongeologic parameters led to evidence of fault locking and alternate fault activity. It also resulted in new structural models for the Western Canadian Sedimentary Basin (WCSB). The presented data sets include earthquakes, drilling, production, well data, aeromagnetic data, and more. Various integrated approaches reveal well-defined fault patterns that are typical of a strike-slip regime and the existence of previously unrecognized detachments that are important for hydrocarbon exploration. Some of the new geometries and associated mechanisms are illustrated here with outcrop analogues and present-day cross sections, maps, and 3D views. Only the most recent of the two identified strike-slip regimes is covered in this paper. Some emphasis is given to the recognition of detachments at various scales. Among these is the importance of megadetachments displacing the sedimentary cover by up to 16 km with respect to the aeromag. Hence, there is a need for reconstruction before making conclusions. The WCSB has a lot more to offer to explorers who understand faults, fractures, and migration paths. Integrating many types of information in map or 3D views offers new tools to identify and characterize faults.
- North America > Canada > Saskatchewan (1.00)
- North America > Canada > Northwest Territories (1.00)
- North America > Canada > Manitoba (1.00)
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- Phanerozoic > Mesozoic (0.69)
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- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (1.00)
- Geology > Structural Geology > Fault (1.00)
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Magnetic Surveying > Magnetic Acquisition > Airborne Magnetic Acquisition (0.91)
- North America > Canada > Saskatchewan > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Northwest Territories > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Manitoba > Western Canada Sedimentary Basin > Alberta Basin (0.99)
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- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
- (2 more...)
The main objective of this work is to understand the impact of fracture, stress, drilling direction and other reservoir properties on the production performance in horizontal well (HW). Taking advantage of seventy available borehole image logs helped to extend analysis beyond individual wells to a field scale evaluation. Three analysis techniques were developed to progress with the study: Digital Interpretation of Borehole Breakout in image log, Favored Drilling Direction Map, and a Reservoir Property Filter to gauge well performance. Results in cross plots showed complicated, cloudy and multi-dimensional relationships. The findings will be used to guide future HW drilling optimization, support dynamic modeling and improve models predictability for effective reservoir management.
- North America > United States (0.46)
- Asia > Kazakhstan > West Kazakhstan Region (0.29)
- Phanerozoic > Paleozoic > Permian (0.94)
- Phanerozoic > Paleozoic > Devonian (0.68)
- Geology > Structural Geology > Tectonics (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock (0.93)
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- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Borehole Seismic Surveying (0.61)
- North America > United States > California > San Joaquin Basin > Lost Hills Field (0.99)
- North America > United States > California > Monterey Formation (0.99)
- Asia > Kazakhstan > West Kazakhstan > Uralsk Region > Precaspian Basin > Karachaganak Field (0.99)
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- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (0.93)
- (5 more...)
_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 3864861, “Geomechanics Modeling of Strain-Based Pressure Estimates: Insights From Distributed Fiber-Optic Strain Measurements,” by Wei Ma and Kan Wu, Texas A&M University, and Ge Jin, Colorado School of Mines. The paper has not been peer reviewed. _ The combination of Rayleigh frequency shift distributed strain sensing (RFS-DSS) and pressure-gauge measurements has been reported recently in field applications. The main objective of the study detailed in the complete paper is to investigate the relationship between strain change and pressure change under various fractured reservoir conditions and provide guidelines for better using this novel strain/pressure relationship to estimate conductive fractures and pressure profiles. Introduction With a spatial resolution of 20 cm and a sensitivity of less than 1 με, RFS-DSS can measure mechanical strain changes along the fiber with higher accuracy and sensitivity than low-frequency distributed acoustic sensing measurements. The field applications of RFS-DSS have improved the understanding of near-well and far-field fracture characteristics and the relationship between stimulation and production in unconventional reservoirs. Although some numerical modeling works have been conducted to study the mechanisms of RFS-DSS data sets, the sensitivity, or influencing factors, of the relationship between strain change and pressure change along the fiber are still unclear. In this work, the authors use a coupled geomechanics and fluid-flow simulator to simulate the strain change and pressure change measured along the producing and monitoring wells during both stable production and shut-in periods. Methodology A 3D multilayer reservoir model with dimensions of 300×400×55.82 m was created using Permian Basin data sets. The reservoir was discretized into 553×129×5 gridblocks. To ensure accurate simulation of field RFS-DSS measurements, the mesh was refined around the fracture and wellbore. The fracture width was set to be the same as the RFS-DSS spatial resolution (0.2 m), and the grid size was set to 5 m except for the refined region. As shown in Fig. 1, the reservoir had 11 perforation clusters along the producing well and the monitoring well was 65 m away from the producing well. A fiber cable was installed on both wells to measure the RFS-DSS data set. The producing well was operated for 240 days before being shut in for 4 days, followed by a 1-day reopening and then continued production for 1 year. The pressure decline was 30–40 psi during the 1-day stable production period. Note that the moment after producing 239 days was taken as the reference time to calculate the strain change during the 1-day production (239–240 days) and the moment after 240 days as the reference time to calculate the strain change during the shut-in period (240–244 days).
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (21 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (0.89)
_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 3871303, “Using a Multidisciplinary Approach to Reservoir and Completion Optimization Within the Woodford Shale Play of the Arkoma Basin,” by Stephen C. Zagurski, SPE, and Steve Asbill, SPE, Foundation Energy Management, and Christopher M. Smith, Advanced Hydrocarbon Stratigraphy, et al. The paper has not been peer reviewed. _ Subsurface complexities related to the formation of peripheral foreland basins can have significant effects on unconventional resource development. In the Arkoma Basin of southeast Oklahoma, the onset of thrusting and tectonic loading induced a complex series of dip/slip and strike/slip faults during basin formation. The operator used a series of technologies to increase understanding of the reservoir and its hazards and provide insight into economic implications for future development plans and strategies. Introduction The Woodford is primarily a Type II kerogen source rock. The formation typically is classified as either siliceous mudstone or cherty siltstone. Variable thermal maturity across the basin places the Woodford in both the wet-gas and dry-gas phase windows (moving west to east across the basin). Complex faulting regimes within the Arkoma add a layer of complexity to horizontal development of the Woodford. The operator wanted to increase the understanding of the Woodford and the effects of faulting through the reservoir in a recent development unit in the liquids-rich fairway. The development unit consists of an existing parent well (Well X) and a pair of child wells (Well Y and Well Z). The background of Unit XYZ begins with the completion of parent Well X 4–6 years before infill development. In this portion of the basin, Well X’s initial production rate and its cumulative production to date rank it in the top 25% of wells. The wellbore is subjected to a pair of faults and was drilled in the upper half of the Woodford. Placement of Well X is substantially further east than most parent wells because it is approximately 1,600 ft from the unit boundary. This limited infill development to two wells instead of three; the Arkoma typically has seen spacing of four, and sometimes five, wells per section. Wells Y and Z were planned and drilled east of Well X with 1,100–1,600 ft of well spacing. Well spacing in the unit was slightly hindered by surface location limitations and limited true vertical depth (TVD) between surface casing and landing point. Structural complexity within the unit partially impaired infill development of the unit. Specifically, Well Y and its lateral length was shortened. In this portion of the Arkoma, fault-derived water production typically is the highest-weighted variable in a well’s operating expenditure. Thus, the ability to limit excess water production within Unit XYZ and the surrounding acreage is of paramount importance.
- Geology > Geological Subdiscipline > Geochemistry (1.00)
- Geology > Petroleum Play Type > Unconventional Play > Shale Play (0.91)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.54)
- North America > United States > Oklahoma > Arkoma Basin > Cana Woodford Shale Formation (0.99)
- North America > United States > Oklahoma > Anadarko Basin > Cana Woodford Shale Formation (0.99)
- North America > United States > Arkansas > Arkoma Basin > Cana Woodford Shale Formation (0.99)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
- Management > Energy Economics > Unconventional resource economics (1.00)