Delaware Basin Horizontal Wolfcamp Case History: HTI Fracture Analysis to Avoid H2S and Extraneous Water Linked to Graben Features

Cook, S. W.; McKee, Mike; Bjorlie, Sid

doi:10.15530/urtec-2019-452

Cited by 6 publications

(1 citation statement)

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“…HF-induced seismicity has been favored in wells that are in proximity to the basement (Brudzinski & Kozłowska, 2019;Skoumal et al, 2018) or stimulated in highly overpressured shale formations (Eaton & Schultz, 2018). All these cases apply to the Delaware Basin, where overpressured shales, the HF target, are on top of the faulted basement rocks (Cook et al, 2019). Thus, association of seismicity with the deepest wells above the depth of seismicity, wells closest to basement, and injection in overpressured formations would prefer association of seismicity with HF over SWD activity in the study area.…”

Section: Association Of Seismicity With Hydraulic-fracturingmentioning

confidence: 99%

Improving Absolute Earthquake Location in West Texas Using Probabilistic, Proxy Ground‐Truth Station Corrections

Lomax¹,

Savvaidis

2019

JGR Solid Earth

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An increase in induced seismicity in the central United States since 2009 led to establishment of TexNet seismic-monitoring in Texas. Accurate, absolute seismic-event location is critical to TexNet, allowing quantitative evaluation of possible association of seismicity with human activity. For the Delaware Basin, western Texas, relocation using different velocity models and TexNet station subsets shows absolute location error up to 4-5 km. The preferred method to reduce absolute error, ground-truth calibration, is not available in this area. Alternatively, we used industrial well activity as proxy, ground-truth for developing probabilistic, proxy ground-truth (PPGT) station corrections for relocation. Assuming well activity causes seismicity, we defined a distance-time probability associating events and well activity. We used these associations and other evidence to show some seismicity in the Delaware Basin is more likely due to hydraulic-fracturing than saltwater disposal. We then probabilistically accumulated PPGT station corrections using event hypocenters constrained to associated fracturing-well locations. We applied this procedure within 12 km of TexNet station PB02, optimizing the procedure through comparison of rates of causal and acausal associations. Relative to the initial locations, final PPGT relocations show smaller residuals and shifts in epicenter as much as 3 km, predominantly toward the north and northwest. PPGT residuals are similar to those from relocation with standard station corrections. The initial hypocenters showed an unreasonable deepening with distance from station PB02, whereas PPGT relocations produced an overall flattening of event depths. These results are consistent with PPGT corrections giving real improvement in absolute location accuracy.Plain Language Summary The TexNet seismic-monitoring program in Texas was established in response to an increase in human-induced earthquakes in the central United States since 2009. Accurate determination of the geographic location and depth in the Earth of earthquakes is critical to TexNet monitoring, allowing potential association of earthquakes with human activity. But accurately locating earthquakes is difficult due to lack of geologic knowledge and sparsity of seismic monitoring stations. For a study area in western Texas, errors in TexNet earthquake location and depth may be as much as 4-5 km. Ideally, accuracy would be improved by calibration of the seismic network using ground-truth seismic events, such as quarry blasts, but such information is unavailable in this area. Instead, assuming that some earthquakes could be caused by hydraulic-fracturing in the study area, we statistically associate earthquakes in space and time to fracturing activity. We then use the known locations of this associated activity as proxy ground-truth to calibrate the seismic network. Our results suggest some earthquakes in west Texas are more likely due to hydraulic-fracturing than saltwater disposal. Quality measures and spatial patterns of earthquakes relo...

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Section: Association Of Seismicity With Hydraulic-fracturingmentioning

confidence: 99%

Improving Absolute Earthquake Location in West Texas Using Probabilistic, Proxy Ground‐Truth Station Corrections

Lomax¹,

Savvaidis

2019

JGR Solid Earth

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Structural characteristics of shallow faults in the Delaware Basin

et al. 2022

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The Delaware Basin of Texas and New Mexico is experiencing elevated levels of seismicity. There have been more than 130 earthquakes with moment magnitudes of at least 3.0 recorded between 2017 and 2021, with earthquakes occurring in spatiotemporally isolated and diffuse clusters. Many of these events have been linked to oilfield operations such as hydraulic fracturing and wastewater disposal at multiple subsurface levels; however, the identification and characterization of earthquake-hosting faults have remained elusive. There are two distinct levels of faulting in the central region of the basin where most earthquakes have been measured. These fault systems include a contractional basement-rooted fault system and a shallow extensional fault system. Shallow faults trend parallel to and rotate along with, the azimuth of S HMAX, are vertically decoupled from the basement-rooted faults, accommodate dominantly dip-slip motion, and are the product of more recent processes including regional exhumation and anthropogenic influences. The shallow fault system is composed of northwest–southeast-striking, high angle, and parallel trending faults which delineate a series of elongate, narrow, and extensional graben. Although most apparent in 3D seismic reflection data, these narrow elongate graben features also are observed from interferometric synthetic aperture radar (InSAR) surface deformation measurements and can be delineated using well-located earthquakes. In contrast to the basin-compartmentalizing basement-rooted fault system, shallow faults do not display any shear movement indicators, and they have small throw displacement given their mapped length, producing an anomalous mean throw-to-length ratio of 1:1000. These characteristics indicate that these features are more segmented than can be mapped with conventional subsurface data. Much of the recent seismicity in the south-central Delaware Basin is associated with these faults and InSAR surface deformation observations find that these faults also may be slipping aseismically.

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Multilayer 3D seismic attribute analysis and fault framework modeling of shallow extensional fault systems in the Delaware Basin

Petkovsek

2024

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Shallow extensional fault systems within the southern Delaware Basin have gained the interest of Permian operators since published works noted them in 2019. These shallow extensional fault systems, referred to as “lineaments” by operators, are seismogenic hazards, pose significant hazards to drilling operations, and are associated with elevated water-oil-ratios (WOR) and H2S concentrations. Previous work using seismic attribute analysis has resulted in the successful mapping of extensional fault systems at the Ochoan/Guadalupian interface, while fault geometry, origin, and depth of penetration have remained elusive. First-and-second-order ant-tracking of the variance cube is rendered on multiple seismic horizons throughout an 856 km2 (approximately 330 mi2) depth-migrated 3D seismic reflection volume to expand interpretation of the deformation zone at depth and guide a robust 3D fault model which forms the framework for the predictive model. A total of 60 previously undocumented features are identified in southwestern Reeves County- 56 that penetrate the Ochoan/Guadalupian interface, 60 that penetrate the middle Guadalupian, 29 that penetrate the early Guadalupian, and 21 that penetrate the early Leonardian. Structural modeling returns an average strike orientation of 318° north-northwest-south-southeast and an average dip of 84°. Spatial and temporal analysis of the model constrains the timing of extension to the Cenozoic. In contrast to previous studies, the improved depth of investigation of the 3D fault model allows for correlation of documented drilling hazards with offset wastewater disposal wells along shared lineaments. Communication is indicated by H2S risking flags from mass spectrometry data along the vertical and horizontal sections of producing and injecting wells. Drilling data validates the seismic characterization and prediction of the 3D faulted architecture within the largest contiguous study of shallow extensional fault systems within the Delaware Basin and establishes a repeatable workflow for mitigating the negative impacts of shallow lineament geohazards on drilling operations and production profiles.

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Delaware Basin Horizontal Wolfcamp Case History: HTI Fracture Analysis to Avoid H2S and Extraneous Water Linked to Graben Features

Cited by 6 publications

References 0 publications

Improving Absolute Earthquake Location in West Texas Using Probabilistic, Proxy Ground‐Truth Station Corrections

Improving Absolute Earthquake Location in West Texas Using Probabilistic, Proxy Ground‐Truth Station Corrections

Structural characteristics of shallow faults in the Delaware Basin

Multilayer 3D seismic attribute analysis and fault framework modeling of shallow extensional fault systems in the Delaware Basin

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