Fracture mapping using seismic amplitude variation with offset and azimuth analysis at the Weyburn CO2 storage site

Cap rock integrity is an essential characteristic of any reservoir to be used for long-term [Formula: see text] storage. Seismic AVOA (amplitude variation with offset and azimuth) techniques have been applied to map HTI anisotropy near the cap rock of the Weyburn field in southeast Saskatchewan, Canada, with the purpose of identifying potential fracture zones that may compromise seal integrity. This analysis, supported by modeling, observes the top of the regional seal (Watrous Formation) to have low levels of HTI anisotropy, whereas the reservoir cap rock (composite Midale Evaporite and Ratcliffe Beds) contains isolated areas of high intensity anisotropy, which may be fracture-related. Properties of the fracture fill and hydraulic conductivity within the inferred fracture zones are not constrained using this technique. The predominant orientations of the observed anisotropy are parallel and normal to the direction of maximum horizontal stress (northeast–southwest) and agree closely with previous fracture studies on core samples from the reservoir. Anisotropy anomalies are observed to correlate spatially with salt dissolution structures in the cap rock and overlying horizons as interpreted from 3D seismic cross sections.

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Fracture detection via correlating P-wave amplitude variation with offset and azimuth analysis and well data in eastern central Saudi Arabia

Interpretation ◽

10.1190/int-2016-0128.1 ◽

2017 ◽

Vol 5 (4) ◽

pp. T531-T544

Author(s):

Ali H. Al-Gawas ◽

Abdullatif A. Al-Shuhail

Keyword(s):

Saudi Arabia ◽

Seismic Data ◽

Production Data ◽

Fracture Zones ◽

Fracture Detection ◽

Amplitude Variation ◽

Data Set ◽

Amplitude Variation With Offset ◽

Well Data ◽

Patch Geometry

The late Carboniferous clastic Unayzah-C in eastern central Saudi Arabia is a low-porosity, possibly fractured reservoir. Mapping the Unayzah-C is a challenge due to the low signal-to-noise ratio (S/N) and limited bandwidth in the conventional 3D seismic data. A related challenge is delineating and characterizing fracture zones within the Unayzah-C. Full-azimuth 3D broadband seismic data were acquired using point receivers, low-frequency sweeps down to 2 Hz, and 6 km patch geometry. The data indicate significant enhancement in continuity and resolution of the reflection data, leading to improved mapping of the Unayzah-C. Because the data set has a rectangular patch geometry with full inline offsets to 6000 m, using amplitude variation with offset and azimuth (AVOA) may be effective to delineate and characterize fracture zones within Unayzah-A and Unayzah-C. The study was undertaken to determine the improvement of wide-azimuth seismic data in fracture detection in clastic reservoirs. The results were validated with available well data including borehole images, well tests, and production data in the Unayzah-A. There are no production data or borehole images within the Unayzah-C. For validation, we had to refer to a comparison of alternative seismic fracture detection methods, mainly curvature and coherence. Anisotropy was found to be weak, which may be due to noise, clastic lithology, and heterogeneity of the reservoirs, in both reservoirs except for along the western steep flank of the study area. These may correspond to some north–south-trending faults suggested by circulation loss and borehole image data in a few wells. The orientation of the long axis of the anisotropy ellipses is northwest–southeast, and it is not in agreement with the north–south structural trend. No correlation was found among the curvature, coherence, and AVOA in Unayzah-A or Unayzah-C. Some possible explanations for the low correlation between the AVOA ellipticity and the natural fractures are a noisy data set, overburden anisotropy, heterogeneity, granulation seams, and deformation.

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Subsea Re-Abandonment Strategies for High-Risk Wells to Minimize Leakage Risk in a Depleted Field for CO2 Storage

10.2118/207944-ms ◽

2021 ◽

Author(s):

Parimal A Patil ◽

Debasis P. Das ◽

Pankaj K. Tiwari ◽

Prasanna Chidambaram ◽

Renato J. Leite ◽

...

Keyword(s):

High Risk ◽

Co2 Storage ◽

Horizontal Stress ◽

Leakage Rate ◽

Storage Site ◽

Co2 Leakage ◽

Well Integrity ◽

Abandoned Wells ◽

Fracture Gradient ◽

Maximum Horizontal Stress

Abstract CO2 storage in a depleted field comes with the risk that is associated with wells integrity which is often defined as the ability to contain fluids with minimum to nil leakage throughout the project lifecycle. The targeted CO2 storage reservoir in offshore Malaysia has existing abandoned exploration/appraisal, and development wells. With a view of developing such CO2 storage sites, it is vital to maintain the integrity of the abandoned wells. High-risk characterized wells need to be analyzed and remedial action plan to be defined by understanding the complexity involved in restoring the integrity. This will safeguard CO2 containment for decades. Abandoned exploration/appraisal wells in the identified field are >40 years old and were not designed to withstand CO2 corrosion environment. Downhole temperature and pressure conditions may have further degraded the wellbore material strength elevating corrosion susceptibility. The reservoir simulation predicts that the CO2 plume will reach to these abandoned wells during the initial phase of total injection period. Single well was selected to assess the loss of containment through the composite structure along the wellbore and to determine the complexity in resorting the well integrity. CO2 leakage rates through all possible pathways were estimated based on numerical models and the well is characterized for its risk. For unacceptable leakage risk, the abandoned well needs to be re-entered to restore the performance of barriers. Minimum plug setting depth (MPSD) and caprock restoration considers original reservoir pressure(3450psia) anticipating the pressure buildup upon CO2 injection and is derived based on fracture gradient and maximum horizontal stress. This paper elaborates unique challenges associated with locating abandoned wells that are submerged below seabed. Top and side re-entry strategies are discussed to overcome challenges. Based on past abandonment scheme, leakage rate modeling calculates estimated leakage rate of ~460SCFD at higher differential pressure of around 3036psia at shallowest barrier and ~15SCFD for differential pressure of 1518psia at deepest barrier. Sensitivity analysis has been carried out for critical barrier parameters (cement permeability, cracks, fractures) to the containment ability and improving understanding of quality of barriers, uncertainties, and complexities for CO2 leakage risk. The paper proposes two(2) minimum plug setting depths (3550ft & 3750ft) derived based on fracture gradient and maximum horizontal stress. Perforate-wash-cement (PWC) and section milling were compared for operational efficiencies to achieve caprock restoration. for MPSD out strategic options to restore well integrity by remediating casing/cement barriers at by performing best fit abandonment technique to contain CO2 in the reservoir. Well integrity risk is assessed for existing plugged and abandoned (P&A) wells in a carbon storage site. Optimized remedial actions are proposed. Quantification of all the uncertainties are resolved that may affect long-term security of CO2 storage site.

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Geological characterization of the Patterson CO2 storage site from 3-D seismic data

Midcontinent Geoscience ◽

10.17161/mg.v1i.15529 ◽

2020 ◽

Vol 1 ◽

pp. 52-90

Author(s):

Jenny Meng ◽

Eugene Holubnyak ◽

Franek Hasiuk ◽

Jenn Hollenbach ◽

Dana Wreath

Keyword(s):

Seismic Data ◽

Co2 Storage ◽

Storage Site ◽

Seismic Attribute ◽

Seal Integrity ◽

Structural Style ◽

Incised Valleys ◽

Structural Relief ◽

Reservoir Description ◽

Carbon Dioxide Co2

Approximately 26 square miles of new 3-D seismic data were acquired in July 2019 over the Patterson Site (Kearny County, Kansas) to assess its potential for carbon dioxide (CO2) storage. Seismic interpretation revealed that the Patterson Site contains multiple structural closures that lie on uplifted fault blocks, bounded by two reverse faults that strike nearly perpendicular to each other. These faults offset Precambrian through Pennsylvanian sections, including several primary reservoir and seal intervals. Fault displacements are maximum at the Precambrian basement and decrease upward. Data indicated a range of structural and combination traps exists at the Patterson Site in the Cambrian-Ordovician Arbuckle through Mississippian Osagian reservoirs. The three-way closures along the NW–SE fault have structural relief of ~130 ft (40 m), and the four-way closures contain relief of ~60 ft (18 m). Erosional surfaces and multiple basement fractures also are observed on the top of the Precambrian. A Mississippian-aged incised valley system also was observed at the Patterson Site. The incised valleys formed during the Meramecian-Chesteran Stages with an incised depth up to 250 ft (76 m). The motion of the reverse faults likely captured existing meandering and linear channels, causing the current deeply incised morphology. The incised valleys observed at Patterson are similar in age, structural style, shape, incision depth, and seismic attribute properties to incised valleys observed by other workers at Pleasant Prairie South, Eubank, and Shuck oil fields (southwest Kansas). Further research should focus on estimating reactivation tendency and sealing characteristics of the reverse faults to evaluate the seal integrity of the saline reservoirs. This will reduce uncertainty concerning the risk of CO2 migration during injection and storage. Further reservoir description, modeling, and simulation are also underway to characterize the storage potential at the Patterson Site.

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Derisking low-saturation gas in Tertiary turbidite reservoirs

Interpretation ◽

10.1190/int-2016-0034.1 ◽

2016 ◽

Vol 4 (3) ◽

pp. SN31-SN43

Author(s):

Krzysztof M. Wojcik ◽

Ezequiel Gonzalez ◽

Robert E. Vines

Keyword(s):

Geophysical Methods ◽

False Positives ◽

Bayesian Probability ◽

Amplitude Variation ◽

Amplitude Variation With Offset ◽

Seal Integrity ◽

Residual Gas ◽

Net To Gross ◽

High Possibility ◽

Proper Context

Occurrences of low-saturation gas (LSG) in tertiary turbidite reservoirs are common and often characterized by anomalous amplitude/amplitude variation with offset (AVO) response, which can be classified as false positives. LSG cases are difficult to derisk with geophysical methods because the anomalous responses may be very similar to success-case (oil or gas) anomalies. LSG failures may represent true residual gas in cases of seal integrity failure (“blown” trap) or variable saturation of gas in low net-to-gross laminated sandstone/siltstone or siltstone/mudstone intervals (“generic LSG”), which represent a type of reservoir failure. Derisking exploration opportunities burdened with a high possibility of LSG failure require an integrated evaluation of the geophysical evidence in the proper context of charge setting, reservoir/seal stratigraphy, structural setting, and trap geometry. Although geophysical methods may not provide fully conclusive predictions, the integration of geophysical observations with a geologic framework and realistic geologic chance factors can result in effective derisking of potential low-saturation failure cases through the estimation of geophysical scenario likelihood values and Bayesian probability updates.

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Amplitude Variation with Offset Responses Modeling Study of Walkaway Vertical Seismic Profile Data at CO2 Geological Storage Site, Ketzin, Germany

Acta Geologica Sinica - English Edition ◽

10.1111/j.1755-6724.2011.00544.x ◽

2011 ◽

Vol 85 (5) ◽

pp. 1118-1126

Author(s):

Can YANG ◽

Sayed Hesammoddin KAZEMEINI ◽

Wenfang FAN ◽

Christopher JUHLIN ◽

Dameng LIU

Keyword(s):

Seismic Profile ◽

Storage Site ◽

Geological Storage ◽

Co2 Geological Storage ◽

Profile Data ◽

Vertical Seismic Profile ◽

Amplitude Variation ◽

Amplitude Variation With Offset ◽

Modeling Study

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Estimates of scCO2 Storage and Sealing Capacity of the Janggi Basin in Korea Based on Laboratory Scale Experiments

Minerals ◽

10.3390/min9090515 ◽

2019 ◽

Vol 9 (9) ◽

pp. 515 ◽

Cited By ~ 2

Author(s):

Jinyoung Park ◽

Minjune Yang ◽

Seyoon Kim ◽

Minhee Lee ◽

Sookyun Wang

Keyword(s):

Storage Capacity ◽

Co2 Storage ◽

Reservoir Rock ◽

Storage Site ◽

Sealing Capacity ◽

Entry Pressure ◽

Before And After ◽

Cap Rock ◽

Capillary Entry Pressure ◽

Xrf Analyses

Laboratory experiments were performed to measure the supercritical CO2 (scCO2) storage ratio (%) of conglomerate and sandstone in the Janggi Basin, which are classified as rock in Korea that are available for CO2 storage. The scCO2 storage capacity was evaluated by direct measurement of the amount of scCO2 replacing the pore water in each reservoir rock core. The scCO2 sealing capacity of the cap rock (i.e., tuff and mudstone) was also compared by measuring the scCO2 capillary entry pressure (Δp) into the rock core. The measured average scCO2 storage ratio of the conglomerate and the sandstone were 30.7% and 13.1%, respectively, suggesting that the scCO2 storage capacity was greater than 360,000 metric tons. The scCO2 capillary entry pressure for the tuff ranged from 15 to 20 bar and for the mudstone it was higher than 150 bar, suggesting that the mudstone layers had enough sealing capacity from the aspect of hydromechanics. From XRF analyses, before and after 90 d of the scCO2-water-cap rock reaction, the mudstone and the tuff were investigated to assure their geochemical stability as the cap rock. From the study, the Janggi Basin was considered an optimal CO2 storage site based on both its high scCO2 storage ratio and high capillary entry pressure.

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