Draupne Formation
Rock physics and seismic reflectivity parameterization for amplitude-variation-with-angle inversion of low-maturity source rocks
Yu, Songhe (China University of Petroleum (East China)) | Zong, Zhaoyun (China University of Petroleum (East China)) | Li, Kun (China University of Petroleum (East China))
ABSTRACT Rock-physics inversion has been widely used in reservoir prediction. However, the prediction and evaluation of source rocks still predominantly rely on data-driven inversion methods. To directly incorporate the rock-physics relationship into the seismic inversion of source rocks, we first introduce a linearization approximation of the rock-physics model through the first-order approximation of the Taylor series. Model examples and well-logging tests substantiate the reliability of this linear approximation in establishing the connection between the elastic moduli and essential physical parameters (EPPs) of source rocks. Subsequently, we develop a novel equation for the P-wave reflection coefficient by combining the linear rock-physics relationship and Gray approximation. The newly developed reflectivity equation is a linear expression of differences in EPPs of source rocks. Model-simulating results demonstrate a favorable agreement between the novel P-wave reflectivity equation and the exact Zoeppritz equation until the incident angle reaches 60°. Furthermore, we explore the amplitude-variation-with-angle (AVA) effects of EPPs to validate their contributions meet the requirement of seismic inversion. Under the Bayesian scheme, we further develop an AVA inversion method, based on the novel P-wave reflectivity equation, to predict the EPPs of source rocks. Our AVA inversion method obtains satisfactory results under noise testing and demonstrates promising application potential in field examples. The predicted EPPs indicate a strong agreement with the actual well loggings. Comparative analysis against data-driven inversion results reveals that the EPPs predicted by our AVA inversion method possess enhanced rock-physics support and significance. Specifically, this study focuses on isotropic clay-rich source rocks with low maturity.
- Asia > Middle East (0.68)
- Europe > Norway > North Sea (0.28)
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Geological Subdiscipline > Geochemistry (1.00)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (1.00)
- Oceania > New Zealand > North Island > Taranaki Basin (0.99)
- Asia > Middle East > Oman > Al Buraymi Governorate > Block 44 > Shams Field (0.99)
- Asia > Middle East > Iran > Khuzestan > Arabian Basin > Widyan Basin > Mesopotamian Basin > West Karoun Block > West Karoun Field > Azadegan Field > Sarvak Formation (0.99)
- (5 more...)
Rock-physics inversion has been widely used in reservoir prediction. However, the prediction and evaluation of source rocks still predominantly rely on data-driven inversion methods. In order to directly incorporate the rock-physics relationship into the seismic inversion of source rocks, we first introduce a linearization approximation of the rock-physics model through the first-order approximation of the Taylor series. Model examples and well-logging tests substantiate the reliability of this linear approximation in establishing the connection between the elastic moduli and essential physical parameters of source rocks. Subsequently, we propose a novel equation for the P-wave reflection coefficient by combining the linear rock-physics relationship and Gray approximation. The newly developed reflectivity equation is a linear expression of differences in essential physical parameters of source rocks. Model-simulating results demonstrate a favorable agreement between the novel P-wave reflectivity equation and the exact Zoeppritz equation until the incident angle reaches 60 degrees. Furthermore, we explore the amplitude versus angle effects of essential physical parameters to validate their contributions meet the requirement of seismic inversion. Under the Bayesian scheme, we further propose an amplitude versus angle inversion method, based on the novel P-wave reflectivity equation, to predict the essential physical parameters of source rocks. The proposed amplitude versus angle inversion method gets satisfactory results under noise testing and demonstrates promising application potential in field examples. The predicted essential physical parameters show a strong agreement with the actual well-loggings. Comparative analysis against data-driven inversion results reveals that the essential physical parameters predicted by the proposed amplitude versus angle inversion method possess enhanced rock-physics support and significance. Specifically, this study focuses on isotropic, clay-rich source rocks with low maturity.
- Asia > Middle East (0.67)
- Europe > Norway > North Sea (0.28)
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Geological Subdiscipline > Geochemistry (1.00)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling > Seismic Inversion (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation > Seismic Reservoir Characterization > Amplitude vs Offset (AVO) (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation > Seismic Reservoir Characterization > Amplitude vs Angle (AVA) (1.00)
- Oceania > New Zealand > North Island > Taranaki Basin (0.99)
- Asia > Middle East > Oman > Al Buraymi Governorate > Block 44 > Shams Field (0.99)
- Asia > Middle East > Iran > Khuzestan > Arabian Basin > Widyan Basin > Mesopotamian Basin > West Karoun Block > West Karoun Field > Azadegan Field > Sarvak Formation (0.99)
- (5 more...)
A Three-Dimensional, Finite Element-Based Study of the Effect of Heterogeneities on Thermo-Hydro-Mechanical Deformation During Cold Fluid Injection
Chaiwan, P. (Imperial College) | Burtonshaw, J. E. J. (Imperial College) | Thomas, R. N. (Imperial College) | Paluszny, A. (Imperial College) | Zimmerman, R. W. (Imperial College)
ABSTRACT This paper investigates the effects of the injection of (relatively) cold CO2 into a saline aquifer, focusing on the effects that local heterogeneities may have on the geomechanical changes observed during injection. Representative properties of the Smeaheia site, a full-scale carbon storage site in the North Sea, are used in the simulation. The geometry of the Smeaheia site is represented by a simplified three-dimensional geometric model containing four rock layers, and a fault that spans multiple layers. Thermo-poro-elastic deformation is modeled using a finite element approach, with the coupled solution of fluid flow, heat transfer, and mechanical deformation of the Smeaheia site. The boundary conditions are based on in situ conditions at the Smeaheia site, along with fixed injection temperature and flow rate. The effects of injection rates, injection periods, injection temperatures, heterogeneities, fault, and fracture properties are investigated. The results show that the changes in temperature, pressure, and stresses are concentrated in the vicinity of the injection point, with a limited effect on the caprock away from the injection well. Thermal stresses dominate the overall stress reduction, shifting the stress state towards the failure condition. The flow rate causes a localized effect on the pressure field, due to the high permeability of the reservoir. Heterogeneity in the Young's modulus yields variations in deformation which are of comparable magnitude to the effects of cold injection. INTRODUCTION Cold fluid injection is a topic of interest in future sustainable technology for both geological carbon storage and geothermal energy. Fluids injected into the subsurface often have lower temperatures than in situ reservoirs (Li et al., 2021; Salimzadeh et al., 2018a). The temperature difference can induce thermal stresses, thermally driven fracture, and contraction of the rock caused by heat transfer between the fluid and reservoir fractures and rock matrix (Celia et al., 2015; Jeanne et al., 2014; Rutqvist, 2012; Taylor & Bryant, 2014).
- Europe > North Sea (0.34)
- Europe > United Kingdom > North Sea (0.25)
- Europe > Norway > North Sea (0.25)
- (2 more...)
- Research Report > New Finding (0.34)
- Overview (0.34)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.69)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 090 > Dunlin Group (0.99)
- North America > United States > New Mexico > Permian Basin > Caprock Field > Queen Formation (0.98)
- Europe > Norway > North Sea > Draupne Formation (0.98)
Robust and Automatic Shale Volume Interpretation Using Adaptive Lithological Thresholds Built on Depth Trends, Statistics, and Geological Units
Westeng, Kjetil (Aker BP) | Van Crombrugge, Yan (Inmeta) | Lehre, Christian Nilsen (Sopra Steria) | Aursand, Peder (Aker BP) | Fjeldberg, Egil Romsås (Aker BP)
ABSTRACT The volume fraction of shale (VSH) throughout the well is of great importance both for formation evaluation, geomechanics and numerous other workflows. Neither porosity, saturation nor permeability can be understood if one not first have a good grasp of the VSH. The objective of this paper is a method for automated VSH calulation which is effective, un-biased, and to lesser degree afftected by the log coverage in the well, as well as able to handle the variation in both radioactivity and density-neutron response as a function of depth and formation. The method combined statistics and dynamic filtering with geological context to create adaptive depth trends representing the log response of shale and sand/carbonates. Algorithm main steps: 1. Calculate dynamic sand and shale trends for each curve within each geological unit 2. Identify section and tool change - centered rolling quantiles are reset where a tool change is identified 3. Identify non-shale intervals by using the trends from 1. and custom thresholds (these can be adjusted by the user) 4. For each non-shale window detect the first inflection point before and after the window and interpolate between these two 5. Combine the interpolated trend curves with the dynamic trend curves from 1. 6. Calculate VSHGR and VSHDENNEU using the respective final trend curves 7. Combine these to produce the final aggregated curve VSHAUT This automated VSH interpretation method has been applied to more than 1000 wells from various areas in the North Sea and the Norwegian Sea. It has been proven to provide a reliable interpretation compared to manual interpretation. In contrast to many other methods for automated VSH interpretation, our proposed method will by design be less affected by which intervals are and are not covered by each log. This work will show how the method can be applied to calculate the VSH from both the gamma ray log and from the density – neutron porosity relationship. The method can, e.g., handle variation in matrix radioactivity within a lithostratigraphic system as well as depth trends in shale properties. The efficiency and avoidance of manual parameterization makes our method ideal for a fast evaluation of the full wellbore, as the starting point for a more detailed manual interpretation, or for fast and consistent massive multi-well evaluations.
- Europe > Norway > North Sea > Draupne Formation (0.99)
- Europe > United Kingdom > North Sea (0.89)
- Europe > Norway > Norwegian Sea (0.89)
- (2 more...)
Abstract Gudrun is a high-pressure, high-temperature (HPHT) field on the Norwegian Continental Shelf which has been in production since 2014. The initial development called for predrilling of the producers prior to commencement of production through depletion drive. In 2020 a second drilling campaign was initiated where the goal was to drill several infill producers and two water injection wells. The issue of drilling in heavily depleted reservoirs was highlighted as a major risk since depletion in some of the layers was expected to be in excess of 450 bar. The operational window was small and uncertain, and several risks were anticipated. Differential depletion in this highly layered reservoir, with the potential for penetrating both heavily depleted layers and non-depleted layers, meant that drilling and completion operations required wellbore pressures in excess of the minimum stress in the heavily depleted layers. There was thus a significant risk for lost circulation and escalation to possible well kick/underground blowout events. To mitigate these risks several actions were taken including Managed pressure drilling (MPD), splitting reservoir drilling into several sections, drilling of near vertical reservoir intervals and the use of active Wellbore Strengthening (WBS)/ Lost Circulation Material (LCM) particles in the mud. The use of optimal background WBS particles was complicated in the first two wells due to risk of plugging of lower completions upon production and so compromises were required to the particle sizes that could be used. This paper summarizes the experience from the successful drilling of these infill wells. It confirms that the use of WBS particles is critical in providing a robust drilling window against losses when the Fracture Gradient (FG) is reliant on near wellbore processes and elevated hoop stress around the wellbore to support downhole pressures that exceed minimum stress deeper in the "body" of the depleted layers. The experience on Gudrun also suggests that the FG is sensitive to the temperature of the mud when drilling the stiff Gudrun layers. The influence of depletion on the minimum horizontal stress, as determined from this drilling campaign, is also discussed and this is related to rock mechanical tests performed on core plugs from the field.
- North America > United States > Texas (0.46)
- Europe > Norway > North Sea (0.46)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.68)
- Europe > Norway > North Sea > Central North Sea > South Viking Graben > PL 187 > Block 15/3 > Gudrun Field > Hugin Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > South Viking Graben > PL 187 > Block 15/3 > Gudrun Field > Draupne Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > South Viking Graben > PL 025 > Block 15/3 > Gudrun Field > Hugin Formation (0.99)
- (3 more...)
Building subsurface models with horizon-guided interpolation and deep learning: Application to the Volve field data
Yan, Shangsheng (University of Science and Technology of China) | Sun, Xiaoming (University of Science and Technology of China) | Wu, Xinming (University of Science and Technology of China) | Zhang, Sibo (Huawei Cloud EI Product Department) | Si, Hongjie (Huawei Cloud EI Product Department)
ABSTRACT Subsurface modeling plays an important role in hydrocarbon exploration but remains a challenging task that typically requires a full and reasonable integration of geophysical observations and geologic constraints. We have developed a workflow to fully use seismic amplitudes, well-log properties, and interpreted seismic structures to build geologically reasonable models. We take the Volve field data as an example and apply our workflow step by step as follows. First, we perform some preprocessing on the provided Volve seismic data, horizons, and well logs to remove anomalous values and adjust seismic-well ties in the depth domain. Second, we use a dynamic-programming-based method to infill gaps and refine the vertical positions of the provided horizons and efficiently pick more horizons. We further use the horizon surfaces to interpolate a relative geologic time (RGT) volume which can be considered as an implicit structural model representing seismic structural and stratigraphic features. Third, we integrate the provided well logs and the computed RGT volume to interpolate a subsurface model that conforms to well-log properties and seismic structural and stratigraphic features. Finally, we propose a multiscale neural network to predict a final subsurface model by using a combination of the seismic data and the interpolated model as inputs and using the well-log data as training labels. Inputting the interpolated model to the network helps to provide a low-frequency control for obtaining a more stable prediction. The results indicate that our workflow is able to produce geologically reasonable subsurface models with high lateral continuity and vertical resolution.
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.47)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling > Seismic Inversion (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation > Well Tie (0.87)
- Europe > Norway > North Sea > Hugin Formation (0.99)
- Europe > Norway > North Sea > Draupne Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > South Viking Graben > PL 046 > Block 15/9 > Volve Field > Shetland Group > Åsgard Formation (0.99)
- (23 more...)
Impact of Undrained Pore Pressure Response on Expected Failure Stress in Anisotropic Shales
Duda, M. I. (Norwegian University of Science and Technology, Trondheim, Norway and SINTEF Industri) | Holt, R. M. (Norwegian University of Science and Technology, Trondheim, Norway and SINTEF Industri) | Stenebråten, J. F. (SINTEF Industri) | Stroisz, A. M. (SINTEF Industri)
ABSTRACT: The connection between undrained pore pressure response to stress in shales and fault reactivation, drilling problems and microseismicity observed at significant distances from hydrocarbon reservoirs and injection zones has not been thoroughly studied and is usually disregarded in geomechanical modelling workflows. In our study, we examine to what extent the inclusion of the pore pressure response affects the amplitude of total stress changes expected to cause shear failure in several overburden and outcrop shales. We combine poroelastic pore pressure coefficients and Mohr-Coulomb failure envelope parameters estimated through triaxial laboratory experiments to model the total stress increases at failure for a wide range of loading scenarios and medium orientations. We consider both isotropic and anisotropic pore pressure parameters - we explore the differences in modelling outcomes the two sets of parameters yield, as well as the impact of the individual parameters on the expected stresses at failure. We observed that shear failure in shales is expected at significantly lower stresses changes and is plausible in a much wider range of loading paths once the undrained pressure response in considered, and therefore we postulate that it should be taken into account during injection or production operations safety assessment. 1. INTRODUCTION Injection into or production from a subsurface reservoir have been documented to lead to fault activation, microseismic activity, and borehole stability issues in the reservoir and its surroundings (e.g., Pine et al., 1983; Raleigh et al., 1976; Zoback & Harjes, 1997). In some cases, these undesired phenomena occurred in the over-and underburden at significant distances from the reservoir subjected to pore pressure change (e.g., Odonne et al., 1999; Rutqvist et al., 2008; Segall, 1989). This has triggered an ongoing discussion of the causes of these events. Until now, it was primarily associated with pore fluid migration through fractures and fault planes throughout low permeable under- and over-burden, as well as with stress transfer (e.g., Vasco et al., 2018; Verdon et al., 2011; Williams-Stroud et al., 2020; Zhou et al., 2008) caused by injection- or production-induced pore pressure changes in the reservoir (e.g., Geertsma, 1973; Morita et al., 1989; Rudnicki, 1999).
- North America > United States (1.00)
- Europe > Norway (0.95)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- North America > United States > Kentucky > Illinois Basin (0.99)
- North America > United States > Indiana > Illinois Basin (0.99)
- North America > United States > Illinois > Illinois Basin (0.99)
- (5 more...)
ABSTRACT: Cement sheath plays important role for the integrity of injection/production wells in subsurface activities. During the life of the well, mechanical and thermal loadings are applied to the casing and can lead to cracking the cement sheath and thus the loss of integrity. Additionally, the placement of the cement can also lead to the casing stand-off. To analyze these effects a modified discrete element method (MDEM) is used. Realistic cement and formation properties are used. Isotropic and anisotropic boundary stresses are investigated. The casing pressures considered are relevant for field operations such as during a casing test, XLOT (extended leak-off test) and hydraulic fracturing. The simulation results, show that in addition to the casing stand-off, several other parameters such as the casing pressure, the boundary stress, the cement, and rock properties, affect the cracks behind the casing. It was also observed that the casing stand-off become important in affecting the crack creation when it is around 0%. For values more 50%, no major difference was observed when compared to a centralized casing (100% stand-off). 1. INTRODUCTION In many subsurface activities including hydrocarbon exploitation, carbon dioxide (CO2) or hydrogen storage, the injection/production wells play important role. These wells are made by drilling a hole in the ground, running a steel tubular (called casing) into that hole, and pumping a cement slurry to fill the space between the outer casing and the rock formation (Figure 1). The cement slurry hardens to become the cement sheath and play an important role as sealing barrier. However, during the above-mentioned subsurface activities, mechanical and thermal loadings are applied to casing and thus to the cement sheath and rock formation around. These can lead to cracks creation in the cement sheath which can propagate into the rock formation, and therefore constitute potential leakage paths (Bois et al., 2011; Petty et al., 2003). Additionally, the placement of the cement can also lead to the casing stand-off vis-à-vis to the cement sheath (De Andrade and Sangesland, 2016; De Andrade et al., 2014; Khodami et al., 2021). The casing stand-off is evaluated by the following formular (De Andrade and Sangesland, 2016; Mendez Restrepo et al., 2018; Weatherford, 2016): (Equation) where A and B are the radius of the hole and the outer radius of the casing, respectively, and C the smallest size between the casing and the hole wall, see Figure 2. A centered casing has stand-off of 100% while the extreme off centered one has a stand-off of 0%. In some regulations, the minimum stand-off of the casing should be 70% (Queensland-Government, 2019). To achieve that, the casing centralizer are used during the running of the casing into the well (Juvkam-Wold and Wu, 1992; Lee et al., 1986; Weatherford, 2016). However, even with the used of centralizers, the stand-off of the casing still be less than 100%. The stand-off may affect the integrity of the well following mechanical and thermal loadings.
- Europe > Norway (0.69)
- North America > United States > Texas (0.46)
- North America > United States > California (0.46)
Abstract The Johan Sverdrup field PRM (permanent reservoir monitoring) system has now recorded 2 monitor surveys documenting the progression of the water flood since production and injection began in October 2019 revealing a clear 4D signal linked to the increase in water saturation. The PRM system was installed in two stages in 2019 and 2020 and is a key component of the reservoir monitoring and data acquisition plan with yearly monitor surveys planned to monitor the water flood development. The first seismic acquisition in 2019, referred to as PRM0, covered the initial first stage of installation on the northern part of the field. Stage two of the installation was completed in 2020 and two monitor surveys have since been acquired covering the entire field, in 2020 (PRM1) and 2021 (PRM2). Clear 4D signals can be seen due to the increase in water saturation and show the waterfront moving updip as it pushes the oil towards the producers. The Johan Sverdrup field consists primarily of the intra-Draupne sandstone and the secondary Statfjord sandstone reservoirs. The intra-Draupne sandstone has excellent reservoir quality with an average porosity of 28% and permeabilities ranging from 30-70D. The Statfjord sandstone has an average porosity and permeability of 24% and 4D, respectively. The reservoir is undersaturated and has good lateral and vertical communication. These properties lead to a measurable 4D response when water replaces oil as the water flood progresses through the reservoir. The 4D data is an integral part of the reservoir management program, and together with the geological and production history data, is being used to update the reservoir model to further our understanding of the field development. Examples of the 4D acoustic impedance change generated via a proprietary geostatistical inversion and how it is integrated into the dynamic model will be shown.
- Geophysics > Time-Lapse Surveying > Time-Lapse Seismic Surveying (1.00)
- Geophysics > Seismic Surveying (1.00)
- Europe > Norway > North Sea > Central North Sea > Viking Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Utsira High > PL 501 > Block 16/5 > Johan Sverdrup Field > Zechstein Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Utsira High > PL 501 > Block 16/5 > Johan Sverdrup Field > Viking Formation (0.99)
- (31 more...)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Four-dimensional and four-component seismic (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management (1.00)
Abstract Seismic characterization of source rocks (SRs) became widely used in exploration risk assessment, partly driven by the evaluation of petroleum systems conditioned by the presence of organic-rich SRs. Generally, rock physics combined with seismic amplitude variation with offset (AVO) analysis and inversion of seismic data are used to detect SR presence and to assess SR lateral and vertical variations measured in total organic carbon (TOC) content (in weight percent [wt%]). Despite its great potential, this method suffers from a range of pitfalls and uncertainties. In this study, based on several data sets, we highlight the variability of seismic responses of SRs. From well data, rock property studies of SRs show that the relation between acoustic impedance, which is the product of density and P-wave velocity, and TOC turns out not to be representative in SRs with TOC contents less than approximately 4–5 wt%. In the screening phase of rock-physics data, SR also reveals a large range of Poisson's ratio values, which relates to P-wave and S-wave velocities and has a direct impact on AVO. Moreover, from real seismic data, AVO analysis gave support for this complex behavior, highlighting AVO class I, III, and IV anomalies. Therefore, the expectation that the top of SR intervals would feature a “clear dimming with offset” (AVO class IV) should not be generalized for SR identification, especially in frontier areas lacking nearby well calibration, as suggested by the results of this study.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Geological Subdiscipline > Geochemistry (1.00)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.35)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Upper Marrat Formation (0.98)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Sargelu Formation (0.98)
- Europe > United Kingdom > North Sea > Northern North Sea > North Viking Graben > Block 2/5 > Heather Field > Brent Group Formation (0.94)
- (4 more...)