Seismic to Simulation Fracture Characterization of a Green Carbonate Reservoir in Presence of Large Uncertainties

Astratti, D.; Souche, Laurent; Faskhoodi, Majid M.; Menegatti, P.

doi:10.2118/136829-ms

Cited by 3 publications

(2 citation statements)

References 4 publications

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“…An aggregate fault cube can become a simple tool to rank the confidence in the fault-extraction results (Astratti et al 2010). Its values indicate the number of times an edge has been detected in each seismic bin: the higher the number, the more attributes have detected the lineament.…”

Section: Aggregate Attributesmentioning

confidence: 99%

“…15c). The colour scale indicates the number of times a connected edge has been detected at each sample location and provides an empirical tool to rank the confidence in the lineaments of a fault cube (Astratti et al 2010). The more seismic attributes that are complementary in nature detect the same lineament, the higher the likelihood that the lineament is a geological feature that can influence reservoir performances.…”

Section: The Fault Cubementioning

confidence: 99%

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Mapping and time-lapse analysis of South Arne Chalk fault network using new developments in seismic dip computation

Astratti

Aarre

Vejbæk³

et al. 2014

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In a reservoir, faults at the limit of the seismic resolution can be crucial to explain production history and to optimize field development. However, in most cases the detail required to describe such subtle features depends on the assistance of seismic attributes and semi-automated interpretation techniques. We generated a detailed description of the fault network in the South Arne Chalk Group using a workflow based on a globally consistent computation of the seismic dip. This led to more accurate seismic edge attributes than gained with standard dip estimation techniques. We analysed each fault set and qualitatively assessed its control on fluid flow. Our investigation suggests that the two fracture sets that influence production developed along the same WNW-ESE structural trend and cannot be separated based on the seismic data alone. These faults were active both during and post Chalk deposition. We observe ENE -WSW lineaments that match the pattern of a time-lapse seismic amplitude anomaly associated with water injection. It remains to be verified whether these lineaments could be an extension of overburden faults, as well as whether the increased intensity of the fault network as seen on the 2005 v. the 1995 3D seismic survey was caused by production effects.

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Section: Aggregate Attributesmentioning

confidence: 99%

Section: The Fault Cubementioning

confidence: 99%

Mapping and time-lapse analysis of South Arne Chalk fault network using new developments in seismic dip computation

Astratti

Aarre

Vejbæk³

et al. 2014

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Computation of Effective Dynamic Properties of Naturally Fractured Reservoirs: Comparison and Validation of Methods

Decroux

Gosselin

2013

All Days

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Naturally Fractured Reservoirs (NFR) are very heterogeneous media containing highly permeable fractures in a poorly permeable rock matrix. Explicit simulations of such reservoirs are complex and computationally time consuming. Alternatively for full-field simulation, dual-medium models are commonly used (dual-porosity, dual-permeability) where fractures are represented as a continuous medium in communication with the rock matrix. Required effective dynamic properties at the coarse continuous scale should produce the same flow simulation results than Discrete Fracture Network (DFN) models with their small-scale properties, using explicit simulation (as reference). Many calculation methods with different accuracy and computational efficiency have been proposed for the estimation of the anisotropic effective permeability tensor of fracture networks. These methods rely on different conceptual models, which are simplified representations of actual complex and partially unknown fracture systems. They are using either a global deterministic DFN, or local representations of DFNs defined by their statistical properties. Analytical methods rely on connectivity assumptions, seldom met in practice. Numerical methods rely on flow simulations, and are supposed to be more accurate but computationally demanding. The development of new simulators using Discrete Fracture and Matrix (DFM) models, where all fractures are represented explicitly as well as the matrix, offers the opportunity to benchmark the accuracy of the different effective permeability calculation methods. Simulations based on effective properties are compared with DFM model simulations, considered as a reference solution.In a first part, 2D Cartesian fracture networks are simulated explicitly with Eclipse. These reference simulations are compared with simulations based on effective properties. In this paper we consider the following effective permeability calculation techniques: an analytical method (the Oda's technique); two flow-based numerical methods with different boundary conditions (impermeable boundaries and linearly varying pressure); and a numerical method using a periodic DFN defined locally, that does not depend on boundary conditions (Image Based Periodic Object Simulation -IBPOSimplemented in GoFraK, a plugin of Gocad). In a second part, a simulation was performed on a much more realistic fracture network with CSMP++, simulation software using DFM models. This simulation is compared with simulations using effective properties calculated with the Oda's method and the two flow-based numerical methods.The first observation concerns the large variability of results, which stresses the large uncertainty produced by the various methods. When compared to the reference, the most accurate effective permeability calculation methods tested in this paper are the numerical methods, using no-flow boundary condition and the IBPOS technique. These results show the importance of the fracture network connectivity for the calculation of the effective permeability, and ...

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Hierarchical Approach to Modeling Karst and Fractures in Carbonate Karst Reservoirs in the Tarim Basin

Shen¹,

Zhao²,

Zhang³

et al. 2019

Day 3 Wed, November 13, 2019

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Karst reservoirs in the Tarim Basin, northwestern China, were formed by subaerial exposure and karstification from the Ordovician formation and represent the main plays. Predicting the storage capacity and quantifying permeability heterogeneities are challenging while important for field development planning. In this paper we present a hierarchical approach to modeling karst and fractures with geoscience and engineering data for selecting locations of new wells and for the reservoir simulation. Karst and fractures at multiple scales contribute significantly to reservoir volumes in place and well productivity. Fracture-karst units in wells were determined using log-based electrofacies validated against core data, image logs and drilling data to quantify different karst features and fracture patterns hosted in units. A 3-D architecture model of karst system was constructed with extracted karst features at the seismic-scale based on multi-attribute seismic facies analysis. The karst network model was generated with karst-fracture units at wells, inverted seismic impedance volume, and 3-D karst architecture model. Porosity estimates of the karst system were conditioned with log data, mud loss data, seismic impedance volume and karst network model. Karst horizontal and vertical conduits were modeled and their permeabilities were empirically derived. Based on fracture length relative to the seismic resolution, fractures were modeled at two scales. Diffuse fractures at a small scale were modeled stochastically conditioned with image log data and the karst fracture unit model. A discrete fracture network (DFN) model at a large scale was deterministically built by meshing fracture lineaments automatically tracked from the curvature enhanced attribute. The DFN model was embedded into a geocellular grid model in which geometries of the large fractures were maintained explicitly. The calculation of effective horizontal and vertical permeabilities of the fracture system was scale dependent and decoupled. Fracture geometric parameters and permeabilities were calibrated against well test data. Streamline simulation was performed in the static model to calibrate spatial fracture densities. After two-step conditioning, fracture models were updated and then upscaled. Flow properties of karst and fractures from the wellbore to the seismic scales were combined based on their impacts on fluid flow. Integration of karst network model and history match of water cut and bottom hole pressure using streamline simulation helped the oil/water contact (OWC) assessment and allowed the identification of dynamic compartments. Combing karst networks, dynamic compartments and modeled geological scenarios allowed targeting potential highly productive zones where new well locations could be selected. The case study demonstrated that the hierarchical approach to karst and fracture modeling and calibration allowed building a realistic reservoir model and better understanding of the reservoir complexity.

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Seismic to Simulation Fracture Characterization of a Green Carbonate Reservoir in Presence of Large Uncertainties

Cited by 3 publications

References 4 publications

Mapping and time-lapse analysis of South Arne Chalk fault network using new developments in seismic dip computation

Mapping and time-lapse analysis of South Arne Chalk fault network using new developments in seismic dip computation

Computation of Effective Dynamic Properties of Naturally Fractured Reservoirs: Comparison and Validation of Methods

Hierarchical Approach to Modeling Karst and Fractures in Carbonate Karst Reservoirs in the Tarim Basin

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