A New Method to Calculate Effective Permeability of a Naturally Fractured Carbonate Reservoir from Seismic Attributes

Li, D.; Al-Harbi, Musaad; Ottinger, Gary; El-Awawdeh, Raed; Brunhuber, P.; Al-Jasmi, S. M.

doi:10.2118/181718-ms

Cited by 2 publications

(1 citation statement)

References 19 publications

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“…The dominating mechanisms of miscible gas flooding to improve oil recovery are lowering interfacial, reducing oil viscosity and increasing capillary number (He et al 2018;Li et al 2016Li et al , 2020Lv et al 2017).…”

Section: Introductionmentioning

confidence: 99%

The impact of permeability heterogeneity on water-alternating-gas displacement in highly stratified heterogeneous reservoirs

Khan

Mandal

2021

J Petrol Explor Prod Technol

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Availability of gases at the field level makes attractive to water-alternating-gas (WAG) process for low viscosity and light oils carbonate reservoir. However, impact of reservoir heterogeneity on WAG performance is crucial before field application. In general, ramp carbonates have heterogeneity due to variation of permeability and porosity. However, WAG performance significantly affected by permeability variations. This article investigates merits and demerits of WAG displacement due to permeability heterogeneities such as permeability anisotropy, high permeability streaks (HKS), matrix permeability, dolomite and thin dense stylolite layers. High-resolution compositional simulations with tuned equation of state (EoS) were carried out using 2D and 3D sector models. The study focuses on WAG performance in terms of oil recovery, vertical sweep, solvent utilization, gas oil ratio (GOR), water cut (WCT), WAG response time, gravity override, hysteresis, un-contacted oil saturation and economics. The results of simulation show that the heterogeneous reservoir provides initially faster WAG response, lower expected ultimate recovery (EUR), faster gas breakthrough, higher GOR and WCT production compared to homogeneous reservoir. The gas gravity override at smaller wells spacing is less in homogeneous reservoir as compared to heterogeneous reservoir, but it is reverse in case of larger well spacing. In heterogeneous reservoir, the HKS shows significant gas override resulting in poor vertical sweep due to capillary holding, and the high permeability dolomite layer shows early water breakthrough. This reservoir has higher solvent utilization in initial stage, and then, it becomes nearly equal to homogeneous reservoir. Simulation in both reservoirs overestimates incremental recovery of 2–3% OOIP at one pore volume injection because of not involving un-contacted oil saturation as predicted in core flood. The findings of this study will help to understand WAG performance and design in highly heterogeneous reservoirs for field applications. Graphical abstract

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Section: Introductionmentioning

confidence: 99%

The impact of permeability heterogeneity on water-alternating-gas displacement in highly stratified heterogeneous reservoirs

Khan

Mandal

2021

J Petrol Explor Prod Technol

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Review of Identification, Characterization and Modeling of different types of Fault & Fracture Systems in a Giant Offshore Carbonate Reservoir, UAE

Shekhar

Edwards

Obeta

2019

Day 3 Wed, November 13, 2019

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The subject field of this study is a geologically complex Lower Cretaceous carbonate system of stacked reservoirs and dense seals, which have been affected by extreme diagenetic modification, including various types of faults & fractures. The purpose of this paper is to summarize several years of comprehensive study of identification, characterization and modeling of different fault/fracture systems within the reservoir stack, integrating different data types, conceptual models and geomodelling approaches for individual, or groups of, reservoirs. Timely identification and appropriate characterization of the fracture-fault systems is extremely important for correct well placement and completion strategy. The field has been producing for more than 30 years under a water-flood recovery strategy. Numerous amounts of different types of data including seismic, cores, image logs, tracers, interference tests, production/injection data etc. has been collected and studied carefully throughout those years. The integration of different data sets combined with regional structural study suggest existence of four different types of fault and fracture systems, with predictable and consistent orientations, that affect the reservoirs: Seismically mapped faults, fracture corridors, diffuse natural fractures, and thermally generated/artificially enhanced fractures. Their impacts on field performance vary, being dependent upon scale (length/throw) and stratigraphic positioning. For example, faults with large throw (30-60ft) can create inter-reservoir communication due to fault juxtaposition whereas diffuse fractures that are generally located at the top and base of the reservoirs (due to mechanical contrast between dense and reservoir rock strength) act as intra-reservoir permeability enhancement. Fracture corridors that can be either restricted to, or cross, reservoirs are most difficult to detect due to small offset and (when oriented NNE) possibly impose greatest impact in terms of flow heterogeneity. Thermally enhanced fracture effects are observed where newly drilled wells enter the water-flood affected area. These fractures can be seen on the image logs, especially where they fracture most brittle dense intervals limestones and their impact in reservoir is noted most from production water cuts. Modeling different types of fractures for simulation studies and field development planning are always very challenging due to limited availability of the critically appropriate data. As a result, an integration of different data types was key to identify and model different faults and fracture systems. Numerous faults were mapped from seismic but only those mapped with high confidence, supported by drilling reports and LWD log evidence, and which show impact on production performance, were included in the model – all faults are considered for other purposes (e.g. well planning). Diffuse fractures were modeled combining traditional methods (fracture density from cores) with ant-track attribute from seismic to determine directionality and distribution away from cored wells; and span the scale range to through-going fracture corridors. A new method has been introduced to assign effective permeability to fractures from seismic attributes by scaling up and down to the well test permeability. The displacement functions for fractures are estimated as effective pseudo-functions, representing the diffuse fracture and matrix media and conditioned to the performance of the well observing such fracture effects. Fracture corridors, whenever observed, were modelled deterministically as effective properties. Given the uncertainties associated with data and sub-surface knowledge, coupled with the classification of all reservoirs in the stacked sequence being fracture-assisted matrix zones, the objective of each and every fracture model approach was to create a representative, simple and fit-for-purpose model that can be modified and updated easily during history-match iterations and that serves business needs.

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A New Method to Calculate Effective Permeability of a Naturally Fractured Carbonate Reservoir from Seismic Attributes

Cited by 2 publications

References 19 publications

The impact of permeability heterogeneity on water-alternating-gas displacement in highly stratified heterogeneous reservoirs

The impact of permeability heterogeneity on water-alternating-gas displacement in highly stratified heterogeneous reservoirs

Review of Identification, Characterization and Modeling of different types of Fault & Fracture Systems in a Giant Offshore Carbonate Reservoir, UAE

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