scholarly journals Acoustic Logging Methods in Fractured and Porous Formations

2020 ◽  
Author(s):  
Sudad H Al-Obaidi ◽  
Khalaf FH
Keyword(s):  
Oil And Gas ◽  
Sound Waves ◽  
Porous Rocks ◽  
Gas Reservoirs ◽  
Transverse Waves ◽  
Reservoir Rocks ◽  
Sonic Log ◽  
Attenuation Rate ◽  
Path Direction ◽  
Wave Path

Formation fractures have significance effect on the permeability of rocks in oil and gas reservoirs. In real conditions, the opening of vertical fractures exceeds the opening of horizontal fractures and the permeability ofreservoirs in conditions of horizontal wells is higher than in vertical conditions. In the sonic log longitudinal waves, unlike the transverse waves, the attenuation rate strongly depends on the wave path direction. It is shown that themechanism of the attenuation of sound waves in porous rocks is represented by the scattering of "soft" microheterogeneousinclusions. For reservoir rocks with porosity (φ) of (10-20)%, the attenuation decrement is several times higher than the decrement of the other mechanisms.

scholarly journals Analysis of Petrophysical Studies of Deep Oil and Gas Reservoirs of Onshore and Offshore Fields in Azerbaijan

2020 ◽  
Vol 20 (3) ◽  
pp. 204-213
Author(s):  
Vagif Sh. Gurbanov ◽  
◽  
Latif A. Sultanov ◽  
Nurlana I. Gulueva ◽  
◽  
...  
Keyword(s):  
Oil And Gas ◽  
Sedimentary Basin ◽  
Oil Industry ◽  
Gas Reservoirs ◽  
Reservoir Rocks ◽  
Deep Wells ◽  
Long Time ◽  
Enhance Efficiency ◽  
The Cost ◽  
Natural Hydrocarbon

The paper presents results of generalized laboratory studies from an array of petrophysical parameters of reservoir rocks (potential hydrocarbon reservoirs). The study is targeted at well-known horizons of productive strata of the Meso- Cenozoic sedimentary basin. The area under study includes oil and gas onshore and deep offshore fields in Azerbaijan that have been under active continuous developments. The development of these natural hydrocarbon accumulations has over a century-long history, which has shown that the major oil and gas deposits are associated with the South Caspian and Kura depressions subjected to an intensive submersion over the Meso-Cenozoic period. Although many of the fields in these depressions have been exploited for a long time, the commercial potential is high enough, especially in deep-seated areas. Nonetheless, problems associated with extracting oil and gas therefrom are pending final resolutions. Subsoil developments in the region are currently performed at an intensive rate at depths above 4-4.5 km, since most oil and gas deposits have already been explored at shallow and moderate depths (even in hard-to-reach areas). As known in oil industry, the wells with a depth of over 4 km are referred to deep wells, while those with a depth of over 6 km are referred to ultra-deep wells. Moreover, drilling of such wells is associated with serious costrelated challenges. For example, the cost of developing deep and even ultra-deep wells is high enough, ranging from $ 2-3 to $ 9-12 million. This fact emphasizes the need to enhance efficiency of such operations, which requires a highscale geological reasoning of a field’s potential and choice of a good location.

Multiphase flow in oil and gas reservoirs

2017 ◽  
Vol 54 (1) ◽  
pp. 5-14
Author(s):  
Monty Hoffman ◽  
James Crafton
Keyword(s):  
Fluid Flow ◽  
Oil And Gas ◽  
Minimum Energy ◽  
Porous Rocks ◽  
Gas Reservoirs ◽  
Pore Networks ◽  
Hydrocarbon Reservoir ◽  
Oil And Gas Reservoirs ◽  
Permeability Damage ◽  
Non Equilibrium

The porous rocks that make up oil and gas reservoirs are composed of complex combinations of pores, pore throats, and fractures. Pore networks are groups of these void spaces that are connected by pathways that have the same fluid entry pressures. Any fluid movement in pore networks will be along the pathways that require the minimum energy expenditure. After emplacement of hydrocarbons in a reservoir, fluid saturations, capillary pressure, and energy are in equilibrium, a significant amount of the reservoir energy is stored at the interface between the fluids. Any mechanism that changes the pressure, volume, chemistry, or temperature of the fluids in the reservoir results in a state of energy non-equilibrium. Existing reservoir engineering equations do not address this non-equilibrium condition, but rather assume that all reservoirs are in equilibrium. The assumption of equilibrium results in incorrect descriptions of fluid flow in energy non-equilibrium reservoirs. This, coupled with the fact that drilling-induced permeability damage is common in these reservoirs, often results in incorrect conclusions regarding the potential producibility of the well. Relative permeability damage, damage that can change which fluids are produced from a hydrocarbon reservoir, can occur even in very permeable reservoirs. Use of dependent variables in reservoir analysis does not correctly describe the physics of fluid flow in the reservoir and will lead to potentially incorrect answers regarding producibility of the reservoir.

Gassmann's fluid substitution and shear modulus variability in carbonates at laboratory seismic and ultrasonic frequencies

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. F173-F183 ◽  
Author(s):  
Ludmila Adam ◽  
Michael Batzle ◽  
Ivar Brevik
Keyword(s):  
Shear Modulus ◽  
Bulk Modulus ◽  
Oil Recovery ◽  
Laboratory Experiments ◽  
Oil And Gas ◽  
Pressure Effects ◽  
Gas Reservoirs ◽  
Reservoir Rocks ◽  
Fluid Saturation ◽  
Seismic Frequencies

Carbonates have become important targets for rock property research in recent years because they represent many of the major oil and gas reservoirs in the world. Some are undergoing enhanced oil recovery. Most laboratory studies to understand fluid and pressure effects on reservoir rocks have been performed on sandstones, but applying relations developed for sandstones to carbonates is problematic, at best. We measure in the laboratory nine carbonate samples from the same reservoir at seismic (3–3000 Hz) and ultrasonic [Formula: see text] frequencies. Samples are measured dry (humidified) and saturated with liquid butane and brine. Our carbonate samples showed typical changes in moduli as a function of porosity and fluid saturation. However, we explore the applicability of Gassmann’s theory on limestone and dolomite rocks in the context of shear- and bulk-modulus dispersion and Gassmann’s theory assumptions. For our carbonate set at high differential pressures and seismic frequencies, the bulk modulus of rocks with high-aspect-ratio pores and dolomite mineralogy is predicted by Gassmann’s relation. We also explore in detail some of the assumptions of Gassmann’s relation, especially rock-frame sensitivity to fluid saturation. Our carbonate samples show rock shear-modulus change from dry to brine saturation conditions, and we investigate several rock-fluid mechanisms responsible for this change. To our knowledge, these are the first controlled laboratory experiments on carbonates in the seismic frequency range.

scholarly journals Integrated petrophysical study to validate water saturation from well logs in Bahariya Shaley Sand Reservoirs, case study from Abu Gharadig Basin, Egypt

2020 ◽  
Vol 10 (8) ◽  
pp. 3139-3155
Author(s):  
Mohamed El-Bagoury
Keyword(s):  
Clay Minerals ◽  
Oil And Gas ◽  
Water Saturation ◽  
Exchange Capacity ◽  
Fine Tuning ◽  
Well Logs ◽  
Gas Reservoirs ◽  
Reservoir Rocks ◽  
Resistivity Logs ◽  
Petroleum Fields

Abstract Water saturation is a key parameter in evaluating oil and gas reservoirs and calculating OIIP and GIIP for petroleum fields. The late Cretaceous Bahariya reservoir contains variable amounts of clay minerals. Bore hole logs are affected with those clay minerals particularly the density and resistivity logs. Several methods are acknowledged to determine the true water saturation from well logs in shaley sand reservoirs. Each method assumes a sort of corrections to amount of shale distributed in the reservoir. The scope of this petrophysical study is to integrate core analysis and bore hole logs to investigate the characteristics of water saturation in the Bahariya reservoirs. Comparison between most of the significant shaley sand methods is presented in this research. Reservoir lithology and mineralogy are explained by Elan-model while bore hole images are used for fine-tuning the electrofacies. Siltstone, shaley sand and clean sandstones are the main electrofacies that is characterizing the Bahariya reservoir rocks. For accurate saturation results, some core samples have been used for validating the log-derived water saturation. Dean stark and cation exchange capacity experiments are integrated with bore hole logs to calculate the error in water saturation for each method for best calibration. The successful integration between logs and core measurements led to convenient log evaluation and accurate understanding for the Bahariya reservoir in the prospective part of Abu Gharadig basin.

scholarly journals MODERN APPROACHES TO DETERMINE THE PERMEABILITY OF RESERVOIR ROCKS BASED ON THE RESULTS OF GEOPHYSICAL INVESTIGATIONS

2018 ◽  
pp. 45-54
Author(s):  
A. Shynkarenko
Keyword(s):  
Oil And Gas ◽  
Complex Structure ◽  
Physical Property ◽  
Space Structure ◽  
Void Space ◽  
Gas Reservoirs ◽  
Reservoir Rocks ◽  
Reservoir Conditions ◽  
Unsteady Fluid

Permeability of rock is its physical property that describes its ability to conduct fluids under the pressure gradient. This paper presents short description and analysis of methods for determination of permeability of oil and gas reservoirs. Permeability is a function of different parameters that leads to difficulties during its estimation. Investigations of the void space structure of rocks, their anisotropy etc.were carried out in order to take into account all factors that have an influence on the permeability. Reservoir conditions could also be modeled for that purpose. Methods for determination of permeability of rocks can be divided into three groups: methods based on the laboratory studies of rocks; methods based on the well logging data; and methods based on the correlations between different parameters of rocks. The first two groups include methods for steady and unsteady fluid flow. Methods for the unsteady flow are usually more precise and rapid, thus prospects of extension of methods for permeability determination are mostly connected with them. Each of the presented methods to determine permeability is characterized by some pros and cons. The most appropriate method for the specific experiment is always chosen according to conditions and requirements and expected results. Further author's investigations will be related to the creation of petrophysical models of permeability of oil and gas reservoir rocks, including reservoirs of complex structure.

scholarly journals Development of Real-Time Time Gated Digital (TGD) OFDR Method and Its Performance Verification

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4865
Author(s):  
Kinzo Kishida ◽  
Artur Guzik ◽  
Ken’ichi Nishiguchi ◽  
Che-Hsien Li ◽  
Daiji Azuma ◽  
...  
Keyword(s):  
Real Time ◽  
Optical Fibers ◽  
High Speed ◽  
Oil And Gas ◽  
Scattered Light ◽  
Oil And Gas Industry ◽  
High Signal ◽  
Chirp Pulse ◽  
Sound Waves ◽  
Industry Applications

Distributed acoustic sensing (DAS) in optical fibers detect dynamic strains or sound waves by measuring the phase or amplitude changes of the scattered light. This contrasts with other distributed (and more conventional) methods, such as distributed temperature (DTS) or strain (DSS), which measure quasi-static physical quantities, such as intensity spectrum of the scattered light. DAS is attracting considerable attention as it complements the conventional distributed measurements. To implement DAS in commercial applications, it is necessary to ensure a sufficiently high signal-noise ratio (SNR) for scattered light detection, suppress its deterioration along the sensing fiber, achieve lower noise floor for weak signals and, moreover, perform high-speed processing within milliseconds (or sometimes even less). In this paper, we present a new, real-time DAS, realized by using the time gated digital-optical frequency domain reflectometry (TGD-OFDR) method, in which the chirp pulse is divided into overlapping bands and assembled after digital decoding. The developed prototype NBX-S4000 generates a chirp signal with a pulse duration of 2 μs and uses a frequency sweep of 100 MHz at a repeating frequency of up to 5 kHz. It allows one to detect sound waves at an 80 km fiber distance range with spatial resolution better than a theoretically calculated value of 2.8 m in real time. The developed prototype was tested in the field in various applications, from earthquake detection and submarine cable sensing to oil and gas industry applications. All obtained results confirmed effectiveness of the method and performance, surpassing, in conventional SM fiber, other commercially available interrogators.

scholarly journals Monitoring geological storage of CO2: a new approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Manzar Fawad ◽  
Nazmul Haque Mondol
Keyword(s):  
Oil And Gas ◽  
Synthetic Data ◽  
Leak Detection ◽  
Hydrocarbon Exploration ◽  
Water Flooding ◽  
Storage Site ◽  
Gas Reservoirs ◽  
New Approach ◽  
Coal Beds ◽  
Spatial Coverage

AbstractGeological CO2 storage can be employed to reduce greenhouse gas emissions to the atmosphere. Depleted oil and gas reservoirs, deep saline aquifers, and coal beds are considered to be viable subsurface CO2 storage options. Remote monitoring is essential for observing CO2 plume migration and potential leak detection during and after injection. Leak detection is probably the main risk, though overall monitoring for the plume boundaries and verification of stored volumes are also necessary. There are many effective remote CO2 monitoring techniques with various benefits and limitations. We suggest a new approach using a combination of repeated seismic and electromagnetic surveys to delineate CO2 plume and estimate the gas saturation in a saline reservoir during the lifetime of a storage site. This study deals with the CO2 plume delineation and saturation estimation using a combination of seismic and electromagnetic or controlled-source electromagnetic (EM/CSEM) synthetic data. We assumed two scenarios over a period of 40 years; Case 1 was modeled assuming both seismic and EM repeated surveys were acquired, whereas, in Case 2, repeated EM surveys were taken with only before injection (baseline) 3D seismic data available. Our results show that monitoring the CO2 plume in terms of extent and saturation is possible both by (i) using a repeated seismic and electromagnetic, and (ii) using a baseline seismic in combination with repeated electromagnetic data. Due to the nature of the seismic and EM techniques, spatial coverage from the reservoir's base to the surface makes it possible to detect the CO2 plume’s lateral and vertical migration. However, the CSEM low resolution and depth uncertainties are some limitations that need consideration. These results also have implications for monitoring oil production—especially with water flooding, hydrocarbon exploration, and freshwater aquifer identification.

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