Carbonate Reservoir Rocks Research Articles

Ultrasonic monitoring of spontaneous imbibition experiments: Precursory moisture diffusion effects ahead of water front

AbstractFluid substitution processes have been investigated in the laboratory on 14 carbonate and siliciclastic reservoir rock analogues through spontaneous imbibition experiments on vertical cylindrical specimens with simultaneous ultrasonic monitoring and imaging. The motivation of our study was to identify the seismic attributes of fluid substitution in reservoir rocks and to link them to physical processes. It is shown that (i) the P wave velocity either decreases or increases when the capillary front reaches the Fresnel clearance zone, (ii) the P wave amplitude is systematically impacted earlier than the velocity is, (iii) this precursory amplitude decrease occurs when the imbibition front is located outside of the Fresnel zone, and (iv) the relative variation of the P wave amplitude is always much larger than that of the P wave velocity. These results suggest that moisture diffuses into the pore space ahead of the water front. This postulate is further supported by a quantitative analysis of the time evolution of the observed P wave amplitudes. In a sense, P wave amplitude acts as a precursor of the arrival of the capillary front. This phenomenon is used to estimate the effective diffusivity of moisture in the tested rocks. The effective moisture diffusivity estimated from the ultrasonic data is strongly correlated with permeability: a power law with exponent 0.96 predicts permeability from ultrasonic monitoring within a factor 3 without noticeable bias. When the effective diffusivity is high, moisture diffusion affects ultrasonic P wave attributes even before the imbibition starts and impacts the P wave reflectivity as evidenced by the variations recorded in the waveform coda.

Microstructural controls on reservoir quality in tight oil carbonate reservoir rocks

In carbonate reservoir rocks the complex interaction between the petrophysical properties corresponds to the various depositional microstructures which are modified by various diagenetic processes that ultimately define the reservoir quality, and pose challenges to the prediction of permeability. The permeability heterogeneity in the carbonate oil reservoirs of northern Iraq varies widely and is thought to be controlled by a number of different factors. In this work, controls of matrix permeability for the Cretaceous Kometan formation selected from five oil fields in Kirkuk embayment zone have been investigated. Helium porosity, helium pulse decay permeability, brine permeability, Nuclear Magnetic Resonance (NMR), Mercury Injection Capillary pressure (MICP), Scanning Electronic Microscopy (SEM), X-Ray diffraction (XRD), and photomicrography of thin section have been used to investigate the effect of microstructure on the variation of permeability in the Kometan Formation. The formation has porosities and permeabilities which range from 0.5 ± 0.5% to 29 ± 0.5% and from 0.65 ± 0.08 μD to 700 ± 0.08 μD respectively. Three types of pore systems have been investigated using pore type, pore size and pore-throat size as characterizing parameters. We have recognized three microstructural types: (i) matrix composed of nano-intercrystalline pores (pore diameter dp smaller than 1 μm and a nanoporous pore-throat size), (ii) matrix composed of micro-intercrystalline pores (1<dp < 10 μm with a corresponding micron-scale pore-throat distribution), and (iii) meso-intragranular and moldic pores (dp > 10 μm) also with microporous pore-throat radii. The nano-intercrystalline pore system is common across northern Iraq and represents the effective pore system type in the reservoirs of the Kirkuk embayment zone. For these tight carbonate reservoirs, the mineralogy, especially of quartz and clay minerals (illite and smectite), has little relationship with the measured Klinkenberg-corrected permeability. Consequently, mineralogy is not a useful controlling factor for permeability. Diagenetic processes have altered the depositional texture significantly, resulting in changes to the pore size and pore-throat size distribution and affecting the permeability. In addition the matrix permeability is sensitive to stress, with permeability decreases between −4 × 10−4 mD/psi and −4 × 10−5 mD/psi in the effective stress range from 0 psi to 4000 psi. It has been found that of the three microstructure pore types the nano-intercrystalline pore system is more sensitive to increasing effective stress compared to the micro-intercrystalline and meso-intragranular pore systems. Laboratory experiments have shown that stylolisation resulting from regional fluid movements has also affected matrix permeability, with the stylolites acting as barriers to fluid flow and considered to be an important source of tightness of the Kometan formation in the Kirkuk embayment fields.

Correlation between porosity and permeability of carbonate rock reservoirs

ABSTRACTIt is critical to use proper definition of effective porosity, i.e., effective porosity as used in the USA minus the irreducible fluid saturation. Inasmuch as logs do not determine the irreducible fluid saturation, a lot of misinformation is spread around.

An integrated approach to study the impact of fractures distribution on the Ilam-Sarvak carbonate reservoirs: A case study from the Strait of Hormuz, the Persian Gulf

Most of the Iranian hydrocarbon reservoirs in the Persian Gulf Basin and the Zagros Fold-Thrust Belt are composed of fractured carbonate rocks. In this regard, determining the spatial distribution of fractures has been a challenging issue. In this study, an integrated approach was applied for understanding the impact of fractures spatial distribution on the Ilam-Sarvak (Cenomanian to Santonian) carbonate reservoir rocks. For this purpose, seismic interpretation techniques along with geomechanical and geostatistical modeling were employed to characterize fractures at different scales.Initially, the relationship between fractures origin and the normal faults was investigated by conducting an in-situ stress analysis. Afterwards, the velocity deviation log (VDL) and fracture intensity log (FIL) were derived as fracture attributes from the interpretation of Formation Micro Imager (FMI) and conventional well logs. A 3D model of VDL and FIL was achieved by using a sequential Gaussian simulation (SGS) method. In order to achieve a more realistic and accurate model of the factures distribution, variations of the shear-wave velocity and geomechanical properties (Young's modulus and Poisson's ratio) were estimated by applying the advanced seismic interpretation techniques in the normal faults domain. The results show that the intensity of fractures increases once they are introduced to the normal faults, especially in the central part of the study area around well#2. Such a fractured zone is verified by fracture density log derived from FMI logs of the mentioned well. Obviously, there is a close-knit relationship between the fracture system and the normal faults.Eventually, secondary porosity caused by features was determined though identification of Hydraulic Flow Units (HFUs). Based on the porosity and permeability data, seven HFUs were determined for the Ilam-Sarvak reservoirs. The very high values of Log FZI indicate the possible presence of fractures. Overall, the fractures contributed to enhance the secondary porosity of the reservoir rocks though increasing matrix permeability. To sum up, the fractures system plays a critical role in controlling reservoir properties especially in the hanging-wall of normal faults where the majority of the macro and micro fractures are distributed.

Petrography, diagenesis and isotope geochemistry of dolostones and dolocretes in the Eocene Dammam Formation, Kuwait, Arabian Gulf

Detailed petrographic and geochemical investigation of an exposed sequence of the Eocene Dammam Formation in Kuwait revealed significant gradational upward changes from friable chalky dolostone to hard dolocretic palaeoduricrust (karst carapace) passing through an extensively karstified dolostone enclosing cavity fill dolocretes. The dolostones were originally deposited as calcareous wackestone and mudstone within tidal flat and backshore lagoons that manifest cyclic sedimentation within minor sea regression and transgression cycles. Dolomitization of these sediments was early, pervasive, fabric selective and non-fabric destructive and it took place by Mg-rich sabkha brine mixed with meteoric fresh water. Regional sea regression was followed by chertification. Three sequential stages of dolocretization were identified within the karst dolostone and the karst carapace. Microscopic and SEM examination as well as stable isotopic analysis of Carbon and Oxygen indicate significant variation in the dolomite textures and genesis of the dolostone and the dolocretes. A suggested paragenesis model elaborated complex diagenetic processes. The results of this research may be applicable for analogues subsurface carbonate reservoir rocks.

Lattice Boltzmann Simulations of Fluid Flow in Continental Carbonate Reservoir Rocks and in Upscaled Rock Models Generated with Multiple-Point Geostatistics

Microcomputed tomography (μCT) and Lattice Boltzmann Method (LBM) simulations were applied to continental carbonates to quantify fluid flow. Fluid flow characteristics in these complex carbonates with multiscale pore networks are unique and the applied method allows studying their heterogeneity and anisotropy. 3D pore network models were introduced to single-phase flow simulations in Palabos, a software tool for particle-based modelling of classic computational fluid dynamics. In addition, permeability simulations were also performed on rock models generated with multiple-point geostatistics (MPS). This allowed assessing the applicability of MPS in upscaling high-resolution porosity patterns into large rock models that exceed the volume limitations of the μCT. Porosity and tortuosity control fluid flow in these porous media. Micro- and mesopores influence flow properties at larger scales in continental carbonates. Upscaling with MPS is therefore necessary to overcome volume-resolution problems of CT scanning equipment. The presented LBM-MPS workflow is applicable to other lithologies, comprising different pore types, shapes, and pore networks altogether. The lack of straightforward porosity-permeability relationships in complex carbonates highlights the necessity for a 3D approach. 3D fluid flow studies provide the best understanding of flow through porous media, which is of crucial importance in reservoir modelling.

Rock Physics Modeling and Seismic Interpretation to Estimate Shally Cemented Zone in Carbonate Reservoir Rock

Carbonate rock are important hydrocarbon reservoir rocks with complex texture and petrophysical properties (porosity and permeability). These complexities make the prediction reservoir characteristics (e.g. porosity and permeability) from their seismic properties more difficult. The goal of this paper are to understanding the relationship of physical properties and to see the signature carbonate initial rock and shally-carbonate rock from the reservoir.&#x0D; To understand the relationship between the seismic, petrophysical and geological properties, we used rock physics modeling from ultrasonic P- and S- wave velocity that measured from log data. The measurements obtained from carbonate reservoir field (gas production). X-ray diffraction and scanning electron microscope studies shown the reservoir rock are contain wackestone-packstone content. Effective medium theory to rock physics modeling are using Voigt, Reuss, and Hill.&#x0D; It is shown the elastic moduly proposionally decrease with increasing porosity. Elastic properties and wave velocity are decreasing proporsionally with increasing porosity and shally cemented on the carbonate rock give higher elastic properties than initial carbonate non-cemented. Rock physics modeling can separated zones which rich of shale and less of shale.

Two intelligent pattern recognition models for automatic identification of textural and pore space characteristics of the carbonate reservoir rocks using thin section images

Over the last two decades pattern recognition approaches have attracted engineers to solve real world problems more accurately through the development of computational technology. In the present research, the capabilities of intelligent systems are employed to develop two algorithms for identification of textural and pore space characteristics of carbonate rocks from thin section images. The texture identifier model classifies the images based on Dunham classification, while the porosity analyzer model determines the percentage of each type of pore spaces in the image. The texture identifier model extracts thirteen features to recognize texture type and the porosity analyzer determines percentage of each type of porosity based on eleven features extracting from the thin section image. Finally, two confusion matrixes are used to evaluate the performance of the developed models. The results show that the models perform reliably from the perspective of petroleum geology for studying carbonate reservoir rocks.

Permeability and acoustic velocity controlling factors determined from x-ray tomography images of carbonate rocks

Carbonate reservoir rocks exhibit a great variability in texture that directly impacts petrophysical parameters. Many exhibit bi- and multimodal pore networks, with pores ranging from less than 1 μm to several millimeters in diameter. Furthermore, many pore systems are too large to be captured by routine core analysis, and well logs average total porosity over different volumes. Consequently, prediction of carbonate properties from seismic data and log interpretation is still a challenge. In particular, amplitude versus offset classification systems developed for clastic rocks, which are dominated by connected, intergranular, unimodal pore networks, are not applicable to carbonate rocks. Pore geometrical parameters derived from digital image analysis (DIA) of thin sections were recently used to improve the coefficient of determination of velocity and permeability versus porosity. Although this substantially improved the coefficient of determination, no spatial information of the pore space was considered, because DIA parameters were obtained from two-dimensional analyses. Here, we propose a methodology to link local and global pore-space parameters, obtained from three-dimensional (3-D) images, to experimental physical properties of carbonate rocks to improve P-wave velocity and permeability predictions. Results show that applying a combination of porosity, microporosity, and 3-D geometrical parameters to P-wave velocity significantly improves the adjusted coefficient of determination from 0.490 to 0.962. A substantial improvement is also observed in permeability prediction (from 0.668 to 0.948). Both results can be interpreted to reflect a pore geometrical control and pore size control on P-wave velocity and permeability.

Geomechanical characterization of a south Iran carbonate reservoir rock at ambient and reservoir temperatures

Geomechanical characteristics of the reservoir and adjacent formations are important inputs to lifetime evaluation, operation and monitoring of E&P projects. Causes and cures for issues such as well instability and production decline often are found in the geomechanical behavior of the rock. Rock testing usually involves destructive tests on core samples, and it is widely acknowledged that properties should be measured at the representative conditions (T, p, σ) from which samples were taken. In this study of a well in an Iranian gas field, geomechanical units were first defined using well logs and lithological assessment. Then, based on the computed tomography images, intact samples were chosen and prepared for uniaxial and triaxial compression in both ambient (20 °C) and reservoir (90 °C) temperature conditions. The geomechanical properties at both temperatures, including uniaxial compressive strength (UCS), Young’s modulus (E), Poisson’s ratio (v), friction angle (φ′) and cohesion (c′) were compared. Porosity is observed as the main factor influencing the geomechanical behavior, and temperature affects UCS and E values of each GMU, in two distinct ways. We noted a transition porosity of 9%; specimens above this porosity respond differently to temperature compared to specimens below this porosity. It is concluded that whenever rock solid components’ thermoelastic expansion is compensated by sufficient available free space (high porosity), the rock matrix will be strengthened. Finally, we noted that this range of ΔT has no significant effect on ν, φ′ and c′.

PETROLEUM SYSTEMS OF THE WEST IBERIAN MARGIN: A REVIEW OF THE LUSITANIAN BASIN AND THE DEEP OFFSHORE PENICHE BASIN

The relatively well‐studied Lusitanian Basin in coastal west‐central Portugal can be used as an analogue for the less well‐known Peniche Basin in the deep offshore. In this paper the Lusitanian Basin is reviewed in terms of stratigraphy, sedimentology, evolution and petroleum systems. Data comes from published papers and technical reports as well as original research and field observations. The integration and interpretation of these data is used to build up an updated petroleum systems analysis of the basin. Petroleum systems elements include Palaeozoic and Mesozoic source rocks, siliciclastic and carbonate reservoir rocks, and Mesozoic and Tertiary seals. Traps are in general controlled by diapiric movement of Hettangian clays and evaporites during the Late Jurassic, Late Cretaceous and Late Miocene. Organic matter maturation, mainly due to Late Jurassic rift‐related subsidence and burial, is described together with hydrocarbon migration and trapping. Three main petroleum systems may be defined, sourced respectively by Palaeozoic shales, Early Jurassic marly shales and Late Jurassic marls. These elements and systems can tentatively be extrapolated offshore into the deep‐water Peniche Basin, where no exploration wells have so far been drilled. There are both similarities and differences between the Lusitanian and Peniche Basins, the differences being mainly related to the more distal position of the Peniche Basin and the later onset of the main rift phase which was accompanied by Early Cretaceous subsidence and burial. The main exploration risks are related to overburden and maturation timing versus trap formation associated both with diapiric movement of Hettangian salt and Cenozoic inversion.

New Digital Methods of Estimation of Porosity of Carbonate Rocks

Carbonate stones consist of about 60% of the global reserves of hydrocarbons. The structure of pore space of carbonate rocks considerably differs morphologically and genetically from such one in clastic stones. In the carbonate rocks interconnected and unconnected voids can be equally important. There exists 3D estimation of porosity by the method of liquid saturation, mainly, aimed at interconnected void volume. Digital methods of thin section estimation of porosity make it possible to fix both types of voids and reveal the importance of one or another type in formation of reservoir properties of rocks. It is considered the possibilities of using the program Cluster Image as alternative and express way for estimation of 2D advantages from thin areas of carbonate stones reservoirs by example of Tournasian oil-bearing deposits, penetrated by the well in the southern slope of the South Tatar crest. The program Cluster Image allows avoiding application of estimated percentage of unclassified pixels in the process of estimating photographs of thin porosity carbonate reservoir rocks with significantly lockable voids in the image. It has been determined the specific variations of porosity by well profile depending on lithotypical rocks and structure of void volume. These variations correspond to the zonal structure of natural carbonate oil-saturated reservoir.

A three-dimensional classification for mathematical pore shape description in complex carbonate reservoir rocks

Porous carbonates display some of the most complex porosity networks in reservoir rocks. This requires a quantitative geometric description of the complex (micro)structure of the rocks. Modern computer tomography techniques permit acquiring detailed information concerning the porosity network in three dimensions. These datasets allow a more objective pore classification based on mathematical parameters. In this study, ratios of the longest, intermediate, shortest dimensions and compactness of the pore shapes, based on an approximating ellipsoid, are analysed to obtain a thorough and objective description of pore shapes. Using intrinsic properties of the latter, the classification can be used at every resolution scale. Five shape classes are defined: rod, blade, plate, cuboid and cube. An additional advantage of this classification is that the data provide information about the orientation of the pores. This allows assessing the anisotropy of the porosity parameter. Apart from having an objective pore-type classification, analysing the shape and orientation of the pores permits to study the relationship with other important petrophysical rock characteristics such as permeability, acoustic properties and rock mechanical behaviour.

Experimental investigation the effect of nanoparticles on the oil-water relative permeability

This paper presents the effects of the nanosilica particles on the water and oil relative permeability curves at reservoir conditions. Real reservoir crude oil sample was employed as an oil phase in relative permeability measurements. In addition, real carbonate reservoir rock samples were employed as a porous media in core displacement experiments. To determine relative permeability curves, the unsteady-state approach was employed in which Toth et al. method was applied to the recovery data points. By increasing the nanosilica content of the aqueous phase the oil relative permeability increased while the residual oil saturation decreased; however, by increasing the nanosilica concentration in the aqueous solution the water relative permeability decreased. The outcomes of this paper can provide a better understanding regarding chemically enhanced oil recovery (EOR) by nanoparticles. Moreover, relative permeability curves help us in the history matching section of reservoir simulation for any further EOR scenarios.

Computed X-ray microtomography as the useful tool in petrophysics: A case study of tight carbonates Modryn formation from Poland

Detailed qualitative and quantitative studies using the X-ray computed microtomography proved to be a reliable source of information about the pore space properties of clastic and carbonate reservoir rocks. X-ray computed tomography with higher resolution (nano) allows improving and completion of porous rocks analysis in aspects of new parameters determination. In this paper, results of the X-ray computed microtomography analysis were presented for core samples probed from the Palaeozoic carbonate intervals (Modryn formation) from the selected wells located in the Central-Eastern Poland. Several parameters were calculated on the basis of microtomographic images (total porosity, tortuosity, homogeneity parameter, mean chord length, Euler number), which allowed to parameterize pore space structure of tight carbonates. In the case of rock hydrocarbon potential determination, e.g. filtration properties, computed X-ray microtomography turned out as an alternative method in rock characterization. It appeared that the Modryn formation consists of rocks with poorly developed pore space with limited filtration abilities.

Understanding the Role of Asphaltene in Wettability Alteration Using ζ Potential Measurements

Wettability study using the ζ potential technique is a novel approach proposed for carbonate reservoir rocks. As opposed to other existing industrial and laboratory methods, such as the Amott–Harvey, United States Bureau of Mines (USBM), and contact angle methods, the ζ potential technique provides a complete wettability profile of limestone versus relative water/oil content in the presence of water for different oil samples. In addition, the study is extended for oil derivatives (i.e., asphaltenes and maltene). A case study was carried out to understand the effect of asphaltenic solutions on wettability of limestone rocks. From the obtained wettability profiles, it was found that different oil samples show the wettability transition, from water-wet to oil-wet. Moreover, the adsorption of maltenes was limited to the water-wet region whereas asphaltenes were found to be the main reason for heavy-fraction deposition.

Low salinity injection into asphaltenic-carbonate oil reservoir, mechanistical study

The impacts of salinity adjustment of displacing fluid have recently gained special attention to enhanced oil recovery (EOR). Different mechanisms have been studied widely in the literature while some of them are still subjugated to more scrutiny. The effects of diluted sea water on the interfacial properties of brine and asphaltenic-acidic crude oil and the wettability alteration of carbonate reservoir rock are investigated in this experimental observational work. The measurements of interfacial tension (IFT) and contact angle (CA) as two main parameters are studied. Besides, the effects of asphaltene and resin in the crude oil on the IFT values between the crude oil and aqueous solution are investigated.The experimental results show that the lowest IFT values are obtained at high salinity conditions, while the surface rock wettability alterations are observed at low salinity conditions. Based on the obtained results, a combined mechanism is proposed to describe the wettability alteration towards more water wet at low salt conditions.

Theses Abstracts in English on Libya 1936–2012

The Maghreb Review, Vol. 41, 1, 2016 © The Maghreb Review 2016 This publication is printed on longlife paper THESES ABSTRACTS IN ENGLISH ON LIBYA 1936–2012 COMPILED AND EDITED BY MOHAMED BEN-MADANI EDITORIAL NOTE Given the large number of theses that are covered in this compilation, we think it best to dedicate this issue of The Maghreb Review to Libyan Theses as it will be a useful reference tool for students, scholars and librarians for years to come. The following theses abstracts in English on Libya covering all fields of research, are published here for the benefit of interested scholars and students. These abstracts have not been included in any bibliographical work in the past and are arranged in Alphabetical order. The largest number of theses on Libya were presented in United Kingdom Universities (297) followed by United States universities (26), Canada (1), Ireland (3) and Sweden (1). We have included some older theses which were not included in our Abstracts of English Language Theses on Libya that was published in Volume 23, Nos. 1-4, 1998. In earlier Volumes we have published similar Abstracts on Morocco (Volume 26, Nos. 2-4, 2001, Volume 39, No. 4, 2014, and Volume 38, No. 2, 2013), Algeria (Volume 27, Nos. 2-4, 2012), Tunisia (Volume 24, Nos. 3-4, 1999), Maghreb (Volume 21, Nos. 3-4, 1996) and Mauritania, (Volume 24, Nos. 1-2, 1999). These Volumes are still available and can be ordered through our website: www.maghrebreview.com. Some theses included here are comparatively short (as few as 74 pages!) and beg the question as to how closely supervised they were and how stringent the criteria are for awarding a PhD in some institutions. 4 COMPILED AND EDITED BY MOHAMED BEN-MADANI ABSTRACTS THAT ARE CURRENTLY INACCESSIBLE The following titles are those theses which I have not been able to access. Some are still under embargo imposed by the authors and will not be publicly accessible for many years. Aburdene, Odeh Felix, An Analysis of the Impact of the Economies of Iraq, Iran, Kuwait, Libya and Saudi Arabia upon the United States Balance of Payments for the period 1963-1968, PhD., Fletcher School of Law and Diplomacy (Tufts University), 1974 Alkhazmi, Rajab Abdussalam, Preliminary Study of the Geology and Geochemistry of Jabal arkeno Ring Complex, Southeast Libya, PhD., South Dakota School of Mines and Technology, 1981 Askew, William C, Europe and Italy’s Acquisition of Libya: A Study in Mediterranean Politics and European Alignments, 1911-1912, PhD., Duke University 1936. Brown, Robert Wylie, A Spatial View of Oil Development in the Desert: Libyan in the First Decade, 1955-1965, PhD., Columbia University 1970. Cuthbertson, Susan Elyse, Politics, empire, and the Italian Nation, 1896-1949 (Libya, Somalia), PhD., University of Virginia, 2006. Dafer, Mohsen Ahmed, An Evaluation of the Educational Psychology Program at Alfateh University, Tripoli, Libya, PhD., The University of New Mexico, 1980. El-Zein, Salah, A, The Tuareq of South-Western Libya, PhD., Hull University, 1979. Feder, Milton, Great Power Relations in the Origin and development of the Kingdom of Libya, PhD., University of Michigan, 1960. Finaish, Mohamed Ali, Libya’s Petroleum Policy, PhD., University of Southern California, 1972. Fowler, Gary Lane, Italian Agricultural colonization in Tripolitania, Libya, PhD., Syracuse University, 1969. Ghuma, Mohamed Ali, The Geology and Geochemistry of the Ben Ghnema Batholith Tibisti Massif, Southern Libya, L.A.R., PhD., Rice University, 1976. Hammuda, Omar Suleiman, Eocene Biostratigraphy of the Derna area, Northeast Libya, PhD., University of Colorado at Boulder, 1973. Khalidi, Ismail Raghib, Constitutional Development in Libya, PhD., Columbia University, 1957. Khoja, Elhadi Razzagh, Petrography and Diagnosis of Lower Paleocene Carbonate Reservoir Rock, Dahra Field, Libya, PhD., Rice University, 1971. Ranck, Gary Laval, The Rodents of Libya: Taxonomy, Ecology and Zoogeographical Relationships, PhD., The University of Utah, 1966. THESES ABSTRACTS IN ENGLISH ON LIBYA 1936–2012 5 ABSTRACTS Abdalaziz, Mohamed, Measuring taxable capacity in Libya, PhD., University of Gloucestershire, 2012. This thesis measures the tax effort and taxable capacity in Libya and examines an important research question: “Has the tax burden reached the level of full tax capacity in Libya?” The main motivation of the study is the need to diversify the sources of the...

Особенности изучения смачиваемости сложнопостроенных карбонатных пород-коллекторов лабораторными методами

Особенности изучения смачиваемости сложнопостроенных карбонатных пород-коллекторов лабораторными методами

Experimental Study of Water and CO2 Flooding in the Tight Main Pay Zone and Vuggy Residual Oil Zone of a Carbonate Reservoir

In this paper, water and CO2 flooding processes in the upper tight main pay zone (MPZ) and lower vuggy residual oil zone (ROZ) of a carbonate light oil reservoir were experimentally studied and compared. First, some carbonate reservoir rock samples from these two zones in the Steelman oilfield (Canada) were characterized using thin-section analysis and X-ray diffraction. Second, the minimum miscibility pressure (MMP) between the light crude oil and CO2 at the actual reservoir temperature was determined. Third, a total of eight coreflood tests were conducted with the tight dolomite or vuggy limestone core plugs to examine the effects of the production pressure, CO2 injection timing, and rock properties on the water- and CO2-based oil recovery processes in the two different zones. It was found that, for the CO2 secondary flooding in the non-waterflooded tight core plugs (i.e., the MPZ), the oil recovery factor (RF) was not dramatically reduced when the production pressure was lower than the MMP. For the CO2...