Oil and Gas Reservoir Characterization Research Papers (original) (raw)

Recent advances in the understanding of the molecular and colloidal structure of asphaltenes in crude oils are codified in the Yen−Mullins model of asphaltenes. The Yen−Mullins model has enabled the development of the industry's first asphaltene equation of state for predicting asphaltene concentration gradients in oil reservoirs, the Flory−Huggins−Zuo equation of state (FHZ EOS). The FHZ EOS is built by adding gravitational forces onto the existing Flory−Huggins regular solution model that has been used widely to model the phase behavior of asphaltene precipitation in the oil and gas industry. For reservoir crude oils with a low gas/oil ratio (GOR), the FHZ EOS reduces predominantly to a simple form, the gravity term only, and for mobile heavy oil, the gravity term simply uses asphaltene clusters. The FHZ EOS has successfully been employed to estimate the concentration gradients of asphaltenes and/or heavy ends in different crude oil columns around the world, thus evaluating the reservoir connectivity, which has been confirmed by the subsequent production data. This paper reviews recent advances in applying the FHZ EOS to different crude oil reservoirs from volatile oil (condensate) to black oil to mobile heavy oil all over the world to address key reservoir issues, such as reservoir connectivity/compartmentalization, tar mat formation, non-equilibrium with a late gas charge, and asphaltene destabilization. The workflow incorporates the integration of new technology, downhole fluid analysis (DFA), coupled with the new scientific advances, the FHZ EOS and Yen−Mullins model. The combination proves a powerful new method of reservoir evaluation. Asphaltene or heavy end concentration gradients in crude oils are treated using the FHZ EOS, explicitly incorporating the size of resin molecules, asphaltene molecules, asphaltene nanoaggregates, and/or asphaltene clusters. All of the parameters in the FHZ EOS are related to DFA measurements, such as compositions, GOR, density, etc. The variations of gas and oil properties with depth are calculated by the classical cubic equation of state (EOS) based on DFA compositions and GOR using specifically developed delumping, characterizing, and oil-based drilling mud (OBM) contamination correcting techniques. Field case studies have proven the value and simplicity of this asphaltene or heavy end treatment. Heuristics can be developed from results corresponding to estimation of asphaltene gradients. Perylene-like resins with the size of ∼1 nm are dispersed as molecules in high-GOR volatile oils with high fluorescence intensity and virtually no asphaltenes (0 wt % asphaltene). Heavy asphaltene-like resins with the size of ∼1.3 nm are molecularly dissolved in volatile oil at a very low asphaltene content. Asphaltene nanoaggregates with the size of ∼2 nm are dispersed in stable crude oil at a bit higher asphaltene content. Asphaltene clusters are found in mobile heavy oil with the size of ∼5 nm at even higher asphaltene content (typically >8 wt % based on stock tank oil). Two types of tar mats are identified by the FHZ EOS: one with a large discontinuous increase in asphaltene content versus depth typically at the base of an oil column (corresponding to asphaltene phase transition) and one with a continuous increase in asphaltene content at the base of a heavy oil column simply by extending the oil column in the downdip direction because of an exponential increase in viscosity with asphaltene content. All of these studies are in accordance with the observations in the Yen−Mullins model within the FHZ EOS analysis.

- by and +1
- •
- Reservoir Characterization, Asphaltenes, Asphalt Pavements, Oil and Gas Reservoir Characterization

Industrial control systems are nowadays exposed in environments with rapid and unstable parameter changes and uses measuring equipments with critical output sensitivity. In the case of thermal gas analyzer, measurement errors are contributed by temperature, gas flow, and pressure. Error compensation is a key problem for these control systems. In recent years, it has been proven in the literature that artificial neural network (ANN) is a reliable and low cost solution to manage errors. Among all the algorithms of ANN, the back propagation is commonly used because of its simplicity and learning methodology is easy to realize. However, it has two notable drawbacks: (a) it is likely to run into local minimum, and (b) convergence is slow. Thermal conductivity gas analyzer often works in adverse surroundings, which requires fast and accurate measurements. Therefore, a strong learning network is needed. This paper proposes a novel thermal gas analyzer using adaptive neuro-fuzzy inference system. The effectiveness and validity of the proposed method is verified by simulation studies using MATLAB. Fuzzy membership rules are created to allow regulation of learning parameters. Further, the fuzzy adaptive network model is constructed to train large data samples while the high precision compensation of sensor error is realized by the improved flow. Simulation results reveal that the convergence speed and output accuracy is improved and the learning parameters in thermal gas analyzer are automatically corrected by the proposed method in comparison with the back propagation algorithm of artificial neural network.

In the oil province of southern Iran like other hydrocarbon zones, thorough understanding and risk management resulting from the rock mass deformation, can be of great help in executing operational processes such as the stabilization of the borehole wall, controlling the sand production in the borehole and hydraulic fracture. In oil well excavation operations, determining maximum and minimum horizontal stresses helps in designing the excavation route in the minimum stress direction so that collapsing of the borehole wall and drilling tube blockage against the rocks is avoided. The aim of this study was removing the main excavation problems especially of the diversion wells through exact geomechanical calculations in the Darian lime formation depth range in the understudy field. In order to develop the geomechanical model, first the bulk, the shear and the Young's modules, the Poisson coefficient and Vp/Vs ratio were calculated using the visual log data integrated with the geomec...

- by naser ebadati
- •
- Geology, Geomechanics, Reservoir Engineering, Petroleum geology

- by naser ebadati
- •
- Geology, Geomechanics, Reservoir Engineering, Petroleum geology

Porosity & permeability are important rock properties which are dependent on rock texture and also on the diagenetic process rock go through upon burial. Rock texture is responsible for primary porosity variation where’s diagenesis deals with secondary porosity enhancement or reduction. Porosity & permeability are the most important parameter for evaluating reservoir quality measuring sealing potential etc.

This Article is about the Unconventional reservoirs; what are they, what are the differences between them and the normal Conventional reservoirs and what made us in need for studying and exploring these reservoirs even if they are very hard to produce and need much money and sacrifices.
It also describes a geological, petrophysical, geochemical and geomechanical study of shale gas/oil characteristics that without it we can’t have a successful exploration and our target is to reach the sweet spots which are defined as the most prospective volumes of the shale play, they are primarily targeted to achieve early economic production. From all these studies we can conclude the methodology of exploration, as well as having a general view about the techniques used for investigation of the shale gas/oil, and also discussing the worldwide production and in Egypt.

- by Basma Ahmed
- •
- Geochemistry, Sedimentology, Production, Geomechanics

Reservoir characterization and structural mapping using integration of well logs and 3-D seismic data was carried out to determine the prolificacy of OVU field, onshore Niger delta. The distribution of reservoir physical parameters (porosity, permeability etc.) and availability of traps that favour hydrocarbon accumulation in the field were evaluated. Four hydrocarbon bearing reservoirs were delineated out of several identified sands in the field out of which three horizons were mapped. Two major growth faults, an antithetic fault and five synthetic faults were delineated. Structural closures were identified as rollover anticlines with the trapping mechanism delineated as a Fault assisted anticlinal structure. The computed range of values for gross thickness, volume of shale, net to gross, water saturation, hydrocarbon saturation, total porosity and absolute permeability with respect to each reservoir are: 18-125m, 9-17%, 83-92%, 18-28%, 62-82%, 21-23%, and 736-3965mD respectively. Hydrocarbon reserves calculations reveals a total reserve of 30.9 billion stock tank barrels of oil. With the very good to excellent calculated values of petrophysical parameters and high hydrocarbon reserve together with the suitable trapping mechanisms makes the study field prolific. Few wells exist in the southwestern corner of the field where a closure is identified in this study. The area should therefore be subjected to further evaluation with a view to increasing the number of wells there.

Schiff base synthesis of 1,3,4 oxadiazole derivatives containing
Indole moiety bearing thiazolidinone ring were synthesized by the
condensation of 2-(3-(4-oxo-3-(p-tolyl) 1H-tetrazol-5-yl)-1Hindol-1-yl)-N-(1,1,1-trifluoropropan-2- ylidene) acetohydrazide
with acetic anhydride. To this reaction was subjected in schiff base
reaction. It forms 2-(1-((4-acetyl-5-methyl-5-(trifluoromthyl)-4, 5-dihyro-1, 3, 4-oxadiazol-2-yl) methyl)-1H-indol-3yl)-3-(p-tolyl)
1H-tetrazol-5-yl). The structure of these newly synthesized
compounds was characterized by
1
H NMR,
13
CNMR, Mass, IR,
and elemental analysis.

Tesis de licenciatura presentada por Lutz Alexander Keferstein Caballero al sínodo respectivo de la Facultad de Derecho de la Universidad Nacional Autónoma de México, campus Aragón.
Primera tesis en la Historia de la Facultad de Derecho de la UNAM con un tema tan actual en aquel entonces, a sólo dos años de la entrada en vigor del TLC de América del Norte.
Dumping, prácticas desleales de comercio internacional y los páneles internacionales para dirimir diferencias.

- by Prof. Hilmi S. Salem
- •
- Petrophysics, Nanomaterials, Nanotechnology, Porosity

The Gulf of Suez in Egypt has a north-northwest–south-southeast
orientation and is located at the junction of the African and Arabian
plates where it separates the northeast African continent from the
Sinai Peninsula. It has excellent hydrocarbon potential, with the
prospective sedimentary basin area measuring approximately
19,000 km2, and it is considered as the most prolific oil province
rift basin in Africa and the Middle East. This basin contains more
than 80 oil fields, with reserves ranging from 1350 to less than 1
million bbl, in reservoirs of Precambrian to Quaternary age. The
lithostratigraphic units in the Gulf of Suez can be subdivided into
three megasequences: a prerift succession (pre-Miocene or Paleozoic–
Eocene), a synrift succession (Oligocene–Miocene), and a
postrift succession (post-Miocene or Pliocene–Holocene). These
units vary in lithology, thickness, areal distribution, depositional
environment, and hydrocarbon importance. Geological and geophysical
data show that the northern and central Gulf of Suez consist
of several narrow, elongated depositional troughs, whereas the
southern part is dominated by a tilt-block terrane, containing numerous
offset linear highs.
Major prerift and synrift source rocks have potential to yield oil
and/or gas and are mature enough in the deep kitchens to generate
hydrocarbons. Geochemical parameters, sterane distribution, and
biomarker correlations are consistent with oils generated from marine
source rocks. Oils in the Gulf of Suez were sourced from potential
source rock intervals in the prerift succession that are typically
oil prone (type I), and in places oil and gas prone (type II), or
are composites of more than one type (multiple types I, II, or III
for oil prone, oil and gas prone, or gas prone, respectively).
The reservoirs can be classified into prerift reservoirs, such as
the Precambrian granitic rocks, Paleozoic–Cretaceous Nubian sandstones,
Upper Cretaceous Nezzazat sandstones and the fractured
Eocene Thebes limestone; and synrift reservoirs, such the Miocene
sandstones and carbonates of the Nukhul, Rudeis, Kareem, and Belayim
formations and the sandstones of South Gharib, Zeit, andpost-Zeit. The majority of oil fields in the region incorporate
multiple productive reservoirs. Miocene
evaporites are the ultimate hydrocarbon seals, whereas
the shale and dense limestones of the prerift and the
synrift stratigraphic units are the primary seals. Structural,
stratigraphic, and combination traps are encountered
in the study area. The Gulf of Suez is the most
prolific and prospective oil province in Egypt, and any
open acreage, or relinquished area, will be of great interest
to the oil industry.

- by Ahmed E. Radwan
- •
- Geology, Structural Geology, Research Methodology, Petroleum

Asphaltene precipitation from live crude oils that occurs due to pressure reduction can foul and clog oil production equipment, at the well surface, in the borehole, and even in the subsurface formation, thus is of considerable interest to oil operating companies. We employ near-infrared (NIR) spectroscopy to characterize this asphaltene precipitation process; in particular, the independent measurements on asphaltene flocculation of wavelength dependence of optical scattering and of sedimentation rates are performed. Here, it is established that different asphaltene flocs form during depressurization of crude oil. Furthermore, the initial precipitate is probably not problematic in the production of crude oil, relaxing constraints imposed by asphaltene considerations. Additionally, the asphaltene precipitation process is shown to be largely reversible in the minutes time frame, but subtle irreversibilities are suggested. Compressibility is measured using NIR techniques to validate our methods. Optical spectroscopy on optically thin samples is found to be a powerful and indispensable tool to characterize asphaltene precipitation.

- by Oliver C Mullins and +1
- •
- Geochemistry, Oil and gas, Asphaltenes, Oil and Gas Reservoir Characterization

Metamorphic processes, leading to mineralogical and structural changes of the rocks in response to physical (pressure, temperature) and chemical conditions, can be associated with the development of sin-metamorphic or post-metamorphic fractures. The post-metamorphic ones are directly related to tectonic stress. In addition, tectonic stress may cause the reorientation of minerals on a direction perpendicular to the stress direction, generating foliations (schistosity).
This paper presents a structural analysis of the pre-Alpine metamorphic basement and its relations with the sedimentary cover by using geophysical data recorded in an exploration well located in the North Dobrogea Promontory (Romania). The analysis was based on Quad-Combo wireline logs, spectral gamma ray, sonic cross-dipole and borehole electrical imaging data. The imaging analysis allowed the identification and characterization of metamorphic foliations, sedimentary bedding, natural fractures and the determination of tectonic stress orientation. A brittleness index was computed by means of elastic parameters derived from density and sonic compressional and shear logs. Also, a fracture intensity characterization by using fracture area per volume of rock was conducted. The integration of geophysical logs with mud logging and drilling data allowed us to carry out a detailed analysis of the metamorphic basement in the studied area.

- by Bogdan NICULESCU and +1
- •
- Geology, Geophysics, Structural Geology, Metamorphic Petrology

A sequence stratigraphic analysis was carried out on the sedimentary packages of parts of the Bengal Basin hydrocarbon province. This paper focuses on the identification of petroleum system of Srikail Gas Field within eastern folded belt of Bengal basin using sequence stratigraphic concept. Three strike and five dip seismic lines are used in this work and data analysis is done using Petrel 2015 software. Seismic line-2 (SK-2) of Srikail is good in resolution and is used here only for identifying potential petroleum system. Seven sequence boundaries were identified on the basis of onlap and reflection truncation. The result of the interpreted sequence boundary has revealed that all the elements which are required to generate a potential prospect are present in the study area. Fine grained sediments deposited during the rising and lowering of sea level might act as a potential source rock. Time contour maps of the study area have revealed that the NW-SE trending anticlinal Srikail structure is largely affected by shale filled channel in the crestal and western flank. The channel filled shale is later acting as a seal on north and western part of the structure. Erosional remnants truncated against shale fill canyon is acting as prospective reservoirs in the Srikail gas field. The NW-SE trending anticlinal structure and shale fill canyon help this sand as potential traps for hydrocarbon accumulation. Hence the petroleum system of the study area become very prospective in terms of hydrocarbon accumulation.

- by Md. Imam Sohel Hossain and +1
- •
- Reservoir Characterization, Oil and Gas Reservoir Characterization

ترجمه قست سوم کتاب شبیه سازی مخزن دانشگاهHeriot Watt

Stratigraphy and the oil industry are intricately intertwined and have been so ever since the early days of hydrocarbon exploitation. Stratigraphic understanding forms the basis for all upstream activity from basin exploration through field evaluation to reservoir development and production. In the quest for hydrocarbons, both the exploration and exploitation programs can be greatly enhanced by applying stratigraphic analysis. This technique provides the explorationist with the capability to recognize, discover and evaluate new hydrocarbon reservoirs and to reduce the risk in management's decision-making.
Stratigraphic approach to hydrocarbon studies can make use of high-resolution biostratigraphic and pale bathymetric data, well-log signatures and seismic-reflection profiles, and well core data to determine the lithostratigraphy, lithofacies, depositional sequences, and the sequence boundaries.
This study explores the integration of seismic and well-log data for stratigraphic studies. The identification of depositional environments from well logs is based on the principle that well log responses are related to changes in thickness, texture, grain size, and lithology along the well path, while the relection pattern recorded on seismic sections can be interpreted in term of depositional environment and lithofacies.
A case study of the Sequence Stratigraphy of Akos Field in the Coastal Swamp Depobelt of the Niger Delta was considered. From which it can be concluded that the integration of seismic and well log data for stratigraphic studies is a valuable tool for oil and gas exploration.

- by Victor Towoju
- •
- Geophysics, Exploration Geophysics, Reservoir Characterization, Applied Geophysics

The paper presents a numerical algorithm that performs accurate lithology corrections for thermal (CNL/TNPH, CNL/NPHI) and epithermal (SNP) neutron logs, in the whole range of porosities normally encountered in practice. It is known that neutron logs respond not only to a formation’s true porosity, but, to some extent, also to its lithology (the so-called "matrix effect"). Because the matrix effect is nonlinear and varies with true porosity, which is unknown beforehand, an iterative process is needed in order to carry out proper lithology corrections and obtain formation's porosity. The relationships between measured neutron porosity and true porosity for the common reservoir lithologies (sandstones, limestones and dolomites), at different formation water salinities, are approximable via suitable regression polynomials. Nonlinear neutron responses thus expressed are combined with the responses of density and sonic velocity logs, together with the volumetric unity constraint, into a system which is solved using a Newton-Raphson root-finding routine. The algorithm, implemented as a set of Matlab™ codes, provides optimal petrophysical models for the interpretation of neutron-density-sonic log suites and is easily adaptable in order to include additional linear or nonlinear log response equations. A case study regarding its applicability is also presented in the paper.

- by Bogdan NICULESCU
- •
- Earth Sciences, Geology, Geophysics, Petrophysics

GOR and asphaltene gradients are routinely measured by downhole fluid analysis (DFA) and analyzed by the cubic EoS and the FHZ EoS, respectively. These results are then placed within a reservoir perspective; for example, equilibrated asphaltenes are known to indicate reservoir connectivity. Therefore, understanding the origins of these gradients is important. The variations of different crude oil components measured in present day are a function of charge history as well as in-reservoir fluid processes that can cause fluid components to equilibrate thermodynamically. Here, petroleum system modeling is used to create different initial reservoir fluid distributions immediately after trap filling, where layer-cake " Stainforth " density stacking trap filling is presumed. Charges that are relatively homogeneous versus those of greatly differing thermal maturities are considered. Subsequent to trap filling, diffusion is forward modeled. For a charge of greatly differing thermal maturity, the initial (post trap filling) versus final equilibrated gradients in GOR and asphaltenes are seen to be similar, equilibrium is attained relatively quickly. In contrast, for this case, the large initial gradient in liquid fingerprints and biomarkers is very dissimilar to the final homogenous equilibrium distribution of these components, thus, longer times are required for equilibrium. Consequently, a single oil column can exhibit equilibrium distributions of GOR and asphaltenes with disequilibrium in oil fingerprints and biomarkers. In contrast, a homogenous charge can yield the opposite, equilibrium of fingerprints and biomarkers, and disequilibrium of GOR and asphaltenes. The 'thermodynamic distance' from the initial condition (at end of trap filling) to equilibrium determines, to a large degree, the diffusive time required to achieve equilibrium.

- by Oliver C Mullins and +1
- •
- Geochemistry, Reservoir Engineering, Reservoir Characterization, Asphaltenes

In this reservoir study, two adjacent fault blocks have
been subject to the same initial liquid and subsequent gas
charges, yet fl uid characteristics are different. Wells in each
fault block have a gas-oil contact (GOC) and an oil-water
contact (OWC), thus all depth-dependent in-reservoir fl uid
geodynamic processes are visible within each well. The
two adjacent fault blocks are found to be at different stages
of the same reservoir fl uid geodynamic process yielding a
‘movie’ with two time frames.
Diffusion of gas, from the late gas charge, into the oil
column causes a signifi cant increase of solution gas initially
at/near the GOC. This increase in solution gas causes the
asphaltenes to migrate down in the oil column. Well 1 is in
the middle of this process exhibiting huge disequilibrium
gradients of gas-oil ratio (GOR), saturation pressure and
asphaltenes. In Well 2, the diffusion of gas reached the
base of the column expelling most of the asphaltenes out
of the oil column creating a 10-m tar mat at the base of
the column. In Well 2, the oil is nearly in thermodynamic
equilibrium in contrast to large disequilibrium in Well 1.
Asphaltene extracts of core plugs are consistent with these
fl uid profi les and reinforce conclusions. The disequilibrium
oil column is associated with low vertical permeability
as seen with pressure interference testing indicating
multiple baffl es. In drillstem tests (DSTs), the equilibrated
oil column exhibited 10x greater production than the
disequilibrium oil column. Equilibrated asphaltenes are
associated with good production; here, disequilibrium
asphaltene gradients and poor vertical permeability are
associated with low production due to reservoir baffl ing.

The study area is located in the northern and western parts of Moldavian Platform, the oldest platform unit of the Romanian territory and representing the margin of the East European Platform. Two hydrocarbon systems are recognized in the Moldavian Platform: a thermogenic system of Paleozoic age and a biogenic system of Miocene age. The Miocene biogenic system comprises significant natural gas fields (including dry gas with more than 98% methane), reservoired especially in Sarmatian (late Middle Miocene) deposits, where suitable conditions for accumulation and sealing are encountered. The Sarmatian stage was marked by permanent changes of the sedimentary conditions, passing from a predominantly marine environment to a transitional one, of deltaic type with lacustrine-continental influences. The gas accumulations are usually hosted in sands/sandstones (observed as good seismic reflectors with continuous or discontinuous character) that pinch out forming lithostratigraphic traps. The sand beds or sand bodies formed during the deltaic construction, especially when they overlap and alternate with pelitic sequences, offer the most favorable settings for such accumulations.
The integrated analysis of recent geophysical well logs (conventional logs and high-resolution electrical imaging logs) and seismic reflection surveys, together with mud logging data and well flow test results, allow a better characterization of the Sarmatian deposits, particularly the gas reservoirs, from the study area. The correlation of three exploration wells along a NW–SE profile indicates that a low-energy, fine-grained depositional environment is developing towards SE, with a prevalence of claystones and with fewer sand reservoirs, if any. This may reflect a deltaic transition from distributary channels and mouth bar sands towards prodelta offshore silts and muds. The processed electrical imaging data recorded in the northernmost exploration well show two dominant dip azimuths (142 and, subordinately, 218 degrees) in the shale intervals. Most likely, these indicate NW to SE and NE to SW sediment paleotransport directions, related to seaward delta progradation. The electrical imaging results also reveal the presence of two high-angle faults (48–54 degrees dip values), which might have provided pathways for gas migration from deeper levels up to shallower Sarmatian reservoirs.

- by Bogdan NICULESCU and +1
- •
- Geology, Geophysics, Structural Geology, Oil and gas
- by Alkis John Corres
- •
- Management, Economics, Energy Economics, Public Administration

MANAGING SUPPLIES AND DISTRIBUTION OF PETROLEUM PRODUCTS IN GHANA: THE WAY FORWARD
ABSTRACT
The dissertation was first and foremost aimed at examining existing systems of supplies and distribution of petroleum products across Ghana and studying how relevant they are. This was due to lack of improvement in the few available systems which the researcher had encountered in his endeavours as an engineer in the petroleum industry. Many developing countries lack a systematic approach towards the management of petroleum products as the study in the West African countries as example depict. In most cases the approaches adopted are ad hoc which is not good enough. This called for an in-depth study of the various systems with their problems or successes in order to see to the implementation of any meaningful solutions to them.
Having examined the existing facilities in the field the dissertation further adopted the strategy in analysing the problems in the management of supplies and distribution of petroleum products. Hence the aims which are as listed in Chapter 1, i.e. to analyse the numerous problems in the management of supplies and distribution of oil and gas in Ghana; to study the state of existing facilities associated with petroleum supplies, storage and distribution; to recommend processes that would bring them to acceptable international standards; to research into recovery of oil from wastes as a result of runoffs; and to recommend for existing and new depots. The findings showed that the existing methods and processes were rather expensive and out-dated. They rather create wastage and incur much to transport smaller amounts of processed products across the length and breadth of the country. More effective means of transportation of the products in the country were arrived at with recommendations given in Chapter 5. In conclusion there is the need for the government of Ghana to source for long term solutions to the problems by constructing various projects as analysed in the research activity with regard to the carting of products to and from their various destinations. This is because petroleum wastage could cost the nation fortunes.

This paper presents a comprehensive review of the effects of production scheme and reservoir properties on the ultimate recovery and production trends of gas condensate reservoirs under bottom water drive mechanism. The aim of this study is to provide reservoir geologists and engineers with a strategy for optimizing the development, prolong field life and maximize recovery of bottom water driven gas condensate reservoirs. The approach focused on the review of the simulated results of various constructed radial numerical models from different producing gas and oil reservoirs in various fields. Technical papers and journals concerning hydrocarbon recovery and production were also reviewed. In this study, all factors that have potential impact on gas and oil ultimate recoveries such as gas production rate, completion length, aquifer size, horizontal permeability and permeability anisotropy were thoroughly studied and reviewed. Technological efforts to outwit challenges facing bottom water driven gas reservoirs such as water coning were also reviewed. Results showed that, low gas production rate is more preferred in order to prolong field production life, minimize water production and water breakthrough time in gas condensate reservoirs. The effect of aquifer size in gas recovery is not very much pronounced though the gas recovery increase with an increase in aquifer size up to aquifer size (M)=10 and then starts to decrease and for maximum gas recovery, the gas zone has to be totally perforated.

- by Aslam khan
- •
- Geology, Oil and gas, Oil and Gas Reservoir Characterization

The objective of this study is to provide information on source organic matter input, depositional conditions and the correlation between crude oils recovered from Sunah oilfield and Upper Jurassic Madbi Formation. A suite of twenty-six crude oils from the Lower Cretaceous reservoirs (Qishn clastic) of the Masila Region (Eastern Yemen) were analysed and geochemically compared with extracts from source rock of the Upper Jurassic (Madbi Formation). The investigated biomarkers indicated that the Sunah oils were derived from mixed marine and terrigenous organic matter and deposited under suboxic conditions. This has been achieved from normal alkane and acyclic isoprenoids distributions, terpane and sterane biomarkers. These oils were also generated from source rock with a wide range of thermal maturity and ranging from early-mature to peak oil window. Based on molecular indicators of organic source input and depositional environment diagnostic biomarkers, one petroleum system operates in the Masila Region; this derived from Upper Jurassic Madbi organic-rich shales as source rock. Therefore, the hydrocarbon exploration processes should be focused on the known location of the Upper Jurassic Madbi strata for predicting the source kitchen.

- by Nabil M . Al-Areeq
- •
- Sedimentology, Petrophysics, Petroleum, Petrology and Geochemistry

Resolute development of the already explored and accessible Ukrainian resources could result in a substantial increase of Ukrainian gas production. The boost would not only enable the country to fully cover its domestic gas needs, but also make Ukraine largely self-sufficient from an energy perspective. In a best-case scenario, increased production could even allow Ukraine to start exporting gas to or via neighboring European states. This would be feasible because Ukraine’s substantial gas transportation system means that the necessary infrastructure is already in place to bring large amounts of gas to the EU.

- by Andreas Umland
- •
- Energy, European Energy Policy, Oil and gas, Politics of Ukraine

Downhole fl uid analysis (DFA) is used to characterize
compositional fl uid gradients, and equations of state
(EoS) models are used for analysis to delineate reservoir
fl uid variations, connectivity and other complexities. A
series of reservoirs is examined to assess the state of the
contained fl uids in terms of thermodynamic equilibrium
in the reservoir. Substantial, systematic fl uid variations
are found using DFA. The cubic EoS is used for gasliquid
analysis, and the Flory-Huggins-Zuo EoS and the
Yen-Mullins model of asphaltenes are used for analysis of
dissolved solid-solution equilibria of reservoir crude oils.
‘Young’ reservoirs exhibit large, nonmonotonic variations
of fl uids (and solids), moderately aged reservoirs exhibit
monotonic, yet disequilibrium properties and ‘aged’
reservoirs are fully equilibrated even when in massive
scale. Nevertheless, these old reservoirs retain signifi cant
fl uid and organic solid variations as a result of sequential
fl uid-related processes in geologic time.
The dynamic behaviors of fl uids within reservoirs
that account for these variations are obtained by linking
a fundamental understanding of petroleum with basic
concepts from fl uid mechanics. In particular, the location
of tar deposition within reservoirs is clarifi ed when formed
due to asphaltene instability upon a secondary reservoir fl uid
charge. Tar deposition can be formed upstructure for rapid
gas charge, as is regularly seen in young reservoirs, or can
be formed at the oil-water contact for a slower gas charge,
as seen in many older reservoirs. The state of the reservoir
fl uids within the context of geologic time is shown to be
tightly coupled to key reservoir concerns for production.
Thus, understanding the context of the reservoir within
the overall geology and petroleum system can be used to
optimize reservoir evaluation. The expanding capabilities
of DFA, plus major advances in asphaltene science, have
revealed dramatic systematic variations of reservoir
fl uids and are becoming indispensable for optimization of
production.

- by Oliver C Mullins and +2
- •
- Geochemistry, Reservoir Engineering, Oil and gas, Reservoir Characterization
- by Joel Krupa
- •
- Mechanical Engineering, Geotechnical Engineering, Energy, Energy Policy

separator test to determine pvt properties of crude oil and gases

The identification of fluid contacts (gas–water contact—GWC, oil–water contact—OWC and gas–oil contact—GOC) is essential for field reserve estimates and field development and, also, for detailed formation evaluation. For the accurate calculation of some petrophysical parameters, such as porosity, the reservoir interval has to be zoned by fluid type, to account for differences in fluid saturations and fluid properties (e.g., hydrogen index, density, sonic transit time) in the various intervals: gas cap, oil column and aquifer zone. The fluid contacts may vary over a reservoir either because of faults, semipermeable barriers, rock quality variations / reservoir heterogeneity, hydrocarbon-filling history or a hydrodynamic activity. Horizontal contacts are typically taken into consideration, although irregular or tilted contacts occur in some reservoirs. The methods used for determining the fluid contacts include fluid sampling, water and hydrocarbons saturation estimation from geophysical well logs, analyses of conventional or sidewall cores, and formation pressure measurements. The pressure profiles obtained with various formation testing tools over reservoir intervals are, frequently, the primary source of data for defining the fluid contacts. When good quality pressure data can be collected, the fluid contacts can be determined by identifying the depths at which the pressure gradients (pressure versus depth trends) change. This study addresses some issues related to the identification of GWC for two gas fields of Early Pliocene age (Dacian stage), belonging to the biogenic hydrocarbon system of western Black Sea basin-Romanian continental shelf. We show that the identification of these contacts based exclusively on pressure gradients analysis is uncertain or may be inaccurate. The pressure gradients approach should be checked against the results of the conventional interpretation of geophysical well logs (e.g. changes in the computed fluid saturations as a function of depth) and, if available, the results of nuclear magnetic resonance (NMR) log investigations, which are able to indicate the intervals with clay-bound water, capillary-bound water and movable fluids.

- by Bogdan NICULESCU
- •
- Geology, Geophysics, Petrophysics, Reservoir Engineering

Recovery Factor (R.F) can be expressed as the ratio of ultimate oil recovery to oil initially in place. In these
work, the study of recovery factor for the water drive reservoir in the Niger Delta oil reservoir was analysed
using a statistical correlation approach. A sensitivity analysis was performed on different parameters affecting
recovery factor of water drive reservoir. The statistical correlation was based on data obtained from (5)
reservoirs, with data based on actual production performance from oil producing reservoir. The material balance
method was used to determine the oil in place and the drive indices. A statistical correlation package (SYSTAT)
was used to correlate the rock and fluid properties to the Recovery Factor (R.F) obtained for the (5) reservoirs.
Models were developed to determine the Recovery Factors; the two models tested were that of Guthrie and
Green Berger Model, and the API correlation model. The results show that the proposed correlation is reliable in
a full range of parameters but the compared simulated values of recovery factors obtained from these models
was not in agreement with the obtained field data. These results confirmed that the recovery factor analysed
only appeared to be conventional.

- by Mahmoud Mohamed
- •
- Oil and Gas Reservoir Characterization

The octane enhancement of light straight run naphtha is one of the significant solid acid catalyzed processes in the modern oil refineries due to limitations of benzene, aromatics, and olefin content in gasoline. This paper aims to examine the role of various catalysts that are being utilized for the isomerization of light naphtha with an ambition to give an insight into the reaction mechanism at the active catalyst sites, and the effect of various contaminants on catalyst activity. In addition, different technologies used for isomerization process are evaluated and compared by different process parameters.

- by Dr. Abdul-Sattar Nizami and +1
- •
- Environmental Engineering, Materials Engineering, Chemical Engineering, Environmental Science

permeability determination

The main objective of this project was to determine reservoir characteristics using gas well test data. The problem assessed in this project was the level of uncertainty that other methods of characterizing reservoir such as well logging, coring and PVT analysis have to meet operation scope. The specific objectives were achieved by analyzing secondary well test data of Songo Songo gas field by using Horner technique, excel program, and different analytical equations.
Results obtained from analysis of buildup test data shows permeability of about 33 md, very high positive skin factor of about 22.7 which resulted to permeability drop of about 6md compared well logs and coring which were 39md and 39.5md.
Evaluation of inflow performance and gas deliverability was done using theoretical deliverability equations. From the analysis the absolute open flow potential for 2015 and 2016 were found to be 65 MMSCD and 52 MMSCD respectively, also showing deliverability of gas well were 53 MMSCD and 45 MSCD for 2015 and 2016 respectively. From the analysis it was concluded that the absolute open flow potential has dropped by 8 MMSCFD which is a normal situation because of declining of reservoir pressure.
In order to monitor the performance of the well it is recommended that these tests should be done at least twice in year.Also due permeability drop of about 6md, the gas well has to be stimulated in order to reduce damage of the reservoir formation and hence increase productivity of the well

- by Vivian Amobi
- •
- Renewable Energy, Energy, Energy Policy, Energy and Environment

Employees today are different. They are not the ones who do not have good opportunities, especially, experienced and talented ones. As soon as they feel dissatisfied with the current employer or the job due to lack of advancement opportunities, salary and remuneration and others, they switch over to the next. The result is that employers lose their invested resources to their competitors, corporate memory is lost, employee-customer relationships are strained and more over the moral of existing staff goes down. It is therefore very important that employers retain their employees, especially the good and experienced ones. Employee retention is a process in which employees are encouraged to remain with the organization for the maximum period of time or until the completion of a particular project. This study looks at the retention practices in Oil & Gas Sector, from the point of view of its employees and what role retention plays in their job performance. The study confirms that lack of advancement opportunities, work-life balance, lack of reward and recognition and salary and remuneration were more common reasons for departure among all employees. Retaining top talent is a primary concern for many organizations today and this study recommends that retention strategies should be aimed at retaining highly skilled personnel and at the same time building up under-performers. Feedback on employee performance is vital to building confidence in the retention practices of the Oil & Gas Sectors. In addition, employee value proposition as enshrined in the vision statement of the Oil & Gas Sectors must be upheld while management should be flexible in terms of work-life balance. This motivation of employees produces a culture of commitment to the objectives of the organization.

Crude oils consist of dissolved gases, liquids,
and dissolved solids—the asphaltenes. The chemical
identity and thermodynamic treatment of gas and liquid
components of crude oil have long been understood. For
example, the cubic equation of state (EoS) is very familiar
to the reservoir engineering community. In contrast, in
years past, the asphaltenes were viewed as complex,
enigmatic and without a thermodynamic foundation.
Consequently, oil􀂿 eld observations related to asphaltenes,
such as asphaltene gradients in crude oil, heavy-oil
gradients, viscosity gradients, tar mat formation, bitumen
deposition and asphaltene 􀃀 ow assurance, were all viewed
very much within a phenomenological context without
a 􀂿 rst-principles foundation. In the recent past, a simple
molecular and nanocolloidal model of asphaltenes, the
Yen-Mullins model, has been shown to apply broadly. This
model, combined with the Flory-Huggins-Zuo Equation
of State (FHZ EoS), accounts for asphaltene gradients
in bulk oil and when combined with the Langmuir EoS
accounts for oil-water interfacial properties. Such success
establishes validation.
These new developments in asphaltene science
have been closely linked with downhole 􀃀 uid analysis
(DFA) to address a wide variety of reservoir concerns.
Consequently, petrophysicists and other geoscientists
traditionally charged with the responsibility of formation
evaluation are left with the task of understanding the
asphaltenes. Here, we provide an overview of asphaltenes
in order to make asphaltenes accessible to technologists
who are not expert in petroleum and asphaltene science.
The emphasis is on the simplicity of asphaltene chemistry.
This discussion naturally leads to basic chemical precepts
of solubility especially because asphaltenes are de􀂿 ned by
their solubility characteristics.

- by Oliver C Mullins and +1
- •
- Geochemistry, Reservoir Engineering, Oil and gas, Reservoir Characterization

Wireline openhole formation evaluation has been the standard in petrophysics and quantitative reservoir evaluation for many years. During the last five years we have witnessed a migration of some of the basic, high-quality openhole... more

- by Ian D Stowe and +2
- •
- Oil and Gas Reservoir Characterization

Penentuan cadangan minyak bumi dilakukan untuk memperkirakan jumlah cadangan yang dapat diproduksikan ke permukaan. Umumnya penentuan cadangan dengan menggunakan metode decline curve dilakukan saat berlangsung proses produksi untuk dapat... more

- by Vandi Perdana
- •
- Chemical Engineering, Petroleum, Reservoir Engineering, Oil and gas

• Chemical composition and effects of oily wastewater • Polymeric and ceramic membrane for wastewater oily treatment • Effect of surface modification and effect of operating parameters of the membrane performance • Combined systems with membrane separation and future outlook for removal of oily wastewater a b s t r a c t Membrane separation processes have become an emerging technology for the treatment of oily wastewater due to high oil removal efficiency and relatively facile operational process. This review will highlight the recent development of advanced membrane technology such as surface modification, addition of inorganic particles in polymer membrane and the development of ceramic membranes. Additionally, the effect of operating parameters on the membrane performance is discussed in detail. Future outlooks in oil–water membrane separation are also discussed to further broaden the research and development related to this technology.

- by ALI MOSLEHYANI
- •
- Chemical Engineering, Chemistry, Catalysis, Oil and gas