Isopach,lithofacies changes,and source rocks chracteristics of Khatatba and Alam El Bueib formations of some wells in North East Western Desert,Egypt

The present work deals with isopach, lithofacies changes, and source rock chracteristics of Khatatba and Alam El Bueib formations of some wells in North East Western Desert. Isopach and lithofacies changes showed that the thickness of Khatatba Formation increases toward the south western direction and decreases toward northern parts, and the sediments consisting of sandstone and shale facies indicate a shallow marine environment. Alam El-Bueib sediments increase toward the north direction, and argillaceous sandstone facies reflect terrestrial-to-shallow marine environment. The geochemical analysis showed that Khatatba Formation bears a mature source rock and has poor-to-good generating capability for both oil and gas and lie within the early generation window and oil window. Alam El Buieb Formation constitutes a mature source rock and has poor-to-good generating capability for both oil and gas. It can be stated that Khatatba and Alam El Buieb are the main source rock for hydrocarbon accumulations rich with organic sediments and could be considered as effective source rocks for generating hydrocarbons in the the studied wells.     

Biomarkers Assessment of Crude Oils and Extracts from Jurassic-Cretaceous Rocks,North Qattara Depression,North Western Desert,Egypt

Abstract

Crude oils together with extracts from the Middle Jurassic (Khatatba Formation), Barremian-Early Aptian Alam El Bueib Formation, and Early Albian Kharita Formation were collected from five wells (Ras Qattara-Zarif-5, Ras Qattara-Zarif-3, and Zarif-1, Zarif-2, SW Zarif-1) in the North Qattara Depression. Biomarkers (pristane/phytane, isoprenoids/n-alkanes, steranes, triterpanes, C₂₉ steranes 20S/20S + 20R, C₂₃ tricyclic/C₃₀ hopane, Ts/Tm, C₃₀ moretane/C₃₀ hopane ratios, homohopane and gammacerane indices) of the saturated hydrocarbon fraction were analyzed in order to assess the source and maturity of the crude oils and the extracts. The results suggested that the oils from Khatatba and Alam El Bueib formations are mature, derived from source rocks containing marine and terrestrial organic matter, respectively. The source environments and maturity of the oil from the Khatatba Formation is similar to that of the Khatatba source rock extract. The oil from the Alam El Bueib formation differs from the extracts of the Alam El Bueib and Kharita formations. The Khatatba formation seems to be an effective source rock in the North Qattara Depression.     

Evaluation of the nature,origin and potentiality of the subsurface Middle Jurassic and Lower Cretaceous source rocks in Melleiha G-1x well,North Western Desert,Egypt

The present work aims to evaluate the nature and origin of the source rock potentiality of subsurface Middle Jurassic and Lower Cretaceous source rocks in Melleiha G-1x well. This target was achieved throughout the evaluation of total organic carbon, rock Eval pyrolysis and vitrinite reflectance for fifteen cutting samples and three extract samples collected from Khatatba, Alam El Bueib and Kharita formations in the studied well. The result revealed that the main hydrocarbon of source rocks, for the Middle Jurassic (Khatatba Fm.) is mainly mature, and has good capability of producing oil and minor gas. Lower Cretaceous source rocks (Alam El Bueib Fm.) are mature, derived from mixed organic sources and have fair to good capability to generate gas and oil. Kharita Formation of immature source rocks originated from terrestrial origin and has poor to fair potential to produce gas. This indicates that Khatatba and Alam El Bueib formations take the direction of increasing maturity far away from the direction of biodegradation and can be considered as effective source potential in the Melleiha G-1x well.     

Crude Oil Geochemistry and Its Relation to the Potential Source Beds for Some Meleiha Oil Fields in the North Western Desert, Egypt

The results of the geochemical evaluation for eleven crude oil samples from some Meleiha oil fields revealed that, these oils have high specific gravity (°API), low sulfur content and rich in saturated hydrocarbons. Two oil classes were recognized. The first is carbonate oils of high maturity level, originated from marine origin. The second, deltaic oils of moderately level of maturation, derived mainly from terrigenous sources. Oil: source correlation for the productive oils and the extracts of the potential source beds revealed a genetic close relationship between oils and extracts of Khatatba and Alam El Bueib formations. This indicates that the source of the oils in the study area may be related to mixed sources of these formations.     

GEOCHEMICAL CHARACTERIZATION OF POTENTIAL JURASSIC/CRETACEOUS SOURCE ROCKS IN THE SHUSHAN BASIN, NORTHERN WESTERN DESERT, EGYPT

Some 180 core and cuttings samples of shales and limestones from the Middle Jurassic – Late Cretaceous succession (Khatatba, Masajid, Alam El-Bueib, Alamein, Kharita, Bahariya and Abu Roash Formations) were collected from wells Ja 27–2, Tarek-1 and Jb 26–1 in the central, structurally-low part of the Shushan Basin and from well Lotus-1 in the structurally-elevated western part of the basin. All samples were screened for total organic carbon (TOC) content. Selected samples were then analyzed by Rock-Eval pyrolysis, and extracted for biomarker analyses. Visual kerogen analysis and vitrinite reflectance measurements were also undertaken and oil - source rock correlations were attempted. The results indicate that the thermal maturity of the samples can be correlated closely with burial depth. Samples from the central part of the basin are more mature than those from the west. Samples from the central part of the basin (except those from the Albian Kharita Formation) have reached thermal maturities sufficient to generate and expel crude oils. Extracts from the Middle Jurasic Khatatba and Early Cretaceous Alam El-Bueib Formations can be correlated with a crude oil sample from well Ja 27–2.
In well Lotus-1 in the west of the basin, four distinct organic facies can be recognized in the Jurassic-Cretaceous interval. One of the facies ("facies 4") has a sufficiently high TOC content to act as a source rock. Thermal maturities range from immature to peak oil generation, and the top of the oil window occurs at approximately 8000 ft.     

Origin of Bahariya oil in Salam oil field,Western Desert- Egypt

The origin of Bahariya oil is a debatable issue. Bahariya Formation produces oil from the Lower sandstone unit by normal pressure mechanism, while the Upper Bahariya shale produces oil by fracking mechanism. The main question is: is there any genetic relationship between the two oils.To answer this question, “50” ditch samples, “12” extract samples and “2” oil samples represent Khatatba and Bahariya formations and Abu Roash ‘G’ Member, collected from six wells drilled in Salam oil field, have been geochemicaly analyzed, using LECO SC632, Rock–Eval- 6 pyrolysis, GC and GC/MS techniques.The analysis shows that the Total Organic Carbon content (TOC) for the studied formations ranges from fair to v.good, with poor to good hydrocarbon potentiality. The maturity evaluation using Tmax, and calculated Vitrinite reflectance (R_o) showed that the studied samples have good thermal maturation reaching the stage of oil generation. Also the analysis revealed that the kerogen is a mixture of type II/III kerogen, reflecting the potential generation of oil and gas. The GC and GC/MS data showed that the organic matter is a mixed marine/terrestrial input deposited in transitional environment under prevailing reducing conditions. The oil samples fingerprint of the saturated hydrocarbons fraction from Baharyia reservoir (Lower and Upper) members suggest that the oil samples have a mixed organic source with significant terrestrial organic matter input deposited under saline to hypersaline environment with slightly oxidizing environment.Based on the obtained results, it is suggested that the Bahariya oil has been sourced mainly from deeper horizons (Khatatba Formation) with some contribution from upper and lower Bahariya source rocks.     

Feasibility study on application of the recent enhanced heavy oil recovery methods (VAPEX,SAGD, CAGD and THAI) in an Iranian heavy oil reservoir

Enhanced oil recovery (EOR) methods assisted by gravity drainage mechanism and application of sophisticated horizontal wells bring new hope for heavy oil extraction. Variety of thermal and non-thermal EOR techniques inject an external source of energy and materials such as steam, solvent vapor, or gas through a horizontal well at the top of the reservoir to reduce in-situ heavy oil viscosity. So, the diluted oil becomes mobile and flows downwards by gravity drainage to a horizontal producer located at the bottom of the reservoir.

In this paper, a sector model of an Iranian fractured carbonate heavy oil reservoir was provided to simulate and evaluate capability of some EOR techniques such as Vapor Extraction (VAPEX), Steam Assisted Gravity Drainage (SAGD), Combustion Assisted Gravity Drainage (CAGD), and Toe to Heel Air Injection (THAI) at its reservoir conditions and fluid properties. The simulation results demonstrated that wet CAGD in comparison with other nominated methods could improve heavy oil recovery factor to around 19% much more than each of SAGD, THAI, and VAPEX techniques. It could also reduce the total energy to produced oil ratio index up to 82% with respect to SAGD process in a year.

Although lower oil recovery has been gained by VAPEX process, but using a proper vaporized solvent could produce a kind of de-asphalted and upgraded oil with increased API gravity up to 29°API with no considerable solvent loss.     

Stratigraphic distribution of the palynomorphs and the particulate organic matter in subsurface Lower/Middle Cretaceous deposits,Western Desert of Egypt: Palynological and geochemical approach

The stratigraphic distribution of the palynomorphs and particulate organic matter was studied in the subsurface Lower/Middle Cretaceous sections in Ii-26-1 and Ig-30-1 wells, located in north Western Desert of Egypt. Some important palynofacies parameters were employed as indicators of proximal–distal trends. The spatial and stratigraphical variations of six palynofacies categories had been illustrated. Optically, the type and nature of the recovered particulate organic matter together with their quantity were combined to reveal the prevailing paleoenvironmental conditions during deposition of the concerning sections. Thirty-seven samples were selected from the two wells to carry the total organic carbon (TOC) and Rock–Eval Pyrolysis analyses in order to geochemically evaluate the source rock.TOC and Rock–Eval Pyrolysis analyses illustrate extremely low TOC and HI values, demonstrating that the Alam El Bueib, Alamein, Dahab, Kharita and Bahariya formations are comprised principally of type IV kerogen and a few type III kerogen components. Therefore, they are inert to slightly gas prone, signifying a strong deficiency of hydrogen-enriched organic matter. Palynofacies analysis implies that all the studied formations have highly oxidized terrestrial organic matter (brown phytoclasts and black woods).     

Treatment and restoration of used Mineral-Oil-Based hydraulic fluids from different machines. Part 1: Dewatering,filtration and effect of viscosity modifier

In this work, characterization and treatment of used hydraulic oil samples were performed in three steps. In the first step, the physical and the chemical properties of fresh and used hydraulic mineral oil samples from various centrifugal casting and pipe drawing machines were investigated according to ASTM D 6158. Results show that water content, solid particles count and depletion of additives have considerably affected most of the oil properties. Used oil samples failed in the appearance, thermal stability, oxidation stability, foaming tendency, water content and particles count.

In the second step, a simple methodology for dewatering and filtration was adopted. This methodology involved settling, followed by dry-air bubbling for oil dehydration and finally vacuum filtration. Such process successfully removed considerable portion of solid particles and water in used oil samples. Appearance, pour point, water content, particles count, and acid number were restored to the allowable limits. While water separability, oxidation stability, thermal stability and foaming tendency still failed the limits after treatment. It is obvious that additives will be needed to restore the latter properties.

In the third step, viscosity modifier additive was added to the oil samples to enhance viscous properties. A linear increase in kinematic viscosity was witnessed at 100°C, while at 40°C, an initial linear increase at low viscosities was followed by lower slopes at higher viscosities.     

鄂尔多斯盆地延长组多烃源层生排烃定量及成藏贡献厘定

鄂尔多斯盆地中生界延长组发育多套烃源层,目前认为长7段烃源层为延长组产油层的主力烃源层,但对其他烃源层的生排烃以及烃源层的成藏贡献缺少评价手段。通过盆地模拟手段,依据大量基础地质资料和勘探成果,建立地质体模型和热史模型,开展基于地质约束下的延长组多烃源层生排烃以及成藏模拟研究。结果表明延长组各烃源岩生烃转换率主体分布于45%~75%之间,仍具有较大生烃潜力,具备开展页岩油原位开采的地质条件。当前累计生烃量达1 233×10⁸ t、排烃900×10⁸ t,主要以{\mathrm{C}}_{{\mathrm{14}}^{+}}的重质烃类为主。烃类大量生成期和排烃期均集中在早白垩世,占总生排烃量的68%~82%。成藏模拟结果揭示白垩系沉积之前延长组各地层只有少量烃类充注,早白垩世为烃类充注成藏的关键时期。各烃源层上下呈“近源成藏”的特征,盆地模拟结果与盆地探明油藏和预测油藏分布范围具有较高的吻合程度。研究提出将“长7段主力烃源层多层系立体勘探”模式跨越到“多烃源层近源成藏”模式,助推鄂尔多斯盆地中生界延长组页岩油和新区新层系的石油勘探。     

A new approach for optimizing productivity/injectivity in naturally fractured reservoirs based on fracture network detection using Fourier – wavelet transform analysis

Fracture detection is a key step for characterization and modeling of reservoirs for optimizing production by shooting to the casing right in fracture muster points. Actually, fractures play crucial role in production of oil and gas by introducing super conductive paths to the porous medium and the challenge is finding where they are.

Many approaches took advantage of sharp changes of rock physical properties in the presence of fractures for fracture detection. Likewise, wavelet transform analysis (WTA) is sensitive to changes in the inlet signal and can be employed for this purpose. Considering petrophysical data as input, fractures can be highlighted with change in near wellbore resistivity in the fairly fixed lithology. Decomposition of such signals after removing high frequency noises shows very valuable data hidden in the low frequency part of the original signal.

In this research, WTA is employed for finding fracture muster points in one of Middle Eastern carbonates. MSFL profile is de-noised and results show good match with interpreted FMI of under studied interval in highlighting open fractures. Application of this approach can help for finding hot spots for perforation or well path design of directional wells and also can eliminate running of image logs.     

MODELLING HYDROCARBON GENERATION IN THE PALAEOZOIC AND MESOZOIC SUCCESSIONS IN SE POLAND AND WEST UKRAINE

The Lower Palaeozoic succession in SE Poland and West Ukraine has source rock potential, particularly the Ordovician and Silurian which contain oil‐prone Type II kerogen. The thermal maturity of these units ranges from early to late‐phase oil window (locally up to gas window). Within the Mesozoic succession, source rock potential is highest in the Middle Jurassic which has TOC of up to 26 wt% and a genetic potential of up to 39 mg/g of rock, with organic matter dominated by gas‐prone Type III kerogen. In SE Poland, the organic matter in this unit is generally immature, whereas maturities in West Ukraine are sufficient for hydrocarbon generation to occur. Modelling of hydrocarbon generation suggested that petroleum in Lower Palaeozoic source rocks began to be generated in the Early Carboniferous. Peak generation took place from the late Visean to the early Namurian, and terminated either as a result of source rock depletion or Variscian inversion. Expelled hydrocarbons migrated during post‐Carboniferous and Mesozoic uplift. Middle Jurassic source rocks in SE Poland have only reached the early oil window. Higher thermal maturities in the Ukraine resulted in hydrocarbon generation and expulsion. This took place after Miocene burial and maturation. A number of small hydrocarbon accumulations occur in Mesozoic reservoirs in SE Poland / West Ukraine, and hydrocarbons have migrated from Cambrian and Ordovician source rocks. However, the prospectivity of the study area is reduced as a result of phases of uplift and intense erosion which allowed hydrocarbons to escape from structural traps.     

Determination of asphaltene precipitation using a CPA equation of state

Asphaltene precipitation during natural depletion and miscible gas injection is a common problem in oilfields throughout the world. Therefore, predicting asphaltene phase behavior through thermodynamic modeling may help to control its precipitation and reduce the associated problems. In this work, a new modified CPA equation of state (EoS) was used to model asphaltene precipitation. This equation is based on a combination of a new physical part and the Wertheim association term.

The results of the new model were compared with the experimental data of five oil samples. The results showed that this modified CPA EoS can predict asphaltene precipitation with good accuracy.     

原油热裂解过程中的红外光谱演化特征及其主控因素

原油的红外光谱能够反映原油中各种分子基团的信息,对于简单、快速识别原油的成因类型和热演化程度有很大的应用潜力。通过对两个不同有机相来源的原油样品开展热解实验,初步研究了原油热解过程中红外光谱的演化特征及其主控因素。结果表明,随着原油热解程度的增加,不同类型原油的红外光谱具有相似的演化模式,可近似划分为两个阶段。在早期阶段(实验温度<370℃),热解油中甲基/亚甲基吸光度比值(A_CH3/A_CH2)变化不明显,而芳环分子基团吸光度(A_aro)及其与烷基分子基团吸光度比值(A_aro/A_sat)减小,这主要是由于原油中部分热稳定性低的化合物发生脱支链作用,形成了饱和烃组分,降低了芳烃/饱和烃比值。在晚期阶段(实验温度>370℃),热解油中A_CH3/A_CH2,A_aro和A_aro/A_sat     

Determination of asphaltene precipitation using a new CPA-based equation of state

Asphaltene precipitation during natural depletion and miscible gas injection is a common problem in oilfields throughout the world. Therefore, predicting asphaltene phase behavior through thermodynamic modeling may help to control its precipitation and reduce the associated problems. In this work, a new modified cubic-plus-association (CPA) equation of state (EoS) was used to model asphaltene precipitation. This equation is based on a combination of a new physical part and an association term.

The new physical part has an evolved cubic equation of state with a new attractive term in this work. The results of the new modification of CPA EoS were compared with the experimental data of two oil samples (oil samples 1 and 2) that belonged to Moradi et al. The results showed that this modified CPA EoS can predict asphaltene precipitation with good accuracy.     

四川盆地西部致密砂岩气来源及运移地球化学示踪

通过典型钻井天然气组分、轻烃、碳同位素以及烃源岩抽提轻烃的系统测试,研究了四川盆地西部致密砂岩气的成因类型和来源。研究表明,研究区致密砂岩气以煤型气为主,须二段（T₃x²）存在部分混合气。天然气来源具有下生上储的特征,其中须二段（T₃x²）天然气主要来源于须二段（T₃x²）自身的烃源岩以及下伏小塘子-马鞍塘组（T₃m+t）烃源岩,须四段（T₃x⁴）天然气主要来源于须三段（T₃x³）烃源岩,天然气运移距离短;而侏罗系天然气则主要来源于下伏须五段（T₃x⁵）烃源岩以及须家河组早期气藏的贡献,天然气运移距离长。在此基础上,优选了3组9类天然气运移地球化学指标,分别为：①天然气运移方向和距离指标为甲烷含量［W（CH₄）］、乙烷含量［W（C₂H₆）］、非烃含量［W（CO₂）］,［W（N₂）］、甲烷碳同位素（δ¹³C₁）;②天然气运移相态指标为苯/正己烷、苯/环己烷;③天然气运移通道指标为iC₄/nC₄和iC₅/nC₅。对研究区陆相天然气的运移进行了示踪,明确了研究区致密砂岩气的运移方向、运移相态以及运移通道。结果表明：研究区上侏罗统天然气主要由下部须家河组天然气沿高速优势通道窜层渗流运移而来,断裂是其最重要的运移通道;中侏罗统部分天然气由须家河组气源沿高速运移通道运移而来,而部分天然气为下部气源以水溶相的方式运移聚集成藏;须四段（T₃x⁴）天然气成藏时,储层相对致密,运移通道发育不佳,天然气以扩散相短距离运移为主;须二段（T₃x²）天然气主要通过断裂及其伴生裂缝以游离相和水溶相短距离运移为主。     

ORGANIC GEOCHEMISTRY OF OIL AND NATURAL GAS IN THE WEST DIKIRNIS AND EL‐TAMAD FIELDS,ONSHORE NILE DELTA,EGYPT: INTERPRETATION OF POTENTIAL SOURCE ROCKS

Crude oil in the West Dikirnis field in the northern onshore Nile Delta, Egypt, occurs in the poorly‐sorted Miocene sandstones of the Qawasim Formation. The geochemical composition and source of this oil is investigated in this paper. The reservoir sandstones are overlain by mudstones in the upper part of the Qawasim Formation and in the overlying Pliocene Kafr El‐Sheikh Formation. However TOC and Rock‐Eval analyses of these mudstones indicate that they have little potential to generate hydrocarbons, and mudstone extracts show little similarity in terms of biomarker compositions to the reservoired oils. The oils at West Dikirnis are interpreted to have been derived from an Upper Cretaceous – Lower Tertiary terrigenous, clay‐rich source rock, and to have migrated up along steeply‐dipping faults to the Qawasim sandstones reservoir. This interpretation is supported by the high C₂₉/C₂₇ sterane, diasterane/sterane, hopane/sterane and oleanane/C₃₀ hopane ratios in the oils. Biomarker‐based maturity indicators (Ts/Tm, moretanes/hopanes and C₃₂ homohopanes S/S+R) suggest that oil expulsion occurred before the source rock reached peak maturity. Previous studies have shown that the Upper Cretaceous – Lower Tertiary source rock is widely distributed throughout the on‐ and offshore Nile Delta. A wet gas sample from the Messinian sandstones at El‐Tamad field, located near to West Dikirnis, was analysed to determine its molecular and isotopic composition. The presence of isotopically heavy δ¹³ methane, ethane and propane indicates a thermogenic origin for the gas which was cracked directly from a humic kerogen. A preliminary burial and thermal history model suggests that wet gas window maturities in the study area occur within the Jurassic succession, and the gas at El‐Tamad may therefore be derived from a source rock of Jurassic age.     

Qom盆地油气成藏系统初步分析

对伊朗中部Qom盆地中、下侏罗系统Shemshak组和渐新统—中新统Qom组两套烃源岩的有机质半度、类型、成熟度及油源对比等地球化学分析表明Shemshak组烃源岩为一套有效的烃源岩层系，Qom组为一类潜在的烃原岩层系。Shemshak组烃源岩在早白型世开始进入生烃门限，大约在距今17Mn时进入湿气和凝析油阶段，上新世早期盆地的快速沉降使侏罗系烃源岩达到过成熟阶段。Qom盆地即存在以Shemshak组（及Qom组）为烃源岩的新近系油气藏，也能存在Shemshak组原生油气藏。     

白云凹陷天然气生成与大中型气田形成关系

通过对白云凹陷源、热、生烃机理、油气成因、资源规模及大中型气田分布特征等进行研究,认为白云凹陷存在文昌组和恩平组2套有效气源岩,其中恩平组浅湖相—沼泽相烃源岩是目前已发现油气的主力烃源岩。白云凹陷烃源灶处于变热流密度地质背景下,烃源岩熟化率早低晚高,主生气期相对较晚,介于23.8～0Ma之间。烃源岩热模拟生气实验表明,文昌组湖相烃源岩以生油为主,高成熟阶段生成的天然气主要为原油裂解气(约80%);恩平组浅湖相—沼泽相烃源岩油气兼生,以生气为主,主要为干酪根裂解气(约80%)。白云凹陷已发现的油气主要来自恩平组浅湖相—沼泽相烃源岩,天然气以来源于恩平组烃源岩干酪根裂解气为主,以原油裂解气和文昌组烃源岩晚期干酪根裂解气为辅。白云凹陷总生烃量为985.442 5×108t,以生气为主(81.5%),生油为辅(18.5%),主生气强度介于(500～3 500)×104t/km2之间。研究认为研究区高生气强度的白云凹陷烃源灶为大中型气田的形成提供了物质基础,近源晚期成藏提高了天然气田聚集的效率,运聚单元的资源规模控制着大中型气田的宏观分布。     

煤系烃源岩油气生成、排出与滞留特征

针对煤系地层烃源岩的油气生成、排出与滞留能力的有效性问题,选取不同沉积环境、不同时代煤岩及其夹层中的碳质泥岩和泥岩,开展了在成岩作用下的高温高压半开放—半封闭体系模拟实验,建立了相应的演化模式。结果表明,不同沉积环境下,Ⅱ₂型煤系烃源岩在生油窗内具有一定的排油能力,也具备较强的烃气生成能力,既可以作为油源岩,也是高效气源岩;而Ⅲ型煤系烃源岩在生油窗内主要以滞留油为主,基本不具备排油能力,主要以排出烃气为主,仅能作为气源岩。生烃转化率主要受控于有机质类型,排烃能力还受控于岩性与丰度,按单位质量岩石而论,煤岩远高于其夹层中的碳质泥岩与泥岩。煤岩在全演化阶段,无论是低阶煤还是高阶煤均具有较强的生成烃气能力和较高的滞留油气能力,都具有煤层气开发潜力。