Unconventional Petroleum Resources Research Articles

Prospect of Controlled Autoxidation to Produce High-Value Products from the Low-Value Petroleum Fractions.

Substantial amounts of low-value light petroleum fractions and low-value heavy petroleum fractions, such as light naphtha, HVGO, and vacuum residue, are generated during the upgrading and refining of conventional and unconventional petroleum resources. The oil industry emphasizes economic diversification, aiming to produce high-value products from these low petroleum fractions through cost-effective and sustainable methods. Controlled autoxidation (oxidation with air) has the potential to produce industrially important oxygenates, including alcohols, and ketones, from the low-value light petroleum fractions. The produced alcohols can also be converted to olefin through catalytic dehydration. Following controlled autoxidation, the low-value heavy petroleum fractions can be utilized to produce value-added products, including carbon fiber precursors. It would reduce the production cost of a highly demandable product, carbon fiber. This review highlights the prospect of developing an alternative, sustainable, and economic method to produce value-added products from the low-value petroleum fractions following a controlled autoxidation approach.

Molecular dynamics investigation of shale oil occurrence and adsorption in nanopores: Unveiling wettability and influencing factors

Shale oil, an unconventional petroleum resource, has gained significant attention in the industry. Understanding how shale oils exist in nanopores is crucial for unraveling their flow mechanisms and production prediction. The molecular dynamics simulations are conducted to explore oil occurrence and adsorption in various mineral nanopores, and the wettability and influencing factors. This study reveals a non-uniform fluid density distribution within nanopores, decreasing from the solid wall to the center. Distinct differences are observed between adsorbed and free-state oil phases. The effects of temperature, pressure, mineral type, and pore size effects on wettability, adsorption layer thickness, and molecule proportion are studied. Adsorption energy is calculated using physicochemical methods. Findings show temperature and mineral properties primarily influence shale oil wettability, with less impact from pressure. Adsorption capacity and layer thickness are affected by temperature, mineral type, and size. Octane distribution in nanopores is non-uniform, with a 1.5–1.75 nm layer on non-polar mineral walls and 0.67–1.35 nm on polar minerals. A positive correlation exists between shale oil adsorption on mineral nanopores, layer thickness, and adsorption energy. This study enhances our understanding of oil behavior in nanopores of shale oil reservoirs.

Log-exponential transformation function for interpreting NMR relaxation measurements of hydrocarbon in organic porous media for enhancing absolute adsorption estimation

Assessing unconventional petroleum resources, particularly shale gas reserve estimation, is challenging due to the adsorption phenomenon. This study presents a new method combining experimental and mathematical procedures to determine the absolute adsorption amount in shale samples. In the experimental section of this study, a new behavior was observed in the NMR decay time series of hydrocarbons in organic porous media. The fast section has a linear relationship with time rather than an exponential one. As a result, a Log-Exponential fit to these decay curves was proposed. Then the logarithmic portion was then used to estimate the absolute adsorbed amount. The method was validated against literature data and conventional methods.Based on this newly developed method, absolute adsorption isotherms were obtained for a Duvernay shale sample and activated carbon packs at pressures ranging from 0.77 MPa to 7 MPa. The model proved to be applicable and consistent with pressure variations. Methane in Duvernay shale exhibited adsorbed isotherm type V, with a methane adsorption capacity of 0.08 g per gram of Total Organic Content (TOC) at 6.24 MPa.In addition to absolute adsorption, the competitive adsorption of methane and CO2 was explored, which is critical for evaluating CO2-enhanced shale gas recovery and storage techniques. The injected CO2 resulted in the displacement of methane from smaller shale pores to larger ones.Adsorption and desorption experiments were conducted to investigate hysteresis. The new method was able to better describe the physical behavior of gaseous hydrocarbons in organic porous media. It was able to capture phase transition and critical pressure specific to organic porous media, which differ from non-organic porous media. This innovative approach enables the accurate characterization of shale reservoirs.

Laboratory Evaluation on the Water Flooding Characteristics in Bottom Water Reservoir Containing Interbeds.

Sandstone reservoirs with bottom water drive are widely distributed all over the world, which are characterized by the complex process of oil and water storage and transmission. At present, the research on the water flooding process and oil-water evolution characteristics in bottom water reservoirs containing interbeds needs to be strengthened. In this study, water flooding experiments with different placements of the interbeds were conducted using a two-dimensional (2D) vertical model. The results demonstrated that the interbeds make the bottom water flow upward more evenly, resulting in decreased incursion speed, increased displacement area, and better displacement effect. Moreover, compared with the tilted interbed model, the horizontal model has a 6% higher oil recovery rate, exhibiting a better oil displacement effect. The results presented herein will provide important guidance on water control in bottom-aquifer oil reservoirs containing interbeds and will promote unconventional petroleum resources recovery.

Model of shear strength of ultra-deep fractured sandstone considering fracture morphology

Ultra-Deep fractured tight sandstone gas reservoir, the hotpot unconventional petroleum resources, has been the subject of investigation recently. Due to the presence of natural fractures, drilling in ultra-deep fractured tight sandstone may cause complicated wellbore instabilities, which resulted in a substantial challenge to the efficient exploitation and production of tight gas resources. In order to understand the rock mechanical properties of the ultra-deep fractured tight sandstone under shear stress, tight sandstone core samples were artificially shear-fractured, the 3D characteristics of the fractures were reconstructed by CT scanning, and the fracture aperture and roughness characteristics were systematically evaluated. Simultaneously, triaxial shear strength tests were conducted to evaluate the mechanical properties of fractured rock subjected to varying confining pressures. Considering the contact relationship of the fracture surface during shearing, two indexes of average effective shear angle and contact area ratio were proposed to correct the fracture roughness, and a new fracture shear strength model was constructed, which served as the failure criterion for the fractured formation. The results show that the intact rock has a high compressive strength and can only collapse under conditions of substantial differential stress. Consequently, shear failure of fracture ought to be the primary source of wellbore instability. The fracture aperture's spatial distribution is irregular and conforms to a Gaussian distribution. A clear anisotropy in the fracture roughness is present, and there is less roughness along the initial shear failure path and more roughness perpendicularly. With an increase in normal stress, the fracture's peak shear strength rises, while the friction angle steadily falls. The innovative model's accuracy in predicting shear strength is higher than that of the weak-surface model and the JRC-JCS model.

Influence of Thermal Treating Temperature on the Performance of EVA Wax Inhibitor for Changqing Shale Oil

Ethylene–vinyl acetate copolymer (EVA) is a kind of efficient wax inhibitor for waxy crude oil. To ensure good performance of EVA, thermal treating at temperatures ≥60 °C is needed for the doped waxy crude oil. Shale oil, which often contains a substantial amount of wax, is an important unconventional petroleum resource and has been exploited all over the world. To better guide the pipeline transportation of shale oil, in this paper, the effect of thermal treating temperature (40–60 °C) on the performance of EVA (with the fixed dosage of 50 ppm) wax inhibitor for specific Changqing shale oil was investigated through the rheological measurement, wax depositing test, microscopic observation of wax crystals, and particle size test of asphaltenes. The results showed that the performance of EVA is poor at thermal treating temperatures <50 °C. At the thermal treating temperatures ≥50 °C, adding 50 ppm EVA could outstandingly improve the flowability and inhibit the wax deposition of the shale oil. Increasing the thermal treating temperature to 50–60 °C greatly facilitates the adsorption of EVA molecules on the asphaltenes and then outstandingly reduces the particle size of asphaltenes (form the average size of 399.75 nm without EVA to 78.54 nm with EVA at a thermal treating temperature of 50 °C). Therefore, the thermal treatment at 50–60 °C favors the formation of more EVA/asphaltene composite particles. The formed EVA/asphaltene composite particles trigger the formation of larger and spherical-like wax crystals, thus further enhancing the performance of the EVA inhibitor.

New biodegradation degree proxies based on acids and neutral nitrogen- and oxygen-containing compounds characterized by high resolution mass spectrometry

Heavy oil is one of the most significant unconventional petroleum resources and one of its formation mechanisms is biodegradation. The characterization of the molecular compositions of petroleum is crucial for determining the various degrees of biodegradation. In this work, detailed investigations of acids and polar NSO compounds in different levels of biodegraded oils from the Bongor Basin (Chad) were carried out by negative ion electrospray ionization (-ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The present findings show that the heteroatomic compounds of biodegraded crude oils are predominantly composed of N1, N1O1, O1, O2, O3 and O4 species. The relative content of N1, N1O1 and O1 species tend to decrease and those of O2, O3 and O4 species appear to increase with the increasing of biodegradation. The ratio of acyclic and cyclic acids (A/C ratio) of the O2 species increase with an increase of biodegradation, indicating the increasing of O2 class during microbial alteration. A new parameter, i.e. the ratio of (O2 + O3 + O4)/(N1 + O1) species, is presented to quantificationally define biodegradation levels. This parameter is inversely proportional to API gravity and has a favorable positive correlation with total acid number (TAN), suggesting acidic compounds are formed by the microbial alteration of N1 and O1 class and are more presented in advanced biodegradation. A modified ternary diagram including N1, O1 and O2 + O3 + O4 species describe the detailed changes of nitrogen- and oxygen- containing compounds. Data points with a high level of biodegradation tend to shift to O2 + O3 + O4 species end-member and retreat from N1 species end-member, showing the relative content of O2 + O3 + O4 species increase and those of N1 species decrease with increasing biodegradation which may due to the formation of organic acids in degradation oil. The ratio of (O2 + O3 + O4)/(N1 + O1) species and the modified ternary diagram provide new parameters to estimate the biodegradation degree and TAN in crude oil.

Degradable preformed particle gel as temporary plugging agent for low-temperature unconventional petroleum reservoirs: Effect of molecular weight of the cross-linking agent

The development of unconventional petroleum resources has gradually become an important succession for increasing oil production. However, the efficient development of this type of reservoir is paying more and more attention to the application of temporary plugging agents. The use of temporary plugging agents can further expand the stimulated reservoir volume (SRV) and facilitate the flow of oil and gas to the bottom of the well. Particle-gels used as temporary plugging agents have the characteristics of the simple injection process, good deformation, high plugging strength, and complete self-degradation performance, which has been widely applied in recent years. In this paper, five samples of DPPG polymerized by different molecular weights of cross-linking agents were prepared. In addition, infrared spectroscopy analysis, differential calorimetry scanning (DSC) analysis, static particle gel swelling and degradation performance evaluation experiments, and dynamic temporary plugging performance experiments in cores were used to study the influence mechanism of the cross-linking agent molecular weight ( M w ) of the DPPG molecule on its temporary plugging performance. Results show that as the molecular weight of the cross-linking agent (at 0.01 g) in the DPPG molecule decreases from 1000 to 200 Daltons, the fewer cross-linking sites of DPPG, the looser the microscopic three-dimensional mesh structure formed, and the swelling ratio is increased from seven to 33 times. However, the complete degradation time increases from 40 to 210 min. Moreover, the DSC scanning results confirmed that the larger the molecular weight of the cross-linking agent, the worse it is chemical stability and the more prone it to self-degradation. The DPPG particle samples have good temporary plugging performance in reservoir cores. The DPPG prepared by the cross-linking agent with smaller molecular weight has a smaller expansion ratio, higher gel strength, and greater plugging strength in the core. Moreover, the degraded DPPG is less damaging to the cores. However, its slower degradation rate takes a slightly longer time to reach complete degradation. The results of this paper can provide new ideas and a theoretical basis for the development of particle gel-based temporary plugging agents (TPA) with controllable degradation time in low-temperature reservoirs. It can help to expand further the application range of existing DPPG reservoir conditions.

Effect of lithological variations on the performance of artificial intelligence techniques for estimating total organic carbon through well logs

By the expansion of production from source-related unconventional petroleum resources, accurate approximation of Total Organic Carbon (TOC) through well logs has become progressively important. Accordingly, recent studies have mainly focused on increasing the precision of TOC estimation by using different types of AI techniques and/or optimizing algorithms. Along with utilizing these approaches, this study emphasized on removing an unaddressed source of error inherited from lithological heterogeneity with the same goal. Like organic matter quantity, lithological variations within a source interval also induce well log responses, which may interfere with the training process of Artificial Intelligence (AI) techniques. In the present research, the effect of lithological variations on the performance of TOC estimators was evaluated by employing Adaptive Neuro Fuzzy Inference System (ANFIS) and Multilayer Perceptron network (MLP). Firstly, ANFIS and MLP models were constructed and trained using a database containing different lithologies (original models). Then, a new methodology was developed based on modeling the relationship between log data and TOC values for each type of lithology (litho-based method). The result showed that the litho-based method estimates more reliable and accurate TOC values, proving the adverse effect of lithological variations on the original models. Furthermore, the litho-based ANFIS models provide the most promising results. Since metaheuristic algorithms are usually employed to optimize AI techniques, Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) were also implemented into the original models (hybrid models). Accuracy of TOC values estimated by the hybrid models is slightly higher than those derived from the original models. However, these hybrid approaches are not as efficient as the litho-based method. Applicability of the proposed approach was guaranteed by performing it over Pabdeh source rocks in a well of SW Iran. Based on its high efficiency, the newly developed litho-based method can be used as a powerful tool to reliably evaluate unconventional hydrocarbon resources, as well as the potential of the conventional petroleum sources. Moreover, it can be utilized, instead of/along with traditional optimization approaches, to approximate other geochemical factors as well as petrophysical parameters from log data.

Unconventional Petroleum Sedimentology: A Key to Understanding Unconventional Hydrocarbon Accumulation

The commercial exploitation of unconventional petroleum resources (e.g., shale oil/gas and tight oil/gas) has drastically changed the global energy structure within the past two decades. Sweet-spot intervals (areas), the most prolific unconventional hydrocarbon resources, generally consist of extraordinarily high organic matter (EHOM) deposits or closely associated sandstones/carbonate rocks. The formation of sweet-spot intervals (areas) is fundamentally controlled by their depositional and subsequent diagenetic settings, which result from the coupled sedimentation of global or regional geological events, such as tectonic activity, sea level (lake level) fluctuations, climate change, bottom water anoxia, volcanic activity, biotic mass extinction or radiation, and gravity flows during a certain geological period. Black shales with EHOM content and their associated high-quality reservoir rocks deposited by the coupling of major geological events provide not only a prerequisite for massive hydrocarbon generation but also abundant hydrocarbon storage space. The Ordovician–Silurian Wufeng–Longmaxi shale of the Sichuan Basin, Devonian Marcellus shale of the Appalachian Basin, Devonian–Carboniferous Bakken Formation of the Williston Basin, and Triassic Yanchang Formation of the Ordos Basin are four typical unconventional hydrocarbon systems selected as case studies herein. In each case, the formation of sweet-spot intervals for unconventional hydrocarbon resources was controlled by the coupled sedimentation of different global or regional geological events, collectively resulting in a favorable environment for the production, preservation, and accumulation of organic matter, as well as for the generation, migration, accumulation, and exploitation of hydrocarbons. Unconventional petroleum sedimentology, which focuses on coupled sedimentation during dramatic environmental changes driven by major geological events, is key to improve the understanding of the formation and distribution of sweet-spot intervals (areas) in unconventional petroleum systems.

Spatiotemporal quantification of organic matter accumulation in the Eocene Green River Formation, Bridger Basin, Wyoming

It has long been recognized that lakes can bury large amounts of organic carbon (CORG) in their sediment, with important consequences for conventional and unconventional petroleum resources and potentially for the global carbon cycle. The detailed distribution of lacustrine organic carbon through space and time is important to understanding its commercial and climatic implications, but has seldom been documented in detail. The Green River Formation offers a unique opportunity to improve this understanding, due to extensive Fischer assay analyses of its oil generative potential and to recently published radioisotopic age analyses of intercalat ed volcanic tuffs. Fischer assay analyses reveal distinctly different patterns of organic matter enrichment that correlate with different lacustrine facies associations. Histograms of oil generative potential for evaporative facies of the Wilkins Peak Member exhibit an approximately exponential distribution. This pattern is interpret ed to result from episodic expansion and contraction of Eocene Lake Gosiute across a low-gradient basin floor that experienced frequent desiccation. In contrast, histograms for fluctuating profundal facies of the upper Rife Bed of the Tipton Member and the lower LaClede Bed of the Laney Member exhibit an approximately normal or log normal distribution, with modes as high as 16–18 gallons per ton. This pattern is interpreted to reflect generally deeper conditions when the lake often intersected basin-bounding uplifts. Within the Bridger basin, burial of CORG was greatest in the south during initial Wilkins Peak Member deposition, reflecting greater rates of accommodation near the Uinta uplift. The locus of CORG burial shifted north during upper Wilkins Peak Member deposition, coincident with a decrease in differential accommodation. CORG burial during deposition of the upper Rife and lower LaClede Beds was greatest in the southeast, due either to greater accommodation or localized influx of river-borne nutrients. Average CORG burial fluxes are consistently ~4-5 g/m2 yr for each interval, which is an order of magnitude less than fluxes reported for small Holocene lakes in the northern hemisphere. Maximum rates of CORG burial during deposition of organic-rich mudstone beds (oil shale) were likely similar to Holocene lakes however. Deposition of carbonate minerals in the Bridger basin resulted in additional, inorganic carbon burial. Overall it appears that carbon burial by Eocene lakes could have influenced the global carbon cycle, but only if synchronized across multiple lake systems.

Quantitative Characterization of the Lower Limit of the Physical Properties of Tight Oil Reservoirs in Nano-Material Porous Media

Tight oil is an unconventional petroleum resource, which occupies a essential position in the global energy structure. The main purpose of this paper is to quantitatively characterize the lower limit of the physical properties of tight oil reservoirs in nanomaterial porous media. This paper starts with the single-phase deionized water flow experiment in micro-nano-quartz tube, combined with the tight oil reservoir core single-phase simulation, formation water seepage experiment, analyzes and characterizes the low-velocity and nonlinear seepage characteristics of tight reservoir fluid. At the same time, combined with the dynamic network simulation technology, the process of water flooding in tight oil reservoirs under different conditions is simulated, and the influence of each influencing factor on the two-phase seepage of water flooding is determined. In addition, combined with different water injection capillary numbers, water flooding nuclear magnetic resonance experiments, the dynamic characteristics and distribution changes of oil and water, in two phases in the water flooding process are analyzed, and the simulation results are used for verification and analysis, to indicate the reasonable and efficient water flooding development of tight oil reservoirs.

Superior Creep Resistance and Remnant Strength of Novel Tempered Ferritic-Martensitic Steels Designed by Element Addition.

The in situ combustion (ISC) technique is promisingly applied in heavy oil recovery, whereas the operation inevitably causes high temperature and high pressure for a long duration in the thermal recovery well. As a critical component, oil casing, traditionally made of plain carbon steel in China, generally suffers from poor creep resistance and degraded remnant strength under such a harsh environment, which leads to frequent casing damage and inferior recovery efficiency. In this study, a strategy was adopted to tackle the issue by adding chromium (Cr) element into the plain carbon steel. We designed two types of novel steel with the respective addition of 1 wt.% and 13 wt.% Cr element into plain carbon steel for oil casing. Surprisingly, the trace addition of Cr element with 1 wt.% effectively lowered the creep rate in a creep test at 600 °C and 400 MPa and maintained high remnant tensile strength after creep. More significantly, prior creep history dramatically enhanced remnant strength when Cr element was added up to 13 wt.%. After a long-term creep time of 96 h, the samples were conferred by a stress increment of ~92.5 MPa (~11.0%) relative to the creep-free counterparts, whereas the value was reduced by ~158.4 MPa (~17.8%) for plain carbon steel under the same deformation conditions. Such superior mechanical performances in the Cr-doped steels are mainly ascribed to precipitation retardation of carbides and sluggish precipitate coarsening, which continuously favors a precipitation–strengthening effect in steel. These findings provide a fundamental understanding of precipitation response and creep behaviors and, more importantly, enable the development of high-performance steels used in the field of unconventional petroleum and gas resources.

Analytical and numerical studies on a moving boundary problem of non-Newtonian Bingham fluid flow in fractal porous media

Non-Darcy flow with a threshold in fractal porous media has been widely used in the development of unconventional petroleum resources such as heavy oil and tight oil. Mathematical modeling of such challenging “threshold flow” problems with strong nonlinearity has great significance in improving petroleum science and technology. Based on a fractal theory, a new non-Darcy kinematic equation with a fractal threshold pressure gradient (TPG) is mathematically deduced in order to describe the non-Darcy flow of a non-Newtonian Bingham fluid with a threshold in fractal porous media. Then mathematical modeling of planar radial non-Darcy flow in a fractal heavy oil reservoir is performed as a nonlinear moving boundary problem. In addition, a steady analytical solution method and a transient numerical solution method are developed. The analytical solution of an ordinary differential equation system for a simple steady model is derived directly, and the transient numerical solution of a partial differential equation system for an unsteady flow model is obtained based on the finite element method with good convergence. These two model solutions are validated by cross-comparisons. It is found from the calculation results that for the steady state, the extremely disturbed moving boundary and its corresponding pressure distribution are affected only by a TPG, production pressure, and a transport exponent; by contrast, for the unsteady state, the moving boundary and its corresponding pressure distribution are affected by many more factors including the fractal dimension. Furthermore, neglect of the fractal TPG and the induced moving boundary can lead to high overestimation of well productivity.

Diverse effects of intragranular fractures on reservoir properties, diagenesis, and gas migration: Insight from Permian tight sandstone in the Hangjinqi area, north Ordos Basin

As petroleum industry tilts towards unconventional petroleum resources, the significance of fractures in exploration and development becomes increasingly prominent. In this study, thin sections and scanning electron microscopic (SEM) observation, porosity and permeability measurement, mercury injection porosimeter (MIP) and computerized tomography (CT) analysis were carried out to investigate the morphology and development characteristics of intragranular fractures, and their effects on physical properties, reservoir diagenesis, and gas migration of the He-1 Member tight sandstones in the Hangjinqi area. Results show that the tight sandstones have intergranular and intragranular dissolved pores, intercrystalline pores and heterogeneous distributed intragranular fractures. The average porosity and permeability of the tight sandstones with intragranular fractures are 12.76% and 4.70 × 10−3 μm2, while those lack of fractures are 6.06% and 0.574 × 10−3 μm2, respectively. The fracture density increases with the enlargement of clastic-grain size and the content of rigid grains. Results indicate that the intragranular fractures greatly enhance permeability, but they have limited direct contribution to total porosity. And the sandstones rich in intragranular fractures have a more homogeneous and connective pore structure with larger radius of pore throat. Intragranular fractures are beneficial to the latter feldspar and debris dissolution caused by organic acids derived from hydrocarbon generation in coal-bearing strata. The dissolved pores directly enhance the porosity of tight sandstones compared to intragranular fractures, and together they form a percolation network to increase permeability. Faults mainly control the lateral petroleum migration from the south to the north, and intragranular fractures affect the local accumulation of gas. This study helps to illustrate the influences of intragranular fractures on reservoir properties, diagenetic difference, and gas migration of the He-1 Member tight sandstones in the Hangjinqi area, and can guide the evaluation and exploration of tight sandstone reservoirs in the Ordos Basin and other basins with similar settings around the world.

Thermal flue gas utilization in delivering unconventional geo-energy

Conventionally, thermal technology of steam-assisted gravity drainage (SAGD) has been an effective method to unlock unconventional petroleum resources with extra-high viscosity. However, in the middle and late stages of SAGD, there are some problems such as low oil production rate and high water cut, and a large amount of greenhouse gases can be generated, which may disrupt the balance of the geo-energy supply and greenhouse-gas mitigation. Therefore, in this study, with a novel thermal SAGD technology with flue gas in the late stage of SAGD, the steam chamber and fluid-steam ratio could be substantially improved, which thereafter results in better production performance. Meanwhile, it can effectively use the flue gas produced by SAGD to reduce carbon emissions. A laboratory-scale three-dimensional (3-D) physical was manufactured to simulate the practical processes, including interwell warm-up, conventional and novel flue gas-assisted SAGD at high-pressure and high-temperature reservoir conditions. The experiments demonstrated the injected flue gas concentrated on the top of the physical model due to the gravity override, which contributes to control the heat loss to the atmosphere and subsurface systems. In this way, the thermal sweep efficiency was substantially increased since the heat retained was employed for the lateral-direction steam chamber development. Meanwhile, the addition of flue gas induced the reduction of steam partial pressure, which finally resulted in chamber temperature decreasing by approximately 10 °C. On the other hand, the instantaneous fluid-steam ratio was found to increase from 0.06 to 0.24 at the highest, while the water cut decreased by around 20%. All the aforementioned changes in physical parameters contribute to 7.75% higher petroleum fluid recovery. Overall, the newly-developed technology has been validated to significantly extend production lifetime and improved recovery efficiency. This study will support the foundation of more general application pertaining to greenhouse gases mitigation and sustainable productions in unconventional geo-energy.

Paleoenvironments and Hydrocarbon Potential of Upper Cretaceous Shales in Agbabu-1 Well, Dahomey Basin – Insight from Geochemistry and Foraminifera Paleontology

Upper Cretaceous shales partially exposed in the northern fringes of the Dahomey Basin are well developed in the subsurface in Southwestern part of the basin where Agbau-1 well is sited. These shales were evaluated in respect to their paleoenvironments and potentials for hydrocarbon using foraminiferal assemblages, biomarkers and Rock Eval pyrolysis studies. The dominance of benthonic foraminifera species suggests a shallow marine environment and high percentage of calcareous to arenaceous benthic www.eujournal.org 195 foraminifera indicate high water salinity and hypersline environment. Dysoxic oxygen condition is also prevalent probably because most of the benthic foraminifera recovered are epifauna that live in a reduced oxygen condition. 1.90 wt%, 244 mgHC/gTOC and 429℃ average values of total organic carbon, hydrogen index and Tmax reveal that the Upper Cretaceous shales have relatively fair to good organic matter, predominantly Type II-III kerogen and currently immature. Though three is a trend of an increase in maturity down the hole. All the steranes have uniform distributions (C27&gt;C28&gt;C29), suggesting a relatively higher input from the marine red algae and a low level of land plant contribution to the source organic matter. Pristane/phytane ratios and C29/C27 steranes confirmed the organic matter type to be a Type II/III and anoxic source rock depositional condition as well as a reducing diagenetic system in the sediment water column. The Upper Cretaceous shales in Dahomey Basin can be targeted for exploration as an unconventional petroleum resource.

A study on the characteristics of Watercut Meter ultrasonic data according to the temperature change of the introduced material

Recently, for the extraction of unconventional petroleum resources, the SAGD (Steam-Assisted Gravity Drainage) method, which uses high-temperature steam to reduce the viscosity of bitumen, is widely used. In particular, the importance of the Watercut meter system is increasing because the oil sand mining technology is an additional and more complicated process than oil extraction in general oil wells. In this study, a numerical analysis of the ultrasonic-based SOR (steam to oil ratio) ratio change for heavy oil was performed. As a result of the analysis, the maximum sound pressure and the ultrasonic arrival time were analyzed using the SOR ratio as a variable. The higher the water-to-oil ratio, the higher the maximum sound pressure and the shorter the ultrasonic arrival time. On the other hand, the higher the oil ratio, the lower the maximum sound pressure and the longer the ultrasonic arrival time. It is judged that the data set on the moisture content in oil can be constructed using the numerical analysis results, and it can be used as a basis for the reverse engineering of Watercut.

Organic matter enrichment of the Chang 7 member in the Ordos Basin: Insights from chemometrics and element geochemistry

The lacustrine black shales of the Chang 7 member are the main source rocks and the most important unconventional (shale oil) petroleum resources in the Ordos Basin, North China. A series of continuous core samples was analysed for main, trace, and rare earth elements. The development of thin or laminar tuffs and tuffaceous mudstones and the enrichment of Fe, Mn, and other elements demonstrate that the Chang 7 member was influenced by event deposition, such as volcanic and hydrothermal activity. The ancient lake had brackish water and a relatively high sedimentation rate during the deposition of the Chang 7 member. The palaeoclimate in the early stage was warmer and wetter than that in the middle-late stage of the Chang 7 period. The geochemical proxies for palaeoproductivity and palaeoredox indicate that the ancient lake had a relatively high primary productivity with an anoxic to euxinic sulphide bottom water in the Chang 73 stage, which decreased to dyoxic-oxic water during the Chang 71+2 periods. A parameter dataset comprising 11 elemental proxies related to the reconstruction or evaluation of the depositional environment and palaeoproductivity was analysed using principal component analysis (PCA). The first principal component (PC1) accounted for 59.88% of the total variance in the original dataset and mainly represented the characteristics of palaeoproductivity and redox conditions; thus, it can be interpreted as an indicator of these factors. Based on the excellent positive linear correlation between the total organic matter content of the Chang 7 samples and the PC1 scores, the enrichment of organic matter in the Chang 7 member was mainly controlled by palaeoproductivity and the preservation environment. PCA is an effective method for dimensionality reduction and visualisation of multi-element geochemical data, which allows for a more comprehensive and in-depth understanding of geological samples. This work provides a practical application of chemometrics in elemental geochemistry. This can serve as a model for other studies.

Simulation of catalytic upgrading in CAPRI, an add-on process to novel in-situ combustion, THAI

Based on the analysis of recent projections by the International Energy Agency (IEA), to meet the growing and subsequently declining demands of oil from now to 2040, we need up to around 770 billion barrels of oil. Since the worldwide total proved reserves of easy-and-cheaper-to-produce conventional oils is roughly only 520.2 billion barrels, the remaining 249.8 billion barrels must be obtained from unconventional petroleum resources (i.e. heavy oils and bitumen). These resources are however very difficult and costly to upgrade and produce due to their inherently high asphaltene contents which are reflected in their very high viscosities and large densities. However, still they should prove attractive development prospects if, as much as practicably possible, their upgrading can be performed in conjunction with in situ or downhole catalytic upgrading processes. Such projects will contribute significantly towards smoother and greener transition to full decarbonisation. Advanced technologies, such as the toe-to-heel air injection coupled to its add-on in situ catalytic process (i.e. THAI-CAPRI processes), have the potential to develop these reserves, but require further developmental understanding to realise their full capability. In this work, a new detailed procedure for numerically simulating the THAI-CAPRI processes is presented. The numerical model is made-up of Athabasca-type bitumen and it has a horizontal producer (HP) well that is surrounded by an annular layer of alumina-supported cobalt-oxide-molybdenum-oxide (CoMo/γ-Al2O3) catalyst. The simulation is performed using the computer modelling group (CMG) reservoir simulator, STARS. This new work has shown that the choice of the frequency factor of the catalytic reactions allowed model validation based on the degree of catalytic upgrading in form of API gravity. Overall, the work herein identifies the important parameters, such as API gravity, peak temperature, oil production rate, cumulative oil production, produced oxygen concentration, temperature distribution profile, extent of coke deposition on the catalyst surface, etc., governing the successful operation of the THAI-CAPRI processes. In particular, this study has shown that even in the vicinities of the mobile oil zone (MOZ) where the catalytic upgrading is expected to be taking place, the catalyst surfaces are covered with high concentration of coke. This finding is in parallel to the observations reported from experiment of CAPRI process alone. Therefore, it is concluded that when experimental studies of the THAI-CAPRI processes are to be conducted, a catalyst regeneration mechanism must be put in place in order to prolong the effectiveness and thus the life of the catalyst so that proper field operation design can be made. Additionally, the study has also shown that the temperature of the MOZ is less than 306 °C and that implies that an external source of heating the annular catalyst layer must be provided in order to effect the catalytic upgrading in the THAI-CAPRI processes. Thus, a new study should look at the feasibility of targeted heating (in the case of microwave) or conductive or resistive heating (in the case of electrical heating) to raise the temperature of the annular catalyst layer to that required to achieve the catalytic upgrading.