Secondary Oil Migration Research Articles

The evolution of the majiang paleoreservoir, west margin of xuefeng uplift: Insights from in situ calcite U–Pb dating and bitumen and shale trace element analysis

The Majiang Reservoir, situated within the Yangtze Block, is the largest paleoreservoir in the region. Employing a comprehensive methodology involving the analysis of trace and rare earth elements in bitumen and shale, in situ U–Pb dating of hydrocarbon-associated calcite, and incorporating previously published data on oil-source correlation and significant stages of reservoir development, we successfully reconstructed the complete evolution of the Majiang Reservoir quantitatively. The bitumen trace elements data show the ratio of V/(V + Ni) ranging from 0.64 to 0.82, Ni/Co exceeding 7.0 and Zr/Cr below 1.0. PAAS-normalized rare earth element distribution patterns of both bitumen and Cambrian shales present zig-zags distributions. In addition, biomarker distribution acquired by catalytic hydropyrolysis and bulk δ13C values of both bitumen and Cambrian shales (−29.1‰ to −34.7‰ vs −30.2‰ to −32.3‰) also show similarity. All the geochemical parameters together indicate that the primary source of bitumen stems from Early Cambrian shales. Integrating fluid inclusion analysis, specifically examining two Th groups with temperatures of 97.2 °C and 142.6 °C, and U–Pb dating on hydrocarbon-bearing calcite (∼300 Ma), referencing prior Re–Os dates on bitumen (∼430 Ma) and pyrobitumen (∼80 Ma) and quartz fluid inclusion Ar–Ar dating (∼225 Ma), we successfully reconstructed the entire hydrocarbon evolution. The findings reveal that initial oil generation occurred during the Caledonian event, followed by secondary continuous oil and gas generation and migration, influenced by the Indosinian event. The combination of fluid inclusion analysis and isotopic geochronology data exemplifies immense potential in precisely determining the progression of petroleum evolution.

Hydrocarbon dominant migration direction and accumulation mode in Qijiang area, Sichuan Basin, China

The high‐quality hydrocarbon source rocks developed in the Longtan Formation of the Qijiang area and the good reservoir capacity of the overlying dolomite of the Jialingjiang Formation indicate that the area has great exploration potential. To clarify the hydrocarbon migration and accumulation characteristics of the area, the fluid potential of the Longtan Formation in the Qijiang area in the Early Jurassic was determined. The direction of the maximum negative gradient of the fluid potential indicates the direction of the primary migration of hydrocarbons, and the structural ridge theory is used to analyse the direction of the secondary migration of hydrocarbons. The results show that the fluid potential of the hydrocarbon source rocks of the Longtan Formation in the Early Jurassic is characterized by the alternate distribution of high potential zones and low‐potential zones. The central syncline, eastern syncline and western syncline are drainage zones and high potential zones, while the Shiyougou structural belt and Fo'er Ya structural belt are supply zones and low‐potential zones. The oil and gas fluids migrate from the east–west direction to the anticlinal zone for the primary migration; the structural ridge controls the secondary migration of oil and gas in the low‐potential area along the north–south direction, resulting in a zonal distribution of oil and gas traps along the structural ridge. By combining fluid potential and structural ridge characteristics to determine the dominant direction of primary and secondary hydrocarbon migration, a model of hydrocarbon migration and accumulation in the Qijiang area is developed, which provides an important basis for finding hydrocarbon reservoirs.

Secondary migration of heavy oil in low dip basins

Secondary migration of heavy oil in low dip basins

Calcite U-Pb ages constrain petroleum migration pathways in tectonic complex basins

Abstract Tracing secondary oil migration pathways is critical for understanding petroleum system evolution histories. Traditional tools (e.g., molecular indicators and numerical modeling) utilized for evaluating oil migration processes either lead to ambiguous interpretations or only provide qualitative estimates. We quantitatively constrain secondary oil migration processes under an absolute time frame by integrating oil-inclusion fluorescence and in situ calcite U-Pb dating on calcite veins and cements hosting primary oil inclusions. Fluorescence spectra of oil inclusions and U-Pb ages were obtained on samples from ultra-deep Ordovician reservoirs along two major faults in the Halahatang oilfield, Tarim Basin (northwestern China). Absolute U-Pb ages suggest two main oil charge events during 475–433 Ma and 294–262 Ma, respectively, and revealed a northward-decreasing trend for oil maturity during single charge events. Vertical migration of oil from in situ source rock through active (or reactivated) faults is believed to be the key process inducing the spatial maturity variation in charged oils and considered as the main mechanism of secondary migration, with brecciated fault zones and dilatant fractures along faults acting as major vertical oil-migration pathways. The successful application of this approach has wider implications for elucidating petroleum migration processes in tectonic complex basins worldwide.

Study on oil and gas filling and migration and accumulation in synclinal reservoir area

In recent years, the focus of oil and gas exploration in western Daqing has changed from a single large structural high point packaged reservoir to a diversified complex structural low point syncline reservoir. Such reservoirs are mainly lithologic traps, with complex rules of oil and gas filling, migration and accumulation, and irregular oil-water distribution, resulting in unclear understanding of the formation and distribution of syncline lithologic traps. The typical GLN area dominated by lithologic reservoirs is selected as the research object. The oil and gas filling research under the condition of reservoir forming power is carried out by using the source reservoir pressure difference. Based on the plane distribution of crude oil density, the secondary migration and accumulation rule of oil and gas is studied. It is considered that GLN can contain oil in a large area, but oil and gas can not migrate in a long distance. The low value area of crude oil density is the breakthrough of primary migration and the starting point of secondary migration, and its formation is controlled by the principle of phase potential coupling. The sand body is highly heterogeneous and the oil-water distribution is complex, while the sheet sand is mainly pure oil layer, and the water layer is formed only in the parts far away from the breakthrough and poor physical properties.

Combination of basin modelling and carbazoles to investigate secondary oil migration pathways in the Dongying depression of the Bohai Bay Basin, China

This study investigates pathways of secondary oil migration, which lead to oil accumulations in the Dongying Depression with both geochemistry and basin modelling techniques. Modelling of oil migration pathways was conducted for the third and fourth members (Es3 and Es4) of the Shahejie Formation, including reconstructions of thermal maturation and hydrocarbon generation processes, which were supported by parameters of carbazoles and further reinforced by distributions of oil wells and fields. The lower interval of the Es3 source rock was deposited under a sub-oxic, freshwater environment, while the upper interval of Es4 source rock was deposited under an anoxic, hypersaline environment. The investigated 38 oil samples are classified into three groups based on oil-source correlation in the Dongying Depression as the Es3-derived oils, the Es4-derived oils, and mixed oils of Es3 and Es4 in their origin. The influence of maturity variations and source facies on carbazole parameters of the non-biodegraded oils can be ignored. Carbazole parameters can be used to trace migration distances of oil for each group of oil. Eight migration pathways are determined based on the analysis of carbazole parameters. Oil migration pathways inferred from basin modelling are consistent with those determined by carbazoles. Our results suggest two favourable oil accumulation areas along the migration pathways in the Es4 member of the Dongying Depression.

Buoyant and countercurrent flow of CO2 with capillary dispersion

Analytical modeling of CO2 flow is essential for the rapid evaluation of CO2 plume evolution and possible leakage risk during geological carbon sequestration (GCS). Here we adapt the model of describing the secondary migration of oil proposed by Siddiqui and Lake (1992) to characterize CO2 upward migration and backfilling for buoyant and countercurrent flow in a saline aquifer. Both water- and CO2-wet reservoirs are examined under typical buoyant fluxes.We present self-similar solutions of CO2 saturation waves without capillary pressure and traveling wave solutions after adding capillarity. We demonstrate that saturation wave types, CO2 migration, and saturation profiles are influenced by buoyant flux, capillary pressure, wettability, and relative permeability. The stabilized zones resulting from capillary dispersion inside a CO2-wet reservoir generally extend wider than those for a water-wet reservoir. The presented model and results are potentially useful to understand field scale CO2 plume behaviors as well as to guide the design of corefloods for studying CO2 buoyant flow characteristics.

Oil origin and secondary migration pathway in the Bonan sag, Bohai Bay Basin, China

The oil origin and secondary migration pathways were investigated in the Bonan sag using basin modeling and petroleum geochemical data including biomarker assemblages of saturated hydrocarbons and pyrrolic nitrogen compounds. The modeling of secondary oil migration pathway was performed based on the reconstruction of burial, thermal maturity and oil generation histories. Modeling results are calibrated by the distribution of oil wells and oil fields as well as traced secondary oil migration pathways inferred from pyrrolic nitrogen compounds. Carbazole parameters were selected to trace the secondary oil migration pathway based on the investigation of oil origin. Three groups of oils sourced from source rocks of the third and fourth members of Shahejie Formation (Es3 and Es4) have been identified in this study. Group Ⅰ oils from Es3 source rocks mainly occurred in the center of sag, group Ⅱ oils from Es4 source rocks occurred in the margin regions. Group Ⅲ oils were interpreted to be the mixed sources from Es3 and Es4 source rocks. Three oil migration pathways can be traced by pyrrolic nitrogen compounds based on varied carbazole parameters. The major stages of oil generation of Es3 and Es4 source rocks occurred at about 30–20 Ma and 5-0 Ma, which coincided with oil charge periods. Secondary oil migration pathways have been predicted successfully by the oil migration modeling in the Bonan sag based on the calibration with oil wells, oil fields and the traced oil migration pathways by pyrrolic nitrogen compounds. Favorable zones located on the primary secondary oil migration pathways at the periods of oil charge may be the prospective regions for oil exploration in the Bonan sag.

Lead isotopes as tracers of crude oil migration within deep crustal fluid systems

Although Pb, U, and Th may be fractionated between crude oil and formation waters, Pb isotopes are not. This unique property makes Pb isotopes a particularly useful marker of hydrocarbon generation and migration. Here we show that Pb isotopes offer a new vision of long-range (secondary) oil migration relevant to the formation of oil fields. North Sea oils are largely generated from Jurassic black shales, yet their Pb isotopes are mixtures of Cenozoic to Proterozoic end-members. The same observation is made for crude oils from the Paris Basin, the Barents Sea, Libya, Kuwait, Kazakhstan, and Australia. Bulk Pb in crude oil therefore, for the most part, is foreign to its source rock(s). Our high-precision Pb isotope data on 195 crude oils worldwide, the first such data set in the published literature, and 17 Northern European black shales indicate that deep-seated Pb components originating beneath the source rocks are ubiquitous in crude oil. This implies that oil fields are embedded in basinal convective systems of hydrous fluids heated from below. Plumes of hot fluids rise from the lower thermal boundary layer, which Pb isotopes require douse the basement, into the core of the porous-flow convective cell where they dissolve the newly formed hydrocarbons sequestered in the source rocks. The fluids finally unload unmixed formation waters and crude oil at the base of the upper (conductive) boundary layer where they can be trapped in favorable sites. Based on these new insights we argue that Pb isotopes in crude oil constitute a good tracer of oil migration.

Molecular and isotopic evaluation of the maturation history of the organic matter in an Ordovician aquiclude (Michigan Basin): Evidence for late diagenetic biodegradation

Previous characterization of a low permeability (10−16 ≤ Kh ≤ 10−12 m s−1) and high salinity (> 5 M of Cl−, > 10× seawater salinity) aquiclude, in Upper Ordovician-aged sediments situated on the eastern flank of the Michigan Basin, where a deep geological repository for low and intermediate level nuclear waste is proposed, suggested a microbial origin for CH4 and CO2 based on their stable isotope values. CH4 is believed to have been produced and trapped during the Paleozoic in a relatively discrete and high organic matter (OM) horizon at the shale/carbonate transition. To further investigate the efficiency of confinement of this aquiclude, here we present detailed isotopic and geochemical stratigraphic profiles of OM and biomarkers, with the objective of understanding the origin of CH4 and its relative timing of confinement. Classical diagnostic ratios of polycyclic aromatic hydrocarbons, relative abundances of hopanes and degraded hopanes coupled to dual compound-specific isotopic analysis of n-alkanes, as well as δ13C analysis on different fractions of OM were measured. A partitioning of the Ordovician sedimentary succession into two systems is observed with an upper system that is self-sourced and confined, hosting the microbially derived CH4 with evidence of late diagenetic OM biodegradation and a lower system that reveals later secondary oil migration which has overprinted the organic geochemical record. We propose a conceptual model that would explain the generation and preservation of this paleo-bioreactor over time using the maturation history reconstruction derived from this dataset. This work not only provides essential field empirical evidence of a relationship between methanogenesis and late diagenetic biodegradation, but also shows the power of dual-compound-specific isotope analyses in deciphering between different maturation processes affecting OM in natural subsurface settings.

Primary Versus Secondary Migration of Oil

Primary Versus Secondary Migration of Oil

Effect of secondary oil migration distance on composition of acidic NSO compounds in crude oils determined by negative-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry

The acidic and neutral NSO compounds in a series of Duvernay-sourced oils in Canada, which are believed to have migrated extensively over relatively long distances such as along the Rimbey-Meadowbrook reef trends, were characterized by negative-ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Heteroatomic compounds were characterized according to their class (number of nitrogen, oxygen and sulfur heteroatoms), degree of aromaticity [rings plus double bonds (DBE)] and carbon number distribution. The N1, N1O1, N1O2, N1S1, O1 and O2 classes were identified in Duvernay-sourced oils. With increasing migration distance, the relative abundance of O2, N1O1 and N1O2 showed a significant decrease, while the O1 class increased from <10% to nearly 30% of the total. With increasing migration along the Rimbey-Meadowbrook reef trend, pyrrolic nitrogen compounds (N1 class) shows an enrichment of alkylcarbazoles (DBE=9) relative to alkylbenzocarbazoles (DBE=12), and of higher homologous relative to the lower homologous. O1 compounds show a relative enrichment of those with low DBE values. Additionally, the N1O1 and N1S1 compounds show a relative enrichment of those with high DBE values, and of higher homologues compared to the lower homologues, indicating great potential for developing new migration indices.

Numerical Study of Buoyancy-Driven Oil Cluster Jumping in Porous Media by a Dynamic Pore-Network Model

Buoyancy-driven oil cluster jumping in porous media is studied by a dynamic pore-network model in relation to secondary oil migration. The model has two novel aspects. First, inertia of fluid and surface roughness of throat are taken into account in simulating the jumping process. Second, a probability technique is proposed to let the model allow a longer time step. The numerical results indicate that the dynamic process of buoyancy-driven cluster jumping is caused not only by porous media heterogeneity, but also by fluid inertia and throat surface roughness. Pressure field characteristics in jumping are studied and a cluster-based pressure solving technique is proposed to reduce the computational demanding of pressure solving. Some statistical characteristics, include cluster size distribution and residual oil saturation, are also studied.

A novel molecular index for secondary oil migration distance.

Determining oil migration distances from source rocks to reservoirs can greatly help in the search for new petroleum accumulations. Concentrations and ratios of polar organic compounds are known to change due to preferential sorption of these compounds in migrating oils onto immobile mineral surfaces. However, these compounds cannot be directly used as proxies for oil migration distances because of the influence of source variability. Here we show that for each source facies, the ratio of the concentration of a select polar organic compound to its initial concentration at a reference point is independent of source variability and correlates solely with migration distance from source rock to reservoir. Case studies serve to demonstrate that this new index provides a valid solution for determining source-reservoir distance and could lead to many applications in fundamental and applied petroleum geoscience studies.

An experimental study of secondary oil migration in a three-dimensional tilted porous medium

A three-dimensional physical experiment was conducted to study secondary oil migration under an impermeable inclined cap. Light-colored oil was released continuously at a slow rate of about 0.1 mL/min from a point at the base of an initially water-saturated porous model. With buoyancy as a primary driving force, a vertical cylindrical shape of an oil migration pathway was observed first, and then a layer-shaped lateral migration pathway was observed beneath the top inclined sealing plate once the oil cluster had reached the top cap. Magnetic resonance imaging was used to observe the migration processesmdashfor example, morphology of the migration pathway, intermittency of oil bubbles, and variation of oil saturation within the migration paths. Results show that the snap-off phenomenon (related to fast local imbibition processes) occurred more commonly during vertical migration than it did during lateral migration. The lateral migration pathway that parallels to the top inclined cap has a typical vertical thickness of 2 to 4 cm (0.8ndash1.6 in.) (i.e., roughly 40ndash80 pores). This thickness is consistent with the prediction derived from scaling laws related to pore size and Bond number. Along the lateral migration direction, the sectional area and the horizontal width of the migration pathway fluctuate significantly, although the average oil saturation along the pathway remains almost the same. After stopping the initial oil injection, the sectional area of the migration pathway shrinks significantly. Therefore, we believe that this significant shrinking of the migration pathway is the main reason why only a relatively small volume of oil and gas has been lost during secondary migration.

Use of biomarkers, porphyrins, and trace elements to assess the origin, maturity, biodegradation, and migration of Alturitas oils in Venezuela

This work is an analysis of crude oil samples from thirty wells in the Alturitas Field (Lake Maracaibo Basin, western Venezuela). Different biomarkers, ten trace elements, and porphyrins were analysed using GC–MS, ICP–OES and UV–visible techniques, respectively. The characterization of these crude oils leads us to conclude that they all fall into a single non-biodegraded oil family derived from a single pulse of hydrocarbon generation, migration and accumulation from the thermally mature calcareous La Luna source rock deposited in an anoxic marine palaeoenvironment under reducing conditions. The main objective of this work is to present a secondary oil migration model for the Marcelina reservoir of the Alturitas Field. The multivariate statistical study of trace-element concentrations, porphyrin contents, and polar compound proportions shows that these parameters can be split into two groups. The first group (Cd, Cu, Mo, Fe, P, Zn, Ca, and Mg) indicates a chalcophic association (Cd, Cu, Mo, and Zn) or colloidal complexes with naphthenic acids (Ca, Mg, and Fe). The other two trace elements (V and Ni), together with porphyrins and polar compounds, reveal that oil compositions has been affected by geochromatography, indicating a highly probable secondary migration pathway along a preferential axis orientated southeast to northwest.

Hydrodynamic stagnation zones: A new play concept for the Llanos Basin, Colombia

Hydraulic heads from a calibrated, three-dimensional, constant-density, ground-water-flow model were used to compute Hubbert oil potentials and infer secondary petroleum migration directions within the Llanos Basin, Colombia. The oil potentials for the C7 reservoir show evidence of the development of two hydrodynamic stagnation zones. Hydrodynamic effects on secondary oil migration are greatest in the eastern Llanos Basin, where structural slopes are lowest and local hydraulic-head gradients drive ground-water flow westward down structural dip. The Rubiales field, a large oil reservoir within the eastern Llanos Basin with no structural closure, is located at the edge of one of these stagnation zones. This oil field hosts heavy oils (12 API) consistent with water washing and biodegradation. The best agreement between model results and field conditions occurred in an oil density of 12 API, suggesting that the Rubiales field position is in dynamic equilibrium with modern hydraulic and oil density conditions. Cross sectional ground-water-flow models indicate that the most likely explanation of observed underpressures are caused by hydrodynamic effects associated with a topography-driven flow system. Late Miocene to present-day ground-water flow likely was an important factor in flushing marine connate porewaters from Tertiary reservoirs. Ground-water recharge along the western margin of the basin could help explain the observed low-temperature gradients (20C/km). However, upward flow rates were not high enough to account for elevated temperature gradients of 50C/km to the east.

Tracking Neutral Nitrogen Compounds in Subfractions of Crude Oil Obtained by Liquid Chromatography Separation Using Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Neutral nitrogen compounds have been used as molecular markers for tracking secondary oil migration in geochemistry. However, the distribution of neutral nitrogen compounds in the separation process is not well-characterized because the conventional analytical technique, such as gas chromatography−mass spectrometry (GC−MS), is non-selective for neutral nitrogen and not capable of detecting non-volatile high-molecular-weight compounds. In this paper, a crude oil was subjected to the traditional two-step open-column liquid chromatography (LC) technique to prepare subfractions, which were characterized for their molecular composition of neutral nitrogen compounds by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The results showed that the two-step LC technique produced a low yield of carbazole in the neutral nitrogen fraction. The neutral nitrogen fraction was enriched with low-molecular-weight neutral nitrogen compounds. Most N1 class speci...

Experimental study of the factors controlling secondary oil migration

Experimental study of the factors controlling secondary oil migration

Experimental investigation of secondary oil migration along subtle pathways: A mechanism for hydrocarbon accumulation in lenticular basinal turbidite reservoirs

Experimental investigation of secondary oil migration along subtle pathways: A mechanism for hydrocarbon accumulation in lenticular basinal turbidite reservoirs