Distribution Of Hydrocarbon Accumulations Research Articles

Fault Controls on Hydrocarbon Migration—An Example from the Southwestern Pearl River Mouth Basin

Faults play a pivotal role in controlling fluid migration and retention within sedimentary basins, particularly in the context of fault-bound hydrocarbon reservoirs. Assessing the stability and sealing capabilities of faults enhances our comprehension of these systems and aids in the identification of pathways for fluid migration. In this study, we focus on a series of fault-bound hydrocarbon accumulations located in the southern Wenchang A subbasin within the Pearl River Mouth Basin. We emphasize the significant influence of faults in governing the processes of hydrocarbon migration and accumulation. By leveraging 3D seismic data and well information, we have assessed the sealing potential of ten faults that either currently retain hydrocarbon columns or have the potential to do so. Our analysis reveals that even faults with a relatively low Shale Gouge Ratio (as low as 15%) can effectively support substantial column heights. Taking into account factors, such as the source rock maturity, fault activity, geometry, sealing potential, and the distribution of hydrocarbon accumulations, we have formulated a conceptual model for hydrocarbon migration and accumulation within the study area. This model underscores potential fluid traps within the rift basin, shedding light on the complex dynamics of hydrocarbon movement in this region.

Refining hydrocarbon reserve location using modern geodynamics

The paper considers some aspects of the theoretical prerequisites for the influence of geodynamic processes on the distribution of hydrocarbon accumulations in natural megareservoirs. The most interesting part to study is the part of Central Siberia, where quite a lot of large and unique oil and gas fields have been discovered in a relatively small area. It is shown that hydrocarbon deposits in the study area are organized into groups according to the size of reserves. This can be explained by geodynamic processes occurring during the geological history of the region. The features of the river network pattern are interpreted as local geodynamic settings of the «pushed block» type. The relationship between the parameters of local geodynamic settings and the scale of oil and gas accumulation is noted. Keywords: geodynamic processes; large and unique reserves; natural mega-reservoirs; geodynamic conditions; scale of oil and gas accumulation.

Regularities of hydrocarbons accumulations in the Meso-Cenozoic complex of the Black Sea-Caspian region

The article considers the regularities in the distribution of hydrocarbon accumulations in the Meso-Cenozoic complex of the Black Sea-Caspian region associated with the evolution of generation-accumulation systems developed in the plate cover of the region. The plate cover, as well as elements of the Mesozoic generationaccumulation systems, began to form in the structure of the Alpine structural-geodynamic systems. An analysis of the areal distribution of structural-geodynamic systems shows that the maximum development of sedimentary basins correlates with the transgressive Cretaceous period, which is characterized by the expansion of the areas of pre-existing basins and the emergence of new depocenters. In this case, two groups of basins are distinguished. The first includes the Karkinitsky, Bolshekavkazsky, West Kuban, Central and Tersko-Caspian basins. The second group includes depocenters Indolsky, East Kuban, Berdyansk, North Azov, West Stavropol, Gudilovsky, Ustyurtsky. The most significant events that determined the features of the evolution of generation-accumulation systems correlate with the latest time. Keywords: Black Sea - Caspian region; development of sedimentary basins; structural and geodynamic system; tectonic conditions; signs of oil and gas content.

Role of abnormally high formation pressures in the distribution of oil-gas bearing content in South Caspian depression

The paper reviews and compares the state of South Caspian depression to the large oil-gas bearing regions of the world genetically not associated but similar to the major geological factors. Geological data on the development and distribution of abnormally high formation pressures (AHFP) and anomaly ratio in the sections of sedimentary strata in various regions of the world has been analyzed. The appearance of abnormally high formation pressure in different geological conditions within South Caspian depression has been reviewed and compared to the corresponding results of similar basins, on the basis of which an adequate model developed as well. In the context of the fields with AHFP within South Caspian basin, it is shown that the significant amount of hydrocarbon reserves may be associated with AHFP zones. The paper presents a brief analysis of views development on the regulations of the distribution of hydrocarbon accumulations in the soil depth. Based on the graphic materials and mathematical statistics, the inequality of distribution of oil reserves on the territory of mentioned basins is justified. Therefore, data analysis on geobaric characteristics of perspective structures, particularly, in deep water zones of SCB, which is top priority for conducting exploration survey may contribute to more reasonable choice.

Западная часть Терско-Каспийского прогиба как зона разгрузки глубинных флюидных систем

The article describes the mechanisms of formation of the Terek and Sunzha anticlinoria as the main zones of oil and gas accumulation. An assumption is made about the formation of high-amplitude anticlinal folds in the Upper Cretaceous deposits as a result of vertical migration of high-pressure fluids along deep faults with a breakthrough of their upper horizons of the sedimentary cover into the late orogenic phases of folding. The main prerequisites for the deep genesis of oil and gas are listed – a pronounced unevenness in the distribution of hydrocarbon accumulations, abnormal pressure, hydrochemical anomalies.

Features of the distribution of hydrocarbon accumulations in lithologically different-type deposits at the ancient continental margins of the North American and South American platforms

Lithologically diverse sedimentary complexes were formed within the North and South American platforms. The most general groups of the sediments are distinguished as follows: continental (alluvial, limnic), deltaic, shallow-marine, and deepwater—for the terrigeneous formations, reef limestones and limestones of other origins (oolitic, algaes, etc.), and dolomites—for carbonate varieties. In addition to this, tuffs, tuff-sandstones, and crystalline schists (quartzites) were studied separately. The lasts were marked only in the Permian Basin. The comparative analysis of the sedimentary basins located in the peripheral parts of the North American and South American platforms showed the following: the most important stage in the evolution of the North American platform is the first stage of existence of the ancient Paleozoic continental margins, which developed under passive tectonic conditions and determined its future potential of oil and gas bearing. At this stage, the main resources of oil and gas hydrocarbons are concentrated in carbonate rocks. As for the sedimentary basins located on the margins of the South American platform, the second stage is the most important stage in their evolution when the foredeeps were formed and developed laying on the earlier structures. This period is related to the oil and gas bearing potential of the basins on the margins of the South American platform. For both platforms, a common circumstance is that, at the second stage of development of all the sedimentary basins, all the resources of hydrocarbons are focused in the terrigeneous sediments.The stratigraphic range of oil and gas occurrence in the basins of the ancient continental margins is determined by the following regularity: the fold structures is younger confining these margins, the age range of the oil and gas reservoirs is broader.

Ancient continental margins and comparative analysis of their oil-and-gas bearing

Analysis of peculiarities in the distribution of hydrocarbon accumulations within the basins of Phanerozoic continental margins, which had completed their evolution, and complicated peripheral regions of ancient Laurasian and Gondwanian platforms nowadays, has enabled us to reveal certain regularities related to two stages in the evolution of sedimentary basins. The first stage of evolution of sedimentary basins (period of existence of the continental margin proper) is related to large accumulations of fluid and gaseous hydrocarbons in the margins of continents belonging to the Laurasian megablock; for the margins of continents belonging to Gondwana, this period was reflected in the formation of large gas accumulation only (in the Permian). At the second stage of sedimentary basin evolution, large oil and gas accumulations were formed in areas associated with fore deeps, which were laid in the boundary of the Gondwanian platforms and fold belts. In comparison, in fore deeps that emerged in the marginal parts of Laurasian platforms, less significant accumulations of fluid and gaseous hydrocarbons were found (Table 1). The results of comparative analysis in oil-and-gas bearing basins located in the margins of the Laurasian and Gondwanian megablocks would help in purposeful exploratory works for oil and gas.

Distribution of hydrocarbon accumulations in a basin: a mathematical model for the West Siberian petroleum province

The distribution of hydrocarbon accumulations in a basin is modeled as a nonstationary Poisson field of points with the average density of accumulations as a function of distance from the basin margin. The model, in which this distance is a unique parameter to define the intensity function, is suitable, in a first approximation, for Monte-Carlo simulation of the real pattern of accumulations. The Poisson random field of points is described with a power function, where the power is a fractal dimension used as an integral numerical parameter of the distribution.

Prediction of the phase state of hydrocarbon accumulations in the Mesozoic deposits of northwestern Siberia

The phase state of hydrocarbon accumulations was predicted using recent drilling data for three oil and gas complexes of the northern regions of the West Siberian petroliferous basin: Lower and Middle Jurassic, Upper Jurassic, and Berriasian-lower Valanginian (Achimov member); these results were compiled in simplified maps presented in the paper. In order to develop a plausible model and distinguish the zones of hydrocarbon accumulation of various phase states, we analyzed and systematized the existing concepts on the distribution of oil, oil-gas condensate, and gas condensate pools in the Mesozoic sequences of this region, types of organic matter in rocks, and stages of catagenetic alterations. Based on the data of the Tyumen SG-6 superdeep well, the oil-generating capacity of source deposits was assessed. Three zones differing in the phase state of hydrocarbons, oil, gas condensate-oil (transitional), and gas condensate, were distinguished in the map of the distribution of hydrocarbon accumulations in the Early-Middle Jurassic petroliferous complex of northwestern Siberia. Only two zones of hydrocarbon accumulations, oil and transitional, were detected in the Late Jurassic complex of the Nadym-Taz and Ust’-Yenisei regions. The same zones but within different boundaries were distinguished in the Achimov sequence. In contrast to the Jurassic beds, the zone of occurrence of oil accumulations in the Achimov member occupies a larger area and extends further north. In terms of density, the oils of the Achimov deposits were subdivided into three types: ultralight, light, and medium. The zones of their occurrence are shown in the map.

Simulating the Spatial Distribution of Undiscovered Petroleum Accumulations

Abstract There are two major problems in the construction of a stochastic model that describes quantitatively the spatial distribution of undiscovered petroleum accumulations: a) available exploration results are biased; and, b) information associated with the locations of accumulations is incomplete. Studies in the Western Canada Sedimentary Basin (WCSB) and elsewhere indicate that the spatial characteristics of petroleum accumulations are fractal. In this paper, we propose the use of these fractal characteristics to calibrate sampling bias, thus deriving an unbiased spatial correlation (covariance function) for the stochastic modelling. The uncertainty in the modelled locations of undiscovered accumulations resulting from insufficient information is captured by equal-probable realizations of the simulation and these are subsequently converted to a probability map of petroleum occurrence. In the example, a pre-1994 exploratory data set for the Rainbow gas play in WCSB was used to derive simulation parameters. A comparison of the simulated results to post-1993 gas discoveries in the same play shows that most of the post-1993 discoveries are located in areas with high predicted probability values. Introduction Spatial characteristics of undiscovered oil and gas accumulations are important for both better natural resource management and improved exploration efficiency. There are two major obstacles associated with the construction of a stochastic model for describing the spatial distribution of undiscovered petroleum accumulations. The first is that the available information is biased with respect to exploration results. The second is that information associated with the locations of petroleum accumulations is incomplete unless all accumulations are discovered. It is well known that the data associated with the discovery of petroleum accumulations in an exploration program is biased. Larger features are generally tested with higher priority(1,2). This sampling bias prohibits the use of conventional methods to estimate stochastic model parameters. Barton et al.(3) and La Pointe(4) studied the data from well-explored petroleum basins in the United States and concluded that the spatial distribution of hydrocarbon accumulations is fractal. Our studies in the WCSB also indicate that the spatial distribution of petroleum accumulations exhibits a similar characteristic. Figure 1 shows the box counting results for the Rainbow gas play in the WCSB. The linear relation between box size and the number of boxes containing gas pools (on a logarithmic scale) indicates fractal geometry of the spatial distribution of gas accumulations. The scaling property of the spatial objects means that spatial characteristics of large objects of petroleum accumulations could be used to infer the spatial characteristics for the smaller ones, which are underrepresented in the data set. Thus, an unbiased spatial structure of petroleum accumulations could be inferred from the biased observations. By transforming the spatial information of discovered hydrocarbon accumulations into a frequency domain using a fast Fourier transform (FFT), it results in an amplitude map and a phase map. The amplitude map contains information associated with spatial correlation, while the phase map contains location specific information. When both the location-specific information in the phase map and the spatial correlation in the amplitude map are complete, the true spatial locations of petroleum accumulation can be inferred.

Fractal Size and Spatial Distribution of Hydrocarbon Accumulations--Implications for Resource Assessment and Exploration Strategies: ABSTRACT

Fractal Size and Spatial Distribution of Hydrocarbon Accumulations--Implications for Resource Assessment and Exploration Strategies: ABSTRACT

Computer-Aided Exploration with THEMISED Software: Pressure, Maturation Analyses, and Migration Studies in Various Geological Environments, Rifts (North Sea), Intracratonic Basins (Paris), Tertiary Deltas (Indonesia): ABSTRACT

The THEMISED software describes on a geologic cross section the progressive compaction of the sediments due to water expulsion, the formation of hydrocarbons as a result of temperature increase with burial, their expulsion from the source rocks, and their migration as a separate flow within the carrier beds toward the traps. This tool points out the main geological factors leading to hydrocarbon accumulation (oil and/or gas) in relatively quiet tectonic settings. It gives an objective geological interpretation on the basis of the geological hypotheses made by the explorationist. In the North Sea basin, the writers show how the difference of behavior of the various source rocks during maturation may affect the distribution and kind of hydrocarbon accumulation. In addition, the pressure buildup within the impervious shaly seal and within the reservoir may lead to hydrocarbon dismigration, because of the seal leakage, or hydrocarbon accumulation per descensum within the reservoirs. In some intracratonic basins like the Paris basin, the hydrodynamic conditions may perturb hydrocarbon migration. The timing of hydrocarbon expulsion is also crucial when considering the timing of traps' structuring. In thick, recent sedimentary basins such as the Mahakam Tertiary delta (Indonesia), the rapid sedimentation causes a specific pressure buildup andmore » a perturbation of the heat flow. The possibilities of carrier bed connections within the delta also influence the pressure regime. As a consequence, the distribution of hydrocarbon accumulations is linked both with the source beds' relations to the carrier beds and the general pressure and temperature history of the basin.« less

Spatial distribution of hydrocarbon accumulations of different phase state

The distribution patterns of oil, oil-gas-condensate, and gas-condensate accumulations in the Jurassic and Cretaceous sediments of the Kuma-Tyulenevo swell in Eastern Ciscaucasia, as well as the regular changes in the physicochemical properties of the oils, by-products gases, and condensates, are associated with the features of differential entrapment of the hydrocarbons along their migration routes. The pattens of differential entrapment of hydrocarbons under different geological conditions are discussed: in the regionally distributed strata during lateral migration along a series of parallel and intersecting or merging anticlinal zones; along different regionally distributed strata in an anticlinal zone; during vertical overflow, etc. The pattens of spatial distribution of oil and gas accumulations may be used for directed prospecting.