In response to the problems of unclear distribution of deep-water pre-salt carbonate reservoirs and formation conditions of large oil fields in the Santos passive continental margin basin,based on comprehensive utiliz...In response to the problems of unclear distribution of deep-water pre-salt carbonate reservoirs and formation conditions of large oil fields in the Santos passive continental margin basin,based on comprehensive utilization of geological,seismic,and core data,and reconstruction of Early Cretaceous prototype basin and lithofacies paleogeography,it is proposed for the first time that the construction of pre-salt carbonate build-ups was controlled by two types of isolated platforms:inter-depression fault-uplift and intra-depression fault-high.The inter-depression fault-uplift isolated platforms are distributed on the present-day pre-salt uplifted zones between depressions,and are built on half-and fault-horst blocks that were inherited and developed in the early intra-continental and inter-continental rift stages.The late intra-continental rift coquinas of the ITP Formation and the early inter-continental rift microbial limestones of the BVE Formation are continuously constructed;intra-depression fault-high isolated platforms are distributed in the current pre-salt depression zones,built on the uplifted zones formed by volcanic rock build-ups in the early prototype stage of intra-continental rifts,and only the BVE microbial limestones are developed.Both types of limestones formed into mound-shoal bodies,that have the characteristics of large reservoir thickness and good physical properties.Based on the dissection of large pre-salt oil fields discovered in the Santos Basin,it has been found that both types of platforms could form large-scale combined structural-stratigraphic traps,surrounded by high-quality lacustrine and lagoon source rocks at the periphery,and efficiently sealed by thick high-quality evaporite rocks above,forming the optimal combination of source,reservoir and cap in the form of“lower generation,middle storage,and upper cap”,with a high degree of oil and gas enrichment.It has been found that the large oil fields are all bottom water massive oil fields with a unified pressure system,and they are all filled to the spill-point.The future exploration is recommended to focus on the inter-depression fault-uplift isolated platforms in the western uplift zone and the southern section of eastern uplift zones,as well as intra-depression fault-high isolated platforms in the central depression zone.The result not only provides an important basis for the advanced selection of potential play fairways,bidding of new blocks,and deployment of awarded exploration blocks in the Santos Basin,but also provides a reference for the global selection of deep-water exploration blocks in passive continental margin basins.展开更多
Rationale: The quality of groundwater in the Mgbede Oil Fields of South-South Nigeria has raised significant concerns due to the risk of contamination from industrial activities, especially gas flaring. Evaluating the...Rationale: The quality of groundwater in the Mgbede Oil Fields of South-South Nigeria has raised significant concerns due to the risk of contamination from industrial activities, especially gas flaring. Evaluating the effects of these operations on groundwater quality is essential for safeguarding the health and well-being of local communities, as well as protecting the environment. Objective: This study aimed to evaluate the quality of groundwater in the Mgbede Oil Fields, specifically examining whether the water meets international drinking water standards and identifying any contaminants present due to gas flaring. Method: Purposeful selection of water sampling points was employed to ensure the objectives of the study were met. Groundwater samples were collected from various locations within the Mgbede Oil Fields and analyzed for key quality parameters, including pH, manganese, and turbidity, among others. Results: The analysis revealed that while most groundwater samples were within acceptable international drinking water limits, there were notable exceptions. pH levels ranged from 5.17 to 6.16, manganese concentrations from 0.001 to 0.136 mg/L, and turbidity levels from 0.00 to 825 mg/L. All sampled locations exhibited traces of manganese and high acidity, indicating particulate pollution likely resulting from gas flaring activities. Conclusions: The study concluded that the groundwater quality in the Mgbede Oil Fields is negatively impacted by continuous gas flaring. Contaminants such as manganese and increased acidity levels exceed acceptable international standards, posing potential risks to environmental health. Recommendations: To mitigate these risks, it is recommended that immediate measures should be taken to reduce gas flaring and its associated particulate emissions. Regular monitoring of groundwater quality should be implemented to track improvements and ensure compliance with international standards. Additionally, introducing filtration systems or alternative water sources could help protect the health of local communities. Significance Statement: This study underscores the significant impact of industrial activities, specifically gas flaring, on groundwater quality in the Mgbede Oil Fields. The findings highlight the urgent need for regulatory measures and continuous monitoring to safeguard environmental health and ensure the availability of safe drinking water.展开更多
Fluctuations in oil prices adversely affect decision making situations in which performance forecasting must be combined with realistic price forecasts.In periods of significant price drops,companies may consider exte...Fluctuations in oil prices adversely affect decision making situations in which performance forecasting must be combined with realistic price forecasts.In periods of significant price drops,companies may consider extended duration of well shut-ins(i.e.temporarily stopping oil production)for economic reasons.For example,prices during the early days of the Covid-19 pandemic forced operators to consider shutting in all or some of their active wells.In the case of partial shut-in,selection of candidate wells may evolve as a challenging decision problem considering the uncertainties involved.In this study,a mature oil field with a long(50+years)production history with 170+wells is considered.Reservoirs with similar conditions face many challenges related to economic sustainability such as frequent maintenance requirements and low production rates.We aimed to solve this decision-making problem through unsupervised machine learning.Average reservoir characteristics at well locations,well production performance statistics and well locations are used as potential features that could characterize similarities and differences among wells.While reservoir characteristics are measured at well locations for the purpose of describing the subsurface reservoir,well performance consists of volumetric rates and pressures,which are frequently measured during oil production.After a multivariate data analysis that explored correlations among parameters,clustering algorithms were used to identify groups of wells that are similar with respect to aforementioned features.Using the field’s reservoir simulation model,scenarios of shutting in different groups of wells were simulated.Forecasted reservoir performance for three years was used for economic evaluation that assumed an oil price drop to$30/bbl for 6,12 or 18 months.Results of economic analysis were analyzed to identify which group(s)of wells should have been shut-in by also considering the sensitivity to different price levels.It was observed that wells can be characterized in the 3-cluster case as low,medium and high performance wells.Analyzing the forecasting scenarios showed that shutting in all or high-and medium-performance wells altogether results in better economic outcomes.The results were most sensitive to the number of active wells and the oil price during the high-price period.This study demonstrated the effectiveness of unsupervised machine learning in well classification for operational decision making purposes.Operating companies may use this approach for improved decision making to select wells for extended shut-in during low oil-price periods.This approach would lead to cost savings especially in mature fields with low-profit margins.展开更多
Consequences of decommissioning oil fields on artisanal fishing activities are still little known in the literature. This paper is intended to shed some light on a process of dismantling and sinking of oil and gas str...Consequences of decommissioning oil fields on artisanal fishing activities are still little known in the literature. This paper is intended to shed some light on a process of dismantling and sinking of oil and gas structures in shallow waters, with severe disturbing impacts on low income artisanal fishing activities. From a socio-economic perspective, the relationship of oil industry with local communities is described, with the main perceived problems pointed out in local fishermen leadership perspective. The notions of ＂damages＂ and ＂mitigation＂ used by the oil industry are discussed in connection to the expansion and dismantling of oil installations during the past 20 yrs. A comparative view of oil fields decommissioning in Europe and Brazil during the late 1990s suggests the need to review transparency and social commitment standards which have been far less prominent in this Brazilian case. The authors believe that the Brazilian oil industry has acquired a social and environmental debt towards the whole society, as far as it has been unable to establish a clear and effective process for decommissioning their oil installations within the artisanal fishing areas of the Todosos Santos Bay. Furthermore, the discussion of fair and specific compensations has been avoided, which otherwise would be instrumental to regain local economic conditions found among fishermen just few decades ago.展开更多
Development strategy for heavy-oil reservoirs is one of the important research interests in China National Offshore Oil Corp. （CNOOC） that plans a highly effective development for heavy oil fields in multilayered fl...Development strategy for heavy-oil reservoirs is one of the important research interests in China National Offshore Oil Corp. （CNOOC） that plans a highly effective development for heavy oil fields in multilayered fluvial reservoirs because of their significant influence on marine oil and even on China＇s petroleum production. The characteristics analysis of multilayered fluvial reservoirs in the heavy oil fields in Bohai Bay indicates that large amounts ofoil were trapped in the channel, point bar and channel bar sands. The reserves distribution of 8 oilfields illustrates that the reserves trapped in the main sands, which is 20%-40% of all of the sand bodies, account for 70%-90% of total reserves of the heavy oil fields. The cumulative production from high productivity wells （50% of the total wells） was 75%-90% of the production of the overall oilfield, while only 3%-10% of the total production was from the low productivity wells （30% of the total wells）. And the high productivity wells were drilled in the sands with high reserves abundance. Based on the above information the development strategy was proposed, which includes reserves production planning, selection of well configuration, productivity design, and development modification at different stages.展开更多
The Class-Ⅲ oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes,an oil recovery of 39%,with remaining reserves accounting for more than 45%of the t...The Class-Ⅲ oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes,an oil recovery of 39%,with remaining reserves accounting for more than 45%of the total geological reserves of the oilfield.Therefore,they have considerable potential for future oil production.The current layered injection technologies fail to achieve effective control over the low single-layer injection rates since they can only produce low throttle differential pressure under low injection rates(5-20 m^(3)/d).In this study,a symmetrically-structured double-offset-hole injection allocator and a novel throttling component were developed.Their spatial layout was constructed and mechanical parameters were optimized using finite element analysis,which allows for expanding the flow rate range at low injection rates.According to experimental results,the throttle differential pressure increased from 0.2 MPa to 0.8 MPa at an injection rate of 5 m^(3)/d,and the range of the single-layer flow rates expanded from 20-70 m^(3)/d to 5-70 m3/d.The field test results show that the effective production of oil layers with medium and low permeability was achieved and that the ratio of producing oil layer thickness to the total reservoir thickness increased by 9.7%on average.Therefore,this study provides valuable technical support for the effective chemical-flooding-based development of Class-Ⅲ oil reservoirs.展开更多
This paper describes coating protection of production facilities of offshore oil fields based on the practice of development of Bohai Offshore Oil Field, with focus laid on the selection of coating systems, surface pr...This paper describes coating protection of production facilities of offshore oil fields based on the practice of development of Bohai Offshore Oil Field, with focus laid on the selection of coating systems, surface preparation, coating application, as well as coating inspection for four types of major production facilities.展开更多
The formation water sample in oil and gas fields may be polluted in processes of testing, trial production, collection, storage, transportation and analysis, making the properties of formation water not be reflected t...The formation water sample in oil and gas fields may be polluted in processes of testing, trial production, collection, storage, transportation and analysis, making the properties of formation water not be reflected truly. This paper discusses identification methods and the data credibility evaluation method for formation water in oil and gas fields of petroliferous basins within China. The results of the study show that: (1) the identification methods of formation water include the basic methods of single factors such as physical characteristics, water composition characteristics, water type characteristics, and characteristic coefficients, as well as the comprehensive evaluation method of data credibility proposed on this basis, which mainly relies on the correlation analysis sodium chloride coefficient and desulfurization coefficient and combines geological background evaluation;(2) The basic identifying methods for formation water enable the preliminary identification of hydrochemical data and the preliminary screening of data on site, the proposed comprehensive method realizes the evaluation by classifying the CaCl2-type water into types A-I to A-VI and the NaHCO3-type water into types B-I to B-IV, so that researchers can make in-depth evaluation on the credibility of hydrochemical data and analysis of influencing factors;(3) When the basic methods are used to identify the formation water, the formation water containing anions such as CO_(3)^(2-), OH- and NO_(3)^(-), or the formation water with the sodium chloride coefficient and desulphurization coefficient not matching the geological setting, are all invaded with surface water or polluted by working fluid;(4) When the comprehensive method is used, the data credibility of A-I, A-II, B-I and B-II formation water can be evaluated effectively and accurately only if the geological setting analysis in respect of the factors such as formation environment, sampling conditions, condensate water, acid fluid, leaching of ancient weathering crust, and ancient atmospheric fresh water, is combined, although such formation water is believed with high credibility.展开更多
Based on the practice of oil and gas exploration in the Huizhou Sag of the Pearl River Mouth Basin,the geochemical indexes of source rocks were measured,the reservoir development morphology was restored,the rocks and ...Based on the practice of oil and gas exploration in the Huizhou Sag of the Pearl River Mouth Basin,the geochemical indexes of source rocks were measured,the reservoir development morphology was restored,the rocks and minerals were characterized microscopically,the measured trap sealing indexes were compared,the biomarker compounds of crude oil were extracted,the genesis of condensate gas was identified,and the reservoir-forming conditions were examined.On this basis,the Paleogene Enping Formation in the Huizhou 26 subsag was systematically analyzed for the potential of oil and gas resources,the development characteristics of large-scale high-quality conglomerate reservoirs,the trapping effectiveness of faults,the hydrocarbon migration and accumulation model,and the formation conditions and exploration targets of large-and medium-sized glutenite-rich oil and gas fields.The research results were obtained in four aspects.First,the Paleogene Wenchang Formation in the Huizhou 26 subsag develops extensive and thick high-quality source rocks of semi-deep to deep lacustrine subfacies,which have typical hydrocarbon expulsion characteristics of"great oil generation in the early stage and huge gas expulsion in the late stage",providing a sufficient material basis for hydrocarbon accumulation in the Enping Formation.Second,under the joint control of the steep slope zone and transition zone of the fault within the sag,the large-scale near-source glutenite reservoirs are highly heterogeneous,with the development scale dominated hierarchically by three factors(favorable facies zone,particle component,and microfracture).The(subaqueous)distributary channels near the fault system,with equal grains,a low mud content(<5%),and a high content of feldspar composition,are conducive to the development of sweet spot reservoirs.Third,the strike-slip pressurization trap covered by stable lake flooding mudstone is a necessary condition for oil and gas preservation,and the NE and nearly EW faults obliquely to the principal stress have the best control on traps.Fourth,the spatiotemporal configuration of high-quality source rocks,fault transport/sealing,and glutenite reservoirs controls the degree of hydrocarbon enrichment.From top to bottom,three hydrocarbon accumulation units,i.e.low-fill zone,transition zone,and high-fill zone,are recognized.The main area of the channel in the nearly pressurized source-connecting fault zone is favorable for large-scale hydrocarbon enrichment.The research results suggest a new direction for the exploration of large-scale glutenite-rich reservoirs in the Enping Formation of the Pearl River Mouth Basin,and present a major breakthrough in oil and gas exploration.展开更多
The Middle Cretaceous Mishrif Formation of the Cenomanian-Turonian age is an important Middle Eastern reservoir.Previous studies have shown that carbonates in the Mishrif Formation are affected by karstification and a...The Middle Cretaceous Mishrif Formation of the Cenomanian-Turonian age is an important Middle Eastern reservoir.Previous studies have shown that carbonates in the Mishrif Formation are affected by karstification and are concentrated at the top of the formation.However,there is a lack of systematic research on the effects of karstification on the formation’s reservoir characteristics.Based on core samples,scanning electron microscopy of thin sections,and geochemical analysis of C,O,and Sr isotopes from wells in the Missan Oil Fields,unconformity was identified at the top of the B21 subzone of the Mishrif Formation.Core and cast-thin-section observations indicate that there is a significant lithological difference above and below the unconformity,and dissolution pores and voids are well-developed beneath it.Vadose silt fills the intragranular pores and geopetal fabric is developed inside some mouldic pores beneath the unconformity surface.The isotopic values of ^(87)Sr/^(86)Sr(0.707270-0.707722)and δ^(18)O(−5.94‰—−2.32‰)suggest that the top of the B21 subzone of the Mishrif Formation has been severely affected by syngenetic karst.Karstification is the key to high-quality reservoir formation and the reservoir’s oil-bearing heterogeneity.This study will inform oil and gas exploration in the Missan Oil Fields and in other areas with similar reservoir characteristics.展开更多
The main objective of this paper is to construct a static model that compress the uncertainties of the stochastic distribution of the reservoir properties of the Bahariya Formation in Heba field,at the northeastern po...The main objective of this paper is to construct a static model that compress the uncertainties of the stochastic distribution of the reservoir properties of the Bahariya Formation in Heba field,at the northeastern portion of the Western Desert.This model has been constructed through the integration of the interpretations of the eighteen 2D seismic sections and the analysis of well logs data for four wells(HEBA 300X,E.BAH-E-1X,E.BAH-D-1X,and HEBA 10X)drilled in the study area.This set of data was implemented in a harmonic workflow.Structural framework was the first step created on the basis of the seismic and well log interpretations.Model zonation was mainly managed by the marine flooding events took place during the Cenomanian period.The trapping faults position uncertainty has been compressed through the tying of the seismic profiles with the identified fault cuts in the well data.Effective porosity spectrum was broke up into three reservoir qualities.The results showed heterogeneous facies qualities for oil production in specific five zones in the topmost part of the Bahariya Formation.The effective porosity model was generated stochastically considering the normal distribution for each reservoir quality.Water saturation was distributed by two methods;1)Sequential Gaussian Simulation that was co-simulated by porosity model.2)Log-based saturation height function for each reservoir quality.This methodology provided as accurate as possible estimates for the volume calculation by quantifying the sensitivity of the important parameters such as oil contact.Additionally,the model was prepared to be used as a front end for dynamic simulation.展开更多
The effect of HCO3^- concentration on CO2 corrosion was investigated by polarization measurement of potentiodynamic scans and weight-loss method, Under the conditions of high pressure and high temperature, the corrosi...The effect of HCO3^- concentration on CO2 corrosion was investigated by polarization measurement of potentiodynamic scans and weight-loss method, Under the conditions of high pressure and high temperature, the corrosion rate of steel X65 decreased with the increase of HCO3^- concentration, while pH of solution increased. SEM, EDS, and XRD results of the corrosion scales indir cated that the typical FeCO3 crystallite was found at low HCO3^- concentration but Ca（Fe,Mg）（CO3）2 was found at high HCO3^- con- centration. Ca^2＋ and Mg^2＋ are precipitated preferential to Fe^2＋ at high pH value. Potentiodynamic polarization curves showed that the cathodic current density decreases with the increase of HCO3^- concentration at low HCO3^- concentration. When the HCO3^- concentration reaches 0.126 mol/L, increasing HCO3^- concentration promotes cathodic reactions. Anodic behavior is an active process at low HCO3^- concentration and the anodic current density decreases with the increase of HCO3^- concentration. An evident active-passive behavior is exhibited in anodic process at 0.126 mol/L HCO3^-.展开更多
There are rich oil and gas resources in marine carbonate strata worldwide.Although most of the oil and gas reserves discovered so far are mainly distributed in Mesozoic,Cenozoic,and upper Paleozoic strata,oil and gas ...There are rich oil and gas resources in marine carbonate strata worldwide.Although most of the oil and gas reserves discovered so far are mainly distributed in Mesozoic,Cenozoic,and upper Paleozoic strata,oil and gas exploration in the Proterozoic–Lower Paleozoic（PLP）strata—the oldest marine strata—has been very limited.To more clearly understand the oil and gas formation conditions and distributions in the PLP marine carbonate strata,we analyzed and characterized the petroleum geological conditions,oil and gas reservoir types,and their distributions in thirteen giant oil and gas fields worldwide.This study reveals the main factors controlling their formation and distribution.Our analyses show that the source rocks for these giant oil and gas fields are mainly shale with a great abundance of type I–II organic matter and a high thermal evolution extent.The reservoirs are mainly gas reservoirs,and the reservoir rocks are dominated by dolomite.The reservoir types are mainly karst and reef–shoal bodies with well-developed dissolved pores and cavities,intercrystalline pores,and fractures.These reservoirs arehighly heterogeneous.The burial depth of the reservoirs is highly variable and somewhat negatively correlated to the porosity.The cap rocks are mainly thick evaporites and shales,with the thickness of the cap rocks positively correlated to the oil and gas reserves.The development of high-quality evaporite cap rock is highly favorable for oil and gas preservation.We identified four hydrocarbon generation models,and that the major source rocks have undergone a long period of burial and thermal evolution and are characterized by early and long periods of hydrocarbon generation.These giant oil and gas fields have diverse types of reservoirs and are mainly distributed in paleo-uplifts,slope zones,and platform margin reef-shoal bodies.The main factors that control their formation and distribution were identified,enabling the prediction of new favorable areas for oil and gas exploration.展开更多
Complicated oil and gas fields occupy an important position in oil and gas exploration. In this paper, complicated oil and gas fields are grouped into four types: fault-block, lithologic, stratigraphic and fissure typ...Complicated oil and gas fields occupy an important position in oil and gas exploration. In this paper, complicated oil and gas fields are grouped into four types: fault-block, lithologic, stratigraphic and fissure types. On the basis of the new theory of petroleum geological exploration in composite oil and gas accumulation areas within continental basins, a new exploration sequence suitable for complicated oil and gas fields has been established, which comprises four stages:(1) initial exploration;(2) preliminary exploration;(3) early step-by-step exploration and development: and(4) late step-by-step exploration and development. The idea of cybernetics has been taken to control various links of a systematic exploration project so as to fully, effectively and comprehensively utilize the new exploration techniques, eventually realizing the optimization of exploration with the aim of raising the efficiency of exploration of complicated oil and gas fields.展开更多
Whole-life-cycle integrity management of underground gas storages(UGSs)has been an important link to ensure its long-term safe and efficient operation.At present,the integrity of UGSs in oil/gasfields and its evaluati...Whole-life-cycle integrity management of underground gas storages(UGSs)has been an important link to ensure its long-term safe and efficient operation.At present,the integrity of UGSs in oil/gasfields and its evaluation techniques focus on surface facilities and injection/withdrawal wells,but its geological integrity lacks clear definition and evaluation object and systematic evaluation techniques.In this paper,relevant research achievements werefirstly summarized.Then,the concept of geological integrity with the gas-storage geological body as the evaluation object was put forward,and the evaluation system for the geological integrity of such UGSs was established.Finally,UGS geological integrity evaluation was carried out with the Hutubi Underground Gas Storage in Xinjiang as an example.And the following research results were obtained.First,UGS geological integrity is defined as the integrity degree of each component of a gas-storage geological body to meet operation requirements and fulfill seasonal and emergency peak shaving safely and economically during the operation of a UGS.Its connotation is that reservoir of geological body,caprock,fault and trap can supply the customers with gas continuously and stably and ensure the safe operation of the UGS in its service life.And its core lies in keeping the reliability,safety and economy of natural gas storage in the service life of a UGS.Second,the geological integrity evaluation system is composed of four evaluation techniques,including trap effectiveness,caprock integrity,fault stability and reservoir stability.Third,the evaluation results show that the Hutubi Underground Gas Storage has the potential of peak-shaving capacity enhancement by increasing the maximum operation pressure.In conclusion,the establishment of the geological integrity evaluation system for such UGSs improves the UGS integrity evaluation technique system and plays an instructive and practical role in ensuring the long-term safe and efficient operation of UGSs,increasing the maximum operation pressure and improving the peak shaving capacity.展开更多
基金Supported by the National Science and Technology Major Project(2016ZX05029001)CNPC Science and Technology Project(2019D-4310)。
文摘In response to the problems of unclear distribution of deep-water pre-salt carbonate reservoirs and formation conditions of large oil fields in the Santos passive continental margin basin,based on comprehensive utilization of geological,seismic,and core data,and reconstruction of Early Cretaceous prototype basin and lithofacies paleogeography,it is proposed for the first time that the construction of pre-salt carbonate build-ups was controlled by two types of isolated platforms:inter-depression fault-uplift and intra-depression fault-high.The inter-depression fault-uplift isolated platforms are distributed on the present-day pre-salt uplifted zones between depressions,and are built on half-and fault-horst blocks that were inherited and developed in the early intra-continental and inter-continental rift stages.The late intra-continental rift coquinas of the ITP Formation and the early inter-continental rift microbial limestones of the BVE Formation are continuously constructed;intra-depression fault-high isolated platforms are distributed in the current pre-salt depression zones,built on the uplifted zones formed by volcanic rock build-ups in the early prototype stage of intra-continental rifts,and only the BVE microbial limestones are developed.Both types of limestones formed into mound-shoal bodies,that have the characteristics of large reservoir thickness and good physical properties.Based on the dissection of large pre-salt oil fields discovered in the Santos Basin,it has been found that both types of platforms could form large-scale combined structural-stratigraphic traps,surrounded by high-quality lacustrine and lagoon source rocks at the periphery,and efficiently sealed by thick high-quality evaporite rocks above,forming the optimal combination of source,reservoir and cap in the form of“lower generation,middle storage,and upper cap”,with a high degree of oil and gas enrichment.It has been found that the large oil fields are all bottom water massive oil fields with a unified pressure system,and they are all filled to the spill-point.The future exploration is recommended to focus on the inter-depression fault-uplift isolated platforms in the western uplift zone and the southern section of eastern uplift zones,as well as intra-depression fault-high isolated platforms in the central depression zone.The result not only provides an important basis for the advanced selection of potential play fairways,bidding of new blocks,and deployment of awarded exploration blocks in the Santos Basin,but also provides a reference for the global selection of deep-water exploration blocks in passive continental margin basins.
文摘Rationale: The quality of groundwater in the Mgbede Oil Fields of South-South Nigeria has raised significant concerns due to the risk of contamination from industrial activities, especially gas flaring. Evaluating the effects of these operations on groundwater quality is essential for safeguarding the health and well-being of local communities, as well as protecting the environment. Objective: This study aimed to evaluate the quality of groundwater in the Mgbede Oil Fields, specifically examining whether the water meets international drinking water standards and identifying any contaminants present due to gas flaring. Method: Purposeful selection of water sampling points was employed to ensure the objectives of the study were met. Groundwater samples were collected from various locations within the Mgbede Oil Fields and analyzed for key quality parameters, including pH, manganese, and turbidity, among others. Results: The analysis revealed that while most groundwater samples were within acceptable international drinking water limits, there were notable exceptions. pH levels ranged from 5.17 to 6.16, manganese concentrations from 0.001 to 0.136 mg/L, and turbidity levels from 0.00 to 825 mg/L. All sampled locations exhibited traces of manganese and high acidity, indicating particulate pollution likely resulting from gas flaring activities. Conclusions: The study concluded that the groundwater quality in the Mgbede Oil Fields is negatively impacted by continuous gas flaring. Contaminants such as manganese and increased acidity levels exceed acceptable international standards, posing potential risks to environmental health. Recommendations: To mitigate these risks, it is recommended that immediate measures should be taken to reduce gas flaring and its associated particulate emissions. Regular monitoring of groundwater quality should be implemented to track improvements and ensure compliance with international standards. Additionally, introducing filtration systems or alternative water sources could help protect the health of local communities. Significance Statement: This study underscores the significant impact of industrial activities, specifically gas flaring, on groundwater quality in the Mgbede Oil Fields. The findings highlight the urgent need for regulatory measures and continuous monitoring to safeguard environmental health and ensure the availability of safe drinking water.
基金support from research grants MGA-2021-42991 and MYL-2022-43726,funded by Istanbul Technical University-Scientific Research Projects,Turkey.Thissupportis gratefully acknowledged.
文摘Fluctuations in oil prices adversely affect decision making situations in which performance forecasting must be combined with realistic price forecasts.In periods of significant price drops,companies may consider extended duration of well shut-ins(i.e.temporarily stopping oil production)for economic reasons.For example,prices during the early days of the Covid-19 pandemic forced operators to consider shutting in all or some of their active wells.In the case of partial shut-in,selection of candidate wells may evolve as a challenging decision problem considering the uncertainties involved.In this study,a mature oil field with a long(50+years)production history with 170+wells is considered.Reservoirs with similar conditions face many challenges related to economic sustainability such as frequent maintenance requirements and low production rates.We aimed to solve this decision-making problem through unsupervised machine learning.Average reservoir characteristics at well locations,well production performance statistics and well locations are used as potential features that could characterize similarities and differences among wells.While reservoir characteristics are measured at well locations for the purpose of describing the subsurface reservoir,well performance consists of volumetric rates and pressures,which are frequently measured during oil production.After a multivariate data analysis that explored correlations among parameters,clustering algorithms were used to identify groups of wells that are similar with respect to aforementioned features.Using the field’s reservoir simulation model,scenarios of shutting in different groups of wells were simulated.Forecasted reservoir performance for three years was used for economic evaluation that assumed an oil price drop to$30/bbl for 6,12 or 18 months.Results of economic analysis were analyzed to identify which group(s)of wells should have been shut-in by also considering the sensitivity to different price levels.It was observed that wells can be characterized in the 3-cluster case as low,medium and high performance wells.Analyzing the forecasting scenarios showed that shutting in all or high-and medium-performance wells altogether results in better economic outcomes.The results were most sensitive to the number of active wells and the oil price during the high-price period.This study demonstrated the effectiveness of unsupervised machine learning in well classification for operational decision making purposes.Operating companies may use this approach for improved decision making to select wells for extended shut-in during low oil-price periods.This approach would lead to cost savings especially in mature fields with low-profit margins.
文摘Consequences of decommissioning oil fields on artisanal fishing activities are still little known in the literature. This paper is intended to shed some light on a process of dismantling and sinking of oil and gas structures in shallow waters, with severe disturbing impacts on low income artisanal fishing activities. From a socio-economic perspective, the relationship of oil industry with local communities is described, with the main perceived problems pointed out in local fishermen leadership perspective. The notions of ＂damages＂ and ＂mitigation＂ used by the oil industry are discussed in connection to the expansion and dismantling of oil installations during the past 20 yrs. A comparative view of oil fields decommissioning in Europe and Brazil during the late 1990s suggests the need to review transparency and social commitment standards which have been far less prominent in this Brazilian case. The authors believe that the Brazilian oil industry has acquired a social and environmental debt towards the whole society, as far as it has been unable to establish a clear and effective process for decommissioning their oil installations within the artisanal fishing areas of the Todosos Santos Bay. Furthermore, the discussion of fair and specific compensations has been avoided, which otherwise would be instrumental to regain local economic conditions found among fishermen just few decades ago.
文摘Development strategy for heavy-oil reservoirs is one of the important research interests in China National Offshore Oil Corp. （CNOOC） that plans a highly effective development for heavy oil fields in multilayered fluvial reservoirs because of their significant influence on marine oil and even on China＇s petroleum production. The characteristics analysis of multilayered fluvial reservoirs in the heavy oil fields in Bohai Bay indicates that large amounts ofoil were trapped in the channel, point bar and channel bar sands. The reserves distribution of 8 oilfields illustrates that the reserves trapped in the main sands, which is 20%-40% of all of the sand bodies, account for 70%-90% of total reserves of the heavy oil fields. The cumulative production from high productivity wells （50% of the total wells） was 75%-90% of the production of the overall oilfield, while only 3%-10% of the total production was from the low productivity wells （30% of the total wells）. And the high productivity wells were drilled in the sands with high reserves abundance. Based on the above information the development strategy was proposed, which includes reserves production planning, selection of well configuration, productivity design, and development modification at different stages.
基金sponsored by the key consulting project of the Chinese Academy of Engineering entitled Research on the Sustainable Development Strategy of China's High Water-cut Old Oilfields(No.2019-XZ-15)the National major project entitled Large Oil and Gas Field and Coalbed Methane Development(No.:2016ZX05010006).
文摘The Class-Ⅲ oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes,an oil recovery of 39%,with remaining reserves accounting for more than 45%of the total geological reserves of the oilfield.Therefore,they have considerable potential for future oil production.The current layered injection technologies fail to achieve effective control over the low single-layer injection rates since they can only produce low throttle differential pressure under low injection rates(5-20 m^(3)/d).In this study,a symmetrically-structured double-offset-hole injection allocator and a novel throttling component were developed.Their spatial layout was constructed and mechanical parameters were optimized using finite element analysis,which allows for expanding the flow rate range at low injection rates.According to experimental results,the throttle differential pressure increased from 0.2 MPa to 0.8 MPa at an injection rate of 5 m^(3)/d,and the range of the single-layer flow rates expanded from 20-70 m^(3)/d to 5-70 m3/d.The field test results show that the effective production of oil layers with medium and low permeability was achieved and that the ratio of producing oil layer thickness to the total reservoir thickness increased by 9.7%on average.Therefore,this study provides valuable technical support for the effective chemical-flooding-based development of Class-Ⅲ oil reservoirs.
文摘This paper describes coating protection of production facilities of offshore oil fields based on the practice of development of Bohai Offshore Oil Field, with focus laid on the selection of coating systems, surface preparation, coating application, as well as coating inspection for four types of major production facilities.
基金Supported by the PetroChina Science and Technology Project(2023ZZ0202)。
文摘The formation water sample in oil and gas fields may be polluted in processes of testing, trial production, collection, storage, transportation and analysis, making the properties of formation water not be reflected truly. This paper discusses identification methods and the data credibility evaluation method for formation water in oil and gas fields of petroliferous basins within China. The results of the study show that: (1) the identification methods of formation water include the basic methods of single factors such as physical characteristics, water composition characteristics, water type characteristics, and characteristic coefficients, as well as the comprehensive evaluation method of data credibility proposed on this basis, which mainly relies on the correlation analysis sodium chloride coefficient and desulfurization coefficient and combines geological background evaluation;(2) The basic identifying methods for formation water enable the preliminary identification of hydrochemical data and the preliminary screening of data on site, the proposed comprehensive method realizes the evaluation by classifying the CaCl2-type water into types A-I to A-VI and the NaHCO3-type water into types B-I to B-IV, so that researchers can make in-depth evaluation on the credibility of hydrochemical data and analysis of influencing factors;(3) When the basic methods are used to identify the formation water, the formation water containing anions such as CO_(3)^(2-), OH- and NO_(3)^(-), or the formation water with the sodium chloride coefficient and desulphurization coefficient not matching the geological setting, are all invaded with surface water or polluted by working fluid;(4) When the comprehensive method is used, the data credibility of A-I, A-II, B-I and B-II formation water can be evaluated effectively and accurately only if the geological setting analysis in respect of the factors such as formation environment, sampling conditions, condensate water, acid fluid, leaching of ancient weathering crust, and ancient atmospheric fresh water, is combined, although such formation water is believed with high credibility.
基金Supported by the CNOOC Major Technology Project During the 14th FIVE-YEAR PLAN PERIOD(KJGG2022-0403)CNOOC Major Technology Project(KJZH-2021-0003-00).
文摘Based on the practice of oil and gas exploration in the Huizhou Sag of the Pearl River Mouth Basin,the geochemical indexes of source rocks were measured,the reservoir development morphology was restored,the rocks and minerals were characterized microscopically,the measured trap sealing indexes were compared,the biomarker compounds of crude oil were extracted,the genesis of condensate gas was identified,and the reservoir-forming conditions were examined.On this basis,the Paleogene Enping Formation in the Huizhou 26 subsag was systematically analyzed for the potential of oil and gas resources,the development characteristics of large-scale high-quality conglomerate reservoirs,the trapping effectiveness of faults,the hydrocarbon migration and accumulation model,and the formation conditions and exploration targets of large-and medium-sized glutenite-rich oil and gas fields.The research results were obtained in four aspects.First,the Paleogene Wenchang Formation in the Huizhou 26 subsag develops extensive and thick high-quality source rocks of semi-deep to deep lacustrine subfacies,which have typical hydrocarbon expulsion characteristics of"great oil generation in the early stage and huge gas expulsion in the late stage",providing a sufficient material basis for hydrocarbon accumulation in the Enping Formation.Second,under the joint control of the steep slope zone and transition zone of the fault within the sag,the large-scale near-source glutenite reservoirs are highly heterogeneous,with the development scale dominated hierarchically by three factors(favorable facies zone,particle component,and microfracture).The(subaqueous)distributary channels near the fault system,with equal grains,a low mud content(<5%),and a high content of feldspar composition,are conducive to the development of sweet spot reservoirs.Third,the strike-slip pressurization trap covered by stable lake flooding mudstone is a necessary condition for oil and gas preservation,and the NE and nearly EW faults obliquely to the principal stress have the best control on traps.Fourth,the spatiotemporal configuration of high-quality source rocks,fault transport/sealing,and glutenite reservoirs controls the degree of hydrocarbon enrichment.From top to bottom,three hydrocarbon accumulation units,i.e.low-fill zone,transition zone,and high-fill zone,are recognized.The main area of the channel in the nearly pressurized source-connecting fault zone is favorable for large-scale hydrocarbon enrichment.The research results suggest a new direction for the exploration of large-scale glutenite-rich reservoirs in the Enping Formation of the Pearl River Mouth Basin,and present a major breakthrough in oil and gas exploration.
基金We thank anonymous reviewers for detailed and constructive feedback that helped improve the manuscript.This work was supported by the Chinese“13th Five-year Plan”National Science and Technology Major Project(No.2017ZX05032004-001).
文摘The Middle Cretaceous Mishrif Formation of the Cenomanian-Turonian age is an important Middle Eastern reservoir.Previous studies have shown that carbonates in the Mishrif Formation are affected by karstification and are concentrated at the top of the formation.However,there is a lack of systematic research on the effects of karstification on the formation’s reservoir characteristics.Based on core samples,scanning electron microscopy of thin sections,and geochemical analysis of C,O,and Sr isotopes from wells in the Missan Oil Fields,unconformity was identified at the top of the B21 subzone of the Mishrif Formation.Core and cast-thin-section observations indicate that there is a significant lithological difference above and below the unconformity,and dissolution pores and voids are well-developed beneath it.Vadose silt fills the intragranular pores and geopetal fabric is developed inside some mouldic pores beneath the unconformity surface.The isotopic values of ^(87)Sr/^(86)Sr(0.707270-0.707722)and δ^(18)O(−5.94‰—−2.32‰)suggest that the top of the B21 subzone of the Mishrif Formation has been severely affected by syngenetic karst.Karstification is the key to high-quality reservoir formation and the reservoir’s oil-bearing heterogeneity.This study will inform oil and gas exploration in the Missan Oil Fields and in other areas with similar reservoir characteristics.
文摘The main objective of this paper is to construct a static model that compress the uncertainties of the stochastic distribution of the reservoir properties of the Bahariya Formation in Heba field,at the northeastern portion of the Western Desert.This model has been constructed through the integration of the interpretations of the eighteen 2D seismic sections and the analysis of well logs data for four wells(HEBA 300X,E.BAH-E-1X,E.BAH-D-1X,and HEBA 10X)drilled in the study area.This set of data was implemented in a harmonic workflow.Structural framework was the first step created on the basis of the seismic and well log interpretations.Model zonation was mainly managed by the marine flooding events took place during the Cenomanian period.The trapping faults position uncertainty has been compressed through the tying of the seismic profiles with the identified fault cuts in the well data.Effective porosity spectrum was broke up into three reservoir qualities.The results showed heterogeneous facies qualities for oil production in specific five zones in the topmost part of the Bahariya Formation.The effective porosity model was generated stochastically considering the normal distribution for each reservoir quality.Water saturation was distributed by two methods;1)Sequential Gaussian Simulation that was co-simulated by porosity model.2)Log-based saturation height function for each reservoir quality.This methodology provided as accurate as possible estimates for the volume calculation by quantifying the sensitivity of the important parameters such as oil contact.Additionally,the model was prepared to be used as a front end for dynamic simulation.
基金financially supported by the National Natural Science Foundation of China Key Program (No.50231020)the National Key Basic Research and Development Plan Program (No. G1999065004)
文摘The effect of HCO3^- concentration on CO2 corrosion was investigated by polarization measurement of potentiodynamic scans and weight-loss method, Under the conditions of high pressure and high temperature, the corrosion rate of steel X65 decreased with the increase of HCO3^- concentration, while pH of solution increased. SEM, EDS, and XRD results of the corrosion scales indir cated that the typical FeCO3 crystallite was found at low HCO3^- concentration but Ca（Fe,Mg）（CO3）2 was found at high HCO3^- con- centration. Ca^2＋ and Mg^2＋ are precipitated preferential to Fe^2＋ at high pH value. Potentiodynamic polarization curves showed that the cathodic current density decreases with the increase of HCO3^- concentration at low HCO3^- concentration. When the HCO3^- concentration reaches 0.126 mol/L, increasing HCO3^- concentration promotes cathodic reactions. Anodic behavior is an active process at low HCO3^- concentration and the anodic current density decreases with the increase of HCO3^- concentration. An evident active-passive behavior is exhibited in anodic process at 0.126 mol/L HCO3^-.
基金sponsored by the National Key Basic Research Program of China (973 Program, 2012CB214806)the National Natural Science Foundation of China (No. 41372144)
文摘There are rich oil and gas resources in marine carbonate strata worldwide.Although most of the oil and gas reserves discovered so far are mainly distributed in Mesozoic,Cenozoic,and upper Paleozoic strata,oil and gas exploration in the Proterozoic–Lower Paleozoic（PLP）strata—the oldest marine strata—has been very limited.To more clearly understand the oil and gas formation conditions and distributions in the PLP marine carbonate strata,we analyzed and characterized the petroleum geological conditions,oil and gas reservoir types,and their distributions in thirteen giant oil and gas fields worldwide.This study reveals the main factors controlling their formation and distribution.Our analyses show that the source rocks for these giant oil and gas fields are mainly shale with a great abundance of type I–II organic matter and a high thermal evolution extent.The reservoirs are mainly gas reservoirs,and the reservoir rocks are dominated by dolomite.The reservoir types are mainly karst and reef–shoal bodies with well-developed dissolved pores and cavities,intercrystalline pores,and fractures.These reservoirs arehighly heterogeneous.The burial depth of the reservoirs is highly variable and somewhat negatively correlated to the porosity.The cap rocks are mainly thick evaporites and shales,with the thickness of the cap rocks positively correlated to the oil and gas reserves.The development of high-quality evaporite cap rock is highly favorable for oil and gas preservation.We identified four hydrocarbon generation models,and that the major source rocks have undergone a long period of burial and thermal evolution and are characterized by early and long periods of hydrocarbon generation.These giant oil and gas fields have diverse types of reservoirs and are mainly distributed in paleo-uplifts,slope zones,and platform margin reef-shoal bodies.The main factors that control their formation and distribution were identified,enabling the prediction of new favorable areas for oil and gas exploration.
文摘Complicated oil and gas fields occupy an important position in oil and gas exploration. In this paper, complicated oil and gas fields are grouped into four types: fault-block, lithologic, stratigraphic and fissure types. On the basis of the new theory of petroleum geological exploration in composite oil and gas accumulation areas within continental basins, a new exploration sequence suitable for complicated oil and gas fields has been established, which comprises four stages:(1) initial exploration;(2) preliminary exploration;(3) early step-by-step exploration and development: and(4) late step-by-step exploration and development. The idea of cybernetics has been taken to control various links of a systematic exploration project so as to fully, effectively and comprehensively utilize the new exploration techniques, eventually realizing the optimization of exploration with the aim of raising the efficiency of exploration of complicated oil and gas fields.
基金Project supported by the Scientific Research&Technical Development Project of PetroChina Company Limited“Research and application of key technologies for geology and gas reservoir engineering of underground gas storage”(No.2015E-400201).
文摘Whole-life-cycle integrity management of underground gas storages(UGSs)has been an important link to ensure its long-term safe and efficient operation.At present,the integrity of UGSs in oil/gasfields and its evaluation techniques focus on surface facilities and injection/withdrawal wells,but its geological integrity lacks clear definition and evaluation object and systematic evaluation techniques.In this paper,relevant research achievements werefirstly summarized.Then,the concept of geological integrity with the gas-storage geological body as the evaluation object was put forward,and the evaluation system for the geological integrity of such UGSs was established.Finally,UGS geological integrity evaluation was carried out with the Hutubi Underground Gas Storage in Xinjiang as an example.And the following research results were obtained.First,UGS geological integrity is defined as the integrity degree of each component of a gas-storage geological body to meet operation requirements and fulfill seasonal and emergency peak shaving safely and economically during the operation of a UGS.Its connotation is that reservoir of geological body,caprock,fault and trap can supply the customers with gas continuously and stably and ensure the safe operation of the UGS in its service life.And its core lies in keeping the reliability,safety and economy of natural gas storage in the service life of a UGS.Second,the geological integrity evaluation system is composed of four evaluation techniques,including trap effectiveness,caprock integrity,fault stability and reservoir stability.Third,the evaluation results show that the Hutubi Underground Gas Storage has the potential of peak-shaving capacity enhancement by increasing the maximum operation pressure.In conclusion,the establishment of the geological integrity evaluation system for such UGSs improves the UGS integrity evaluation technique system and plays an instructive and practical role in ensuring the long-term safe and efficient operation of UGSs,increasing the maximum operation pressure and improving the peak shaving capacity.
