In this paper, we propose a hybrid PML （H-PML） combining the normal absorption factor of convolutional PML （C-PML） with tangential absorption factor of Mutiaxial PML （M-PML）. The H-PML boundary conditions can be...In this paper, we propose a hybrid PML （H-PML） combining the normal absorption factor of convolutional PML （C-PML） with tangential absorption factor of Mutiaxial PML （M-PML）. The H-PML boundary conditions can better suppress the numerical instability in some extreme models, and the computational speed of finite-element method and the dynamic range are greatly increased using this HPML. We use the finite-element method with a hybrid PML to model the acoustic reflection of the interface when wireline and well logging while drilling （LWD）, in a formation with a reflector outside the borehole. The simulation results suggests that the PS- and SP- reflected waves arrive at the same time when the inclination between the well and the outer interface is zero, and the difference in arrival times increases with increasing dip angle. When there are fractures outside the well, the reflection signal is clearer in the subsequent reflection waves and may be used to identify the fractured zone. The difference between the dominant wavelength and the model scale shows that LWD reflection logging data are of higher resolution and quality than wireline acoustic reflection logging.展开更多
The vector finite element method of tetrahedral elements is used to model 3D electromagnetic wave logging response. The tangential component of the vector field at the mesh edges is used as a degree of freedom to over...The vector finite element method of tetrahedral elements is used to model 3D electromagnetic wave logging response. The tangential component of the vector field at the mesh edges is used as a degree of freedom to overcome the shortcomings of node-based finite element methods. The algorithm can simulate inhomogeneous media with arbitrary distribution of conductivity and magnetic permeability. The electromagnetic response of well logging tools are studied in dipping bed layers with the borehole and invasion included. In order to simulate realistic logging tools, we take the transmitter antennas consisting of circular wire loops instead of magnetic dipoles. We also investigate the apparent resistivity of inhomogeneous formation for different dip angles.展开更多
The Hutubi （呼图壁） River reservoir of well block DX12 is a lithologic hydrocarbon reservoir that is under tectonic settings. The main oil-bearing sand body in this area is thin and has a poor transverse connectivit...The Hutubi （呼图壁） River reservoir of well block DX12 is a lithologic hydrocarbon reservoir that is under tectonic settings. The main oil-bearing sand body in this area is thin and has a poor transverse connectivity. Because of the complexity of the oil-water relationship, the oil reservoir presents a low resistivity feature, which brings great difficulties to hydrocarbon reservoir identification. This article develops an effective method of well log interpretation that can meet the requirement of low resistivity reservoir well logging evaluation. The authors combine the oil reservoir geology feature, the oil well logging curve characteristics and chemical analytical data to analyze the reasons for low resistivity, then establish the appropriate reservoir parameter explanation model, which uses different saturation computational methods according to different generations. When the clay content is more than 5%, we select W-S dual water model; when the shale content is more than 13%, we use the Schlumberger formula; when the shale content is less then 13%, we use Archie＇s formula. The well logging evaluation method of low resistivity reservoir has been improved by the irreducible water saturation formula which is established by the permeability, the porosity, the coefficient of pore structure and the shale content, hydrocarbon reservoir recognition charts, and the non-resistivity logging methods （repeat formation test （RFT）; modular dynamic test （MDT）, etc.）. The coincidence rate for this arrangement of the well logging integrated interpretation is 82.6% in the well block DX12. It is a powerful direction for low resistivity well log interpretation.展开更多
Based on the well logging knowledge graph of hydrocarbon-bearing formation(HBF),a Knowledge-Powered Neural Network Formation Evaluation model(KPNFE)has been proposed.It has the following functions:(1)extracting charac...Based on the well logging knowledge graph of hydrocarbon-bearing formation(HBF),a Knowledge-Powered Neural Network Formation Evaluation model(KPNFE)has been proposed.It has the following functions:(1)extracting characteristic parameters describing HBF in multiple dimensions and multiple scales;(2)showing the characteristic parameter-related entities,relationships,and attributes as vectors via graph embedding technique;(3)intelligently identifying HBF;(4)seamlessly integrating expertise into the intelligent computing to establish the assessment system and ranking algorithm for potential pay recommendation.Taking 547 wells encountered the low porosity and low permeability Chang 6 Member of Triassic in the Jiyuan Block of Ordos Basin,NW China as objects,80%of the wells were randomly selected as the training dataset and the remainder as the validation dataset.The KPNFE prediction results on the validation dataset had a coincidence rate of 94.43%with the expert interpretation results and a coincidence rate of 84.38%for all the oil testing layers,which is 13 percentage points higher in accuracy and over 100 times faster than the primary conventional interpretation.In addition,a number of potential pays likely to produce industrial oil were recommended.The KPNFE model effectively inherits,carries forward and improves the expert knowledge,nicely solving the robustness problem in HBF identification.The KPNFE,with good interpretability and high accuracy of computation results,is a powerful technical means for efficient and high-quality well logging re-evaluation of old wells in mature oilfields.展开更多
Total organic carbon(TOC)content is one of the most important parameters for characterizing the quality of source rocks and assessing the hydrocarbon-generating potential of shales.The Lucaogou Formation shale reservo...Total organic carbon(TOC)content is one of the most important parameters for characterizing the quality of source rocks and assessing the hydrocarbon-generating potential of shales.The Lucaogou Formation shale reservoirs in the Jimusaer Sag,Junggar Basin,NW China,is characterized by extremely complex lithology and a wide variety of mineral compositions with source rocks mainly consisting of carbonaceous mudstone and dolomitic mudstone.The logging responses of organic matter in the shale reservoirs is quite different from those in conventional reservoirs.Analyses show that the traditional△logR method is not suitable for evaluating the TOC content in the study area.Analysis of the sensitivity characteristics of TOC content to well logs reveals that the TOC content has good correlation with the separation degree of porosity logs.After a dimension reduction processing by the principal component analysis technology,the principal components are determined through correlation analysis of porosity logs.The results show that the TOC values obtained by the new method are in good agreement with that measured by core analysis.The average absolute error of the new method is only 0.555,much less when compared with 1.222 of using traditional△logR method.The proposed method can be used to produce more accurate TOC estimates,thus providing a reliable basis for source rock mapping.展开更多
In the Sichuan Basin,carbonate reservoirs are characterized by deep burial depth and strong heterogeneity,so it is difficult to conduct structure steering,pore space reservoir tracking and trajectory control in the pr...In the Sichuan Basin,carbonate reservoirs are characterized by deep burial depth and strong heterogeneity,so it is difficult to conduct structure steering,pore space reservoir tracking and trajectory control in the process of geosteering logging while drilling.In this paper,a series of corresponding techniques for structure,reservoir and formation tracking were proposed after analysis was conducted on multiple series of carbonate strata in terms of their geologic and logging response characteristics.And investigation was performed on the adaptabilities of the following logging technologies to geosteering while drilling,including gamma ray imaging while drilling,resistivity imaging while drilling,density imaging while drilling,gamma ray logging while drilling,resistivity logging while drilling,neutron logging while drilling and density logging while drilling.After while drilling information was thoroughly analyzed,the logging suites for four common types of complicated reservoirs(thin layered reservoirs,thick massive reservoirs,denuded karst reservoirs and shale gas reservoirs)were optimized,and five logging combinations suitable for different formations and reservoirs were proposed,including gamma ray logging t porosity t resistivity imaging,gamma ray logging t resistivity imaging,gamma ray logging t porosity t resistivity logging,gamma ray imaging t resistivity logging,and gamma ray logging.Field application indicates that it is of great reference and application value to use this method for the first time to summarize logging while drilling combinations for different types of carbonate reservoirs.展开更多
Carbonate gas reservoir in the eastern area on the Right Bank of the Amu Darya River,Turkmenistan,are of low-porosity and with developed fractures.In this area,fractures control reservoir properties and natural gas pr...Carbonate gas reservoir in the eastern area on the Right Bank of the Amu Darya River,Turkmenistan,are of low-porosity and with developed fractures.In this area,fractures control reservoir properties and natural gas production,and karst fractures are the most important kind of fractures,so their identification and evaluation are quite necessary.In this paper,fracture types were identified and their occurrence was extracted by using conventional logging and image logging data after core calibration.Then,the distribution characteristics of karst fractures and their controlling effect on reservoirs were studied according to the identification results.And the following research results were obtained.First,karst fractures are mainly of high angle with the characteristic of mono system and the interactive relation of genesis.Second,they are mainly distributed in the upper XVhp layer of CallovianeOxford Stage and the lower XVa2eXVI layer.Third,they are the main effective fractures in this area.The dissolved pores are connected effectively through the expanded karst fractures by dissolution,and consequently reservoirs of high porosity and permeability are formed and they are the important reservoir type and high-yield gas reservoir in this area.Fourth,karst fractures are related to high-yield wells and high-yield layers in this area,and they also control the distribution of high-yield reservoirs in the lower part of CallovianeOxford Stage.It is concluded that by virtue of imaging logging and conventional logging data,karst fractures,unfilled fractures,semi-filled fractures and fullyfilled fractures can be identified and evaluated better.Furthermore,the identification and evaluation of karst fractures deepen the understanding on fractured reservoirs in this area,improve the reservoir evaluation effect,and provide the basis for the target horizon and azimuth optimization of horizontal wells and highly deviated wells.And it is also indicated that the reservoirs with developed karst fractures are the subsequent important drilling targets.展开更多
The geological and geophysical characteristics of the basement oil and gas reservoir in block Y are very complex, and the lithology is metamorphic rock. Matrix porosity is very small and dense, but fractures are devel...The geological and geophysical characteristics of the basement oil and gas reservoir in block Y are very complex, and the lithology is metamorphic rock. Matrix porosity is very small and dense, but fractures are developed, which is a good reservoir space.In this paper, imaging logging combined with conventional logging curve, especially resistivity logging curve, is the main means to identify fractures. Meanwhile, the base oil and gas in block Y is condensate oil and gas and there is no water.Conventional logging has no obvious identification of fluid properties in this block, and PLT logging has obvious identification effect on fluid properties in this block. It can be combined with imaging logging to identify basement reservoir fluid.展开更多
In the process of directional well drilling, the key to construction is to use various data to mark the horizon, control the trajectory to enter the target accurately, and control the construction risk well. Kuwait...In the process of directional well drilling, the key to construction is to use various data to mark the horizon, control the trajectory to enter the target accurately, and control the construction risk well. Kuwait's Burgan Oilfield is a typical high temperature, high pressure and high sulfur-bearing oil and gas field, which is difficult to construct. In the development of directional wells in Burgan Oilfield, comprehensive logging technology can be used to successfully compensate for the decrease in resolution of logging and LWD equipment in oil-based mud. We have successfully achieved accurate reservoir sticking, fine interpretation of oil and gas reservoirs, target prediction and trajectory control. At the same time, the formation pressure monitoring while drilling technology has played a very important role in reducing the risk of well control during drilling. The application of comprehensive logging technology has greatly reduced the drilling construction risks and is also an important basis for later oil production and well location deployment.展开更多
China's shale oil and gas resources are widely distributed in shale-sandstone interbedded reservoirs,whose complex lithology and strong heterogeneity pose significant challenges to hydraulic fracturing design.To a...China's shale oil and gas resources are widely distributed in shale-sandstone interbedded reservoirs,whose complex lithology and strong heterogeneity pose significant challenges to hydraulic fracturing design.To address issues such as the difficulty in controlling fracture height and the challenge of forming an effective fracture network,this study utilizes synthetic rock samples that can represent the characteristics of interbedded reservoirs and investigates the initiation and propagation of hydraulic fractures under different viscosity,injection rate,and construction scheme.By combining real-time monitoring of injection pressure with acoustic emission,the temporal and spatial evolution characteristics of hydraulic fractures as well as the mechanisms of their vertical and horizontal extension are revealed.The results indicate that a higher fracturing fluid viscosity is essential for ensuring the vertical cross-layer propagation of hydraulic fractures,while a lower fluid viscosity facilitates the activation of weak interlayer surfaces,promoting sufficient horizontal propagation along these planes and forming branched fractures.Although a higher injection rate enhances the vertical cross-layer propagation of hydraulic fractures,it also causes greater diversion of the main fracture plane,resulting in simpler fracture morphology and limiting the stimulation effect.Additionally,an alternating injection of high and low viscosity fracturing fluids allows hydraulic fractures to both break through weak interlayer surfaces and achieve uniform horizontal propagation,resulting in a more complex fracture morphology.The findings are expected to provide a scientific basis and practical guidance for optimizing hydraulic fracturing designs in interbedded reservoir conditions.展开更多
Pore structure characteristics are important to oil and gas exploration in complex low-permeability reservoirs. Using multifractal theory and nuclear magnetic resonance （NMR）, we studied the pore structure of low-pe...Pore structure characteristics are important to oil and gas exploration in complex low-permeability reservoirs. Using multifractal theory and nuclear magnetic resonance （NMR）, we studied the pore structure of low-permeability sandstone rocks from the 4th Member （Es4） of the Shahejie Formation in the south slope of the Dongying Sag. We used the existing pore structure data from petrophysics, core slices, and mercury injection tests to classify the pore structure into three categories and five subcategories. Then, the T2 spectra of samples with different pore structures were interpolated, and the one- and three-dimensional fractal dimensions and the multifractal spectrum were obtained. Parameters a （intensity of singularity） andf（a） （density of distribution） were extracted from the multifractal spectra. The differences in the three fractal dimensions suggest that the pore structure types correlate with a andf（a）. The results calculated based on the multifractal spectrum is consistent with that of the core slices and mercury injection. Finally, the proposed method was applied to an actual logging profile to evaluate the pore structure of low-permeability sandstone reservoirs.展开更多
LWD（logging while drilling） data has been used to explore complex subtle reservoirs by realtime visual interpretation and geo-steering.The method comprises of computer communication,well log data processing,formatio...LWD（logging while drilling） data has been used to explore complex subtle reservoirs by realtime visual interpretation and geo-steering.The method comprises of computer communication,well log data processing,formation recognition,reservoir modeling and model updating in real time.We studied the key technologies related to real-time LWD data visual interpretation and geo-steering and developed computer software with Chinese intellectual property rights covering the following important aspects： 1） real-time computer communication of well site LWD data;2） visualization of geological model and borehole information;3） real-time interpretation of LWD data;4） real-time geological model updating and geo-steering technology.We use field application examples to demonstrate the feasibility and validity of the proposed technologies.展开更多
Clay has a significant influence on the relationship between resistivity index I and water saturation Sw （i.e, I-Sw relationship） of reservoir rocks because it complicates the current paths of these rocks. It is dif...Clay has a significant influence on the relationship between resistivity index I and water saturation Sw （i.e, I-Sw relationship） of reservoir rocks because it complicates the current paths of these rocks. It is difficult to reveal the physical mechanisms of these clay effects on the conductivities of various rocks by physical laboratory measurements because the pore structure, micro distribution and content of clay inside a rock can not be observed and controlled during the experiments. We present a digital rock approach to study these clay effects on the electrical transport properties of reservoir rocks at pore scale using lattice gas automation （LGA） method. The digital rock samples are constructed with the information of grain size distribution from SEM images of reservoir rocks. The LGA is then applied on these digital rocks fully saturated with fluids to simulate the electrical transport properties for revealing the effects of volume and distribution patterns of clay on the non-Archie behaviors of the I-Sw relationship. The very good agreement between the simulated results and the laboratory measurements clearly demonstrates the validity of the LGA in numerical research of rock physics. Based on these studies, a new model has been developed for quantitatively describing the relationship between the saturation exponent and the volume of clay （Vsh）. This development may improve the evaluation for the fluid saturations in reservoir rocks.展开更多
Matrix porosity calculations of fractured and vuggy reservoirs, such as volcanics and weathered dolomite, are one of the problems urgently needed to solve in well-log evaluation. In this paper, we first compare the an...Matrix porosity calculations of fractured and vuggy reservoirs, such as volcanics and weathered dolomite, are one of the problems urgently needed to solve in well-log evaluation. In this paper, we first compare the an empirical formula for porosity calculation from full diameter rhyolite core experiments with the matrix porosity formulas commonly used. We discuss the applicability of the empirical formula in fractured and vuggy reservoirs, such as intermediate-basic volcanics and weathered dolomite. Based on core analysis data, the error distribution of the calculated porosity of our empirical formula and the other porosity formulas in these reservoirs are given. The statistical error analysis indicates that the our empirical formula provides a higher precision than the other porosity formulas. When the porosity is between 1.5% and 15%, the acoustic experiment formula can be used not only for acidic volcanics but also in other fractured and vuggy reservoirs, such as intermediate-basic volcanics and weathered dolomite. Moreover, the formula can reduce the effects of borehole enlargement and rock alteration on porosity computation.展开更多
Nearly half of coal mine disasters in China have been found to occur in clusters or to be accompanied by earthquakes nearby,in which all the disaster types are involved.Stress disturbances seem to exist among mining a...Nearly half of coal mine disasters in China have been found to occur in clusters or to be accompanied by earthquakes nearby,in which all the disaster types are involved.Stress disturbances seem to exist among mining areas and to be responsible for the observed clustering.The earthquakes accompanied by coal mine disasters may be the vital geophysical evidence for tectonic stress disturbances around mining areas.This paper analyzes all the possible causative factors to demonstrate the authenticity and reliability of the observed phenomena.A quantitative study was performed on the degree of clustering,and space-time distribution curves are obtained.Under the threshold of 100 km,47%of disasters are involved in cluster series and 372 coal mine disasters accompanied by earthquakes.The majority cluster series lasting for 1-2 days correspond well earthquakes nearby,which are speculated to be related to local stress disturbance.While the minority lasting longer than 4 days correspond well with fatal earthquakes,which are speculated to be related to regional stress disturbance.The cluster series possess multiple properties,such as the area,the distance,the related disasters,etc.,and compared with the energy and the magnitude of earthquakes,good correspondences are acquired.It indicates that the cluster series of coal mine disasters and earthquakes are linked with fatal earthquakes and may serve as footprints of regional stress disturbance.Speculations relating to the geological model are made,and five disaster-causing models are examined.To earthquake research and disaster prevention,widely scientific significance is suggested.展开更多
Digital core models reconstructed using X-ray tomography(X-CT)enable the quantitative characterization of the pore structure in three dimensions(3D)and the numerical simulation of petrophysics.When the X-CT images acc...Digital core models reconstructed using X-ray tomography(X-CT)enable the quantitative characterization of the pore structure in three dimensions(3D)and the numerical simulation of petrophysics.When the X-CT images accurately reflect the micro structures of core samples,the greyscale threshold in the image segmentation determines the accuracy of digital cores and the simulated petrophysical properties.Therefore,it is vital to investigate the comparison parameter for determining the key greyscale threshold and the criterion to describe the accuracy of the segmentation.Representative coquina digital core models from X-CT are used in this work to study the impact of grayscale threshold on the porosity,pore percolation,connectivity and electrical resistivity of the pore scale model and these simulations are calculated by Minkowski functions,component labeling and fi nite element method,respectively,to quantify the pore structure and simulate electrical resistivity.Results showed that the simulated physical properties of the digital cores,varied with the gradual increase of the greyscale threshold.Among the four parameters related to the threshold,the porosity was most sensitive and chose as the comparison parameter to judge the accuracy of the greyscale threshold.The variations of the threshold change the micro pore structures,and then the electrical resistivity.When the porosity of the digital core model is close to the experimental porosity,the simulated porosity exponent matches the experimental porosity exponents well.The good agreement proved that the porosity is the critical comparison parameter to describe the accuracy of image segmentation.The criterion is that the porosity of the digital core after segmentation should be close to the experimental porosity.展开更多
The electrophysical property of saturated rocks is very important for reservoir identification and evaluation. In this paper, the lattice Boltzmann method （LBM） was used to study the electrophysical property of rock...The electrophysical property of saturated rocks is very important for reservoir identification and evaluation. In this paper, the lattice Boltzmann method （LBM） was used to study the electrophysical property of rock saturated with fluid because of its advantages over conventional numerical approaches in handling complex pore geometry and boundary conditions. The digital core model was constructed through the accumulation of matrix grains based on their radius distribution obtained by the measurements of core samples. The flow of electrical current through the core model saturated with oil and water was simulated on the mesoscopic scale to reveal the non-Archie relationship between resistivity index and water saturation （I-Sw）. The results from LBM simulation and laboratory measurements demonstrated that the I-Sw relation in the range of low water saturation was generally not a straight line in the log-log coordinates as described by the Archie equation. We thus developed a new equation based on numerical simulation and physical experiments. This new equation was used to fit the data from laboratory core measurements and previously published data. Determination of fluid saturation and reservoir evaluation could be significantly improved by using the new equation.展开更多
To understand the electrical structure of the Sulu（苏鲁） terrane,we analyzed the resis-tivity logs of the Chinese Continental Scientific Drilling main hole（CCSD-MH） and obtained the statis-tical characteristics of...To understand the electrical structure of the Sulu（苏鲁） terrane,we analyzed the resis-tivity logs of the Chinese Continental Scientific Drilling main hole（CCSD-MH） and obtained the statis-tical characteristics of the resistivity log of ultrahigh-pressure（UHP） metamorphic rocks.To check the logs＇ quality,we compared the resistivity log data with the core test data.The two datasets show a good coherence.On the whole,the resistivity of the UHP metamorphic rocks from the CCSD-MH is very high（mostly higher than 1 000 ？？m）.From orthogneiss to paragneiss,amphibolite,retrograded eclogite,rutile eclogite,phengite eclogite,and ultramafic rock,the resistivity decreases gradually.The fracture zone,enrichment of metal minerals,and serpentinization of peridotite can probably cause the decrease of resistivity.Comparing the electrical structure of the crust of Dabie（大别） terrane and Sulu terrane,we can conclude that（1） the electrical structure of the crust of Dabie terrane and Sulu terrane shows a very big difference,（2） the high-resistivity zone of the north Sulu orogen extended to a very great depth（60 km）,but the high-resistivity zone of Dabie orogen is over the depth of 25 km.展开更多
A perforating hole is a channel through which the oil and gas in a reservoir pass into the production well bore.During the process of perforating due to explosion,the surrounding sandstone will be damaged to a certain...A perforating hole is a channel through which the oil and gas in a reservoir pass into the production well bore.During the process of perforating due to explosion,the surrounding sandstone will be damaged to a certain extent,which will increase the well bore skin and lead to the decrease of production consequently.In this work a mechanical model of perforating damage is developed to describe the influences of perforating due to explosion on the porosity and permeability of the surrounding sandstone near the compaction zone.Based on this developed model,the important data related to the damage of sandstone,such as matrix effective stress,plastic deformation,volumetric strain,and so on,can be numerically simulated.Especially the behaviors of plasticity kinematic hardening at high strain rate due to impact loads,which are the important characteristics in the sandstone,is taken into account in this developed model.Both numerical and testing results show that the damage due to perforation in the sandstone can be accurately predicted by the developed model together with the porosity and permeability evolving model of perforation in a compaction zone.As a practical application,a methodology for the analysis of damage of porosity and permeability around a perforation tunnel is supposed based on the developed model and the core flow efficiency test of interparticle pore spaced sandstone target in China Shengli Oilfield and the computed tomography test.展开更多
Organic reef reservoirs in the platform margin of Kaijiang-Liangping trough in Damaoping area, Sichuan Basin are thin in single layer, fast in lateral variation, and have small P-impedance difference from the surround...Organic reef reservoirs in the platform margin of Kaijiang-Liangping trough in Damaoping area, Sichuan Basin are thin in single layer, fast in lateral variation, and have small P-impedance difference from the surrounding rock, it is difficult to identify and predict the reservoirs and fluid properties by conventional post-stack inversion. Through correlation analysis of core test data and logging P-S wave velocity, this work proposed a formula to calculate the shear wave velocity in different porosity ranges, and solved the issue that some wells in the study area have no S-wave data. AVO forward analysis reveals that formation porosity is the main factor affecting the variation of AVO type, the change of water saturation cannot affect the AVO type, but it has an effect on the change range of AVO. Through cross-plotting analysis of elastic parameters, it is found that fluid factor is a parameter sensitive to gas-bearing property of organic reef reservoir in the study area. By comparing results of post-stack impedance inversion, post-stack high frequency attenuation property, pre-stack simultaneous inversion and AVO anomaly analysis of angle gathers, it is found that the gas-bearing prediction of organic reef reservoirs by using fluid factor derived from simultaneous pre-stack inversion had the highest coincidence rate with actual drilling data. At last, according to the characteristics of fluid factor distribution, the favorable gas-bearing area of the organic reef reservoir in Changxing Formation was predicted, and the organic reef trap at the top of Changxing Formation in Block A of Damaoping area was sorted out as the next exploration target.展开更多
基金supported by the National Natural Science Foundation of China(No.41204094)Science Foundation of China University of Petroleum,Beijing(No.2462015YQ0506)
文摘In this paper, we propose a hybrid PML （H-PML） combining the normal absorption factor of convolutional PML （C-PML） with tangential absorption factor of Mutiaxial PML （M-PML）. The H-PML boundary conditions can better suppress the numerical instability in some extreme models, and the computational speed of finite-element method and the dynamic range are greatly increased using this HPML. We use the finite-element method with a hybrid PML to model the acoustic reflection of the interface when wireline and well logging while drilling （LWD）, in a formation with a reflector outside the borehole. The simulation results suggests that the PS- and SP- reflected waves arrive at the same time when the inclination between the well and the outer interface is zero, and the difference in arrival times increases with increasing dip angle. When there are fractures outside the well, the reflection signal is clearer in the subsequent reflection waves and may be used to identify the fractured zone. The difference between the dominant wavelength and the model scale shows that LWD reflection logging data are of higher resolution and quality than wireline acoustic reflection logging.
文摘The vector finite element method of tetrahedral elements is used to model 3D electromagnetic wave logging response. The tangential component of the vector field at the mesh edges is used as a degree of freedom to overcome the shortcomings of node-based finite element methods. The algorithm can simulate inhomogeneous media with arbitrary distribution of conductivity and magnetic permeability. The electromagnetic response of well logging tools are studied in dipping bed layers with the borehole and invasion included. In order to simulate realistic logging tools, we take the transmitter antennas consisting of circular wire loops instead of magnetic dipoles. We also investigate the apparent resistivity of inhomogeneous formation for different dip angles.
基金supported by the PetroChina Xinjiang Oilfield Exploration & Production Research Institute
文摘The Hutubi （呼图壁） River reservoir of well block DX12 is a lithologic hydrocarbon reservoir that is under tectonic settings. The main oil-bearing sand body in this area is thin and has a poor transverse connectivity. Because of the complexity of the oil-water relationship, the oil reservoir presents a low resistivity feature, which brings great difficulties to hydrocarbon reservoir identification. This article develops an effective method of well log interpretation that can meet the requirement of low resistivity reservoir well logging evaluation. The authors combine the oil reservoir geology feature, the oil well logging curve characteristics and chemical analytical data to analyze the reasons for low resistivity, then establish the appropriate reservoir parameter explanation model, which uses different saturation computational methods according to different generations. When the clay content is more than 5%, we select W-S dual water model; when the shale content is more than 13%, we use the Schlumberger formula; when the shale content is less then 13%, we use Archie＇s formula. The well logging evaluation method of low resistivity reservoir has been improved by the irreducible water saturation formula which is established by the permeability, the porosity, the coefficient of pore structure and the shale content, hydrocarbon reservoir recognition charts, and the non-resistivity logging methods （repeat formation test （RFT）; modular dynamic test （MDT）, etc.）. The coincidence rate for this arrangement of the well logging integrated interpretation is 82.6% in the well block DX12. It is a powerful direction for low resistivity well log interpretation.
基金Supported by the National Science and Technology Major Project(2016ZX05007-004)。
文摘Based on the well logging knowledge graph of hydrocarbon-bearing formation(HBF),a Knowledge-Powered Neural Network Formation Evaluation model(KPNFE)has been proposed.It has the following functions:(1)extracting characteristic parameters describing HBF in multiple dimensions and multiple scales;(2)showing the characteristic parameter-related entities,relationships,and attributes as vectors via graph embedding technique;(3)intelligently identifying HBF;(4)seamlessly integrating expertise into the intelligent computing to establish the assessment system and ranking algorithm for potential pay recommendation.Taking 547 wells encountered the low porosity and low permeability Chang 6 Member of Triassic in the Jiyuan Block of Ordos Basin,NW China as objects,80%of the wells were randomly selected as the training dataset and the remainder as the validation dataset.The KPNFE prediction results on the validation dataset had a coincidence rate of 94.43%with the expert interpretation results and a coincidence rate of 84.38%for all the oil testing layers,which is 13 percentage points higher in accuracy and over 100 times faster than the primary conventional interpretation.In addition,a number of potential pays likely to produce industrial oil were recommended.The KPNFE model effectively inherits,carries forward and improves the expert knowledge,nicely solving the robustness problem in HBF identification.The KPNFE,with good interpretability and high accuracy of computation results,is a powerful technical means for efficient and high-quality well logging re-evaluation of old wells in mature oilfields.
基金This research was funded by the National Natural Science Foundation of China(Grant No.41504103).
文摘Total organic carbon(TOC)content is one of the most important parameters for characterizing the quality of source rocks and assessing the hydrocarbon-generating potential of shales.The Lucaogou Formation shale reservoirs in the Jimusaer Sag,Junggar Basin,NW China,is characterized by extremely complex lithology and a wide variety of mineral compositions with source rocks mainly consisting of carbonaceous mudstone and dolomitic mudstone.The logging responses of organic matter in the shale reservoirs is quite different from those in conventional reservoirs.Analyses show that the traditional△logR method is not suitable for evaluating the TOC content in the study area.Analysis of the sensitivity characteristics of TOC content to well logs reveals that the TOC content has good correlation with the separation degree of porosity logs.After a dimension reduction processing by the principal component analysis technology,the principal components are determined through correlation analysis of porosity logs.The results show that the TOC values obtained by the new method are in good agreement with that measured by core analysis.The average absolute error of the new method is only 0.555,much less when compared with 1.222 of using traditional△logR method.The proposed method can be used to produce more accurate TOC estimates,thus providing a reliable basis for source rock mapping.
基金Supported by“Well logging-based shale gas evaluation”,a sub-project of National Science and Technology Major Project(No.2011ZX05018-003)“Interpretation and supporting system development for electromagnetic wave imaging and well logging while drilling”,a China National Petroleum Corporation Science and Technology Major Project(No.2013E-3809).
文摘In the Sichuan Basin,carbonate reservoirs are characterized by deep burial depth and strong heterogeneity,so it is difficult to conduct structure steering,pore space reservoir tracking and trajectory control in the process of geosteering logging while drilling.In this paper,a series of corresponding techniques for structure,reservoir and formation tracking were proposed after analysis was conducted on multiple series of carbonate strata in terms of their geologic and logging response characteristics.And investigation was performed on the adaptabilities of the following logging technologies to geosteering while drilling,including gamma ray imaging while drilling,resistivity imaging while drilling,density imaging while drilling,gamma ray logging while drilling,resistivity logging while drilling,neutron logging while drilling and density logging while drilling.After while drilling information was thoroughly analyzed,the logging suites for four common types of complicated reservoirs(thin layered reservoirs,thick massive reservoirs,denuded karst reservoirs and shale gas reservoirs)were optimized,and five logging combinations suitable for different formations and reservoirs were proposed,including gamma ray logging t porosity t resistivity imaging,gamma ray logging t resistivity imaging,gamma ray logging t porosity t resistivity logging,gamma ray imaging t resistivity logging,and gamma ray logging.Field application indicates that it is of great reference and application value to use this method for the first time to summarize logging while drilling combinations for different types of carbonate reservoirs.
文摘Carbonate gas reservoir in the eastern area on the Right Bank of the Amu Darya River,Turkmenistan,are of low-porosity and with developed fractures.In this area,fractures control reservoir properties and natural gas production,and karst fractures are the most important kind of fractures,so their identification and evaluation are quite necessary.In this paper,fracture types were identified and their occurrence was extracted by using conventional logging and image logging data after core calibration.Then,the distribution characteristics of karst fractures and their controlling effect on reservoirs were studied according to the identification results.And the following research results were obtained.First,karst fractures are mainly of high angle with the characteristic of mono system and the interactive relation of genesis.Second,they are mainly distributed in the upper XVhp layer of CallovianeOxford Stage and the lower XVa2eXVI layer.Third,they are the main effective fractures in this area.The dissolved pores are connected effectively through the expanded karst fractures by dissolution,and consequently reservoirs of high porosity and permeability are formed and they are the important reservoir type and high-yield gas reservoir in this area.Fourth,karst fractures are related to high-yield wells and high-yield layers in this area,and they also control the distribution of high-yield reservoirs in the lower part of CallovianeOxford Stage.It is concluded that by virtue of imaging logging and conventional logging data,karst fractures,unfilled fractures,semi-filled fractures and fullyfilled fractures can be identified and evaluated better.Furthermore,the identification and evaluation of karst fractures deepen the understanding on fractured reservoirs in this area,improve the reservoir evaluation effect,and provide the basis for the target horizon and azimuth optimization of horizontal wells and highly deviated wells.And it is also indicated that the reservoirs with developed karst fractures are the subsequent important drilling targets.
文摘The geological and geophysical characteristics of the basement oil and gas reservoir in block Y are very complex, and the lithology is metamorphic rock. Matrix porosity is very small and dense, but fractures are developed, which is a good reservoir space.In this paper, imaging logging combined with conventional logging curve, especially resistivity logging curve, is the main means to identify fractures. Meanwhile, the base oil and gas in block Y is condensate oil and gas and there is no water.Conventional logging has no obvious identification of fluid properties in this block, and PLT logging has obvious identification effect on fluid properties in this block. It can be combined with imaging logging to identify basement reservoir fluid.
文摘In the process of directional well drilling, the key to construction is to use various data to mark the horizon, control the trajectory to enter the target accurately, and control the construction risk well. Kuwait's Burgan Oilfield is a typical high temperature, high pressure and high sulfur-bearing oil and gas field, which is difficult to construct. In the development of directional wells in Burgan Oilfield, comprehensive logging technology can be used to successfully compensate for the decrease in resolution of logging and LWD equipment in oil-based mud. We have successfully achieved accurate reservoir sticking, fine interpretation of oil and gas reservoirs, target prediction and trajectory control. At the same time, the formation pressure monitoring while drilling technology has played a very important role in reducing the risk of well control during drilling. The application of comprehensive logging technology has greatly reduced the drilling construction risks and is also an important basis for later oil production and well location deployment.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFF0614102 and 2023YFE0110900)the National Natural Science Foundation of China(Grant Nos.52374004,52204005,and 52304003)the Natural Science Foundation of Sichuan Province(Grant Nos.2024NSFSC0961 and 2023NSFSC0940).
文摘China's shale oil and gas resources are widely distributed in shale-sandstone interbedded reservoirs,whose complex lithology and strong heterogeneity pose significant challenges to hydraulic fracturing design.To address issues such as the difficulty in controlling fracture height and the challenge of forming an effective fracture network,this study utilizes synthetic rock samples that can represent the characteristics of interbedded reservoirs and investigates the initiation and propagation of hydraulic fractures under different viscosity,injection rate,and construction scheme.By combining real-time monitoring of injection pressure with acoustic emission,the temporal and spatial evolution characteristics of hydraulic fractures as well as the mechanisms of their vertical and horizontal extension are revealed.The results indicate that a higher fracturing fluid viscosity is essential for ensuring the vertical cross-layer propagation of hydraulic fractures,while a lower fluid viscosity facilitates the activation of weak interlayer surfaces,promoting sufficient horizontal propagation along these planes and forming branched fractures.Although a higher injection rate enhances the vertical cross-layer propagation of hydraulic fractures,it also causes greater diversion of the main fracture plane,resulting in simpler fracture morphology and limiting the stimulation effect.Additionally,an alternating injection of high and low viscosity fracturing fluids allows hydraulic fractures to both break through weak interlayer surfaces and achieve uniform horizontal propagation,resulting in a more complex fracture morphology.The findings are expected to provide a scientific basis and practical guidance for optimizing hydraulic fracturing designs in interbedded reservoir conditions.
基金supported by the National Natural Science Foundation of China(Grant No.41202110)Open Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)(Grant No.PLN201612)+1 种基金the Applied Basic Research Projects in Sichuan Province(Grant No.2015JY0200)Open Fund Project from Sichuan Key Laboratory of Natural Gas Geology(Grant No.2015trqdz07)
文摘Pore structure characteristics are important to oil and gas exploration in complex low-permeability reservoirs. Using multifractal theory and nuclear magnetic resonance （NMR）, we studied the pore structure of low-permeability sandstone rocks from the 4th Member （Es4） of the Shahejie Formation in the south slope of the Dongying Sag. We used the existing pore structure data from petrophysics, core slices, and mercury injection tests to classify the pore structure into three categories and five subcategories. Then, the T2 spectra of samples with different pore structures were interpolated, and the one- and three-dimensional fractal dimensions and the multifractal spectrum were obtained. Parameters a （intensity of singularity） andf（a） （density of distribution） were extracted from the multifractal spectra. The differences in the three fractal dimensions suggest that the pore structure types correlate with a andf（a）. The results calculated based on the multifractal spectrum is consistent with that of the core slices and mercury injection. Finally, the proposed method was applied to an actual logging profile to evaluate the pore structure of low-permeability sandstone reservoirs.
基金funded by several Co. of CNPC and SINOPECChina National Science and Technology Major Projects of Oil & Gas (2011ZX05009-003)"863" Projects (2006AA060105)
文摘LWD（logging while drilling） data has been used to explore complex subtle reservoirs by realtime visual interpretation and geo-steering.The method comprises of computer communication,well log data processing,formation recognition,reservoir modeling and model updating in real time.We studied the key technologies related to real-time LWD data visual interpretation and geo-steering and developed computer software with Chinese intellectual property rights covering the following important aspects： 1） real-time computer communication of well site LWD data;2） visualization of geological model and borehole information;3） real-time interpretation of LWD data;4） real-time geological model updating and geo-steering technology.We use field application examples to demonstrate the feasibility and validity of the proposed technologies.
基金sponsored by the National Natural Science Foundation of China（Grant No.41074103） the National Key Fundamental R＆D Project（Grant No.2007CB209601） the China National Petroleum Cooperation Fundamental Research Program（Grant No.06A30102）
文摘Clay has a significant influence on the relationship between resistivity index I and water saturation Sw （i.e, I-Sw relationship） of reservoir rocks because it complicates the current paths of these rocks. It is difficult to reveal the physical mechanisms of these clay effects on the conductivities of various rocks by physical laboratory measurements because the pore structure, micro distribution and content of clay inside a rock can not be observed and controlled during the experiments. We present a digital rock approach to study these clay effects on the electrical transport properties of reservoir rocks at pore scale using lattice gas automation （LGA） method. The digital rock samples are constructed with the information of grain size distribution from SEM images of reservoir rocks. The LGA is then applied on these digital rocks fully saturated with fluids to simulate the electrical transport properties for revealing the effects of volume and distribution patterns of clay on the non-Archie behaviors of the I-Sw relationship. The very good agreement between the simulated results and the laboratory measurements clearly demonstrates the validity of the LGA in numerical research of rock physics. Based on these studies, a new model has been developed for quantitatively describing the relationship between the saturation exponent and the volume of clay （Vsh）. This development may improve the evaluation for the fluid saturations in reservoir rocks.
基金sponsored by the Science Research and Technology Development Project of Petrochina Company Limited "Well Logging Interpretation and Integrative Evaluation of the Complex Lithology"(Grant No.2008A-2705)
文摘Matrix porosity calculations of fractured and vuggy reservoirs, such as volcanics and weathered dolomite, are one of the problems urgently needed to solve in well-log evaluation. In this paper, we first compare the an empirical formula for porosity calculation from full diameter rhyolite core experiments with the matrix porosity formulas commonly used. We discuss the applicability of the empirical formula in fractured and vuggy reservoirs, such as intermediate-basic volcanics and weathered dolomite. Based on core analysis data, the error distribution of the calculated porosity of our empirical formula and the other porosity formulas in these reservoirs are given. The statistical error analysis indicates that the our empirical formula provides a higher precision than the other porosity formulas. When the porosity is between 1.5% and 15%, the acoustic experiment formula can be used not only for acidic volcanics but also in other fractured and vuggy reservoirs, such as intermediate-basic volcanics and weathered dolomite. Moreover, the formula can reduce the effects of borehole enlargement and rock alteration on porosity computation.
文摘Nearly half of coal mine disasters in China have been found to occur in clusters or to be accompanied by earthquakes nearby,in which all the disaster types are involved.Stress disturbances seem to exist among mining areas and to be responsible for the observed clustering.The earthquakes accompanied by coal mine disasters may be the vital geophysical evidence for tectonic stress disturbances around mining areas.This paper analyzes all the possible causative factors to demonstrate the authenticity and reliability of the observed phenomena.A quantitative study was performed on the degree of clustering,and space-time distribution curves are obtained.Under the threshold of 100 km,47%of disasters are involved in cluster series and 372 coal mine disasters accompanied by earthquakes.The majority cluster series lasting for 1-2 days correspond well earthquakes nearby,which are speculated to be related to local stress disturbance.While the minority lasting longer than 4 days correspond well with fatal earthquakes,which are speculated to be related to regional stress disturbance.The cluster series possess multiple properties,such as the area,the distance,the related disasters,etc.,and compared with the energy and the magnitude of earthquakes,good correspondences are acquired.It indicates that the cluster series of coal mine disasters and earthquakes are linked with fatal earthquakes and may serve as footprints of regional stress disturbance.Speculations relating to the geological model are made,and five disaster-causing models are examined.To earthquake research and disaster prevention,widely scientific significance is suggested.
基金We thank Patrick Corbett of Herriot–Watt University for providing the CT scans of the samples.The investigation is financially supported by the National Science&Technology Major Special Project(No.2016ZX05006-002)China Postdoctoral Science Foundation Funded Project(No.2018M632716)+1 种基金Shandong Province Post Doctor Innovative Project Special Fund,Open Project Fund of the National and Local Joint Engineering Research Center of Shale Gas Exploration and Development(No.YiqKTKFGJDFLHGCYJZX444-201901)Chongqing Basic Research and Frontier Exploration Project(No.cstc2018jcyjax0503).
文摘Digital core models reconstructed using X-ray tomography(X-CT)enable the quantitative characterization of the pore structure in three dimensions(3D)and the numerical simulation of petrophysics.When the X-CT images accurately reflect the micro structures of core samples,the greyscale threshold in the image segmentation determines the accuracy of digital cores and the simulated petrophysical properties.Therefore,it is vital to investigate the comparison parameter for determining the key greyscale threshold and the criterion to describe the accuracy of the segmentation.Representative coquina digital core models from X-CT are used in this work to study the impact of grayscale threshold on the porosity,pore percolation,connectivity and electrical resistivity of the pore scale model and these simulations are calculated by Minkowski functions,component labeling and fi nite element method,respectively,to quantify the pore structure and simulate electrical resistivity.Results showed that the simulated physical properties of the digital cores,varied with the gradual increase of the greyscale threshold.Among the four parameters related to the threshold,the porosity was most sensitive and chose as the comparison parameter to judge the accuracy of the greyscale threshold.The variations of the threshold change the micro pore structures,and then the electrical resistivity.When the porosity of the digital core model is close to the experimental porosity,the simulated porosity exponent matches the experimental porosity exponents well.The good agreement proved that the porosity is the critical comparison parameter to describe the accuracy of image segmentation.The criterion is that the porosity of the digital core after segmentation should be close to the experimental porosity.
基金sponsored by the project No.50404001 from the National Natural Science Foundation of Chinathe National Key Fundamental Research & Development Project(Grant No.2007CB209601)+1 种基金the China National PetroleumCorporation Fundamental Research Program (Grant No.06A30102)the China Postdoctoral Science Foundation(Project No.2004035350)
文摘The electrophysical property of saturated rocks is very important for reservoir identification and evaluation. In this paper, the lattice Boltzmann method （LBM） was used to study the electrophysical property of rock saturated with fluid because of its advantages over conventional numerical approaches in handling complex pore geometry and boundary conditions. The digital core model was constructed through the accumulation of matrix grains based on their radius distribution obtained by the measurements of core samples. The flow of electrical current through the core model saturated with oil and water was simulated on the mesoscopic scale to reveal the non-Archie relationship between resistivity index and water saturation （I-Sw）. The results from LBM simulation and laboratory measurements demonstrated that the I-Sw relation in the range of low water saturation was generally not a straight line in the log-log coordinates as described by the Archie equation. We thus developed a new equation based on numerical simulation and physical experiments. This new equation was used to fit the data from laboratory core measurements and previously published data. Determination of fluid saturation and reservoir evaluation could be significantly improved by using the new equation.
基金supported by the Fundamental Research Funds for the Central Universities (No. CUG090106)the National Natural Science Foundation of China (No. 41074086)the Ph.D. Programs Foundation of Ministry of Education of China (No. 20100145120006)
文摘To understand the electrical structure of the Sulu（苏鲁） terrane,we analyzed the resis-tivity logs of the Chinese Continental Scientific Drilling main hole（CCSD-MH） and obtained the statis-tical characteristics of the resistivity log of ultrahigh-pressure（UHP） metamorphic rocks.To check the logs＇ quality,we compared the resistivity log data with the core test data.The two datasets show a good coherence.On the whole,the resistivity of the UHP metamorphic rocks from the CCSD-MH is very high（mostly higher than 1 000 ？？m）.From orthogneiss to paragneiss,amphibolite,retrograded eclogite,rutile eclogite,phengite eclogite,and ultramafic rock,the resistivity decreases gradually.The fracture zone,enrichment of metal minerals,and serpentinization of peridotite can probably cause the decrease of resistivity.Comparing the electrical structure of the crust of Dabie（大别） terrane and Sulu terrane,we can conclude that（1） the electrical structure of the crust of Dabie terrane and Sulu terrane shows a very big difference,（2） the high-resistivity zone of the north Sulu orogen extended to a very great depth（60 km）,but the high-resistivity zone of Dabie orogen is over the depth of 25 km.
文摘A perforating hole is a channel through which the oil and gas in a reservoir pass into the production well bore.During the process of perforating due to explosion,the surrounding sandstone will be damaged to a certain extent,which will increase the well bore skin and lead to the decrease of production consequently.In this work a mechanical model of perforating damage is developed to describe the influences of perforating due to explosion on the porosity and permeability of the surrounding sandstone near the compaction zone.Based on this developed model,the important data related to the damage of sandstone,such as matrix effective stress,plastic deformation,volumetric strain,and so on,can be numerically simulated.Especially the behaviors of plasticity kinematic hardening at high strain rate due to impact loads,which are the important characteristics in the sandstone,is taken into account in this developed model.Both numerical and testing results show that the damage due to perforation in the sandstone can be accurately predicted by the developed model together with the porosity and permeability evolving model of perforation in a compaction zone.As a practical application,a methodology for the analysis of damage of porosity and permeability around a perforation tunnel is supposed based on the developed model and the core flow efficiency test of interparticle pore spaced sandstone target in China Shengli Oilfield and the computed tomography test.
基金Supported by the National Natural Science Foundation of China(41430316)China National Science and Technology Major Project(2017ZX05008-004-008).
文摘Organic reef reservoirs in the platform margin of Kaijiang-Liangping trough in Damaoping area, Sichuan Basin are thin in single layer, fast in lateral variation, and have small P-impedance difference from the surrounding rock, it is difficult to identify and predict the reservoirs and fluid properties by conventional post-stack inversion. Through correlation analysis of core test data and logging P-S wave velocity, this work proposed a formula to calculate the shear wave velocity in different porosity ranges, and solved the issue that some wells in the study area have no S-wave data. AVO forward analysis reveals that formation porosity is the main factor affecting the variation of AVO type, the change of water saturation cannot affect the AVO type, but it has an effect on the change range of AVO. Through cross-plotting analysis of elastic parameters, it is found that fluid factor is a parameter sensitive to gas-bearing property of organic reef reservoir in the study area. By comparing results of post-stack impedance inversion, post-stack high frequency attenuation property, pre-stack simultaneous inversion and AVO anomaly analysis of angle gathers, it is found that the gas-bearing prediction of organic reef reservoirs by using fluid factor derived from simultaneous pre-stack inversion had the highest coincidence rate with actual drilling data. At last, according to the characteristics of fluid factor distribution, the favorable gas-bearing area of the organic reef reservoir in Changxing Formation was predicted, and the organic reef trap at the top of Changxing Formation in Block A of Damaoping area was sorted out as the next exploration target.
