Search

Based on literature research in combination with the practice of CO2 flooding and storage in Jilin Oilfield, this study assesses the key problems in CO2 flooding and storage, proposing the corresponding countermeasures from five aspects of CO2 gas source condition, namely geological condition evaluation, scheme design incoordination with other production methods, economic and effectiveness evaluation, together with dynamic monitoring and safety evaluation. The results show that CO2 flooding is the most economic and effective CO2 storage method. In eastern China, inorganic origin CO2 gas reservoirs are widely developed and are especially the most enriched in the Paleozoic carbonate rock strata and the Cenozoic Paleogene–Neogene system, which provide a rich resource base for CO2 flooding and storage. In the future, CO2 generated in the industrial field will become the main gas source of CO2 flooding and storage. The evaluation of geological conditions of oil and gas reservoirs is the basis for the potential evaluation, planning scheme design and implementation of CO2 flooding and storage. CO2 storage should be below the depth of 800 m, the CO2 flooding and storage effects in low‐permeability oil reservoirs being the best. CO2 geological storage mechanisms primarily consist of tectonic geological storage, bound gas storage, dissolution storage, mineralization storage, hydrodynamic storage and coalbed adsorption storage. The practice of CO2 flooding and storage in Jilin Oilfield demonstratesthat the oil increment by CO2 flooding is at least 24% higher than by conventional water flooding. The most critical factor determining the success or failure of CO2 flooding and storage is economic effectiveness, which needs to be explored from two aspects: the method and technology innovation along with the carbon peaking and carbon neutrality policy support. After CO2 is injected into the reservoir, it will react with the reservoir and fluid, the problem of CO2 recovery or overflow will occur, so the dynamic monitoring and safety evaluation of CO2 flooding and storage are very important. This study is of great significance to the expansion of the application scope of CO2 flooding and storage and future scientific planning and deployment. [ABSTRACT FROM AUTHOR]

Because it is necessary to focus on differences in regional oil reservoirs and determine the priority of the CCUS‐EOR (Carbon capture, utilization, and storage‐enhanced oil recovery) deployment under China's net‐zero CO2 emission target, systematic and regional evaluations of CO2 sequestration capacity in major oil basins are needed considering the geofluid properties—carbon sequestration capacity in place (CSCIP)—where the 'in place' indicates actual geological formation conditions underground, e.g., formation temperature and pressure. Therefore, physical properties of geofluids at different depths with different geologic temperatures and pressure conditions are considered for the CO2 sequestration capacity evaluation in place, including shallow (800–2000 m), medium (2000–3500 m), deep (3500–4500 m) and ultra‐deep (4500–8000 m) depth intervals. A modified evaluation model with four grading levels is proposed, combining the P‐V‐T equations of state (EOS) and evaluation equations of the Carbon Sequestration Leadership Forum (CSLF), including theoretical, effective, practical, and CCUS‐EOR CSCIP, which is more consistent with geofluid physical properties underground, to make the grading evaluation and ranking of the CSCIP in China's major oil basins. Then, the grading CSCIP of 29 major oil basins in China was evaluated based on the petroleum resources evaluation results of the Ministry of Natural Resources of China (MNRC) during China's 13th Five‐Year Plan period. According to the grading evaluation results, suggestions for China's CCUS‐EOR prospective regions are given as follows: shallow oil fields of the Songliao Basin in Northeast China, shallow–medium oil fields of the Bohai Bay Basin in East China, medium oil fields of the Zhungeer Basin in West China, and medium oil fields of the Ordos Basin in Central China; all are potential areas for the CCUS‐EOR geological sequestration in China's onshore oil basins. In addition, in China's offshore oil basins, shallow–medium oil fields of the Bohai Sea and shallow oil fields of the Pearl River Mouth Basin have potential for CCUS‐EOR geological sequestration. [ABSTRACT FROM AUTHOR]

The origin and source of the petroleum in the Jurassic reservoirs within the eastern Fukang sub‐depression were geochemically investigated. They show thermal maturities matching the peak generation stage, while the condensates are at the early stage of intense cracking. Oils and condensates may have experienced mild evaporative fractionation, while mixing of severely biodegraded with non‐biodegraded oils has occurred. Using biomarkers and isotopes, petroleums were classified into Group I, II and III genetic groups, with Group III further divided into IIIa and IIIb subgroups. Group I petroleum displays heavy carbon isotopes, a strong predominance of pristine over phytane, high C19 and C20 tricyclic and C24 tetracyclic terpanes, low gammacerane, and dominant C29 steranes, while Group II shows light carbon isotopes, a predominance of phytane over pristine, high C21 and C23 tricyclic with low C24 tetracyclic terpanes, high gammacerane and dominant C27 steranes. Group IIIa petroleum shows mixing compositions of Group I and II, while Group IIIb displays similar compositions to Group I, but with significantly higher Ts, C29Ts and C30 diahopane proportions. Oil‐source rock correlation suggests Group I and II petroleums originate from Jurassic and Permian source rocks, respectively, while Group IIIa are mixtures sourced from these rocks and IIIb are mixtures from Jurassic and Triassic source rocks. [ABSTRACT FROM AUTHOR]

CO2 dissolution into an aqueous phase and water evaporation into a gaseous phase takes place during CO2 injection into an oil reservoir. This study aims to evaluate the phase behaviors of the oil‐gas‐water system in the displacement of crude oil by CO2. The composition of the JL oilfield in the northeast of China is taken as an example. The flash calculation of the oil‐gas‐water system was performed, based on the method presented by Li and Nghiem. The research results show that CO2 dissolution in the aqueous phase declines as the NaCl concentration in formation water rises. CO2 injection is beneficial for the evaporation of formation water. The NaCl concentration in formation water has little effect on water evaporation and dissolved‐gas escape. When the injection‐gas mole fraction of CO2 is 0.5, CO2 injection can reverse the phase behavior of the petroleum mixture and the oil‐gas system is converted to a pure gas‐condensate system. For CO2 injection, water vapor has little effect on the miscibility of multiple contacts, but can reduce the miscibility of the first contact. [ABSTRACT FROM AUTHOR]

The transportation of magma in sedimentary basins often occurs through extensive dyke‐sill networks. The role of sills on the plumbing system in rifted margins and the impact of sills on hydrocarbon reservoirs of prospective sedimentary basins has long been an area of great industrial interest and scientific debate. Based on 2D seismic reflection, we present data on how the sills emplaced to form a magmatic plumbing system of the volcanic system for the Zhongjiannan Basin (ZJNB). The results show that sixty‐nine sills and fourteen forced folds have been identified. The distribution and geometry of the sills suggest that magma flowed from west to east and then ascended to near the surface. The onlap relationship of the forced folds indicates that the timing of magmatic activities can be constrained at ca. 0.2 Ma. The spatial and temporal occurrences of intrusions imply that the strong post‐rift magmatism in ZJNB was associated with the Hainan mantle plume arising from the core‐mantle boundary. Furthermore, these forced folds could produce several types of hydrocarbon traps, due to accommodation through bending and uplift of the overlying rock and free surface, but it is critical to evaluate the effect of such emplacement when setting exploration targets. [ABSTRACT FROM AUTHOR]

Following consideration of the characteristics of high temperature, high pressure and high in‐situ stress in ultra‐deep sedimentary basins, together with the existence of hydrocarbon phase state transformation, hydrocarbon‐water‐rock interaction and rock mechanical property transition at those depths, the evaluation index system for hydrocarbon preservation was established. The physical leakage evaluation indexes can be divided into three categories: the dynamic efficiency indexes of micro‐sealing, caprock integrity and natural gas diffusion. The chemical loss evaluation indexes can be divided into two categories: the thermochemical sulfate reduction (TSR) index in marine gypsum‐bearing carbonate strata and the thermochemical oxidation of hydrocarbons (TOH) index in clastic strata. The slippage angle and overconsolidation ratio (OCR) are the key evaluation indexes in the evaluation of the integrity of shale caprocks. TSR intensity can be quantitatively calculated by use of the ZnPVT state parameter method. The TOH strength can be used to estimate the degree of hydrocarbon chemical loss, based on the TOH‐related authigenic calcite cement content or the degree of negative δ13C of authigenic calcite. For the evaluation of ultra‐deep preservation in specific areas, key indexes can be selected according to the local geological conditions, instead of all indexes needing to be evaluated for every scenario. [ABSTRACT FROM AUTHOR]

Crude oil and source rock samples from one of the main oilfields of the Abadan Plain, Zagros, Iran were analyzed geochemically. Rock‐Eval pyrolysis was conducted on Kazhdumi (Upper Cretaceous) and Gadvan (Lower Cretaceous) formations, which are the probable source rocks for the oil in the region. The results indicated that the Kazhdumi Formation can be classified as a fair‐to‐excellent source rock, while the Gadvan Formation can be identified as having poor‐to‐good source rock in the basin. Based on the cross‐plots of HI versus OI and S2 versus TOC, types II and III kerogen were identified from studied source samples in the area. Determination of the main fraction percentages of the Sarvak and Fahliyan crude oils represented that the oils from the Sarvak reservoir are paraffinic‐naphthenic and aromatic‐intermediate, whilst that from the Fahliyan reservoir is paraffinic and paraffinic‐naphthenic. Biomarker ratios of the saturated fractions of oil from both reservoirs indicate that the source rocks formed in reducing marine environments with carbonate‐shale lithology. Furthermore, biomarker data helped to distinguish the degree of biodegradation in the studied oils. According to geochemical analysis, oil samples from the Fahliyan reservoir were generated at a higher thermal maturity than the Sarvak reservoir samples. [ABSTRACT FROM AUTHOR]

Petrophysical properties have played an important and definitive role in the study of oil and gas reservoirs, necessitating that diverse kinds of information are used to infer these properties. In this study, the seismic data related to the Hendijan oil field were utilised, along with the available logs of 7 wells of this field, in order to use the extracted relationships between seismic attributes and the values of the shale volume in the wells to estimate the shale volume in wells intervals. After the overall survey of data, a seismic line was selected and seismic inversion methods (model‐based, band limited and sparse spike inversion) were applied to it. Amongst all of these techniques, the model‐based method presented the better results. By using seismic attributes and artificial neural networks, the shale volume was then estimated using three types of neural networks, namely the probabilistic neural network (PNN), multi‐layer feed‐forward network (MLFN) and radial basic function network (RBFN). [ABSTRACT FROM AUTHOR]

Exploration potential is huge and the oil resources are rich in the Ordovician reservoirs of the Tarim Basin. However, the mechanism of hydrocarbon accumulation is complex and not yet fully understood. In the Tuoputai area, the hydrocarbon migration pathways and characteristics of deep hydrocarbon accumulation are revealed through analyses of the physical data of rich oil and gas, the geochemical parameters of oil, and fluid inclusions. The results show that the Ordovician oils in the Tuoputai area have the same geochemical characteristics as the mixed oil from the Lower Cambrian source rock and the Middle–Upper Ordovician source rock. The Ordovician reservoirs have been charged three times: in the late Caledonian, late Hercynian, and Himalayan stages. Oil charging occurred in the Hercynian stage, in particular, as it is the main filling period of hydrocarbon. The north‐northeast (NNE)‐trending TP12CX major fault, active in in these times and is dominant migration channel of hydrocarbon, but there is segmentation affected by the difference of activities. Oil maturity is higher in the south than in the north and is abnormally high near the major fault. Parameters related to migration indicate that oil migrated northeastward along the NNE‐trending TP12CX major fault and adjusted laterally along the secondary faults and weathering crust, forming the present characteristics of oil and gas distribution. [ABSTRACT FROM AUTHOR]

A total of 6 oil samples were systematically selected from six Asmari Reservoir wells in the Cheshmeh‐Khush Oilfield for geochemical evaluation of the hydrocarbon system, based on reservoir geochemistry and oil fingerprints. An investigation of the distribution patterns of normal alkanes and tricyclic and tetracyclic terpanes along with characteristic biomarkers of the depositional environment and sedimentary facies, indicated that the source rock of the studied hydrocarbons was deposited in a reducing aquatic environment with a low input of terrigenous material and predominantly carbonate lithology derived from organic algal matter. The studied oil samples exhibited moderate maturity, as was further confirmed by the parameters extracted from the light hydrocarbons. Statistical clustering based on different biomarker parameters indicated the presence of two oil families. Additionally, the application of branched and cyclic compounds in the light hydrocarbons (C5–C11) to evaluate lateral continuity of the Asmari reservoir further supported the presence of the two oil families. Other evidence proved the presence of a NE–SW trending fault separating wells X5 and X6 from the other wells in the field. In other wells across the field, good lateral reservoir continuity was observed, despite the presence of faults on the northern and southern plunges of the structure. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the complete distribution of reservoir space in tight oil sandstone combining casting slices, field emission scanning electron microscopy (FE‐SEM), the pore‐throat theory model, high‐resolution image processing, mathematical statistics, and other technical means. Results of reservoir samples from the Xin'anbian area of Ordos Basin showed that the total pore radius curve of the tight oil sandstone reservoir exhibited a multi‐peak distribution, and the peaks appeared to be more focused on the ends of the range. This proved that pores with a radius of 1–50,000 nm provided the most significant storage space for tight oil, indicating that special attention should be paid to this range of the pore size distribution. Meanwhile, the complete throat radius curve of the tight oil sandstone reservoir exhibited a multi‐peak distribution. However, the peak values were distributed throughout the scales. This confirmed that the throat radius in the tight oil sandstone reservoir was not only in the range of hundreds of nanometers but was also widely distributed in the scale approximately equal to the pore size. The new rapid determination method could provide a precise theoretical basis for the comprehensive evaluation, exploration, and development of a tight oil sandstone reservoir. [ABSTRACT FROM AUTHOR]

Based on core observation, cast and fluorescent thin sections, FESEM and ESEM, coquina in Da'anzhai Member of Jurassic in Sichuan Basin were examined systematically. Together with production data and logging evaluation, a method for lacustrine coquina evaluation based on geological theory was established up. In the article, two aspects of the study were elaborated, characteristics of favorable reservoirs, and a "five‐step" evaluation method for favorable coquina reservoir. According to the correlation between porosity and production data, porosity is not effective in finding high quality coquina reservoir of this area. Whereas micro research of reservoir samples from a high productivity well revealed that sparry coquina is the best lithofacies, with the most developed micro storage space of various kinds. After the favorable reservoir was sorted out, a five‐step method evaluating the coquina reservoir was worked out. Correlation of GR value and rock types suggests that GR<30 API is an effective evaluation parameter in identifying profitable reservoir lithofacies. Meanwhile, the combination of profitable reservoir rock thickness and production data revealed that the reservoirs with the highest potentiality are those with thickness of 3–18 m. Fractures are more developed in faults, folds and structural noses in the study area. Organic acid is discharged massively before the peak of hydrocarbon generation, leading to the formation of dissolution pores in the reservoir. The evaluation of organic acid was made by using the source rock indexes. After evaluating the four factors, and compiling their distribution maps, the maps were overlapped to predict favorable reservoir zones, and 7 first class and 9 second class favorable zones of coquina were picked out. [ABSTRACT FROM AUTHOR]

The sedimentary, paleogeomorphological and reservoir characteristics of the Jurassic Yan'an Formation in the southwestern Ordos Basin, northwestern China, were studied by means of casting thin sections, scanning electron microscopy, inclusion analysis and identification of low‐amplitude structures. A model for reservoir formation is established, and the controlling effects of sedimentary facies, paleotopography, low‐amplitude structures and formation water on oil reservoirs are revealed. There are significant differences in the sedimentary characteristics, structural morphology and paleowater characteristics between the reservoirs above the Yan 10 Member and those in the Yan 9 to Yan 7 Members. The Yan 10 Member contains fluvial sediments, whereas the Yan 9 to Yan 7 members contain delta‐plain anastomosing‐river deposits. The distribution of high‐permeability reservoir is controlled by pre‐Jurassic paleogeomorphology and sedimentary facies. Some of these facies exhibit high porosity and high permeability in a low‐permeability background. The main hydrocarbon accumulation period was the late Early Cretaceous, filling was continuous, and the charging strength altered from weak to strong and then from strong to weak. The Yan 10 reservoir is mainly controlled by the paleogeomorphology: hydrocarbons migrated upward at a high speed through the unconformity surface, and accumulated in the favorable traps formed by paleogeomorphic structural units, such as gentle slopes or channel island. Furthermore, groundwater alternation in these areas was relatively stagnant, providing good reservoir preservation conditions. The reservoirs in the Yan 9 and higher members are controlled by the sedimentary facies, low‐amplitude structure and paleowater characteristics. Hydrocarbons migrated through the three‐dimensional delivery system, influenced by favorable sedimentary facies and high‐salinity groundwater, then accumulated in the favorable low‐amplitude structural traps that formed during the hydrocarbon production period. [ABSTRACT FROM AUTHOR]

The Cenozoic continental strata of the Bohai Bay Basin are rich in shale oil resources, and they contain various types of reservoir spaces that are controlled by complex factors. Using field emission scanning electron microscopy (FESEM), automatic mineral identification and characterization system (AMICS), CO2 and N2 gas adsorption, and focused ion beam scanning electron microscopy (FIB‐SEM), the types of shale reservoir spaces in the Bohai Bay Basin are summarized, the spatial distribution and connectivity of the various types of pores are described in detail, the microscopic pore structures are characterized, and the key geological mechanisms affecting the formation and evolution of the reservoir spaces are determined. Three conclusions can be drawn in the present study. First, the shale reservoir spaces in the Bohai Bay Basin can be divided into three broad categories, including mineral matrix pores, organic matter pores, and micro fractures. Those spaces can be subdivided into seven categories and fourteen sub‐categories based on the distribution and formation mechanisms of the pores. Second, the complex pore‐throat structures of the shale reservoir can be divided into two types based on the shape of the adsorption hysteresis loop. The pore structures mainly include wedge‐shaped, flat slit‐shaped, and ink bottle‐shaped pores. The mesopores and micropores are the main contributors to pore volume and specific surface area, respectively. The macropores provide a portion of the pore volume, but they do not significantly contribute to the specific surface area. Third, the factors controlling the development of microscopic pores in the shale are complex. The sedimentary environment determines the composition and structure of the shale and provides the material basis for pore development. Diagenesis controls the types and characteristics of the pores. In addition, the thermal evolution of the organic matter is closely related to inorganic diagenesis and drives the formation and evolution of the pores. [ABSTRACT FROM AUTHOR]

Downhole microseismic data has the significant advantages of high signal‐to‐noise ratio and well‐developed P and S waves and the core component of microseismic monitoring is microseismic event location associated with hydraulic fracturing in a relatively high confidence level and accuracy. In this study, we present a multidimensional DIRECT inversion method for microseismic locations and applicability tests over modeling data based on a downhole microseismic monitoring system. Synthetic tests inidcate that the objective function of locations can be defined as a multi‐dimensional matrix space by employing the global optimization DIRECT algorithm, because it can be run without the initial value and objective function derivation, and the discretely scattered objective points lead to an expeditious contraction of objective functions in each dimension. This study shows that the DIRECT algorithm can be extensively applied in real downhole microseismic monitoring data from hydraulic fracturing completions. Therefore, the methodology, based on a multidimensional DIRECT algorithm, can provide significant high accuracy and convergent efficiency as well as robust computation for interpretable spatiotemporal microseismic evolution, which is more suitable for real‐time processing of a large amount of downhole microseismic monitoring data. [ABSTRACT FROM AUTHOR]

This work investigated the pore structure characteristics and reservoir features of the finegrained tight reservoirs in the lower member of the Xinhe Formation (J2x1) in the Xiaohu subsag, Yabulai Basin based on core samples through various techniques. Interbedded silt/fine sandstones and mudstones are developed in the study area. Scanning electron microscopy (SEM) images were used to delineate different types of pores, including primary intergranular pores, secondary intergranular and intragranular pores, organic pores and fractures. The pore types were distinguished by pore size, pore area, location and formation process. The pore radii of the fine‐grained rocks range from 1 nm to 1.55 μm, mainly concentrated between 5 and 300 nm by low pressure N2 adsorption and MICP analyses. The pore structure parameters of pore throat size and pore throat sorting coefficient are both positively correlated with porosity, while pore throat sorting coefficient has a negative correlation with permeability. The pore structures of the studied samples are much related to the mineral type and content and grain size, followed by TOC content. In these rocks with relatively low TOC and low maturity, the rigid minerals protect pores with pressure shadow from collapse, and dissolution‐related pores contribute a lot to inorganic porosity. In contrast, these rocks with abundant TOC contain a large number of organic pores. The permeability of the fine‐grained tight reservoir is mainly dominated by larger pore throats, while a large number of small pores (mostly <0.1 μm) contribute considerably to porosity. These results have deepened our understanding of the interbedded fine‐grained tight reservoirs and can be applicable to fine‐grained reservoirs in a similar setting. [ABSTRACT FROM AUTHOR]

Abundant organic inclusions are present in the Qinglong antimony deposit. However, the source rocks of these organic matters have not been reliably identified. Recently, a paleo-oil reservoir was found in the Qinglong antimony deposit. In view of similar components of gaseous hydrocarbon, we propose that the organic matters observed in inclusions in Qinglong antimony deposit would come from this paleo-oil reservoir. We used the Re-Os dating method to determine the age of the bitumen from this paleo-oil reservoir, and obtained an isochron age of 254.3±2.8 Ma. The age indicates that the oil-generation from source rock occurred in the early Late Permian, earlier than the Sb mineralization age (∼148±8.5 Ma) in the Qinglong antimony deposit area. After oil generation from Devonian source rock, first and secondary migration, the crude oil have probably entered into the fractures and pores of volcanic rocks and limestone and formed a paleo-oil reservoir in the western wing of Dachang anticline. As burial process deepened, the crude oil has turned into natural gas, migrates into the core of Dachang anticline and formed a paleo-gas reservoir. The hydrocarbons (including CH4) in the reservoirs can serve as reducing agent to provide the sulfur required for Sb mineralization through thermal chemical reduction of sulfates. Therefore, the formation of oil-gas in the area is a prerequisite for the Sb mineralization in the Qinglong antimony deposit. [ABSTRACT FROM AUTHOR]

This work aims to reconstruct the burial history of various kinds of sandstones penetrated by the well YS201 in the Yaoyingtai region of the Changling Fault Depression, southern Songliao Basin, China. Analyses of fluid inclusions in the reservoir rocks, combined with a review of the regional tectonic evolution, revealed the hydrocarbon accumulation stage and accumulation age of the Early Cretaceous Denglouku group and the first member of the Quantou group reservoir, which are the future exploration focus for deep gas reservoirs in this region. Acoustic time data and sedimentary rates calculated for sediments in the YS201 well yielded thicknesses for the Yingcheng, Nenjiang, and Mingshui groups of 506, 539.18, and 144.85 m, respectively, thereby revealing the burial history of the sediments in the well. Fluid inclusions of the Denglouku group reservoir and the first member of the Quantou group reservoir contain oil inclusions and hydro-carbonaceous salt water inclusions. The main peaks of the homogenization temperature and salinity of these saltwater inclusions in the first member of the Quantou group reservoir are generally 110-120°C and 6wt%-8wt%, respectively, and for the Denglouku group are 130-140°C and 4wt%-6wt%. The data for both reservoirs show only one main peak, indicating that they both have experienced single-stage accumulation. Combining the homogenization temperature of the reservoir fluid inclusions with the burial and thermal history of the sediments in the YS201 well, we infer that the hydrocarbon gas in these two intervals accumulated at 79 Ma (middle Late Cretaceous). [ABSTRACT FROM AUTHOR]

The Baxian depression is a typical half-graben located in the Jizhong sub-basin, north China. Commercial petroleum traps have been discovered in the Jizhong sub-basin. However, the 3rd and 4th members of the Shahejie Formation in this sub-basin have been poorly explored. These two members, belonging to the Lower Paleogene age, are buried deeply in the depression. Favorable petroleum reservoir conditions exist in such deep intervals of the half-graben due to the presence of different types and extent of deltas and turbidity fans in various areas. In fact, three types of turbidite fans are developed in the sag below the transitional belt on the eastern gentle slope. This work summarized three stratigraphic trap belts, i.e., the steep slope, gentle slope, and sag. On the steep slope, structural-stratigraphic traps with small-scale delta fronts and turbidite sandbodies are well developed. On the gentle slope, hydrocarbons generally accumulate in the large-scale delta front, onlapping beds and those sandbodies adjacent to unconformities. In the sag, petroleum trap models are typically characterized by pinched-out turbidite sandbodies. Stratigraphic traps were easily formed in turbidite fans below the eastern transitional belt. The petroleum traps that have already been discovered or predicted in the study area indicate that stratigraphic traps have favorable petroleum exploration potential in deeply buried areas (depth >5000 m) in a half-graben basin or depression. [ABSTRACT FROM AUTHOR]

The article presents a study which aims to assess the tight oil in tight sandstone reservoirs in the Sanzhao Sag, northern Songliao Basin, China. Methods including small bin volumetric, resource abundance analogy, and estimated ultimate recovery (EUR) analogy methods were used in the study. Results indicated that migration and accumulation coefficient depends on the total hydrocarbon generation volume and are key parameters of tight oil resource assessment of hydrocarbons in the Basin.

The article discusses a research concerning controlling function of overlying high-quality source rock in tight oil reservoirs in China, based on above-generation and below-storage controlling action. Topics include the geologic aspects of the research, evaluation standard of high-quality source rocks, and development characteristic of overpressure value and depth of oil.

The article discusses a research concerning the influence factors of tight oil Estimated Ultimate Recovery (EUR) evaluation. It offers an analysis of the factors that related to EUR estimation from aspects including decline model combination, economic production, and production period. It examines the correlation and coupling between EUR and related factors, which include declined model selection, transition-point of different declined model, and initial maximum production rate.

The article discusses a research concerning the key technology of micro area visualization applied in oil and gas exploration and development. It highlights the importance of micro area visualization technology for engineers in solving reservoir problems as well as cites some of the technical problems in micro area visualization technology. Key technologies addressed include high precision digital image matching technology and frozen core grinding slice oil-water rock technology.

The article focuses on the authigenic illite on relatively high-quality tight sandstones reservoirs. It discusses the formation and distribution of authigenic illite, a common clay mineral which is generally formed in rich potassium water medium. It describes the occurrence characteristics of authigenic illite and its formation analysis.

The article reports on the application of experimental analysis technology in the tight reservoirs research of Jimusaer Sag. It describes the multi-parameters joint test technology and applies it in a study of source rock features, reservoir lithology, physical property, oil bearing property and their inner relationship to promote the geological cognition in said area.

Just like in sedimentary stratigraphy, the volcanostratigraphic boundary is an important factor for constructing volcanostratigraphic framework. The fundamental factor of volcanostratigraphic boundaries is to classify the types and define their characteristics. Based on field investigation and cross-wells section analysis of Mesozoic volcanostratigraphy in NE China, 5 types of volcanostratigraphic boundaries have been recognized, namely eruptive conformity boundary (ECB), ernptive unconformity boundary (EUB), eruptive interval unconformity boundary (EIUB), tectonic unconformity boundary (TUB) and intrusive contacts boundary (ICB). Except ICB, the unconformity boundaries can be divided into angular unconformity and paraconformity. The time spans and signs of these boundaries are analyzed by using age data of some volcanic fields that have been published. The time spans of ECB and EUB are from several minutes to years. In lava flows, cooling crust is distributed above and below ECB and EUB; in pyroclastic flows, airfalls and lahars, a fine layer below these boundaries has no discernable erosion at every part of the boundary. EUB may be curved or cross curved and jagged. The scale of ECB/EUB is dependent on the scale of lava flow or pyroclastic flows. The time span of EIUB is from decades to thousands of years. There is also weathered crust under EIUB and sedimentary rock beds overlie EIUB. In most instances, weathered crust and thin sedimentary beds are associated with each other laterally. The boundary is a smooth curved plane. The scale of EIUB is dependent on the scale of the volcano or volcano groups. The characteristics of TUB are similar to EIUB's. The time interval of TUB is from tens of thousands to millions of years. The scale of TUB depends on the scale of the basin or volcanic field. Both the lab data and logging data of wells in the Songliao Basin reveal that the porosity is greatly related to the boundaries in the lava flows. There is a high-porosity belt below ECB, EUB or EIUB, and the porosity decreases when it is apart from the boundary. The high-porosity belt below ECB and EUB is mainly contributed by primary porosity, such as vesicles. The high-porosity belt below EIUB is mainly contributed by primary and secondary porosity, such as association of vesicles and spongy pores, so the area near the boundary in lava flows is a very important target for reservoirs. [ABSTRACT FROM AUTHOR]

The Ordos Basin is an important intracontinental sedimentary basin in western China for its abundant Mesozoic crude oil resources. The southern part of the Tianhuan Depression is located in the southwestern marginal area of this Basin, in which the Jurassic and Triassic Chang-3 are the main oil-bearing strata. Currently, no consensus has been reached regarding oil source and oil migration in the area, and an assessment of oil accumulation patterns is thus challenging. In this paper, the oil source, migration direction, charging site and migration pathways are investigated through analysis of pyrrolic nitrogen compounds and hydrocarbon biomarkers. Oil source correlations show that the oils trapped in the Jurassic and Chang-3 reservoirs were derived from the Triassic Chang-7 source rocks. The Jurassic and Chang-3 crude oils both underwent distinct vertical migration from deep to shallow strata, indicating that the oils generated by Chang-7 source rocks may have migrated upward to the shallower Chang-3 and Jurassic strata under abnormally high pressures, to accumulate along the sand bodies of the ancient rivers and the unconformity surface. The charging direction of the Jurassic and Chang-3 crude oils is primarily derived from Mubo, Chenhao, and Shangliyuan, which are located northeast of the southern Tianhuan Depression, with oils moving toward the west, southwest, and south. The results show that an integration of biomarker and nitrogen-bearing compound analyses can provide useful information about oil source, migration, and accumulation. [ABSTRACT FROM AUTHOR]

Marine strata in the Jianghan Plain area are widely distributed with a total depth of more than 8,000 m from the Upper Sinian to the Middle Triassic. Six reservoir caprock units, named Z-€2, €2-O, S, D-C, P and T1, can be identified with each epoch. The geology, stratigraphy, drilling, oil testing and other basic data as well as the measured inclusion and strontium isotope data in the study area are used in the analysis of the formation and evolution process of marine petroliferous reservoirs in the Jianghan Plain area. This study aims to provide a scientific basis for the further exploration of hydrocarbons in the Jianghan Plain and reduce the risks by analyzing the key factors for hydrocarbon accumulation in the marine strata. Our findings show that in the Lower Palaeozoic hydrocarbon reservoir, oil/gas migration and accumulation chiefly occurred in the early period of the Early Yanshanian, and the hydrocarbon reservoir was destroyed in the middle-late period of the Early Yanshanian. In the Lower Triassic-Carboniferous hydrocarbon reservoir, oil/gas migration and accumulation chiefly occurred in the Early Yanshanian, and the hydrocarbon reservoir suffered destruction from the Late Yanshanian to the Early Himalayanian. The preservation conditions of the marine strata in the Jianghan Plain area have been improved since the Late Himalayanian. However, because all source beds have missed the oil/gas generation fastigium and lost the capacity to generate secondary hydrocarbon, no reaccumulation of hydrocarbons can be detected in the study area's marine strata. No industrially exploitable oil/gas reservoir has been discovered in the marine strata of Jianghan Plain area since exploration began in 1958. This study confirms that petroliferous reservoirs in the marine strata have been completely destroyed, and that poor preservation conditions are the primary factor leading to unsuccessful hydrocarbon exploration. It is safely concluded that hydrocarbon exploration in the marine strata of the study area is quite risky. [ABSTRACT FROM AUTHOR]

The article focuses on detection of dissolution pores in the marginally mature calcareous Lucaogou Shale. Topics inlude the calcareous shale in semi-deep and deep lacustrine facies has regarded as an oil shale exploration target, the shale formations possess excellent storage capacity has caused by widely developed internal particle pores, and the dissolution pores being responsive to hydraulic fracturing due to the high content of carbonates.

The article presents a study which investigates the hydraulic fracturing operation in the tight oil reservoir hybrid grid block (HGB) in the Songliao Basin, China to find out the reason for the low productivity after the fracturing operation. A comparison of oil saturation distribution and pressure distribution of different fracture length is offered. The investigation of completed simulations of hydraulic fracture pumping stage and flow-back stage is also revealed.

The article presents a study on the essence of tight oil reservoir wettability on the influencing factor to find out how it effects exploration and development of reservoir. The role played by the wettability of rock in aspects in the exploration and development of oil field is outlined. The need to carry out a lot of wettability quantitative research for discovering how the wettability changes is also tackled.

The article discusses development in research methods on fluid-diagenesis interactions of fractures in tight reservoirs. It relates the status of fluid-diagenesis interactions of fractures in geological processes. The techniques include scanning electron microscope (SEM)-based cathodoluminescence (SEM-CL).

The article presents a study to describe the Raman spectrum characteristics of Lower Paleozoic Carbonaceous shale in Middle Yangtze Region. The study has taken samples from Lower Paleozoic Carbonaceous shale of the edge of the basin and the nappe zone in Middle Yangtze Region. Findings of the study indicate that Raman temperature parameter of the said samples from the nappe zone is lower than that of the contemporary samples near the basin area.

The article examines the formation conditions of the dolomite tight oil in Fengcheng Formation of Fengcheng area in Junggar Basin, Northwest China. It discusses the variation and characterization of P1f reservoirs, as well as its main rock types. It reveals the development of abnormal overpressure for the P1f formation.

The article discusses a study which shows the application of nuclear magnetic resonance (NMR) on quantificational characterization of tight glutenite reservoirs pore size. In the study, NMR T2 spectra were calibrated by a method and the pore size distribution characters of tight glutenite reservoirs of Shahezi Formation were examined.

The article focuses on the accumulation pattern of Jurassic tight oil in Sichuan Basin and its exploration and development prospect. It discusses the impact of Jurassic tight sandstone distribution on tight oil distribution. It describes various pore-throat systems which developed in Jurassic reservoirs. It suggests that source, reservoir, and the association of source and reservoir are the essential factors for tight-oil accumulation.

The article presents a study to distinguish the evaluation of permeability damage to coal reservoir from conventional oil and gas reservoirs. In the study, permeability damage experiment was conducted with coal samples from No.15 Coal Seam in Qinshui basin. It also compares and examines the pore structure and surface characteristics before and after the effect of fracturing fluids on coal.

The article presents a study to examine the formation conditions and exploration potential of tight oil in the Kong2 member of Cangdong depression. Results of the study found that there was a humid subtropical climate during the deposition period in Kong2 member. Moreover, the source rock has maximum abundance of organic matter which shows strong yellow fluorescence.

The article examines the characteristics of petroleum migration and accumulation in tight sandstone reservoir and oilfield in Chang 8 of Heshui area in Ordos Basin. It uses the focused ion beam (FIB) technology and three dimensional computed tomography (CT) to reveal the nano-macro pore and throat systems of the tight sandstone reservoir.

The article focuses on a study about the characterization of tight oil and gas reservoir's micro-pore structure in the fourth member of the Shahejie Formation in the Damintun sag. It discusses the implementation of nuclear magnetic resonance, gas adsorption-desorption, and field emission scanning electron microscope.

The article focuses on a study conducted to assess hydrocarbon resource factor of hydrogen index to calculate potential petroleum resources. For different geological conditions, the value of hydrogen index was assigned. The study found that the liquid hydrocarbon productivity is 2.6 times to the normal one at the mature stage when the deep-derived fluid activities occurred simultaneously to the first hydrocarbon generation process.

The article presents a study which discusses the diagenetic influences on reservoir properties of Chang 2 reservoirs in Renshan region, Zhidan Oilfield. Topics discussed include studies based on X-ray diffraction and scanning electron microscope (SEM), diagenetic influences on Chang2 sandstones, and pores of sandstones being composed of residual primary pores.

The article presents a study which discusses recent advances and prospects of mixed siliciclastic-carbonate sediments (S-MSCSs) in China. Topics discussed include (S-MSCSs) as indicator of sea-level history and varying sedimentation, effects of facies dynamics and changes in relative sea-level, and penecontemporaneous metasomatic dolomite as tight-oil reservoir in China.

The article focuses on findings of a study on orderly accumulation theory of shale system petroleum resource and its prospecting significance. Topics include prominence of shale formations as mineral resource and unconventional petroleum resource; the petroleum geology theory and kerogen hydrocarbon generation theory related to lithologic reservoir and stratigraphic reservoir; and the unconventional petroleum resource in Chang 7 shale formation in Ordos Basin which includes oil shale.

The article focuses on findings of a study on application of attributes fusion technology in prediction of deep reservoirs in Paleogene of Bohai Sea. Topics include analysis of correlation between attributes and reservoir lithology; different attributes fusion techniques, namely seismic image based on RGB-IHS transform, which is technique of spatial standardization of sliced multi-attribute image, and cluster analysis attributes fusion technology; and use of data distribution law.

The article focuses on a research related to genesis of the Sinian solid bitumen and its significance for hydrocarbon accumulation in the Anyue Gas Field of the Sichuan Basin in China. Topics discussed include characteristics of different generations of bitumen and the genesis; core and thin-section observation and organic geochemical testing of bitumen of two epochs; and multi-stage fluid charging in Sinian reservoir and destruction of early ancient oil reservoirs.

The article discusses the study regarding the mechanism of strike-slip faults and their control on differential hydrocarbon enrichment in carbonate karst reservoirs. Topics discussed include the association of fracture development with strike-slip faults and carbonate reservoir transformation, its impact on oil and gas reservoirs, and the use of three-dimensional seismic attribute analysis and formation micro-scanner image (FMI).

The article discusses the impact of the poor reservoir property and exploitation, refracturing and other conventional measures conducted for tight reservoir in peripheral oilfield of Daqing placanticline in China. The need to consider systematic study on standard of candidate selection for petroleum reservoir engineering is tackled. The effect of cumulative oil production on fracturing and the comprehensive evaluation of grey correlation method are outlined.