Combination and distribution of reservoir space in complex carbonate rocks

This paper discusses the reservoir space in carbonate rocks in terms of types,combination features,distribution regularity,and controlling factors,based on core observations and tests of the North Truva Oilfield,Caspian Basin.According to the reservoir space combinations,carbonate reservoirs can be divided into four types,i.e.,pore,fracture-pore,pore-cavity-fracture,and pore-cavity.Formation and distribution of these reservoirs is strongly controlled by deposition,diagenesis,and tectonism.In evaporated platform and restricted platform facies,the reservoirs are predominately affected by meteoric fresh water leaching in the supergene-para-syngenetic period and by uplifting and erosion in the late stage,making both platform facies contain all the above-mentioned four types of reservoirs,with various pores,such as dissolved cavities and dissolved fractures,or structural fractures occasionally in favorable structural locations.In open platform facies,the reservoirs deposited continuously in deeper water,in an environment of alternative high-energy shoals（where pore-fracture-type reservoirs are dominant） and low-energy shoals（where pore reservoirs are dominant）.

Identification, evolution and geological indications of solid bitumen in shales: A case study of the first member of Cretaceous Qingshankou Formation in Songliao Basin, NE China

On the basis of sorting out current understanding of solid bitumen (SB) in shales and taking organic-rich shales in the first member of the Cretaceous Qingshankou Formation in the Songliao Basin as an example, the definition, classification, occurrence and evolution path of SB are systemtically studied, and the indicative significance of SB reflectance (Rob) on maturity and its influence on the development of reservoir space are discussed and summarized. The results show that the difference of primary maceral types is primarily responsible for the different evolution paths of SB. Most of the pre-oil bitumen is in-situ SB with only a small amount being of migrated SB, while most of the post-oil bitumen and pyrobitumen are migrated SB. From the immature to early oil maturity stage, bituminite, vitrinite, and inertinite can be distinguished from SB based on their optical characteristics under reflected light, and alginite can be differentiated from SB by their fluorescence characteristics. Under scanning electron microscope, in-situ SB and migrated SB can be effectively identified. Rob increases linearly with increasing vitrinite reflectance (Ro), as a result of a decrease of aliphatic structure and the enhancement of aromatization of SB. Within the oil window three types of secondary pores may develop in SB, including modified mineral pores, devolatilization cracks and bubble holes. At a high maturity stage spongy pores may develop in pyrobitumen. Scanning electron microscopy combined with in-situ SEM-Raman spectroscopy can further reveal the structral information of different types of SB, thus providing crucial data for understanding for understanding OM migration paths, dynamics, and distances at micro-scale.

Accumulation and exploration of continental shale gas resources of Cretaceous Shahezi Formation in Lishu fault depression,Songliao Basin,NE China

Distribution characteristics,organic matter development characteristics,gas-bearing characteristics,reservoir characteristics,and preservation conditions of the Shahezi Formation shale of Lower Cretaceous in the Lishu fault depression,Songliao Basin,NE China,are analyzed using organic geochemical,whole rock,and SEM analysis data,and CO_(2)and N_(2) adsorption and high-pressure mercury injection experiment data in combination with the tectonic and sedimentation evolution of the region to reveal the geological conditions for enrichment and resource potential of continental shale gas.The organic-rich shale in the Lower Cretaceous of the Lishu fault depression is mainly developed in the lower submember of the second member of the Shahezi Formation(K_(1)sh_(2)^(1) Fm.)and is thick and stable in distribution.The shale has high TOC,mainly types II_(1) and II_(2) organic matter,and is in the mature to the over-mature stage.The volcanic activity,salinization,and reduction of the water environment are conducive to the formation of the organic-rich shale.The shale reservoirs have mainly clay mineral intergranular pores,organic matter pores,carbonate mineral dissolution pores,and foliated microfractures as storage space.The pores are in the mesopore range of 10–50 nm,and the microfractures are mostly 5–10μm wide.Massive argillaceous rocks of lowland and highstand domains are deposited above and below the gas-bearing shale separately in the lower submember of the K_(1)sh_(2)^(1) Fm.,act as the natural roof and floor in the process of shale gas accumulation and preservation,and control the shale gas enrichment.Based on the above understandings,the first shale gas exploration well in Shahezi Formation was drilled in the Lishu fault depression of Songliao Basin.After fracturing,the well tested a daily gas production of 7.6×10^(4) m^(3),marking a breakthrough in continental shale gas exploration in the Shahezi Formation(K1 sh Fm.)of the Lishu fault depression in Songliao Basin.The exploration practice has reference significance for the exploration of continental shale gas in the Lower Cretaceous of Songliao Basin and its periphery.

The status quo and prospect of geothermal resources exploration and development in Beijing-Tianjin-Hebei region in China

The Beijing-Tianjin-Hebei region boasts rich geothermal resources and new achievements have been made in the exploration and development of geothermal resources in this region based on previous regional investigation.In detail,geothermal reservoirs of Gaoyuzhuang Formation of Jixian System and Changcheng System in Xiongan New Area have been recently discovered,opening up the second space of geothermal resources;the calculation method of the recoverable resources of geothermal fluid with reinjection being considered has been improved in Beijing-Tianjin-Hebei region,and uniform comprehensive assessment of shallow geothermal energy,hydrothermal geothermal resources,and hot dry rocks(HDR)geothermal resources in the whole Beijing-Tianjin-Shijiazhuang region has been completed.The scientific research base for cascade development and utilization of geothermal resources in Beijing-Tianjin-Hebei region has applied hydraulic fracturing technology to the geothermal reservoirs in Gaoyuzhuang Formation.As a result,the production capacity doubled and two-stage cascade utilization composed of geothermal power generation and geothermal heating were realized,with the first-phase installed capacity of 280 kW and the geothermal heating is 30000 m2.In this way,a model of the exploration,development,and utilization of geothermal resources formed.Large-scale utilization has become the future trend of geothermal resource development in Beijing-Tianjin-Hebei region,and great efforts shall be made to achieve breakthroughs in reinjection technology,geothermal reservoir reconstruction technology,thermoelectric technology and underground heat exchange technology.

Effects of magnetic field on photon-induced quantum transport in a single dot-cavity system

In this study,we show how a static magnetic field can control photon-induced electron transport through a quantum dot system coupled to a photon cavity.The quantum dot system is connected to two electron reservoirs and exposed to an external perpendicular static magnetic field.The propagation of electrons through the system is thus influenced by the static magnetic and the dynamic photon fields.It is observed that the photon cavity forms photon replica states controlling electron transport in the system.If the photon field has more energy than the cyclotron energy,then the photon field is dominant in the electron transport.Consequently,the electron transport is enhanced due to activation of photon replica states.By contrast,the electron transport is suppressed in the system when the photon energy is smaller than the cyclotron energy.

Characteristics of dolomite karstic reservoir in the Sinian Dengying Formation,Sichuan Basin

The Sinian dolomite reservoir in Dengying Formation was developed extensively in the Sichuan Basin,and typically was the facies-controlled dolomite karstic reservoir.The development of this kind of the reservoir was related with the special deposits,diagenetic environment as well as the multi-phase and multi-type dissolution and fracturing actions.The arid-hot/dry paleo-climate was favourable to develop the large-scale microbial reef-shoal bodies and moundeshoal bodies,which was characterized by the organic framework and the sea floor hardening,thus forming primary matrix pore-type reservoir.In the background of the arid-hot/dry paleo-climate,the water-rock interaction was weak,the mineral stabilization process was slowly,and the vadose pisoliths,aragonite and high-magnesium calcite were well preserved,therefore,this diagenetic environment especially was beneficial for pore preservation.Moreover,the syngenetic and penecontemporaneous dissolution,especially three phases of weathered crust karstification due to three episodes of the Tongwan movement,led to further dissolution of spaces and form numerous non-fabric selective dissolution fractures and dissolution caves along faults and fractures.Multi-phase fractures,especially the late Yanshanian-Himalayan tectonic fractures,resulted in connection among pores,vugs and dissolution caves,and improved quality of the reservoir tremendously.

The reservoir characteristics research of Devonian Jinbaoshi Formation,Northwest Sichuan Basin,SW China

A great breakthrough was achieved on the Middle Devonian's oil-gas exploration in the Longmenshan area in northwestern Sichuan.However,only the Guanwushan Formation was researched in detail.The underlying formation-Jinbaoshi Formation as a set of the potential well reservoir and its reservoir characteristics have not been discussed.Based on the section's fine description,thin section analysis,and core borehole logging,combined with petrophysical analysis,the reservoir characteristics,controlling factors,and evolution process of the Jinbaoshi Formation reservoir in the Longmenshan area are deeply studied in this paper.The results showed that the Jinbaoshi Formation has developed a set of sand-shale interbedding deposit of terrigenous clastic and carbonate rocks.The reservoir lithology is mainly quartz sandstone and calcareous quartz sandstone.The quartz sandstone reservoir has good physical properties,but the calcareous quartz sandstone has the characteristics of strong heterogeneity,low porosity,and permeability.Residual intergranular pores are mainly developed in the reservoir space.And the development of intercrystalline pores and intergranular dissolved pores can also be seen,but the development frequency is low,and the scale is small.Among them,the Devonian Jinbaoshi Formation quartz sandstone's average porosity is about 8%,and the highest is 18.43%.The main diagenesis types of the Jinbaoshi Formation are compaction,recrystalization,and dissolution.Compaction is the main reason for the destruction of original pores,and dissolution is the main driving force for later porosity and permeability improvement.Rock fragments,calcareous silty clasts,and bioclastic grains are the main dissolution objects.The formation of intergranular dissolved pores significantly improves the physical properties of the reservoir.Therefore,the reservoir development of the Jinbaoshi Formation is mainly controlled both by favourable sedimentary facies and diagenesis.Quartz sandstone and calcareous sandstone of the Jinbaoshi Formation were controlled by early sedimentary facies in the syngenetic rock stage and developed more early intergranular pores;in the early diagenesis stage,compaction-pressure solution and cementation resulted in residual intergranular pores.In the middle-late diagenesis stage,the calcareous cement is dissolved,and more pores were formed.

Shale oil development techniques and application based on ternary-element storage and flow concept in Jiyang Depression,Bohai Bay Basin,East China

The ternary-element storage and flow concept for shale oil reservoirs in Jiyang Depression of Bohai Bay Basin,East China,was proposed based on the data of more than 10000 m cores and the production of more than 60 horizontal wells.The synergy of three elements(storage,fracture and pressure)contributes to the enrichment and high production of shale oil in Jiyang Depression.The storage element controls the enrichment of shale oil;specifically,the presence of inorganic pores and fractures,as well as laminae of lime-mud rocks,in the saline lake basin,is conducive to the storage of shale oil,and the high hydrocarbon generating capacity and free hydrocarbon content are the material basis for high production.The fracture element controls the shale oil flow;specifically,natural fractures act as flow channels for shale oil to migrate and accumulate,and induced fractures communicate natural fractures to form complex fracture network,which is fundamental to high production.The pressure element controls the high and stable production of shale oil;specifically,the high formation pressure provides the drive force for the migration and accumulation of hydrocarbons,and fracturing stimulation significantly increases the elastic energy of rock and fluid,improves the imbibition replacement of oil in the pores/fractures,and reduces the stress sensitivity,guaranteeing the stable production of shale oil for a long time.Based on the ternary-element storage and flow concept,a 3D development technology was formed,with the core techniques of 3D well pattern optimization,3D balanced fracturing,and full-cycle optimization of adjustment and control.This technology effectively guides the production and provides a support to the large-scale beneficial development of shale oil in Jiyang Depression.

Characteristics and origin of high-quality lacustrine carbonate reservoirs in the gentle slope area of the Qikou Sag, Bohai Bay Basin

Lacustrine carbonate reservoirs in the gentle slope(ramp)area of Qikou Sag are highly heterogeneous.Some researches about characteristics and distribution of these high quality reservoirs are less.In this study,an integrated investigation was conducted on the high-quality lacustrine carbonate reservoirs in the ramp area of Qikou Sag based on data of thin section examination,lithological log response,testing results,and mercury-injection capillary pressure measurement.In the study area,grainstone reservoirs in the lower 1st member of the Shahejie Formation are high-quality reservoirs characterized by high-medium porosity,moderate permeability,low displacement pressure,and relative large pore throat.Lithologically,these reservoirs are mainly composed of bioclastic and oolitic sparite,and reservoir storage space consists of secondary intergranular dissolved pores and fractures.Hydrodynamic conditions generally control distribution of these reservoirs,as limestone grains filled intergranularly with sparry calcite cement are usually formed under strong hydrodynamic conditions.Sparry calcite cemented limestone is subject to late dissolution with abundant soluble substances,which is one of the direct causes for the well developed secondary dissolved pores.Oolitic bank and bioclastic bank are under high-energy hydrodynamic conditions with the best reservoir petrophysical properties.Rims of beach bars are usually in an intermittently-turbulent highly-hydrodynamic environment with medium reservoir petrophysical properties.Lake bays and supratidal zones are under low-energy tranquil hydrodynamic conditions,with poor reservoir petrophysical properties.During late diagenesis,large quantities of organic acid and slightly acidic water were released from surrounding shale and migrated along the top unconformity of the 3rd member of the Shahejie Formation,resulting in development of numerous secondary dissolved pores in carbonate reservoirs,which is the main cause of high-quality reservoir formation in the sag.Additionally,early charge of hydrocarbons restrained occurrence of authigenic minerals and metasomatism of calcite,and thus promoted excellent preservation of dissolved pores.

APPROXIMATE FORMULA FOR THE VOLUME OF OIL-STORING SPACE OF A RESERVOIR

In the prospecting and exploiting of oil, to estimate the reserves and boundaries of areservoir has a great significance. Therefore, we propose approximate formulas to estimatethe volume of oil-storing space of a reservoir.

Characteristics of the Cretaceous Magmatism in Huanghua Depression and Their Relationships with Hydrocarbon Enrichment

The Huanghua depression located in the hinterland of the Bohai Bay Basin in eastern China is a typical area for the research of multistage magmatic activities with hydrocarbon enrichment,many high-yield wells related to igneous rocks were discovered within the Cretaceous strata in recent years.However,the spatial and temporal distribution of Cretaceous igneous rocks remains unclear,and the relationships among magmatic sequence,lithology,and hydrocarbon enrichment have been poorly studied.In order to solve these problems,core observation,logging analysis,major element analysis,zircon U-Pb chronology,oil-bearing grade statistics and reservoir spaces analysis were used to subdivide the magmatism cycles and to investigate the characteristics of igneous reservoirs.Our results show that the Mesozoic magmatism in Huanghua depression started in 140.1±1.4 Ma and could be divided into two stages including the Early Cretaceous stage and Late Cretaceous stage.The Early Cretaceous magmatism principally developed basic-intermediate rocks in the north zone,and could be subdivided into 3 cycles with their forming ages of 140,125–119,and 118–111 Ma,respectively.By contrast,the late stage mainly developed intermediate-acid rocks centralized in the south zone and formed at 75–70 Ma.The GR and SP curves are good indicators for the contrast of different lithologies,lithofacies and for magmatic sequences division.Intensive magmatism may have an advantage to form reservoirs,since basalt in cycle III in the Early Cretaceous and dacite porphyrite in the Late Cretaceous have great exploration potential.Lithology and tectonic fractures have an important influence on the formation of reservoir spaces and hydrocarbon enrichment.The characteristics of Cretaceous magmatism and igneous reservoirs in Huanghua depression and adjacent areas are summarized,providing important information for igneous reservoirs research and oil-gas exploration in the Cretaceous in related areas.