Genesis Types and Diagenesis Compaction Mechanisms of Sandstone Rreservoirs in Dynamic Environments in Oil/Gas Basins in China

The diversity of sandstone diagenesis mechanisms caused by the complex geological conditions of oil/gas basins in China could hardly be reasonably explained by the traditional concept of burial diagenesis. Three genesis types of thermal diagenesis, tectonic diagenesis and fluid diagenesis are presented on the basis of the dynamic environment of the oil/gas basins and.the controlling factors and mechanisms of sandstone diagenesis. Thermal diagenesis of sandstone reservoirs is related not only to the effect of formation temperature on diagenesis, but also to the significant changes in diagenesis caused by geothermal gradients. The concept of thermal compaction is presented. Thermal compaction becomes weaker with increasing depth and becomes stronger at a higher geothermal gradient. At the same formation temperature, the sandstone porosity in the region with a lower geothermal gradient is e^0.077＋0.0042T times higher than that in the region with a higher geothermal gradient. Both sudden and gradual changes are observed in diagenetic evolution caused by structural deformation. Average sandstone compaction increased by 0.1051% for every 1.0MPa increase of lateral tectonic compressional stress, while late tectonic napping helped to preserve a higher porosity of underlying sandstone reservoir. Fluid diagenesis is a general phenomenon. The compaction caused by fluid properties is significant. The coarser the grain size, the stronger the fluid effect on compaction. The greater the burial depth, the weaker the fluid effect on compaction for the specific reservoir lithology and the greater the difference in the fluid effects on compaction between different grain sizes.

Fluid property identification of the Lower Cretaceous reservoirs with complex oil-water contacts in Deseo Basin,Chad

Recently,exploration breakthroughs have been made in the Lower Cretaceous sandstone reservoirs in the Doseo Basin,but the identification of reservoir fluid property is difficult due to variable reservoir lithology,complex oil-water contact within and faint responses of the oil zone,which causes the lower accuracy of reservoir fluid property identification with conventional mudlogging and wirelogging techniques.Applying the geochemical logging,fluorescent logging,mud logging and cutting logging technology,in combination with formation test data,this paper distinguishes the crude oil types,analyzes the logging response characteristics of oil zone after water washing,and establishes the interpretation charts and parameter standards for reservoir fluid properties.The crude oil can be divided into two types,namely viscous-heavy and thin-light,based on total hydrocarbon content and component concentration tested by mud logging,features of pyrolysis gas chromatogram and fluorescence spectroscopy.The general characteristics of oil layers experienced water washing include the decrease of total hydrocarbon content and component concentration from mud logging,the decrease of S1 and PS values from geochemical logging,the decrease of hydrocarbon abundance and absence of some light components in pyrolysis gas chromatogram,and the decrease of fluorescence area and intensity from fluorescence logging.According to crude oil types,the cross plots of S1 versus peak-baseline ratio,and the cross plots of rock wettability versus fluorescence area ratio are drawn and used to interpret reservoir fluid property.Meanwhile,the standards of reservoir fluid parameter are established combining with the parameters of PS and the parameters in above charts,and comprehensive multiparameter correlation in both vertical and horizontal ways is also performed to interpret reservoir fluid property.The application in the Doseo Basin achieved great success,improving interpretation ability of fluid property in the reservoir with complex oil-water contact,and also provided technical reference for the efficient exploration and development of similar reservoirs.

Study on the Impact of Massive Refracturing on the Fracture Network in Tight Oil Reservoir Horizontal Wells

Class III tight oil reservoirs have low porosity and permeability,which are often responsible for low production rates and limited recovery.Extensive repeated fracturing is a well-known technique to fix some of these issues.With such methods,existing fractures are refractured,and/or new fractures are created to facilitate communication with natural fractures.This study explored how different refracturing methods affect horizontal well fracture networks,with a special focus on morphology and related fluid flow changes.In particular,the study relied on the unconventional fracture model(UFM).The evolution of fracture morphology and flow field after the initial fracturing were analyzed accordingly.The simulation results indicated that increased formation energy and reduced reservoir stress differences can promote fracture expansion.It was shown that the length of the fracture network,the width of the fracture network,and the complexity of the fracture can be improved,the oil drainage area can be increased,the distance of oil and gas seepage can be reduced,and the production of a single well can be significantly increased.

Factors influencing oil recovery by surfactant-polymer flooding in conglomerate reservoirs and its quantitative calculation method

This study aims to clarify the factors influencing oil recovery of surfactant-polymer(SP)flooding and to establish a quantitative calculation model of oil recovery during different displacement stages from water flooding to SP flooding.The conglomerate reservoir of the Badaowan Formation in the seventh block of the Karamay Oilfield is selected as the research object to reveal the start-up mechanism of residual oil and determine the controlling factors of oil recovery through SP flooding experiments of natural cores and microetching models.The experimental results are used to identify four types of residual oil after water flooding in this conglomerate reservoir with a complex pore structure:oil droplets retained in pore throats by capillary forces,oil cluster trapped at the junction of pores and throats,oil film on the rock surface,isolated oil in dead-ends of flow channel.For the four types of residual oil identified,the SP solution can enhance oil recovery by enlarging the sweep volume and improving the oil displacement efficiency.First,the viscosity-increasing effect of the polymer can effectively reduce the permeability of the displacement liquid phase,change the oil-water mobility ratio,and increase the water absorption.Furthermore,the stronger the shear drag force of the SP solution,the more the crude oil in a porous medium is displaced.Second,the surfactant can change the rock wettability and reduce the absorption capacity of residual oil by lowering interfacial tension.At the same time,the emulsification further increases the viscosity of the SP solution,and the residual oil is recovered effectively under the combined effect of the above two factors.For the four start-up mechanisms of residual oil identified after water flooding,enlarging the sweep volume and improving the oil displacement efficiency are interdependent,but their contribution to enhanced oil recovery are different.The SP flooding system primarily enlarges the sweep volume by increasing viscosity of solution to start two kinds of residual oil such as oil droplet retained in pore throats and isolated oil in dead-ends of flow channel,and primarily improves the oil displacement efficiency by lowing interfacial tension of oil phase to start two kinds of residual oil such as oil cluster trapped at the junction of pores and oil film on the rock surface.On this basis,the experimental results of the oil displacement from seven natural cores show that the pore structure of the reservoir is the main factor influencing water flooding recovery,while the physical properties and original oil saturation have relatively little influence.The main factor influencing SP flooding recovery is the physical and chemical properties of the solution itself,which primarily control the interfacial tension and solution viscosity in the reservoir.The residual oil saturation after water flooding is the material basis of SP flooding,and it is the second-most dominant factor controlling oil recovery.Combined with the analysis results of the influencing factors and reservoir parameters,the water flooding recovery index and SP flooding recovery index are defined to further establish quantitative calculation models of oil recovery under different displacement modes.The average relative errors of the two models are 4.4%and 2.5%,respectively;thus,they can accurately predict the oil recovery of different displacement stages and the ultimate reservoir oil recovery.

A novel type curve for estimating oil recovery factor of gas flooding

A novel type curve is presented for oil recovery factor prediction suitable for gas flooding by innovatively introducing the equivalent water-gas cut to replace the water cut,comprehensively considering the impact of three-phase flow(oil,gas,water),and deriving the theoretical equations of gas flooding type curve based on Tong’s type curve.The equivalent water-gas cut is the ratio of the cumulative underground volume of gas and water production to the total underground volume of produced fluids.Field production data and the numerical simulation results are used to demonstrate the feasibility of the new type curve and verify the accuracy of the prediction results with field cases.The new type curve is suitable for oil recovery factor prediction of both water flooding and gas flooding.When a reservoir has no gas injected or produced,the gas phase can be ignored and only the oil and water phases need to be considered,in this case,this gas flooding type curve returns to the Tong’s type curve,which can evaluate the oil recovery factor of water flooding.For reservoirs with equivalent water-gas cuts of 60%-80%,the regression method of the new type curve works well in predicting the oil recovery factor.For reservoirs with equivalent water-gas cuts higher than 80%,both the regression and assignment methods of the new type curve can accurately predict the oil recovery factor of gas flooding.

Formation conditions and exploration direction of large natural gas reservoirs in the oil-prone Bohai Bay Basin, East China

The Bohai Bay Basin is a typical oil-prone basin, in which natural gas geological reserves have a small proportion. In this basin, the gas source rock is largely medium-deep lake mudstone with oil-prone type Ⅱ2-Ⅱ1 kerogens, and natural gas preservation conditions are poor due to active late tectonic movements. The formation conditions of large natural gas fields in the Bohai Bay Basin have been elusive. Based on the exploration results of Bohai Bay Basin and comparison with large gas fields in China and abroad, the formation conditions of conventional large-scale natural gas reservoirs in the Bohai Bay Basin were examined from accumulation dynamics, structure and sedimentation. The results show that the formation conditions of conventional large natural gas reservoirs in Bohai Bay Basin mainly include one core element and two key elements. The core factor is the strong sealing of Paleogene "quilt-like" overpressure mudstone. The two key factors include the rapid maturation and high-intensity gas generation of source rock in the late stage and large scale reservoir. On this basis, large-scale nature gas accumulation models in the Bohai Bay Basin have been worked out, including regional overpressure mudstone enriching model, local overpressure mudstone depleting model, sand-rich sedimentary subsag depleting model and late strongly-developed fault depleting model. It is found that Bozhong sag, northern Liaozhong sag and Banqiao sag have favorable conditions for the formation of large-scale natural gas reservoirs, and are worth exploring. The study results have important guidance for exploration of large scale natural gas reservoirs in the Bohai Bay Basin.

Oil oxidation in the whole temperature regions during oil reservoir air injection and development methods

The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into four different parts: dissolving and inflation region, low temperature oxidation region, medium temperature oxidation region and high temperature oxidation region. The reaction mechanisms of different regions were explained. Based on the oil oxidation characteristics and filed tests results, light oil reservoirs air injection development methods were divided into two types: oxygen-reducing air flooding and air flooding;heavy oil reservoirs air injection in-situ combustion development methods were divided into two types: medium temperature in-situ combustion and high temperature in-situ combustion. When the reservoir temperature is lower than 120 ℃, oxygen-reducing air flooding should be used for light oil reservoir development. When the reservoir temperature is higher than 120 ℃, air flooding method should be used for light oil reservoir development. For a normal heavy oil reservoir, when the combustion front temperature is lower than 400 ℃, the development method is medium temperature in-situ combustion. For a heavy oil reservoir with high oil resin and asphalting contents, when the combustion front temperature is higher than 450 ℃, the development method at this condition is high temperature in-situ combustion. Ten years field tests of air injection carried out by PetroChina proved that air has advantages in technical, economical and gas source aspects compared with other gas agents for oilfield gas injection development. Air injection development can be used in low/super-low permeability light oil reservoirs, medium and high permeability light oil reservoirs and heavy oil reservoirs. Air is a very promising gas flooding agent.

浅水三角洲分流河道砂体沉积特征——以松辽盆地三肇凹陷扶Ⅱ-Ⅰ组为例

松辽盆地三肇凹陷扶Ⅱ-Ⅰ组隐蔽性岩性油气藏埋藏相对较浅,油气资源极其丰富,已成为下一步致密油勘探、增储上产的重点目标区。三肇凹陷扶Ⅱ-Ⅰ组以浅水三角洲沉积体系为主,相带变化复杂,分流河道砂体构成扶Ⅱ-Ⅰ组的主体储层格架。通过53口井岩心精细观察,利用1 000多口测、录井等资料,分析三肇凹陷扶Ⅱ-Ⅰ组浅水三角洲平原分流河道砂体沉积特征,识别出11种岩相类型,根据不同基准面旋回,总结3种岩石相组合类型。研究表明,单一分流河道内部存在泥质、钙质以及含砾粉砂岩3种夹层类型,进而精细解剖单一分流河道内部建筑构型。利用分流河道砂体顶端拉平,建立同期河道砂体及夹层对比模型,从岩性、夹层类型以及测井曲线形态等方面进行对比,探讨了等时地层格架内近井距井间砂体同期分流河道的识别方法及分布规律。在上述砂体对比方法基础上,采用栅状图进行井间砂体对比,结合地震属性分析,刻画单一分流河道砂体平面展布特征,以期能够进一步为致密油藏水平井布置、勘探开发提供地质依据。

Ⅱ类稠油油藏蒸汽驱先导试验研究

优选辽河油田锦45块构造发育较为完整的9个井组,将其作为Ⅱ类稠油油藏进行蒸汽驱先导试验。严格保证注汽质量,并强化提高采注比。经过1年多的汽驱生产,大多数油井明显收效。蒸汽腔正逐步延伸扩展,试验进入蒸汽有效驱替阶段,试验区日产液、日产油明显上升。同时,地层压力保持稳定,油层温度普遍上升,采注比、油汽比不断提高。试验初步证明:在锦45块Ⅱ类稠油藏实施蒸汽驱开发,在技术及经济上均是可行的。将为辽河油区1.8亿吨Ⅱ类稠油储量的汽驱开发起到重要指导和借鉴作用。

Ⅱ类稠油油藏蒸汽驱先导试验研究

锦45块是辽河油田最大稠油区块，2008年优选该块构造发育较为完整的9个井组，将其作为Ⅱ类稠油油藏进行蒸汽驱先导试验，通过借鉴齐40块Ⅰ类稠油油藏成功汽驱经验和做法，并充分结合区块本身的实际特点，通过严格保证注汽质量及强化提高采注比等措施手段，经过1年多的汽驱生产，大多数油井明显受效，蒸汽腔正逐步延伸扩展，试验进入蒸汽有效驱替阶段，试验区日产液、日产油明显上升的同时，地层压力保持稳定，油层温度普遍上升，采注比、油汽比不断提高，试验初步证明在锦45块Ⅱ类稠油藏实施蒸汽驱开发，在技术及经济上均是可行的，将会为辽河油区1．8亿吨Ⅱ类稠油储量的汽驱开发起到重要指导和借鉴作用。

Shale oil enrichment evaluation and production law in Gulong Sag,Songliao Basin,NE China

Based on the results of drilling,tests and simulation experiments,the shales of the Cretaceous Qingshankou Formation in the Gulong Sag of the Songliao Basin are discussed with respect to hydrocarbon generation evolution,shale oil occurrence,and pore/fracture evolution mechanism.In conjunction with a substantial amount of oil testing and production data,the Gulong shale oil enrichment layers are evaluated and the production behaviors and decline law are analyzed.The results are drawn in four aspects.First,the Gulong shales are in the stage of extensive hydrocarbon expulsion when R_(0) is 1.0%-1.2%,with the peak hydrocarbon expulsion efficiency of 49.5%approximately.In the low-medium maturity stage,shale oil migrates from kerogen to rocks and organic pores/fractures.In the medium-high maturity stage,shale oil transforms from adsorbed state to free state.Second,the clay mineral intergranular pores/fractures,dissolution pores,and organic pores make up the majority of the pore structure.During the transformation,clay minerals undergo significant intergranular pore/fracture development between the minerals such as illite and illite/smectite mixed layer.A network of pores/fractures is formed by organic matter cracking.Third,free hydrocarbon content,effective porosity,total porosity,and brittle mineral content are the core indicators for the evaluation of shale oil enrichment layers.Class-I layers are defined as free hydrocarbon content equal or greater than 6.0 mg/g,effective porosity equal or greater than 3.5%,total porosity equal or greater than 8.0%,and brittle mineral content equal or greater than 50%.It is believed that the favourable oil layers are Q2-Q3 and Q8-Q9.Fourth,the horizontal wells in the core area of the light oil zone exhibit a high cumulative production in the first year,and present a hyperbolic production decline pattern,with the decline index of 0.85-0.95,the first-year decline rate of 14.5%-26.5%,and the single-well estimated ultimate recovery(EUR)greater than 2.0×10^(4)t.In practical exploration and production,more efforts will be devoted to the clarification of hydrocarbon generation and expulsion mechanisms,accurate testing of porosity and hydrocarbon content/phase of shale under formation conditions,precise delineation of the boundary of enrichment area,relationship between mechanical properties and stimulated reservoir volume,and enhanced oil recovery,in order to improve the EUR and achieve a large-scale,efficient development of shale oil.

Water-cut rising mechanism and optimized water injection technology for deepwater turbidite sandstone oilfield: A case study of AKPO Oilfield in Niger Delta Basin, West Africa

Through the analysis of the reservoir connection relationship and the water-cut rising rules after water breakthrough in the highly volatile oil AKPO oilfield, a new model of water-cut rising was established, and the timing and strategy of water injection were put forward. The water-cut rising shapes of producers after water breakthrough can be divided into three types, and their water-cut rising mechanism is mainly controlled by reservoir connectivity. For the producers which directly connect with injectors in the single-phase sand body of the single-phase channel or lobe with good reservoir connectivity, the water-cut rising curve is "sub-convex". For the producers which connect with injectors through sand bodies developed in multi-phases with good inner sand connectivity but poorer physical property and connectivity at the overlapping parts of sands, the response to water injection is slow and the water-cut rising curve is "sub-concave". For the producers which connect with injectors through multi-phase sand bodies with reservoir physical properties, connectivity in between the former two and characteristics of both direct connection and overlapping connection, the response to water injection is slightly slower and the water-cut rising curve is "sub-S". Based on ratio relationship of oil and water relative permeability, a new model of water cut rising was established. Through the fitting analysis of actual production data, the optimal timing and corresponding technology for water injection after water breakthrough were put forward. Composite channel and lobe reservoirs can adopt water injection strategies concentrating on improving the vertical sweep efficiency and areal sweep efficiency respectively. This technology has worked well in the AKPO oilfield and can guide the development of similar oilfields.

Compositional heterogeneity of crude oil and its origin in the Linnan subsag,Linyi County,Shandong Province

The Linnan subsag is the main oil producer of the Linpan oil zone. Based on the oil group composition,gas chromatography data and biomarker analysis,it was indicated that crude oils from different oilfields varied greatly in group composition and showed obvious heterogeneities in the aspects of precursor type,crude oil maturity and hydrocarbon depositional environment. According to the characteristics of source rocks,three oil populations can be distinguished,i.e.,the southern,northern and transitional oil populations. Furthermore,on the basis of post-reservoir reworking processes,the medium conditions of hydrocarbon-generating environment and differences in maturity,six oil families and twelve sub-families were distinquished. An integrated study suggested that the fac-tors leading to such heterogeneities in crude oil composition mainly include different source rocks,multi-stage oil/gas charging,geo-chromatographic effects during oil/gas migration,reservoir heterogeneities and various post-reservoir secondary alterations.

Geochemical Characteristics of Oilfield Waters fromthe Turpan Depression, Xinjiang and Their Petroleum Geological Significance

This paper, based on the fundamental inorganic chemical and organic geochemical characteristics of oilfield waters from the Turpan Depression, presents the contents of organic matter, the distribution of low-carbon fatty acids and the contents of aromatic hydrocarbons as well as their principal ultraviolet absorption spectral and fluorescence spectral characteristics in oilfield waters from different oil/gas-bearing areas. The oil/gas reservoirs in this depression are classified in terms of their conserving conditions. In addition, the paper also discusses the chemical characteristics of oilfield waters from different types of oil/gas reservoirs with an emphasis on the characteristics of their localization in the γ_Na/γCa-γNa/γ_Cl correction diagram. On this basis it is attempted to expound the fundamental geochemical characteristics of oilfield waters from the Turpan Depression and their geological significance.

塔里木盆地顺北油气田少井高产地质工程一体化做法与关键技术

塔里木盆地顺北油气田埋藏深度为7300~9000m,脆性地层破碎形成的缝洞型储层沿高陡走滑断裂带发育,断裂破碎带内部非均质性极强,且流体性质差异大。面对这类超深复杂的断控缝洞型油气藏,高效成井面临世界级挑战,单井费用高,效益开发难度大,没有现成的经验、技术可借鉴。顺北油气田以项目管理为抓手,建立了独有的“五有五提升”地质工程一体化管理模式,创新形成了“少井高产”七要素关键技术。近几年,少井高产地质工程一体化实现了质的飞跃,落实了4号、8号断裂带2个亿吨级资源阵地,新增石油探明储量为1.53×10^(8)t、天然气探明储量为1620×10^(8)m^(3),4号断裂带共部署井位20口,两年建成了130×10^(4)t油当量产能阵地。与2016年开发动用的1号断裂带相比,高产井成功率提升了35%、单井产能提升了316%、单井发现探明储量提升了55%,实现了高效勘探,效益开发,其经验对其他同类型油藏开发具有较好的借鉴意义。

苏北盆地古近系阜宁组二段页岩油储层岩石力学特征及其控制因素

为查明苏北盆地页岩油储层可压性特征及压后孔、缝变化规律,以古近系阜宁组二段(阜二段)为研究对象,对岩石力学特征、压裂效果及其影响因素进行研究。用计算机高分辨断层扫描成像技术(多尺度CT扫描)对岩样进行三维重构,获取孔、缝结构参数;开展地层围压下三轴力学实验,获取岩石力学参数;将压裂后的岩样按相同位置和方向再次进行多尺度CT扫描,获取压裂后三维孔、缝结构图像。根据应力-应变曲线特征,将本区页岩划分为3种类型。①1型页岩,为破裂曲线波浪下降,压后形成复杂网状缝页岩。②2型页岩,为破裂曲线类型多样,具波浪下降和垂直下降形状,压后缝网较发育的页岩。③3型页岩,为破裂曲线垂直下降,破裂后整体较完整,压后多形成纵向劈裂缝、缝网不发育的页岩。这3种类型页岩压后孔隙变化特征是:1型和2型页岩直径10~50μm孔隙占比减少,直径50~100μm孔隙增多,直径300μm以上孔隙孔容贡献增大;3型页岩压裂前、后孔径分布及孔容贡献变化不明显。研究表明,抗压强度与弹性模量、剪切模量具有正相关关系,与泊松比具有V型曲线关系;碳酸盐和黏土矿物含量是控制本区页岩力学性质的主要因素,石英和有机碳含量为次要因素。孔隙度及纹层发育特征是页岩储层可压性特征的重要影响因素。

致密砂岩气藏与页岩气藏展布模式

在阐述美国和中国致密砂岩气和页岩气资源潜力和年产量的基础上,系统梳理致密砂岩气藏与页岩气藏展布的研究沿革,分析页岩气藏、致密砂岩气藏展布特征及致密砂岩气成因类型。研究表明:(1)美国致密砂岩气在天然气总产量中占比由2008年的35%降至2023年的8%左右;美国页岩气2023年产量为8310×10^(8)m^(3),在天然气总产量中占比由2000—2008年的5%~17%升至2023年的70%以上。(2)中国致密砂岩气占天然气总产量比例由2010年的16%升至2023年的28%以上;2012年中国开始生产页岩气,2023年产量达250×10^(8)m^(3),约占天然气全国总产量的11%。(3)页岩气藏展布模式为连续型,根据页岩气藏是否有断层切割及断距与气层厚度的关系,连续型页岩气藏可分为连续式和断续式两种。(4)与以往大部分学者认为致密砂岩气藏展布模式为连续型的认识不同,致密砂岩气藏展布模式不是连续型;根据圈闭类型,致密砂岩气藏可分为岩性型、背斜型和向斜型3种。(5)中国3大克拉通盆地和埃及Obavied次盆的致密砂岩气为煤成气,美国阿巴拉契亚盆地和阿曼迦巴盐盆地的致密砂岩气为油型气。

鄂尔多斯盆地胡尖山地区长7段页岩型页岩油源储特征及勘探前景

鄂尔多斯盆地三叠系延长组长7段发育一套以富有机质泥页岩为主夹砂质沉积的烃源岩层系,其中长7段源内夹层型页岩油已取得勘探突破并实现规模效益开发,但页岩型页岩油前期研究相对较少,是否具有勘探开发前景还不够明确。为此,以长7段烃源岩为研究对象,开展基于岩心分析化验、测井资料解释的烃源岩源储特征评价和矿场开发试验,用以评价胡尖山地区长7段页岩型页岩油勘探前景。长7段岩心测试分析表明,页岩主要发育粒间孔、晶间孔及有机质孔,常见层理缝及有机质收缩缝,游离态轻质油主要赋存于粒间孔及页理缝;运用多溶剂连续分步抽提方法实验结果表明,长7段页岩中游离态轻质油比例可达到54.3%。通过地球化学特征分析,长7段页岩平均TOC为14.03%、平均生烃潜量为57.73mg/g,为优质烃源岩;有机质热演化程度较高,平均R_(o)为1.08%、平均T_(max)为450℃;岩石热解可动烃含量达到4.34mg/g,表明页岩型页岩油具有良好的资源基础。研究区长7段页岩有机质类型好、有机质含量高、岩石可压裂性好,盆地内直井试油试采表明页岩含油性较好,利用岩石热解法估算该地区页岩型页岩油可动烃资源量为4.1×10^(8)t,综合认为研究区页岩具有水平井体积压裂提产的勘探开发前景。

深地、深海油气藏储量评估中针对不确定性的可靠技术选择与应用

对于新领域和复杂类型油气藏,储量评估关键参数的确定意义重大,也是勘探开发的难点和重点,建立可靠技术开展储量评估是目前国际主流做法,但国内强调勘探开发主体技术却少有关于储量评估可靠技术的研究。近年来国内石油公司不断在近万米深层和水深超过500m海域取得重大油气突破,在勘探评价阶段发现的超深层大型碳酸盐岩缝洞型油气藏和深海油气藏储量评估面临资料有限、投资约束和井控程度低等问题,如何选择或建立可靠技术开展储量评估已成为该领域的研究重点。从可靠技术的定义和适用性出发,重点针对深海和深地油气藏勘探投资大、不能大面积部署探井,以及深地和深海油气藏储量评估过程中的复杂性、特殊性及不确定性,开展可靠技术在储量评估关键参数选取中的适用条件和应用范围研究,通过典型案例解剖认为,深海油气藏地震振幅随偏移距变化(AVO)、直接烃指标(DHI)和压力系统法等可靠技术可识别油气藏的油水界面,4个区块验证成功率高达92%,应用该技术降低了勘探评价阶段的投资及开发风险。深地缝洞型碳酸盐岩油气藏利用地震敏感属性分析技术确定含油气边界和含油气面积,该技术通过钻井放空漏失、测井解释结果和生产动态等证实储层预测的可靠性较高,地震储层预测与实钻吻合率达84%,从而使储量评估结果更加接近油藏实际,确保了少井情况下储量评估结果的合理性,同时也推动了可靠技术在储量评估领域的应用。

准噶尔盆地盆1井西凹陷侏罗系三工河组凝析气藏特征及成因机制

基于油气地球化学、试油结果与凝析气相态分析实验等资料,采用盆地模拟技术分析了准噶尔盆地盆1井西凹陷前哨井区侏罗系三工河组凝析气藏特征,并对凝析气藏的成藏过程与成因机制进行了详细研究。研究结果表明:①盆1井西凹陷侏罗系三工河组凝析气藏为构造-岩性油气藏,优质储层岩性主要为灰色细—中粒长石岩屑砂岩,孔隙度为2.70%~16.10%,平均为12.10%,渗透率为0.016~109.000 mD,平均为14.170 mD,属于中孔、低渗储层,与下伏的二叠系风城组和下乌尔禾组2套烃源岩形成了良好的储-盖组合。②研究区凝析油表现为低密度、低黏度、低凝固点和低含蜡量等特征,正构烷烃以低—中碳数为主,为下乌尔禾组烃源岩成熟—高成熟阶段的产物。③研究区凝析气藏天然气组分以烃类气为主,甲烷与乙烷碳同位素值分布集中,分别为-37.40‰~-36.84‰与-27.55‰~-26.54‰,为腐殖型烃源岩裂解气,来源于下乌尔禾组烃源岩。④研究区下乌尔禾组烃源岩于古近纪早期生成的凝析油气经过不断调整最终于新近纪早期充注形成凝析气藏,从成藏至现今储层流体组分未发生改变,油气藏相态类型也未发生改变,为原生型凝析气藏。