Spatial-temporal coupling between high-quality source rocks and reservoirs for tight sandstone oil and gas accumulations in the Songliao Basin, China

The spatial-temporal relationship between high-quality source rocks and reservoirs is a key factor when evaluating the formation,occurrence,and prospectivity of tight oil and gas reservoirs.In this study,we analyze the fundamental oil and gas accumulation processes occurring in the Songliao Basin,contrasting tight oil sand reservoirs in the south with tight gas sand reservoirs in the north.This is done using geochemical data,constant-rate and conventional mercury injection experiments,and fluid inclusion analyses.Our results demonstrate that as far as fluid mobility is concerned,the expulsion center coincides with the overpressure zone,and its boundary limits the occurrence of tight oil and gas accumulations.In addition,the lower permeability limit of high-quality reservoirs,controlled by pore-throat structures,is 0.1×10^-3μm^2 in the fourth member of the Lower Cretaceous Quantou Formation(K1q^4)in the southern Songliao Basin,and 0.05×10^-3μm^2 in the Lower Cretaceous Shahezi Formation(K1sh)in the northern Songliao Basin.Furthermore,the results indicate that the formation of tight oil and gas reservoirs requires the densification of reservoirs prior to the main phase of hydrocarbon expulsion from the source rocks.Reservoir“sweet spots”develop at the intersection of high-quality source rocks(with high pore pressure)and reservoirs(with high permeability).

Features and genesis of Paleogene high-quality reservoirs in lacustrine mixed siliciclastic–carbonate sediments, central Bohai Sea, China

The characteristics and formation mechanisms of the mixed siliciclastic-carbonate reservoirs of the Paleogene Shahejie Formation in the central Bohai Sea were examined based on polarized light microscopy and scanning electron microscopy observations, X-ray diffrac- tometry, carbon and oxygen stable isotope geochemistry, and integrated fluid inclusion analysis. High-quality reservoirs are mainly distributed in Type I and Type II mixed siliciclastic-carbonate sediments, and the dominant pore types include residual primary intergranular pores and intrafossil pores, feldspar dissolution pores mainly devel- oped in Type II sediments. Type I mixed sediments are characterized by precipitation of early pore-lining dolo- mite, relatively weak mechanical compaction during deep burial, and the occurrence of abundant oil inclusions in high-quality reservoirs. Microfacies played a critical role in the formation of the mixed reservoirs, and high-quality reservoirs are commonly found in high-energy environ- ments, such as fan delta underwater distributary channels, mouth bars, and submarine uplift beach bars. Abundant intrafossil pores were formed by bioclastic decay, and secondary pores due to feldspar dissolution further enhance reservoir porosity. Mechanical compaction was inhibited by the precipitation of pore-lining dolomite formed during early stage, and oil emplacement has further led to the preservation of good reservoir quality.

Controlling factors of high-quality volcanic reservoirs of Yingcheng Formation in the Songnan gas field

Predicting high-quality volcanic reservoirs is one of the key issues for oil and gas exploration in the Songnan gas field.Core,seismic,and measurement data were used to study the lithologies,facies,reservoir porosity,and reservoir types of the volcanic rocks in the Songnan gas field.The primary controlling factors and characteristics of the high-quality volcanic reservoirs of the Yingcheng Formation in the Songnan gas field were investigated,including the volcanic eruptive stage,edifice,edifice facies,cooling unit,lithology,facies,and diagenesis.Stages with more volatile content can form more high-quality reservoirs.The effusive rhyolite,explosive tuff,and tuff lava that formed in the crater,near-crater,and proximal facies and in the high-volatility cooling units of large acidic-lava volcanic edifices are the most favorable locations for the development of the high-quality reservoirs in the Songnan gas field.Diagenesis dissolution,which is controlled by tectonic action,can increase the size of secondary pores in reservoirs.Studying the controlling factors of the high-quality reservoirs can provide a theoretical basis for the prediction and analysis of high-quality volcanic reservoirs.

A well test model for stress-sensitive and heterogeneous reservoirs with non-uniform thicknesses

In view of the anisotropy,heterogeneity and stress-sensitive permeability in low permeability reservoirs,an analytical well test model was established by introducing the concept of permeability modulus.This model considered the permeability stress-sensitivity,wellbore storage effect,and the skin effect.The perturbation technique and Laplace transformation were used to solve the mathematical model analytically in Laplace space,and the bottom-hole pressure type curves were plotted and analyzed in real space by using the Stehfest numerical inversion.

Influences of gas bubble and ice density on ice thickness measurement by GPR

Lake ice thickness changes with regional hydrometeorology and is closely associated with global climate change.We tested the detection of ice thickness using ground penetrating radar（GPR）in the Hongqipao reservoir.Ice crystals,gas bubbles,ice density and ice thickness were also determined by concurrently drilling for validation.During the tests the gas bubble content was high in the upper and low in the bottom,ice density varied with the bubble content,and the ice thickness was not homogeneous.By comparisons between radar detected and in-situ measured ice thicknesses with theoretical analyses of the influence of gas bubble content on the dielectric constant,a three-layer model with snow, granular ice,and columnar ice was established and the transmission speed of radar wave within the ice was determined.Experience reveals that the equivalent dielectric constant can be used to evaluate the wave speed and the values at 1/3 ice cover depth can be used as equivalent values.Besides,the difference between the theoretical transmission time and the real detection time induced by large gas bubbles increases nonlinearly with the theoretical transmission time or ice thickness.

Fractal Characteristics and Main Controlling Factors of High-Quality Tight Sandstone Reservoirs in the Southeastern Ordos Basin

Due to the complex conditions and strong heterogeneity of tight sandstone reservoirs,the reservoirs should be classified and the controlling factors of physical properties should be studied.Cast thin section observations,cathodoluminescence,scanning electron microscopy(SEM),X-ray diffraction(XRD),and high-pressure mercury injection(HPMI)were used to classify and optimize the reservoir.The Brooks-Corey model and stepwise regression were used to study the fractal dimension and main controlling factors of the physical properties of the high-quality reservoir.The results show that the reservoirs in the study area can be divided into four types,and the high-quality reservoir has the best physical properties and pore-throat characteristics.In the high-quality reservoir,the homogeneity of transitional pores was the best,followed by that of micropores,and the worst was mesopores.The porosity was controlled by depth and kaolinite.The model with standardized coefficients is y=12.454−0.778×(Depth)+0.395×(Kaolinite).The permeability was controlled by depth,illite/montmorillonite,and siliceous cement,and the model with standardized coefficients is y=1.689−0.683×(Depth)−0.395×(Illite/Montmorillonite)−0.337×(Siliceous Cement).The pore-throat evolutionary model shows that the early-middle diagenetic period was when the reservoir physical properties were at their best,and the kaolinite intercrystalline pores and residual intergranular pores were the most important.

Quantifying a critical marl thickness for vertical fracture extension using field data and numerical experiments

In fractured reservoirs characterized by low matrix permeability,fracture networks control the main fluid flow paths.However,in layered reservoirs,the vertical extension of fractures is often restricted to single layers.In this study,we explored the effect of changing marl/shale thickness on fracture extension using comprehensive field data and numerical modeling.The field data were sampled from coastal exposures of Liassic limestone-marl/shale alternations in Wales and Somerset(Bristol Channel Basin,UK).The vertical fracture traces of more than 4000 fractures were mapped in detail.Six sections were selected to represent a variety of layer thicknesses.Besides the field data also thin sections were analyzed.Numerical models of fracture extension in a two-layer limestone-marl system were based on field data and laboratory measurements of Young's moduli.The modeled principal stress magnitude σ3 along the lithological contact was used as an indication for fracture extension through marls.Field data exhibit good correlation(R^2=0.76) between fracture extension and marl thickness,the thicker the marl layer the fewer fractures propagate through.The model results show that almost no tensile stress reaches the top of the marl layer when the marls are thicker than 30 cm.For marls that are less than 20 cm,the propagation of stress is more dependent on the stiffness of the marls.The higher the contrast between limestone and marl stiffness the lower the stress that is transmitted into the marl layer.In both model experiments and field data the critical marl thickness for fracture extension is ca.15-20 cm.This quantification of critical marl thicknesses can be used to improve predictions of fracture networks and permeability in layered rocks.Up-or downsampling methods often ignore spatially continuous impermeable layers with thicknesses that are under the detection limit of seismic data.However,ignoring these layers can lead to overestimates of the overall permeability.Therefore,the understanding of how fractures propagate and terminate through impermeable layers will help to improve the characterization of conventional reservoirs.

基于二维散射变换的湖相碳酸盐岩储层厚度预测方法研究

济阳坳陷沙四段湖相碳酸盐岩受湖盆内沉积环境和构造运动等因素控制,储层厚度变化大,非均质性强,油气开发难度大.为了准确预测湖相碳酸盐岩储层的厚度,本文提出一种基于二维散射变换和随机森林的储层厚度预测方法.首先,引入二维散射变换提取地震时频属性,该变换是在二维小波变换的基础上,通过迭代小波分解和非线性操作来实现的.与传统的二维小波变换对比,散射变换提取的时频属性具有局部形变稳定性以及对噪声鲁棒性的优点,有助于提高储层厚度预测的准确率.在此基础上,在有限测井数据的条件下,利用随机森林算法建立多尺度时频属性与测井解释厚度之间的非线性关系,实现湖相碳酸盐岩储层预测.模型数据的预测结果表明,与基于传统地震振幅属性的厚度预测和基于二维小波变换的储层厚度预测对比,本文所提的厚度预测方法具有最优的性能.叠后三维地震数据的预测结果表明,与基于传统地震振幅属性的厚度预测和基于二维小波变换的储层厚度预测对比,本文所提方法的厚度预测结果与实际钻井数据误差更小,提高了储层厚度预测的精度,清晰刻画了灰礁、灰滩与灰泥等三种沉积亚相的空间展布,有利于后续井位部署和优化.

胜利油区储层测井评价技术发展及展望

胜利油区油气资源丰富,储层类型众多,测井评价在勘探开发工作中发挥了重要的作用。值此建院60周年之际,系统回顾储层测井评价技术发展历程和特色技术,总结经验,展望未来,对于测井专业领域的发展和应用有着积极的意义。根据储层特点和评价难点,系统梳理了常规砂岩、复杂类型和非常规3种类型储层中形成的系列成熟测井评价技术。常规砂岩储层,系统地形成了适用性强的油层标准确定方法,创新了多层合试条件下的岩性、含油性下限约束的电性标准建立方法,开创性地提出了依据不同成岩带划分的储层参数解释技术;复杂类型储层,先后形成了陡坡带砂砾岩岩性测井识别、低渗透砂岩储层有效性评价、低电阻率油层识别及评价等技术;非常规储层,以评价储集性和含油性为主要目的,初步形成了基于二维核磁共振实验的储层参数测井评价技术。这些不同类型储层测井评价技术,都体现了井筒资料与地质认识的结合、岩石物理与测井模型的综合,展现了测井为地质、为油藏服务的能力,并取得了良好的应用效果。展望未来,剩余资源主要分布在隐蔽油气藏及深层,为满足勘探开发的发展和需求,有必要加强实验资料、气测录井和测试生产资料的分析,加强测井评价与地质结合,加强随钻测井、成像、核磁等测井新技术的应用,开展综合研究与评价,从评价目标上拓展产层性质评价和产量预测,从研究手段上,在常规技术的基础上,充分依托专家经验做好样本选取,深化大数据人工智能应用,一定会取得良好效果。

中东巨厚复杂碳酸盐岩油藏分层系均衡注水开发技术

基于中东碳酸盐岩油藏注水开发实践,以两伊地区(伊拉克和伊朗)白垩系巨厚生物碎屑灰岩油藏为例,针对笼统注采导致开发效果差的难题,提出以隐蔽隔夹层为格架精细划分开发层系、多类型多井型井网有机组合、构建均衡注采体系为核心的巨厚复杂碳酸盐岩油藏均衡注水开发技术。两伊地区巨厚碳酸盐岩油藏具有垂向非均质性强、多成因超高渗透层发育、隔夹层隐蔽性强等特征,基于隐蔽隔夹层识别与刻画技术、封隔能力评估技术,提出均衡注水开发技术,形成常规层系架构、精细层系架构、深化层系架构3种均衡注水开发模式和技术。数值模拟表明,均衡注水开发技术可实现两伊地区巨厚复杂碳酸盐岩油藏精细高效注水开发、均衡动用不同类型储量,并为同类油藏的开发优化提供借鉴。

生态库区超厚硬岩条件下大直径长桩桩基施工关键技术

针对生态库区超厚硬岩条件桥梁大直径长桩相对复杂的施工环境,常规施工工艺易造成环境污染、硬岩地层钻进速度慢、维护费用高。为了保护环境也方便施工,提出一种桩基新型施工技术,通过潜孔锤和旋挖钻结合,高效快速完成桩基施工且绿色环保。依托工程实例,对相关施工工艺进行详细阐述。

基于实验的碳酸盐岩气藏储量计算——以X气藏为例

四川盆地X气藏为碳酸盐岩储层,储层层间及层内都具有较强的非均质性,是气藏储量计算面临的困难之一。针对此问题,本文采用实验方法支撑储量计算,首先通过实验测量得到气藏各小层岩心的孔隙度、渗透率等基础物性参数,将小层渗透率校正为克氏渗透率,并根据物性差异将储层分类为孔隙型储层、孔隙-孔洞型储层,再通过产能模拟实验计算得到气藏工业产能对应的有效储层孔隙度和渗透率等储层物性下限。继而通过液膜厚度实验测得各目标储层的液膜厚度,并结合压汞实验测得的孔径分布曲线,得到有效储层中含烃孔隙体积比例,最后通过地质储量计算公式得到气藏储量。研究结果表明:①利用基础物性测试实验、产能模拟实验、水膜厚度实验等实验方法,确定储层物性下限以及有效孔隙体积比例,为气藏储量计算奠定基础,X气藏有效储层孔隙度下限为1.21%~1.56%;②气藏有效储层中含烃孔隙体积比例范围在42.62%~67.73%,通过地质储量计算公式可得到该气藏的有效储量;③该方法对于非均质性较强的碳酸盐岩储层气藏的储量确定具有理论意义和现场指导意义。

库车山前超深巨厚致密砂岩纵向细分层改造技术

塔里木油田库车山前白垩系储层为超深巨厚裂缝性致密砂岩储层,天然裂缝发育,非均质性强,已改造井产气剖面测试显示常规笼统改造纵向厚储层动用不充分,产能释放不彻底。为了解决这一问题,对于油层厚度大且中间有明显隔层的井可实施分层压裂,提高纵向改造程度。通过工程地质一体化研究,利用多种测井数据,建立了一套多尺度近远井裂缝精细识别方法;基于钻井漏失量与产量关系认识,建立了一套综合考虑构造位置、钻井井漏、裂缝发育情况、力学活动性等资料的储层评估分类方法;通过双封隔器管柱力学精细校核,增加伸缩管,优化暂堵材料粒径,形成了“机械+暂堵”软硬分层压裂技术。该技术实现了巨厚储层高效动用,应用20口井,改造后单井产气量由6.7×10^(4)m^(3)/d提高至34.0×10^(4)m^(3)/d,平均增产4倍,提产效果显著,为巨厚致密砂岩储层高效开发提供了技术支撑。

四川盆地南部中二叠统茅口组岩溶古地貌恢复及特征

岩溶古地貌是含油气盆地沉积微相类型、分布范围及储层发育的主控因素,恢复岩溶古地貌对指导油气勘探至关重要。基于钻井、测井及地震等资料,采用沉积速率法和地层厚度对比法对四川盆地南部地区中二叠统茅口组顶部不整合界面的剥蚀厚度进行了精确计算,并根据剥蚀厚度的地区差异及古地貌指示,对岩溶古地貌单元进行了进一步划分。研究结果表明:①四川盆地南部中二叠统茅口组顶部主要发育平行不整合,仅在局部地区形成角度不整合。早中二叠世,上扬子地台内部沉积稳定,构造运动较弱,沉积速率法与地层厚度对比法相对更适用于研究区的岩溶古地貌恢复。②研究区中二叠统茅口组顶部剥蚀厚度为0~120m,其中北部剥蚀最强烈,如LG1井区、W4井区代表了岩溶古地貌地势的最高位置,向东南方向剥蚀强度逐渐减弱,地势逐渐降低;剥蚀最薄弱地区位于LS1井东北部,代表了岩溶古地貌地势的最低位置,整体呈现北部高,南部低,东北部最低的地貌格局。③研究区茅口组古地貌特征控制了岩溶作用的发育强度,可划分为岩溶高地、岩溶斜坡、岩溶盆地等3个二级岩溶古地貌单元以及溶峰盆地、溶丘洼地、丘丛谷地、丘丛洼地、丘丛沟谷、峰林平原、残丘平原等7个三级古地貌单元,其中岩溶斜坡易形成良好的储集空间,为油气圈闭的形成奠定了良好的基础,是下一步有利勘探方向。

基于特征优选和机器学习的第四系空间信息提取研究

【目的】第四系土体是土质滑坡的主要物源,其分布及厚度是开展土质滑坡隐患识别的重要基础。随着机器学习技术的兴起,图像分类技术与人工智能算法结合已成为遥感识别的主流。【方法】以三峡库首秭归向斜盆地为研究区,以Landsat-8影像为基础数据源,以区内现有土质滑坡数据构建样本,采用机器学习软件EnMAP-Box,建立第四系厚度及空间分布信息的随机森林分类模型,筛选出用于识别第四系土体厚度的最优特征子集,得出第四系相对厚度空间分布。【结果】结果表明:Landsat-8遥感影像的光谱特征、主成分、植被指数、湿度、坡度、绿度、均值等与第四系厚度具有强相关性,可作为识别第四系土体厚度的重要特征因子;随机森林模型能有效识别第四系土体厚度信息,且对岩质区提取精度较高;经实地调查验证,模型性能均衡,预测结果合理,可用于多植被中低山区环境的第四系识别。【结论】研究成果可为土质滑坡隐患识别和风险防控提供重要数据支撑。

四川盆地天府地区上三叠统须家河组四段致密储层砂体刻画及有利储层预测

四川盆地天府地区上三叠统须家河组四段(简称须四段)厚层砂岩夹薄层泥岩发育,为当前致密砂岩气的重要勘探层系。但受限于地震纵向分辨率,常规方法难以区分薄层泥岩,对该层段砂岩的精细刻画一直缺乏有效的手段,制约了对盆地砂体展布规律和有利目标区的认识。针对上述问题,建立钻井资料与地震相映射关系,在自然伽马曲线约束下,寻找最佳反演频率参数,提高井间砂体预测精度。采用波形指示模拟的方法精细刻画了上三叠统须家河组四段砂岩的展布特征。结果表明:须四段砂岩具有西厚(55.0~100.0 m)、东薄(15.0~50.0 m)的特征;与须三段相比,砂体厚薄变化转换带(坡折带)向克拉通内部迁移。统计地震工区内22口井数据,坡折带以西砂岩平均孔隙度高(8.0%)、储层厚度大(45.4 m)。结合构造演化、沉积相带展布、砂岩厚度和孔隙度变化,认为四川盆地天府地区上三叠统须家河组四段具有构造控坡折带、坡折带控储层的规律。坡折带以西的储层物性好、厚度大,为勘探有利区。研究结果对须四段勘探深入具有借鉴作用。

厚油层注采模式对纵向波及特征影响研究

注采模式优选对缓解厚油层层内矛盾,提高纵向波及效率具有重要意义。目前尚未形成油水井同时部分打开的井间解析渗流模型,无法支撑厚油层波及特征的研究。为此,采用保角变换方法,将油水井同时部分打开剖面地层依次变换为圆形边界偏心裂缝井地层、单位圆形边界两分支裂缝井地层、注水井全部打开采油井部分打开剖面地层,之后重复上述变换,将注水井全部打开采油井部分打开剖面地层变换为油水井全部打开剖面地层,从而将原始二维渗流过程变换为一维渗流过程,实现了不同注采模式下厚油层层内压力及流线分布的解析计算。与精细数值模拟方法的对比表明,该方法对不同井距/厚度比的情形均可获得较高计算精度。利用该方法,开展了注采模式对纵向波及特征的研究。结果表明:对于底注高采模式,注水井顶部为主力注入层段,注水井顶部1/3的井段控制超过1/2的地层,使超过2/3的采油井段受效;注水对地层的波及主要作用于注水突破前的阶段。在相同的打开厚度下,底注高采的注水突破最晚、波及效率最高,底注中采、中注高采次之,高注高采、底注底采注水突破最早、波及效率最低。采油井的打开厚度越大,注水突破时间越短,但注水突破时的波及系数增大,应综合考虑注水突破时间和波及系数两方面的因素,优选最佳打开厚度。

杭州湾富浅层气区工程超前排气井井距优化研究

对遭遇浅层气灾害地质的工程,一般防治措施多为建设前期布设超前排气井进行控制性排气。深入了解排气过程中气藏内部的气水运移规律,对于排气井井距的设计和高效率排气有重要意义。基于非饱和土两相渗流原理和杭州湾富浅层气区的典型概化地质模型,利用数值模拟方法研究了有控排气条件下气藏内部气水界面运移过程,探讨了影响超前排气井布设的因素,提出一种井距优化方法,并在实际工程中应用。结果表明:不同井口排气速率下,气藏内部气水分布形态与气体排放效果显著不同;工程超前排气井井距的设置可以淹井时间最长和剩余气藏厚度最小进行优化;原始气藏压力是影响井距优化的最显著因素,而储气层下部渗水系数、气藏厚度等并不影响最优井距的确定;调节井距对改善竖向排气井的排气效果随原始气藏压力系数减小而减弱;原始气藏压力系数大,井距适当减小,反之,可适度增加;对于气藏压力系数小的工程,建议发展水平排气井布设技术,以改善排气效果。此外,工程超前排气井的井距设置还应考虑与建(构)筑物的合理安全距离,达到高效、安全和避免投资浪费的目的。

地震多属性储层厚度半定量预测--以鄂尔多斯盆地东南部山2段储层为例

鄂尔多斯盆地东南部山2段致密气储层薄、埋深大、构造平缓、上下围岩存在煤、灰岩等强反射界面,利用低频、弱信号黄土塬二维地震资料,定量预测储层厚度难度大。以延安气田延113-延133井区二叠系山西组山23储层为研究对象,对储层厚度进行分级,基于二维地震资料标准化处理的结果提取地震属性,分析二维地震属性与实钻储层厚度级别之间的关系,建立了多个随机森林算法融合多属性预测方案,进行优化筛选半定量储层厚度预测方案。优选方案预测山23砂体厚度与实钻结果相关系数达0.77。该方法可加深对研究区山23河道展布认识,落实并增加该区地质储量,取得了显著的建井成效。

伊拉克X油田碳酸盐岩隔夹层隐蔽性特征及封隔性评价

基于钻井取芯、试验分析和生产测试等资料,以伊拉克X油田白垩系Mishrif油藏为例,分析生物碎屑灰岩隔夹层隐蔽性特征,以渗透率作为隔夹层主判别参数,宏观与微观互相验证,动静态数据相结合,统计地层压力梯度异常段的渗透率值,确定具有封隔能力的隔夹层识别标准。在统计地层压力梯度异常段时,基于生产测试数据,确定产层的渗透率下限,排除产液造成的地层压力异常;基于微观结构分析确定非渗透层上限,排除压力异常段中渗透层对统计结果的影响。结果表明,生物碎屑灰岩隔夹层的隐蔽性体现在:岩性多样,包括含粒泥晶灰岩、粒泥灰岩、泥粒灰岩、亮晶颗粒灰岩等,颗粒组分为复杂的生物介壳碎屑;低能环境中可发育岩性隔夹层,高能环境与胶结作用相耦合可发育物性隔夹层;孔渗相关性差,隔夹层可具有较高的孔隙度,喉道半径通常小于0.5μm,但孔喉结构差异大;厚度从十几厘米到几十米变化,侧向尖灭快,叠置样式多样;隔夹层的低渗特征在测井上响应较弱,测井判别易发生“误判”或“漏判”。X油田Mishrif油藏隔层渗透率小于0.5×10^(-3)μm^(2),厚度大于2.5 m,夹层渗透率小于0.65×10^(-3)μm^(2),厚度大于1 m。MA段和MB1段封隔性较好,可作为两套开发层系部署不同井网;MB1段和MB2段封隔性较差,分层系注水开发中垂向上存在窜流风险;MB2和MC封隔性较好,将其作为一套开发层系不合理,底注顶采的开发方式将会受效较差。层间封隔性分析论证了巨厚油藏分层系注水开发的可行性,为开发策略调整提供地质依据。