鄂尔多斯盆地定北地区致密砂岩储层AVO研究及应用

AVO技术是利用振幅随炮检距(或入射角)变化的规律,求取地下地层的岩性信息.鄂尔多斯盆地是典型克拉通盆地,构造平缓(倾角不到1°),断层不发育,非常适用AVO理论假设反射层为水平层这一基本条件.根据工区的地震地质特征,在AVO分析的基础上,对用钻井地质、测井资料设计的模型进行AVO正演研究,总结了一套在现有地震分辨率条件下的鄂尔多斯盆地上古生界致密砂岩储层AVO响应特征,即:无论砂岩储层是否含气,其底部反射振幅随入射角增加,均会出现从强到弱一极性反转一从弱到强的现象,只是反转的角度有所差异;在梯度剖面上,含气砂岩与不含气砂岩的亮点特征差异小于较大,据此响应特征预测了有利的储集区.     

基于多矿物模型的致密砂岩脆性指数常规测井评价方法——以鄂尔多斯盆地桐川地区长7段为例

脆性指数是致密砂岩储层评价的重要参数,利用常规测井资料计算脆性指数,对致密砂岩油、气资源的勘探、开发具有重要意义．因此,本文以鄂尔多斯盆地桐川地区长7段为例,开展致密砂岩储层脆性指数常规测井评价方法研究．首先,利用全岩矿物X射线衍射分析、阵列声波测井资料,定量计算了脆性指数;第二,构建岩石矿物组分模型,利用常规测井曲线,通过最优化求解方法,预测了脆性指数;第三,在验证了预测结果的准确性后,将基于多矿物模型的脆性指数计算方法在研究区内推广、应用,并精细刻画脆性指数平面分布规律．研究表明：基于岩石矿物组分和声波特性的脆性指数计算结果具有较高的一致性,利于方法的结合和计算结果的相互验证;研究区内脆性指数与常规测井参数具有一定的相关性,但未达到参数间数学关系定量拟合的要求;以基于声波特性计算的脆性指数为参考值,通过多矿物模型并利用常规测井资料的计算结果具有较高的准确性;研究区东部脆性指数高于西部,相应的工业油流井点也主要分布在东部．本文提出的脆性指数常规测井评价方法,可在无岩心测试、特殊测井资料的条件下计算岩石脆性指数,为致密砂岩油、气资源勘探、开发丰富了技术手段．     

鄂尔多斯盆地陇东地区特低渗透砂岩储层裂缝分布规律及其渗流作用

为了研究鄂尔多斯盆地上三叠统延长组特低渗透砂岩储层裂缝对开发的影响,利用地表露头、岩心、薄片、测井和实验等资料,对裂缝的成因类型、分布特征及其控制因素进行了分布,并对裂缝的渗流作用进行了讨论.研究区主要发育高角度构造裂缝以及水平层理缝、粒内缝和粒缘缝等成岩裂缝,粒内缝和粒缘缝是沟通储层基质粒间孔和粒内溶孔的重要通道,使特低渗透砂岩储层孔隙的连通性变好.裂缝的形成与分布受古构造应力场以及储层岩性、岩层厚度和岩层非均质性等内外因素的影响,现今应力场影响裂缝的保存状态与渗流作用.在燕山期和喜马拉雅期构造作用下,该区分布有北东向、北西向、近东西向和近南北向4组裂缝,但由于岩层非均质性的影响,在某一部位主要表现为两组近正交的裂缝分布型式.受现今应力场的影响,北东向裂缝的连通性好,张开度大,渗透率最高,开启压力最小,是该区的主渗流裂缝方向.随着油田开发,不同方向裂缝的渗透性还将发生动态变化.     

鄂尔多斯盆地上三叠统延长组致密砂岩储层绿泥石对润湿性的影响

润湿性是储层的重要性质,对提高采收率和油气运移研究至关重要.岩石矿物组成影响储层的润湿性,但对其具体作用仍没有明确认识.文章以鄂尔多斯盆地延长组储层为例,开展了储层岩石学特征和润湿性特征的综合研究,分析了绿泥石对砂岩储层润湿性的影响作用.结果表明,延长组储层内绿泥石非常发育,主要包括碎屑状绿泥石、绿泥石膜和黑云母转化的...     

鄂尔多斯盆地延长组高自然伽马砂岩储层特征

鄂尔多斯盆地延长组岩芯分析与测井特征研究表明,相对高自然伽马砂岩具有高长石、高Th、局部高U、K含量变化不大的共同特征,Th、U含量特征与凝灰岩极为相似;相对高自然伽马砂岩具有相对高自然伽马、高声波时差、低电阻率值的测井曲线特征,与凝灰岩测井曲线特征也极其相似;再者,从长6到长4+5油层组的各亚组,凝灰岩层逐渐不发育的同时,伴随相对高自然伽马砂岩发育程度依次增强;上述3项特征预示着延长组相对高自然伽马砂岩可能为同沉积期或较先期沉积的凝灰岩经搬运后作为砂岩组成部分再沉积形成的.四性关系研究表明：（1）依据自然伽马-自然电位曲线重叠图、声波时差-自然电位曲线重叠图,可快速识别相对高自然伽马砂岩;（2）相对高自然伽马砂岩具有相对发育的次生孔隙,非均质性强,一般物性越好,声波时差-自然电位曲线重叠图幅度差越大;（3）计算自然电位-自然电位曲线重叠图的幅度差,反映相对高自然伽马砂岩含油性,幅度差越大,表明其含油性越好.     

基于改进Stacking算法的致密砂岩储层测井流体识别

致密砂岩储层物性差,测井响应对孔隙流体不敏感,应用传统测井解释图版划分流体类型精度较低.机器学习技术通过学习更多维度的特征,可以建立合适的流体识别模型.相较于单一算法,集成学习可以通过联合多个专家模型提升预测精度,但是不同的集成学习策略性能差距较大.本文提出了一种改进的Stacking算法,通过平均影响值法寻找敏感测井曲线作为输入,利用不同的特征集构建多个子模型,并使用不同集成策略将其组合为若干性能更佳的专家模型进行训练,同时引入独立专家避免过拟合,将专家模型的预测结果通过交叉验证的方式进行模拟预测,最后应用元学习器预测最终结果.将该方法用于库车坳陷迪北气藏致密砂岩储层流体识别,测试准确率可达93%,优于CatBoost模型和XGBoost模型,证明了该方法的有效性和适用性.为致密砂岩储层流体识别提供了新的思路.     

鄂尔多斯盆地天然气有效储层识别与评价方法

针对鄂尔多斯盆地天然气勘探开发存在的问题,通过对测井资料及天然气测试资料的分析,建立适合识别天然气有效储层的测井响应特征归一化方法,以及根据测井资料重构天然气有效储层特征曲线的方法,探索了根据测井资料评价天然气产能的方法.本文还分析了目前常用的预测天然气产能方法存在的问题及实际应用中欠缺的条件,形成了以中子、声波、密度测井资料为基本特征参数,用自然伽马、自然电位或电阻率比值参数等作为约束条件的天然气有效储层识别技术及天然气产能评价方法,并对实际测井资料进行了处理.没有试图通过井径校正的方法将受井径扩大影响的曲线恢复到原始地层的响应状态,而是通过极值变化消除井径扩大对声波、密度测井资料在天然气有效储层识别及天然气产能评价方面应用的影响.     

鄂尔多斯盆地东胜地区砂岩型铀矿成岩作用研究

为了解东胜地区砂岩型铀矿含矿砂岩的成岩演化与成矿响应,进而探讨该矿床的成因,采用了薄片鉴定、电镜扫描、电子探针、能谱分析、阴极发光、同位素分析及包裹体测温等多种分析方法,对东胜地区直罗组砂岩进行了详细的成岩作用研究.研究表明,直罗组含矿砂岩的岩石类型主要为岩屑石英砂岩、长石岩屑砂岩和岩屑砂岩;成岩矿物有粘土矿物、碳酸盐、硅质矿物和铁质矿物;砂岩的物性明显受到成岩作用的控制,物性良好的砂岩有利于成矿流体在其中运移、存储并最终成矿.直罗组砂岩经历了早成岩阶段A,B期和表生成岩阶段;成岩环境演化可分为酸性氧化-碱性还原-酸性-氧化还原、酸碱过渡阶段;铀分别以预富集的铀酰离子、活化的铀酰离子、分散吸附状铀和铀矿物沉淀的形式存在.研究指出,在表生成岩阶段,砂岩型铀矿的形成不仅与氧化-还原过渡环境有关,而且与酸性-碱性过渡成岩环境密切相关;氧化-还原、酸性-碱性过渡带有利于铀在砂岩中富集成矿.     

鄂尔多斯盆地致密油储层启动压力梯度对比分析

为探讨非常规致密砂岩油藏储层启动压力梯度问题,以鄂尔多斯盆地HQ、HS地区长6、长8储层为研究对象,开展启动压力实验,对比分析不同储层的启动压力梯度.研究表明,单相水状态水相、束缚水状态油相,均具有随渗透率降低,拟启动压力梯度、真实启动压力梯度升高的趋势.当渗透率低于0.3×10-3 μm2,拟启动压力梯度、真实启动压...     

GBDT识别致密砂岩储层岩性

岩性识别是一项重要的地质基础研究内容.以交会图为代表的常规岩性识别工具虽然在构建的二维或三维图版中能够依据手动归类的测井数据点集来明确各种岩性的一系列测井响应判定,但却无法适用于致密砂岩储层,其原因是该类储层的岩性成分不仅复杂,且较多岩性的测井响应特征具有相似性.根据机器学习在数据分析上的强大性能,本文提出利用在模式识别方面能力出众的GBDT模型来解决岩性识别问题.本文以姬塬油田西部长4+5段致密砂岩储层测井资料为基础,通过设计两种实验来验证提出模型的岩性识别能力.为提高验证效果,在实验中加入BP、PNN和KNN三种传统模式识别模型进行对比.实验结果显示,GBDT识别准确率最高,分别为90.14％和90.41％.基于GBDT较传统模式识别模型能够给出更为准确的预测值,实验结果充分证明了提出模型不仅能有效识别致密砂岩储层岩性,在岩性识别研究领域上还具有良好的推广应用前景.     

Impact of chlorites on the wettability of tight oil sandstone reservoirs in the Upper Triassic Yanchang Formation,Ordos Basin,China

Wettability is an essential property of reservoirs that is of great importance for enhancing oil recovery(EOR) and oil migration. The wettability of reservoirs is generally believed to be strongly affected by mineral compositions but it is not always the case. An integrated study of petrography and wettability was carried out to determine the impact of chlorite minerals on the wettability of the sandstone reservoirs in the Upper Triassic Yanchang Formation. Chlorites are found to be commonly present in the reservoir sandstones as detrital grains, rim-shaped cements, and biotite-chloritized forms with the pore peripheries being largely coated by chlorite, which is the main mineral in direct contact with pores. At pore scale, the wetting state of chlorites can either be oil-wet or water-wet in the tight sandstone reservoirs depending on wettability alteration by oil charge. Chlorites in contact with pores occupy a large of proportions of oil-wet pore walls and are crucial for the formation of oil-wetting state of reservoir sandstones. At core scale, the contents of chlorites in direct contact with pores do not correlate well with the AmottHarvey index due to other factors such as heterogeneity, oil-bearing degrees of samples.     

基于扩径校正和新的气敏感因子的杭锦旗致密砂岩气层识别方法

杭锦旗地区十里加汗区带是中石化高度关注的地区,但其下石盒子组和山西组存在储层井眼条件差、储层致密物性差、岩性复杂、地层水矿化度变化较大等问题,导致气水层识别难.分析了前人研究工作存在的问题,提出削弱或排除井眼扩径影响,突出流体贡献,构建流体识别的气敏感因子和综合多种敏感测井参数进行综合识别的思路和方法,并将其应用于十里...     

Diagenetic fluids evolution and genetic mechanism of tight sandstone gas reservoirs in Upper Triassic Xujiahe Formation in Sichuan Basin,China

The reservoirs of the Upper Triassic Xujiahe Formation in Sichuan Basin have the characteristics of low compositional maturity, low contents of cements and medium textural maturity. The general physical properties of the reservoirs are poor, with low porosity and low permeability, and there are only a few reservoirs with medium porosity and low permeability in local areas. Based on the diagenetic mineral association, a diagenetic sequence of cements is established: early calcites (or micrite siderites) →first quartz overgrowth→chlorite coatings→dissolution of feldspars and debris→chlorite linings→ second quartz overgrowth (quartz widen or filled in remain intergranular pores and solution pores)→dissolution→third quartz overgrowth (quartz filled in intergranular and intragranular solution pores)→intergrowth (ferro) calcites→dolomites→ferro (calcites) dolomites→later dissolution→veins of quartz and calcites formation. Mechanical compaction is the main factor in making the reservoirs tight in the basin, followed by the second and third quartz overgrowth. In a long-term closed system, only feld-spars and some lithic fragments are dissolved by diagenetic fluids, while intergranular cements such as quartz and calcit are not dissolved and thus have little influence on the porosity of the Xujiahe Formation. This is the third factor that may have kept the sandstones of Xujiahe Formation tight finally. The hydrocarbon was extensively generated from organic materials after the second quartz overgrowth, and selectively entered favorable reservoirs to form tight sandstone gas reservoirs.     

基于岩石物理转换模型的苏里格致密砂岩储层测井评价与产能预测

苏里格地区致密砂岩储层勘探开发难度很大,测井解释遇到了储层参数计算和产能预测不准确的问题.本文针对这些难点,基于已有的转换模型,推导并验证了T₂-I和T₂-K_r转换模型,提出了采用转换模型应用于测井综合解释和产能预测的方法.基于实验数据设定孔径大于1 μm的孔隙为大孔,中孔孔径在1 μm和0.03 μm之间,小孔孔径为0.03 μm以下.并建立了不同孔径范围模型中关键参数α与核磁参数T_2lm的关系,这为转换模型在测井解释中的应用提供了必要条件.本文在苏里格西区分别应用T₂-I和T₂-K_r转换模型求取含水饱和度和相对渗透率曲线,并进行产能预测,处理结果显示该方法具有很好的应用效果.

     

The deep-lake deposit in the Upper Triassic Yanchang Formation in Ordos Basin,China and its significance for oil-gas accumulation

The deep-lake facies of the Yanchang Formation represents a large outflowing lake basin in the Ordos area. Its deposition can be divided into four stages: lake genetic and expanding stage, peak stage, inversion stage and dying stage. All the stages are obviously consistent with the evolution of depositional environment and the paleoclimate in the region. The study indicates that the lake basin has evolution fluctuations from highstand to lowstand for four times in its evolution history, and the deposition center of the lake has not obviously moved, staying along the Huachi-Yijun belt. The deep lake sedimentary system mainly consists of deep water deltas and turbidite fans during the entire evolution course of the lake basin in the Late Triassic. The former mainly developed on the slope of steep shore of the delta in the early period of the deep-water expansion and gradually experienced a big shift from deep-water deltas to shallow-water platform delta. And the latter appeared almost in all the above stages and had two types of turbidite fans, slope-moving turbidite fans and slump turbidite fans. The slope-moving turbidite fans have relatively complete facies belts overlapping one another vertically and consist of the slope channel of inter fans, the turbidite channel, inter turbidite channel and turbidite channel front of middle fans and outer fans (or lakebottom plain). However, the slide-moving turbidity fans are formed in the deep lake with their microfacies difficult to be distinguished, and only the center microfacies and edge microfacies can be determined. The two types of the turbidity fans are similarly distributing in the near-root-slope and far-root-slope regions. The deep-lake deposition governs the distribution of the hydrocarbon and reservoir, while the slope-moving turbidite fans are excellent reservoirs for oil-gas exploration due to their great thickness, widespread distribution and accumulation properties.

     

The first extra-large helium-rich gas field identified in a tight sandstone of the Dongsheng Gas Field,Ordos Basin,China

Science China Earth Sciences - Helium gas is a scarce but important strategic resource, which is usually associated with natural gas. Presently, only one extra-large helium-rich gas field has been...     

The deep-lake deposit in the Upper Triassic Yanchang Formation in Ordos Basin, China and its significance for oil-gas accumulation

The deep-lake facies of the Yanchang Formation represents a large outflowing lake basin in the Ordos area. Its deposition can be divided into four stages lake genetic and expanding stage, peak stage, inversion stage and dying stage. All the stages are obviously consistent with the evolution of depositional environment and the paleoclimate in the region. The study indicates that the lake basin has evolution fluctuations from highstand to lowstand for four times in its evolution history, and the deposition center of the lake has not obviously moved, staying along the Huachi-Yijun belt. The deep lake sedimentary system mainly consists of deep water deltas and turbidite fans during the entire evolution course of the lake basin in the Late Triassic. The former mainly developed on the slope of steep shore of the delta in the early period of the deep-water expansion and gradually experienced a big shift from deep-water deltas to shallow-water platform delta. And the latter appeared almost in all the above stages and had two types of turbidite fans, slope-moving turbidite fans and slump turbidite fans. The slope-moving turbidite fans have relatively complete facies belts overlapping one another vertically and consist of the slope channel of inter fans, the turbidite channel, inter turbidite channel and turbidite channel front of middle fans and outer fans (or lakebottom plain). However, the slide-moving turbidity fans are formed in the deep lake with their microfacies difficult to be distinguished, and only the center microfacies and edge microfacies can be determined. The two types of the turbidity fans are similarly distributing in the near-root-slope and far-root-slope regions. The deep-lake deposition governs the distribution of the hydrocarbon and reservoir, while the slope-moving turbidite fans are excellent reservoirs for oil-gas exploration due to their great thickness, widespread distribution and accumulation properties.