Reservoir Geochemistry of the Kuche Petroleum System in the Tarim Basin, China

The geochemical characteristics of crude oils and reservoir core extracts from the Kuche petroleum system are described and studied systematically by means of various geochemical techniques and methods to acquire molecular information. The results suggest crude oils from the petroleum system can be divided into two groups: marine oils and non-marine oils. The former represents the dominant oils found in the area. Tar mats were firstly discovered and determined accurately in terrestrial oil and gas reservoirs, with Lower Tertiary sandstone reservoirs in the Yaha oilfield of the Tarim Basin. However, based on the ratio of 20S/(20S 20R)C29 sterane as a maturity parameter, lacustrine oils filled into the Tertiary reservoirs in the direction toward the western part of the petroleum system. In contrast, according to the fact that methylcyclohexane indices of eastern oils are greater than those of western oils, the location in which coalgenerated oils filled into the Tertiary reservoirs lies in the eastern part of the petroleum system.     

Reducing the dimensionality of compositional data sets

The high-dimensionality of many compositional data sets has caused geologists to look for insights into the observed patterns of variability through two dimension-reducing procedures: (i)the selection of a few subcompositions for particular study, and (ii)principal component analysis. After a brief critical review of the unsatisfactory state of current statistical methodology for these two procedures, this paper takes as a starting point for the resolution of persisting difficulties a recent approach to principal component analysis through a new definition of the covariance structure of a composition. This approach is first applied for expository purposes to a small illustrative compositional data set and then to a number of larger published geochemical data sets. The new approach then leads naturally to a method of measuring the extent to which a subcomposition retains the pattern of variability of the whole composition and so provides a criterion for the selection of suitable subcompositions. Such a selection process is illustrated by application to geochemical data sets.     

石油储层地球化学的原理及应用

储层地球化学是一门新兴的地学边缘学科，近几年，它已成为评价储层含油特征的重要手段，其核心内容是研究储层流体的非均质性。储层中石油组成的变化除由生物降解和水洗引起外，油源岩相和成熟度的变化同样能造成石油组成的非均质性。识别储层流体的非均质性不仅是重建油气聚集史的基础，而且还能为石油开发提供重要信息。这样能降低勘探目标的风险和油田开发费用。储层流体特征的旧纳依赖于油气、岩心抽提物的地化分析，其研究成果在勘探早期到油田生产结束过程中都能得到应用。     

阜东斜坡区头屯河组短期旋回不同结构类型内储层非均质性研究

探讨准噶尔盆地阜东斜坡区头屯河组短期旋回不同结构类型内储层非均质性,为后期储集层精细开发以及采油率的提高提供理论指导。主要利用岩心、测井以及地震资料,对两个重点短期旋回不同结构类型中的非均质性特征进行详细分析,发现SSC4主要发育A2和C1两种结构类型;SSC7发育C1和C2两种结构类型,且SSC7的C1结构类型中储集砂体非均质性程度中等-强,为最有利勘探目标;次要勘探目标为SSC4的A2和C1两种结构类型中较强非均质性的储集砂体,SSC7的C2结构类型中储集砂体非均质性程度中等,但本身物性较差,勘探意义不大。这为研究区头屯河组的勘探提供地质指导和依据。     

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 factors 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.     

A Review of Formation Mechanism Study on Reservoirs with Tilted Oil-water Contacts

The distribution characteristics of the oil-water contact are the basis for the reservoir exploration and development and reserves evaluation. The reservoir with a tilted oil-water contact has a unique formation mechanism, and the understanding of its distribution and formation mechanism will directly affect the evaluations for the reservoir type, well deployment, selection of well pattern and type, determination of test section, and reserves evaluation. Based on the analysis of reservoir characteristics, petrophysical properties and geological structure in 40 reservoirs worldwide with tilted oil-water contacts, the progress of the research on the formation mechanisms of titled oil-water contacts is summarized in terms of the hydrodynamic conditions, reservoir heterogeneity, neotectonic movement and oil-gas exploitation. According to the formation mechanism of tilted oil-water contacts and the needs of exploration research, different aspects of research methods are summarized and classified, such as the calculation of equipotential surfaces for oil and water in the formation, analysis of formation pressure and analysis of reservoir physical properties and so on. Based upon statistical analysis, it is suggested that the degree of the inclination of the oil-water contact be divided based on the dip of oil-water contact(DipTOWC). The tilted oil-water contact is divided into three categories: large dip(DipTOWC≥55 m/km), medium dip(4 m/km≤DipTOWC55 m/km), and small dip(DipTOWC4 m/km). The classification and evaluation method can be combined with structure amplitude and reservoir property. The formation mechanism of domestic and international reservoirs with tilted oil-water contacts are summarized in this paper, which have important significance in guiding the exploration and development of the oilfield with tilted oil-water contacts, reserves evaluation, and well deployment.     

Quantifying and testing differences among means of compositional data suites

Commonly, geological studies compare mean values of two or more compositional data suites in order to determine if, how, and by how much they differ. Simple approaches for evaluating and statistically testing differences in mean values for open data fail for compositional (closed) data. A new parameter, an f-value, therefore has been developed, which correctly quantifies the differences among compositional mean values and allows testing those differences for statistical significance. In general, this parameter quantifies only therelative factor by which compositional variables differ across data suites; however for situations where, arguably, at least one component has neither increased nor decreased, anabsolute f-value can be computed. In situations where the compositional variables have undergone many perturbations, arguments based upon thef-values and the central limit theorem indicate that logratios of compositional variables should be normally distributed.     

Water-rock interactions and chemical compositional variations during ductile deformation of the NW-striking shear zone in the Jiapigou gold belt,China

Two kinds of mylonite series rocks, felsic and mafic, have been recognized in the NW-striking shear zone of the Jiapigou gold belt. During ductile deformation, a large amount of fluid interacted intensively with the mylonite series rocks: plagioclases were sericitized and theAn values declined rapidly, finally all of them were transformed to albites; dark minerals were gradually replaced by chlorites (mostly ripidolite). Meanwhile, large-scale and extensive carbonation also took place, and the carbonatization minerals varied from calcite to dolomite and ankerite with the development of deformation. The δ¹³C values of the carbonates are −3.0‰ – −5.6‰ suggesting a deep source of carbon. The ductile deformation is nearly an iso-volume one (f _v≈1). With the enhancement of shear deformation, SiO₂ in the two mylonite series rocks was depleted, while volatile components suchs as CO₂ and H₂O, and some ore-forming elements such as Au and S were obviously enriched. But it is noted that the enrichment of Au in both the mylonite series rocks did not reach the paygrade of gold. The released SiO₂ from water-rock interactions occurred in the form of colloids and absorbed gold in the fluid. When brittle structures were formed locally in the ductile shear zone, the ore-forming fluids migrated to the structures along microfractures, and preciptated auriferous quartz because of reduction of pressure and temperature. Fluid inclusion study shows that the temperature and pressure of the ore-forming fluids are 245–292°C and 95.4–131.7 MPa respectively; the salinity is 12.88–16.33wt% NaCl; the fluid-phase is rich in Ca²⁺, K⁺, Na⁺, Mg²⁺, F⁻ and Cl⁻, while the gaseous phases are rich in CO₂ and CH₄. The δD and δ¹⁸O, values of the ore-forming fluid are −84.48‰ – −91.73‰ and −0.247‰ – +2.715‰ respectively, suggesting that the fluid is composed predominantly of meteoric water. This project is financially supported by the National Natural Science Foundation of China (No. 9488010).     

珍珠的成分特点研究

运用ICP-MS、IC、XRD、IR等分析方法,对我国不同成因、不同产地的珍珠及其贝壳的成分进行了系统的研究,结果表明:淡水养殖珍珠中的P、Mn、Ba的含量相对较高,而海水珍珠中的Sr、Zn、Cr、Ni的含量相对较高;与淡水养殖珍珠相比,海水养殖珍珠中的阴、阳离子种类多,含量高,氨基酸总含量高而稳定;海水养殖珍珠及其贝壳或淡水养殖珍珠及其贝壳在成分上的变化基本一致,而海水养殖珍珠的珍珠层与珍珠核之间差异较大。该结论对于珍珠的鉴定及其理论药理研究具有重要的意义。     

高升油田储层流体非均质性研究

高升油田的主力产层沙三层莲花油层由阵发性的浊积砂岩构成，储层的非均质性强，储层流体－石油的总体组成和分子组成同样存在明显的非均质性，它依赖于储集砂岩的孔隙度和渗透率以及它们所处的地层和构造位置，流体非均质性的空间分布反映了油田的聚集史，后期的蚀变作用使储层流体的非均质性更加复杂化，正确认识储层流体的非均质性能为石油开采提供有用信息。     

八面河油田沙三段储层砂体层内非均质性研究与探讨

以八面河油田沙三段为例,从测井解释储层参数、储层砂体韵律性、沉积相分析和非均质类型研究分析,探讨了层内非均质性类型及其特征。研究表明该区层内非均质类型共有箱型、钟型、漏斗型、中间突变型和复合型等五种。沙三沉积期不同微相非均质程度不同,席状砂、远砂坝、水下分流河道等微相属强非均质体,河口砂坝非均质程度弱,属最好储集层。     

大北油田萨尔图油层特低渗储层宏观非均质性研究

大北油田萨尔图油层属于特低渗透储层。从沉积微相的角度对萨尔图油层宏观非均质性研究表明,储层非均质性较强,而其非均质性主要受控于沉积环境、成岩作用及裂缝发育情况等因素。萨尔图油层在本区发育水下分流河道、席状砂、远砂坝和浊积扇(滑塌沉积)等4种储层微相,油层非均质性在各种沉积微相之间的过渡部位及浊积扇微相中较强;其次为席状砂微相和远砂坝微相,在水下分流河道中相对较弱。     

大庆油田葡萄花油层组储层非均质性主控因素分析

本文对萨尔图油田中部葡萄花油层组的非均质性进行定量半定量研究,认为葡萄花油层组PⅠ2小层层内非均质性最严重,与沉积微相密切相关;单砂层垂向上渗透率的变化以正韵律和复合式韵律为主,局部发育反韵律模式;层内非均质性强弱依次为PⅠ2a、PⅠ3、PⅠ2b、PⅠ1、PⅠ4;层间非均质性在PⅠ3和PⅠ4间表现得最强,其它相对要弱;各小层平面非均质性相差无几,整体表现为较强的非均质性。     

Some aspects of transformations of compositional data and the identification of outliers

The statistical analysis of compositional data is based on determining an appropriate transformation from the simplex to real space. Possible transfonnations and outliers strongly interact: parameters of transformations may be influenced particularly by outliers, and the result of goodness-of-fit tests will reflect their presence. Thus, the identification of outliers in compositional datasets and the selection of an appropriate transformation of the same data, are problems that cannot be separated. A robust method for outlier detection together with the likelihood of transformed data is presented as a first approach to solve those problems when the additive-logratio and multivariate Box-Cox transformations are used. Three examples illustrate the proposed methodology.     

海平面升降对海相临滨储层宏观非均质性控制机理—以哈得逊东河砂岩储层为例

本文研究海平面变化对海相单一亚相储层宏观非均质性的影响。以经典层序地层学理论为指导,应用岩心测试、测井数据,对哈得油田东河砂岩段临滨亚相储层宏观非均质性进行了分析,提出了海平面升降对临滨亚相储层宏观非均质性控制机理,确定了海平面相对变化控制的储层宏观非均质性分布模式。结果表明,准层序、准层序组及体系域内不同级次的海平面变化,对沉积物形成的水动力条件及沉积后所处表生环境产生较大影响,各项储层宏观非均质参数表现出明显的规律性,使准层序内单一临滨亚相储层宏观非均质性表现为向上减弱的变化趋势;准层序组内由于准层序堆砌特征差异,使退积式准层序组内临滨亚相储层宏观非均质性呈向上变强的特征,而进积式准层序组内表现为由强到弱的趋势;高位体系域内单一临滨亚相储层宏观非均质性总体表现为向上逐渐减弱。     

坪北油田延长组长6油组储层层内非均质性研究

在坪北油田应用岩心观察、岩心分析化验资料、测井解释成果、测试及开发动态等方面的资料分析长6储层的非均质性,重点解剖层内非均质性特点,总结了正韵律,反韵律,复合韵律和交互韵律4种类型的层内非均质性。夹层分布较广泛,加剧了层间非均质性。     

Molecular and isotopic fractionation of light hydrocarbons between oil and gas phases

Oil-gas phase equilibria is likely to represent one of the main causes of observed compositional heterogeneities in fields. Our research has been focused mainly on the light C₁₄-hydrocarbons fraction and can be divided into two parts. The first part was performed with a fluid mixture of a Middle East crude oil and a synthetic gas, and includes PVT experiments, high resolution-gas chromatography (HR-GC) and ¹³C gas chromatography-combustion-isotopic ratio mass spectrometry (GC-C-IR-MS) analyses. Our observations show that under a given set of PT conditions there is a preferential separation of aromatics into the oil phase and isoalkanes into the gas phase. Moreover, the data from ¹³C GC-C-IRMS suggest a small isotopic fractionation between the two phases, with the gas being relatively isotopically lighter. The second part is theoretical, and uses Equation of State (EOS) calculations which successfully simulate the previous experiment.     

The analysis of compositional effects as exemplified by the study of elections

Some people are influenced by other people who live near them. They vote for the same political party as their neighbours and they go to church on Sunday because that is what most other people in the area do. This phenomenon is known as the compositional effect of the environment. This article offers a survey of the history of the analysis of such effects, of the explanations that can be given for them and of the research methods that can be used to establish them. The most important conclusions regarding political preference are given, and a direction in which research into compositional effects should develop is also indicated.     

油藏地球化学在沈家铺断块油田的应用

首先采用色谱、色谱-质谱等分析技术研究了本区枣Ⅴ油组原油地球化学特征及断块间油藏流体连通性，然后利用岩石热解(Rock-Eval)和薄层色谱-火焰离子检测技术(TLC—FID)，结合试油及测井资料，建立了枣Ⅴ油组油干水层划分的地球化学标准，研究了流体(原油)及其性质在纵向上和平面上的变化及分布规律。研究结果表明，枣Ⅴ油组原油为低成熟原油，其源岩形成于微咸水一半咸水湖相还原环境，主要由菌藻类有机质组成，但某些藻类可能是其源岩有机质的主要贡献者；枣Ⅴ油组断块间油藏流体不连通；纵向上，储层流体非均质性强，总体而言，随深度增加枣Ⅴ油组储层含油性逐渐变差，但原油性质逐渐变好。平面上，储层流体非均质性强，不同断块含油性不同，同一断块不同部位含油性不同；不同断块原油性质不同，总体而言，从NE到SW，枣Ⅴ油组的原油性质逐渐变好。