Tricyclic terpane geochemistry of source rocks from Northwestern and Central Niger Delta

This distribution of tricyclic terpanes in source rocks from the northwestern and central Niger Delta was used to evaluate their origin, depositional environment and thermal maturity. The rock samples were extracted using Soxhlet extraction method and the saturated hydrocarbon fraction was analysed for biomarkers using gas chromatography-mass spectrometry (GC-MS). The values of soluble organic matter (SOM) and total hydrocarbons for wells AW and OP source rock samples exceeded the minimum 500 ppm and 300 ppm, respectively with values indicating very good to excellent potential source rocks. The tricyclic terpane source parameters and the complementary distribution of hopanes, regular C₂₇-C₂₉ steranes, n-alkanes and acyclic isoprenoid hydrocarbons showed that samples from well AW consist of mixed marine/terrestrial organic matter while those from well OP consist of organic matter largely from terrestrial origin. The values of Pr/Ph ratio for source rock samples from wells AW and OP indicate deposition of the organic matter under suboxic conditions. Sterane and hopane biomarker maturity parameters indicated that the source rock samples from wells AW and OP are at onset of oil generation and main oil window, Most of the source rock samples from well AW are more thermally mature than those from well OP. The results of tricyclic terpane maturity parameters indicated low thermal maturity for the rock samples from both wells with samples from well AW more thermally mature than those from well OP.     

Recognition of the Source Rock Using Biomarkers From Eocene Reservoir Oils

The source rocks of 20 oils in Eocene reservoir from Lengdong oil field have been evaluated using geochemical biomarkers. Most of the oil samples have been undergone light to moderate biodegradation and four of these oil samples suffered heavy biodegradation. The oils were originated from low maturity source rocks within early to middle oil window according to the thermal-maturation-dependent biomarker ratios. Source-related biomarkers indicated that the oils originated from carbonate source rock possessed both high plants and algae organic matter input, while high plants' input was dominant in almost all the oils. The source rocks concerning the oils were deposited under anoxic to suboxic (low EH), salinity to hypersaline, and lacustrine environment with deep water.     

Light hydrocarbon geochemistry of crude oils from Eastern Niger Delta

Abstract

Geochemical evaluation of oil samples from the eastern part of the Niger Delta divided into western, eastern, and central sections of the study area was carried out for the characterization of their light hydrocarbons content in order to correlate oils from different parts. The hydrocarbons in the oil samples were determined using gas chromatographic (GC) technique. The results obtained showed that CPI, Pr/Ph, Pr/nC₁₇, and Ph/nC₁₈ ratios ranged from 0.99–1.55, 2.19–4.79, 0.92–2.35, and 0.27–0.47, respectively. The Pr/nC₁₇ versus Ph/nC₁₈ plot showed that the oils were derived from terrestrial organic materials that were deposited under oxic to suboxic conditions. They are moderately matured with minimal effect of biodegradation on most of the oil samples although two of the oils showed relatively higher degradation. Both bivariate and multivariate plots of the light hydrocarbon ratios differentiated the western and central oils from the eastern oils. The classification of the oils into families was not based on origin but rather on post generative alterations that include reservoir conditions and possibly migration effects. The light hydrocarbon parameters identified can be used in the correlation tools.     

Characterization of groundrolls in the North-West of Niger Delta Nigeria,West Africa

A study of the character and dispersion patterns of groundrolls during seismic survey in the North – West of Niger Delta was undertaken in order to provide information and data for its suppression. Eighty – three raw monitor records were analysed for their frequency, velocity and wavelength characteristics. The results showed that the predominant phase velocities ranged from 278 to 726 m/s with a mean of 376 m/s, the frequency values were 5.3 to 14.1 Hz with a mean of 6.5 Hz. The results showed that the groundrolls in this area were dispersive and this is consistent with the theory of groundrolls in nature and velocity layering and non – homogenous nature of the Niger Delta. Vistal – 12 processing software was also used to carry out F–K analysis on the raw monitor records with groundrolls and the output showed clear monitor record without groundroll. The groundrolls could be suppressed by keeping the geophones arrays and source patterns at distances of not less than 10 m and 70 m respectively instead of 5 m and 50 m used in the survey.     

也门探区1区块第一口风险探井烃源岩地球化学特征

也门探区1区块第一口风险探井自上而下存在下白垩统Saar组、上侏罗统Nayfa组、Lam组和Meem组4套海相烃源岩。依据烃源岩中有机质丰度、有机质类型和有机质成熟度资料,发现Saar组属于潜在的较好烃源岩;Nayfa组和Lam组属有效的中等烃源岩;Meem组则属有效的优质烃源岩。生物标志物的分析结果表明4套烃源岩均富含重排甾烷,但在萜烷系列组成上存在较大差异,主要表现为Lam组以富含伽马蜡烷和C34和C35升藿烷的优势为主要特征,显示咸水环境水体分层下的产物;而Meem组因新藿烷系列异常丰富而有别于其他层位烃源岩,显示浅水、弱还原环境下的沉积特点;尽管Nayfa组也具有C34和C35升藿烷的优势现象,且正构烷烃具有偶碳优势,但伽马蜡烷含量很低,显示强还原条件下水体没有分层的沉积特征;Saar组的正构烷烃系列呈奇碳优势,姥植比高,贫新藿烷和伽马蜡烷物,表明它形成于浅水、还原性弱的沉积环境。     

尼日尔三角洲石油地质特征

尼日尔三角洲盆地是非洲西部近年来油气勘探开发活动最活跃的地区之一.从沉积地层、生储盖组合、构造与圈闭以及油气藏分布等方面简要阐述了尼日尔三角洲石油地质特征.新生界自下而上划分为3个组,印阿卡塔组、阿格巴达组和贝宁组,均为穿时的地层单元,阿卡塔组为主要烃源岩层,阿格巴达组砂泥岩互层为主要的油气储盖层.滚动背斜及其伴生构造...     

大杨树盆地杨参1井烃源岩评价及油源对比

对大杨树盆地杨参1井甘河组、九峰山组和龙江组钻遇的暗色泥岩的有机质丰度、类型和成熟度进行了评价,并对甘河目的3个玄武岩抽提物（原油）的来源进行了分析,生油岩评价结果表明,杨参1井暗色泥岩为中等－非烃源岩,有机质类型为Ⅲ型和Ⅳ型,九峰山组烃源岩处于低成熟阶段,龙江组烃源岩已经达到生油高峰或裂解气体阶段,油源对比证实,杨参1井甘河组含油玄武岩中萃取出来的原油与该井九峰山组生油岩关系不密切,可能来自于浅部成熟度更低的烃源岩。     

伪声波曲线构建方法在尼日尔三角洲地区的应用研究

岩性油气藏勘探开发的关键是地震储层预测,声波测井曲线又是地震储层预测不可缺少的基础资料,但由于种种原因很多地区得不到较好的声波测井曲线,这就需要构建伪声波曲线。构建伪声波曲线是根据能够反映储层特征的非声波储层地球物理测井信息构建的具有声波量纲的新曲线。声波曲线在本质上是一条速度曲线,它包含两个分量：①高频分量,反映井旁不同岩层的层速度;②低频分量,反映地层速度随深度加深而增大。在构建伪声波曲线时,则选用与声波具有良好相关性的测井曲线拟合高频速度分量,利用VSP速度拟合低频速度分量,最后将二者有机结合,就可得到所需的伪声波曲线。     

南鄱阳坳陷原油的地球化学特征

鄱阳盆地是在古生代海相盆地之上发育起来中新生代陆相盆地,南鄱阳坳陷是其次级单元。南鄱阳坳陷油气显示活跃,且主要以油显示为主,乐探1井是显示最好的一口浅层油气探井。从南鄱阳坳陷原油的地球化学特征与新疆非树皮煤成因的煤成油对比可以看到,南鄱阳坳陷原油既具有煤成油的一般特征(如原油物性、族组分、姥植比、碳同位素特征),又有树皮煤的特殊性(如轻烃甲基环己烷指标MCH-Ⅰ、规则甾烷和萜烷的组成特征等),认为南鄱阳坳陷原油是一种主要由树皮煤形成的煤成油,且与该区广泛分布的海陆交互相的二叠系龙潭组树皮煤有亲缘关系。     

合肥盆地大桥凹陷油苗地球化学特征及油源分析

合肥盆地沉积有厚度较大的中新生代地层,但目前尚未发现工业性油流,甚至油气显示也很微弱,所以,证实盆地内部含油气系统的存在具有重要性和迫切性。合肥盆地东北部发现了确切的原油显示,对该原油显示饱和烃气相色谱、色谱-质谱、单体烃碳同位素分析以及油源对比表明,这一原油显示为一成熟原油,母质来源为菌藻类低等水生生物,油源可能为下白垩统朱巷组,朱巷组暗色泥岩可能是一套有效烃源岩。     

渤南洼陷沙三段原油地球化学特征及油源对比

通过对渤南洼陷沙河街组部分烃源岩、原油、含油砂岩抽提物中的饱和烃化合物进行GC和GC—MS分析,研究饱和烃色谱和生物标志物特征,讨论了沙三段原油的来源问题。结果表明,沙四段和沙三段烃源岩均可分为两类,沙三段原油可以分为差别明显的三类。油源对比表明,第一类原油来自沙四上亚段膏岩层段的暗色泥岩夹层,第二类原油来自沙四段膏岩层下部的泥岩层段,第三类原油来自沙三段时期淡水-微咸水还原环境下的暗色泥岩。     

葡深1井深层烃源岩地球化学特征

采用地球化学和盆地模拟技术相结合的方法。研究了松辽盆地北部葡深1井深层烃源岩的地球化学特征,内容包括有机质的丰度、类型以及有机质热演化特征。利用盆地模拟技术模拟烃源岩各地质时期的热演化阶段。结果表明,葡深井下白垩统的登娄库组、营城组,少河子组均发育有暗色泥岩,有机质丰度为中一差,有机质类型较差,有机质成熟较高（多处于高－过成熟状态）。综合认为生油潜力较差,以生气为主。     

Impact of structural setting on hydrocarbon trapping mechanism of onshore Niger Delta basin,Nigeria, using seismic attribute analysis

The evaluation of hydrocarbon trapping system in an onshore Niger Delta basin, Nigeria was studied using well log and seismic data. This is very important in estimation of production cost and assessment of viable reservoir units in petroleum industry. It is the main aim in reservoir characterization, in order to estimate the geometry and trapping mechanism of any particular field under investigation. These were achieved through the integration of 3D seismic and well log data that was acquired from an Onshore Niger Delta basin, Nigeria. From the well logs, three reservoir units was identified namely RS1, RS2, RS3 and these were mapped based on the curve signatures of the geophysical logs. These identified hydrocarbon bearing intervals were mapped on the seismic section using checkshot dataset for time to depth conversion. Four horizons and a total of thirteen fault traces were mapped within the region, with two characterized building structural faults of F2 and F3 features. Fault F4 and F7 are antithetic fault that trends north east to south west and the trapping mechanisms for the region are both a four way closure and fault assisted closure, as the trap is an up dip fault closure against the up thrown side of fault F8. Amplitude, variance and coherence attributes shows the faulting structure of hydrocarbon migration channels and path ways, through which hydrocarbon migration and accumulation occurs within the region. A significant level of contribution was achieved with the variance attributes showing a better resolution of an instant fault detection or identification compared to other attributes studied within the field of interest. The identified hydrocarbon bearing units lies within the same depth across the entire wells. This proved that the region has exhibits little or no tectonic deformation. The presence of structural features such as antithetic and synthetic is responsible for the hydrocarbon entrapment within the region. A detailed analysis of the study location revealed highly faulted region that exhibits a typical Niger Delta tectonic settings.     

Characterization and Quantification of Bakam Field,Offshore Niger Delta,Nigeria

Abstract

Structural maps of horizons in four wells containing hydrocarbon bearing zones with tops and bases at subsea depth range of ?9,491 to ?11,053 ft were produced, showing the trapping mechanism to be mainly fault-assisted anticlinal closures. Petrophysical parameters, time–depth structure, and isopach maps were obtained. The result indicated that the total net volume of the reservoirs yielded oil-in-place of 41.54 MMbbl and gas-in-place of 121.9 tcf. Potential prospects were identified from seismic attributes and reservoir models generated. The results from this study will contribute immensely to a greater understanding of the Niger Delta basin if integrated with geochemical and biostratigraphic studies.     

Preliminary hydrocarbon analysis of crude oils from Umutu/Bomu fields,south west Niger Delta Nigeria

Seven different crude oil samples were collected from two oil fields in the Niger Delta Nigeria. The bulk properties of these crude oils which include API gravity, reid vapour pressure; kinematic viscosity, dynamic viscosity, moisture, gum content and cloud point were analysed. Aliphatic biomarkers were used as supporting tool to deduce the geochemical characteristics such as thermal maturity, depositional environments, source of organic matter and extent of biodegradation. Results show that API° gravity ranged from 29.00° to 85.00°, specific gravity 0.65 to 0.88, 3.00 to 9.00, reid vapour pressure 3.00 to 9.00 kPa, kinematic viscosity 0.90 to 10.10 cSt, dynamic viscosity 0.70 to 8.90 cP, moisture content 0.13% to 26.00%, gum content 6.27 to 45.84 mg/L, cloud point 3.00 to 12.00 °C, pour point ?7.00 to 4.00 °C and flash point <30.00 °C. Distribution of n-alkanes (Pr/Ph, and isoprenoide/n-alkanes ratios) reflects that the oil samples originated mainly from terrestrial organic sources deposited in an oxic paleoenvironment.     

苏北盆地管镇次凹陷阜四段低熟烃源岩生烃史与排烃史模拟

苏北盆地管镇次凹陷阜四段烃源岩属低熟烃源岩（Ｒ０≤０．７％）。在重建该套烃源岩埋藏史和地热史并应用其干酪根Ｃ／Ｓ原子比确定其有机质化学动力学类型和相应的化学动力学参数的基础上，对该套烃源岩的生烃史和排烃史进行了模拟。结果表明，阜四段烃源岩分别在始新世中晚期和渐新世早期进入了生烃期和排烃期。综合地质、油源地球化学资料的研究表明，阜四段低熟烃源岩含油气系统为一个未完成的、目前仍处于持续阶段的含油气系统。该含油气系统的原油具有低熟油的特征。阜四段烃源岩的低成熟和低含油饱和度，且进入排烃期后未经进一步的压实作用，导致该套烃源岩的排烃效率较低，进而造成该含油气系统的油源不足。此外，该区主要断层（管镇断裂）对油气运移起隔挡作用，油气二次运移的距离短，因此，该含油气系统受管镇断裂的控制，其区域展布局限在管镇断裂靠油源的东南一侧。     

油源对比对凹陷勘探的指导意义

应用生物标记化合物、碳同位素等地球化学参数对N凹陷进行了油 -源对比 ,指出原油来自AJ组烃源岩。通过油 -油对比 ,分析了中央隆起带两个含油构造的原油特征 ,指出它们地化特征一致性较好 ,但成熟度高于隆起带上的烃源岩 ,据此推断目前隆起带上所发现的原油应主要来自两侧生油洼陷。建议本区下步油气勘探应选择中央隆起带两侧的有利构造进行钻探 ,有望获得新的突破。     

兰坪坳陷三叠系源岩地球化学特征

通过兰坪坳陷三叠系烃源岩可溶组分族组成、碳同位素、饱和烃馏份生物标志物、岩石热解等方面的综合对比和研究表明 ,该套源岩有机质丰度中等 ,有机质类型以II型有机质为主 ,沉积环境水体盐度较高 ,热演化处于成熟早期 ,属于中等—较好生油岩     

测井资料在生油岩评价中的应用

介绍了生油岩的测井响应特征、有机质特点及生油岩定性、定量评价方法.依据生油岩在不同测井曲线上的响应特征,利用电阻率、声波时差、自然伽马能谱等测井信息,采用自然伽马能谱测井定性识别生油岩、声波-电阻率法定量计算生油岩参数、利用岩心分析的有机碳含量与铀、钍、钾的关系回归计算评价生油岩等不同的方法,以滋2井、林30井、莱64井生油岩的定性、定量测井评价为例,分析测井资料在生油岩评价中的应用,在对不同的计算方法的结果进行误差对比分析后,认为测井资料在生油岩评价方面的应用效果明显.     

Source Rock Characterization Within the Stratigraphic Settings of the Orange Basin,South Africa

abstract

The petroleum source rock potential of different system tracts of a Cretaceous unit of the Orange Basin, South Africa, was evaluated using Rock-Eval pyrolysis. Forty rock samples from eight wells were obtained within the systems tract, Lowstand System Tracts (LST), Transgressive System Tracts (TST), and Highstand System Tracts (HST), in the basin. The results revealed that LST is characterized by mainly marginally organic rich shale samples with a few organic rich rocks, variable organic matter types ranging from Type II to Type IV, and a few samples that are thermally mature but have low organic matter quality. Four samples from two wells (A_F1 and O_A1) in the LST had good petroleum generative potential but were not sufficiently mature for petroleum generation. TST is characterized with a few samples being marginally organic rich, with only one being organic rich, mainly Type III kerogen with few Type IV kerogen, and only a few samples are thermally mature that have low organic matter quality. HST is characterized by many marginally organic rich rock samples, mainly Type III with a few mixed Type II/III kerogen, and only a few samples were thermally mature. The results of this study show that the LST has the best prospect in terms of petroleum generation potential, followed by HST and TST in that order. The study also reveals that limited petroleum source rocks exist, which are also impacted by low thermal maturity levels. The basin is more gas prone than oil.