HYDROCARBON GENERATION POTENTIAL AND DEPOSITIONAL ENVIRONMENT OF SHALES IN THE CRETACEOUS NAPO FORMATION,EASTERN ORIENTE BASIN,ECUADOR

Marine shale samples from the Cretaceous (Albian‐Campanian) Napo Formation (n = 26) from six wells in the eastern Oriente Basin of Ecuador were analysed to evaluate their organic geochemical characteristics and petroleum generation potential. Geochemical analyses included measurements of total organic carbon (TOC) content, Rock‐Eval pyrolysis, pyrolysis — gas chromatography (Py—GC), gas chromatography — mass‐spectrometry (GC—MS), biomarker distributions and kerogen analysis by optical microscopy. Hydrocarbon accumulations in the eastern Oriente Basin are attributable to a single petroleum system, and oil and gas generated by Upper Cretaceous source rocks is trapped in reservoirs ranging in age from Early Cretaceous to Eocene. The shale samples analysed for this study came from the upper part of the Napo Formation T member (“Upper T”), the overlying B limestone, and the lower part of the U member (“Lower U”).The samples are rich in amorphous organic matter with TOC contents in the range 0.71–5.97 wt% and Rock‐Eval T_max values of 427–446°C. Kerogen in the B Limestone shales is oil‐prone Type II with δ¹³C of ?27.19 to ?27.45‰; whereas the Upper T and Lower U member samples contain Type II–III kerogen mixed with Type III (δ¹³C > ?26.30‰). The hydrocarbon yield (S₂) ranges from 0.68 to 40.92 mg HC/g rock (average: 12.61 mg HC/g rock). Hydrogen index (HI) values are 427–693 mg HC/g TOC for the B limestone samples, and 68–448 mg HC/g TOC for the Lower U and Upper T samples. The mean vitrinite reflectance is 0.56–0.79% R₀ for the B limestone samples and 0.40–0.60% R₀ for the Lower U and Upper T samples, indicating early to mid oil window maturity for the former and immature to early maturity for the latter. Microscopy shows that the shales studied contain abundant organic matter which is mainly amorphous or alginite of marine origin. Extracts of shale samples from the B limestone are characterized by low to medium molecular weight compounds (n‐C₁₄ to n‐C₂₀) and have a low Pr/Ph ratio (≈ 1.0), high phytane/n‐C₁₈ ratio (1.01–1.29), and dominant C₂₇ regular steranes. These biomarker parameters and the abundant amorphous organic matter indicate that the organic matter was derived from marine algal material and was deposited under anoxic conditions. By contrast, the extracts from the Lower U and Upper T shales contain medium to high molecular weight compounds (n‐C₂₅ to n‐C₃₁) and have a high Pr/ Ph ratio (>3.0), low phytane/n‐C₁₈ ratio (0.45–0.80) with dominant C₂₉ regular steranes, consistent with an origin from terrigenous higher plant material mixed with marine algae deposited under suboxic conditions. This is also indicated by the presence of mixed amorphous and structured organic matter. This new geochemical data suggests that the analysed shales from the Napo Formation, especially the shales from the B limestone which contain Type II kerogen, have significant hydrocarbon potential in the eastern part of the Oriente Basin. The data may help to explain the distribution of hydrocarbon reserves in the east of the Oriente Basin, and also assist with the prediction of non‐structural traps.     

Chemical and isotope characteristics of the Chachimbiro geothermal fluids (Ecuador)

The parent geothermal water proposed for the Chachimbiro geothermal area has calculated values of 2250 mg/L Cl and approximately 5 bar P_CO2. It comes from a reservoir having an estimated temperature of 225–235 °C, although temperatures somewhat higher than 260 °C may be present at the roots of the system. The geothermal reservoir at Chachimbiro is recharged mainly by meteoric water (about 92%) and secondarily by arc-type magmatic water. Carbon and sulfur isotope data support a magmatic origin for the C and S species entering the geothermal system from below, consistent with indications provided by He isotopes.The thermal springs of Na–Cl to Na–Cl–HCO₃ type located in the Chachimbiro area originate through dilution of the parent geothermal water and have reached different degrees of re-equilibration with country rocks at lower temperatures.     

厄瓜多尔Guayas流域综合规划研究

Guayas流域是厄瓜多尔的农业主产区、工商业中心、科技和教育中心,在全国占有极其重要的地位。通过分析Guayas流域在水资源、防洪、水质和水环境方面存在的主要问题,提出了一系列的水资源配置、防洪、水资源保护、水土保持等工程和非工程措施,可有效解决干旱、防洪、水质、水土流失等问题,为顺利实现该国宪法和美好生活规划提出的系列目标提供了保障,同时将产生巨大的社会效益和经济效益。     

厄瓜多尔水力资源及重点水电项目开发时序构想

介绍了厄瓜多尔的水力资源总量及其分布情况,并对水力资源开发利用过程中存在的主要问题进行了剖析。基于厄瓜多尔电力需求预测及电源发展规划,结合该国区位优势及安第斯共同体电力联网战略,对厄瓜多尔国内、国际电力市场发展空间进行了论述。以已有的水电站规划成果为基础,对所推荐的具有开发价值的重点水电项目进行了分析研究,同时结合不同的规划水平年电力市场情况及重点水电项目的地理位置、交通条件及其前期工作深度,提出了相应的开发时序初步构想,以期为我国的能源企业实施"走出去"战略、深入开拓厄瓜多尔水电市场提供决策与参考。     

超薄砂岩储层预测方法研究与应用——以厄瓜多尔安第斯14和17区块为例

目前在油气勘探开发领域,针对中等埋深（2 500～3 500 m）砂岩储层预测的极限厚度一般可以达到5～10 m,而小于5 m的超薄储层准确预测仍为工业界难题。基于厄瓜多尔安第斯14和17区块不同时期采集和处理的多工区叠后地震数据,采用构造趋势面驱动叠后连片一致性处理,压制了多工区相位、能量、频率及闭合差等因素对薄层反射的干扰,降低了储层预测的多解性。基于时-频衰减高精度合成记录标定方法,消除由于地层吸收产生的时间累积误差,精确标定和解剖薄层反射特征,确定了超薄储层分辨的最低主频。基于无井驱动的“稳态变时频子波”叠后宽频有效信号高分辨率处理技术,有效恢复了薄层弱反射系数。基于宽频地震波形约束,优化了相控非线性反演的算法与工作流程。通过上述研究,形成了一套有效的超薄砂岩储层综合预测方法和技术体系,成功地实现了埋深3 000 m、厚度2～5 m潮汐水道砂体的精准预测,新钻滚动评价井和开发井验证其预测准确率达到90%以上。     

Decrease of soil fertility and release of mercury following deforestation in the Andean Amazon, Napo River Valley, Ecuador

Soil erosion and degradation provoked by deforestation in the Amazon is a global concern, and recent studies propose a link between deforestation, soil erosion and the leaching of naturally occurring mercury (Hg). In the Ecuadorian Amazon, elevated deforestation rates and the proximity of volcanoes could play an important role in soil fertility and soil Hg levels. The goal of this study is to evaluate the impacts of deforestation on Andisol and Inceptisol fertility and Hg levels in the Napo River Valley, Ecuador. Results show a significant decrease in surface soil organic matter (-15% to -70% of C and N) and exchangeable cations (-25% to -60%) in deforested plots. Hg concentrations at the surface (0-5 cm), higher in Andisols (225 ng/g average) than in Inceptisols (95 ng/g average), show a decrease of up to 60% following deforestation. Soil erosion exposes the mineral horizon, a layer with a higher Hg burden, to the elements thus provoking and accelerating Hg leaching. These results suggest that deforestation and the associated Hg leaching could contribute to the fish Hg contamination measured in the Napo River watershed.     

NEOGENE OIL AND GAS RESERVOIRS IN THE PROGRESO BASIN, OFFSHORE ECUADOR AND PERU: IMPLICATIONS FOR PETROLEUM EXPLORATION AND DEVELOPMENT

The Progreso Basin is an Oligocene to Recent forearc basin of pull‐apart/translational origin. In Peru, the basin contains proven petroleum reservoir sandstones of Early Miocene age at the Albacora field and the Barracuda‐4 well. In Ecuador, Middle Miocene sandstones tested oil at well Golfo de Guayaquil‐1, and Middle/Upper Miocene and Pliocene (?) sandstones produce gas at the Amistad field. Neogene sandstones are dominated by litharenites and feldspathic litharenites derived from uplifted and eroded Andean, Amotape (metamorphic), and oceanic crustal terranes. These are interpreted to have been deposited in neritic, brackish/coastal, and continental environments with locally steep gradients. The oil‐producing sandstones at Golfo de Guayaquil‐1 (∼12,300 to 12,418 ft RKB) and a gas‐producing sandstone of anomalously high porosity and permeability at Amistad‐1 (9,870 to 9,895 ft RKB) are of interpreted fluvio‐deltaic origin. Sidewall core and wireline log data indicate that reservoir storage capacity is good to very good. Porosity ranges from 15% to 30%, and is consistently greater than 20% where overburden is less than 10,000 ft. Compaction is the principal porosity occluding mechanism; sequential precipitation of authigenic chlorite, clinoptilolite (zeolite), and authigenic calcite has occluded porosity to a variable extent. Porosity preservation is assisted by disequlibrium compaction related to overpressuring throughout the basin. Reservoirs at the Amistad field have variable flow capacity. While the permeability of many sandstones is less than 20 mD, other sandstones, with probable Darcy‐scale permeability, have sustained commercial flows of gas since the onset of production in 2002. The flow capacity of offshore Peruvian reservoirs is limited. The most productive well at the Albacora field flowed at an average rate of only 451 b/d oil prior to abandonment. DST data from the Amistad field and the interpreted fluvio‐deltaic environment of deposition of some sandstones indicate that stratigraphic compartmentalization can be expected locally. Structural compartmentalization due to faulting occurs at Albacora field and is likely in other tectonically active areas. The sands are multistoried; they are interbedded with mudrocks and they typically are on the order of 100 ft or less in thickness. Gross‐sand thickness decreases westward and reservoir‐presence risk increases westward due to a number of factors including increasing distance from the sediment source; erosion of Miocene strata and complete truncation of Pliocene strata at an intra‐Pleistocene unconformity; onlap of the Neogene sequence onto the accretionary complex; and the presence of local bathymetric highs related to active mud diapirism.     

厄瓜多尔Oriente盆地南部区块沉积相模式及有利目标区预测

厄瓜多尔Oriente盆地南部区块Napo组处于海陆交互沉积环境,碎屑岩和灰岩频繁互层.通过分析钻井、测井等相标志,识别出研究区存在海岸平原、潮坪、陆棚和局限台地4种沉积相.通过联井和平面相演化分析,认为研究区为缓坡型混积陆棚边缘沉积相模式,这一相模式以发育广阔的潮坪和混积陆棚为典型特征.潮坪砂岩主要出现在各段的下部,陆棚相的水下浅滩砂岩和灰岩滩出现在各段中部.潮汐水道砂体是最好的储层,灰岩滩为差储层.Wanke,Hormiguero,Horm_sur和Kupi地区为勘探的有利目标区.     

TAMBOCOCHA43区块尾管固井难点及对策

厄瓜多尔TAMBOCOCHA区块单井日产量300~1100 t。因开采需求导致井身结构特殊,φ244.5 mm技术套管下深距产层小于30 m,随钻井径数据失真严重,水泥浆用量难以确定,φ177.8 mm尾管固井施工风险高。下尾管前不通井、窄间隙顶替效率低、产层油水活跃等问题导致固井质量难以保证。通过对复合前置液体系设计,微膨胀胶乳水泥浆体系研究及窄间隙旋转尾管固井施工工艺研究,形成了TAMBOCOCHA区块底水油藏旋转尾管固井技术,该技术有助于尾管下入到位,准确估算裸眼段环空容积,有效提高套管居中度;前置液冲洗效率为93%,水泥浆12 h抗压强度为36.4MPa。现场应用15口井,固井质量优质率达95%,为强底水油藏大斜度小间隙井固井提供技术支撑,解决了厄瓜多尔TAMBOCOCHA区块特殊井身结构的固井难题。      

厄瓜多尔矿业现状与投资前景

厄瓜多尔位于南美洲西北部,是南美洲第三大石油储量国,2017年已探明石油储量82.73亿桶。厄瓜多尔地处环太平洋成矿带,具有丰富的矿产资源,其铜矿和金矿蕴藏丰富,两大铜矿储量达800万t,弗鲁塔北金矿资源量948万Oz,但是已勘探地区仅占厄瓜多尔境内10%。本文以铜金矿矿产资源和石油区块开发为切入点,系统分析了中资企业在厄瓜多尔的投资现状,在此基础上提出了建议:未来合作的优选领域应以石油和金铜矿为主,并建设配套的冶炼加工基地;加大基础设施投资,提供专业技术、人才培养,实现中厄互利共赢。