大民屯凹陷西部沙河街组沙三、沙四段储层特征及影响因素

研究区位于辽河坳陷大民屯凹陷西部,南起沈281井,北至沈299井,东起胜11井,西至大民屯凹陷边界,面积约为300km2。研究区沙四段扇三角洲相扇群状分布,前缘砂砾岩体沉积厚度大,为有利沉积相带。沙三段三角洲、河流相沉积砂体分布相对稳定。沙河街组含油层系主要分布在沙四段和沙三段中下部。近年来,大民屯凹陷主要勘探工作集中在潜山上,古近系勘探少有发现。从沉积学和储层岩石学特征入手,结合常规岩石薄片、铸体薄片、扫描电镜、孔渗分析、压汞实验分析结果,对辽河盆地大民屯凹陷沙河街组沙三段、沙四段储层特征及影响因素进行研究。结果表明,沙四段多为低孔特低渗储层,储集空间为原生孔隙、次生孔隙和裂缝。沙三段储层成分成熟度和结构成熟度相对较高,原生孔隙得到一定保存,储集性能好,发育中孔中-低渗储层。沉积作用、成岩作用、物源区母岩岩性及断裂活动,是导致储层物性复杂化的主要影响因素。     

火山岩储集层岩性识别的研究及应用

火山岩的岩性复杂,难以识别;矿物成分复杂,岩石骨架参数难以确定;储集空间一般为孔隙和裂缝的双重介质。在对辽河油田火山岩储层测井数据资料的研究基础上,探讨了火山岩储层的特征。结合多种测井方法,以地层元素测井(ECS)技术为主要手段,对火山岩进行了岩性识别研究,建立了一套火山岩储集层的岩性识别方法。     

成岩作用对川西遂宁组气藏储层质量的控制

洛带气田上侏罗统遂宁组气藏是"十五"期间在川西坳陷致密砂岩领域的重大发现之一,其储层具有特低—超低孔隙度、低渗透率的特点,是川西浅中层少见的储层类型。在对洛带气田遂宁组沉积特征研究的基础上,利用岩石常规薄片、铸体薄片及扫描电境等微观储层研究方法,对该气藏储层的成岩作用及其对储集岩质量的影响进行了研究,建立了成岩作用序列。研究表明:①对遂宁组储层起破坏作用的是压实作用、胶结作用和交代作用,而溶蚀作用、压裂作用则对储层起到建设性作用;②遂宁组最主要的成岩相组合为铁泥膜-硬石膏-白云石-方解石成岩相;③由压实破裂、压实滑动和构造动力形成的微裂缝、粒缘缝有效改善了储层的渗透性。     

裂谷火山型地热系统——奥卡瑞地热田基本特征

东非裂谷是世界著名的四大高温地热带之一,肯尼亚奥卡瑞地热田位于东非裂谷带中部,是典型的大陆裂谷火山型高温地热田。奥卡瑞地区断裂系统十分复杂,按走向可分为5组,其中以北西向为主要断裂,与裂谷走向一致。地热田整体面积约100km2,目前投入生产的主要是东北区、东区和穹顶区,已落实热储面积约42km2,主要有3个热源分别对东区、西区和穹顶区供热。奥卡瑞地热田是肯尼亚目前已知的热储温度最高的地热田,热储埋深为500～3000m,最高温度370℃,平均温度240℃。奥卡瑞高温地热系统的形成,与该地区晚第四纪强烈的火山活动有关,热田的盖层是最近一次火山活动的喷发物,以流纹岩为主,透水性差且裂缝不发育,使盖层成为良好的隔水层。热田热储主要为第四系火山岩,其中西区以凝灰岩为主,东区以粗面岩为主。地热水来源主要为大气降水,部分为渗入来源。综合分析认为,奥卡瑞地热田是一个由新近浅层侵入岩浆提供热源,由断裂、裂缝和有一定孔渗条件的火山岩构成热储,蚀变火山岩、流纹岩提供盖层,断裂作为热流体交换通道的火山型高温地热系统。     

辽河凹陷西部东营组低电阻率油层成因分析与识别

辽河凹陷西部东营组油层电阻率普遍偏低,一般低于8Ω·m,常常与邻近水层电阻率相近或者出现倒置,这种现象严重影响了测井识别精度。在研究区岩石物理实验资料和测井、试油等资料的基础上,综合分析了各地质因素与电阻率之间的关系,结果表明:影响研究区油层电阻率偏低的主要控制因素为砂泥岩薄互层;其次是储层不动水饱和度高,高不动水主要是由于储层岩性细、孔隙结构复杂和泥质含量高等3个因素综合引起,这3个因素单独对储层电阻率影响较小;而储层导电矿物含量、地层水矿化度和泥浆侵入对储层电阻率基本无影响。通过建立东营组Ⅱ主力油层厚度与电阻率的交会图,确定低阻油层厚度界限为0.8~2.7m,电阻率界限为2.5~5.6Ω·m,将低阻油层的界限应用到其他主力油层二次测井解释中,再结合试油结果 ,识别符合率达到80%以上。     

河北献县东部雾迷山组碳酸盐岩热储酸化压裂试验研究

通过对河北献县东部雾迷山组碳酸盐岩进行大尺寸高地应力酸化压裂物理模拟试验与小尺寸温度应力耦合环境下酸化压裂试验,讨论地应力、温度、酸液排量以及压裂模式等因素与碳酸盐岩压裂效果之间的关系,找到碳酸盐岩储层压裂裂缝的生长规律。研究表明：将裂缝发育与裂缝不发育储层碳酸盐岩压裂曲线对比发现,储层岩石裂缝发育程度可明显降低破裂压力;压裂试验中储层岩石内裂缝激活对破裂压力具有显著影响,现场压裂过程中应当考虑到储层工程地质中裂缝发育程度的问题;酸液处理可显著降低破裂压力,更有利于形成复杂裂缝网络,破裂过程中诱发更多声发射事件,同时储层岩石裂缝发育程度直接影响到压裂效果。     

雷家白云岩致密储层改造发展历程与认识

辽河坳陷陈家洼陷北部的雷家地区沙四段发育一套湖相碳酸盐岩致密储层,储集岩性以含泥泥晶云岩、泥晶粒屑云岩为主,具有薄互层发育、天然裂缝发育不均、原油流度低等特点。雷家地区沙四段纵向分为杜家台油层和高升油层上下两段,杜家台组又划分为杜一、杜二、杜三等3个小层。根据油气显示情况,杜三组和高升组是"甜点"相对集中发育的层段。经过大规模加砂、高导流通道、直井复合压裂、水平井体积压裂等4个储层改造发展阶段,得出4点经验认识:地质评价提高"甜点区"辨识是储层改造的基础前提,体积压裂是储层改造理念的发展方向,控破裂泵注方式可有效提高压裂施工成功率,较高的储层钻遇率是水平井分段体积压裂的必要条件。目前雷家致密储层已经形成了相对成熟的水平井分段压裂体积改造工艺,应用于3口水平井,压后平均产量达到13.8m3/d。     

洞穴型碳酸盐岩储层识别及预测技术

塔里木轮古西地区奥陶系灰岩是古岩溶发育的有利场所。根据储层岩电特征的差异,将轮古西地区碳酸盐岩储层划分为孔洞型、裂缝型、裂缝—孔洞型及洞穴型四种类型。其中,裂缝型以及孔洞型储层很难形成稳定的产能;裂缝—孔洞型储层既有较好的储集能力,又有良好的渗透性能,能够形成稳定的产能,是本区一类重要产层(如Lg9、Lg42井);洞穴型储层具有最好的储集能力和渗透性能,是本区最有价值的储层类型。根据地球物理正演模拟和过井地震剖面分析,洞穴型储层在地震剖面上表现为"串珠状"强反射的特点。通过地震属性敏感性分析,优选出了平均反射强度、均方根振幅、平均能量、能量半衰时斜率以及相干属性。利用这些地震属性参数,通过模糊神经网络的方法,对碳酸盐岩储层进行综合预测与评价。多属性综合预测结果与实际钻井资料十分吻合,该区岩溶作用与断裂的关系非常密切,多呈条带状分布,展布方向与断裂发育方向具有比较高的一致性。     

新疆油田火山岩气藏体积压裂机理研究及应用

进行火山岩气藏压裂改造时,通常采用形成单一裂缝的增产改造技术,气井稳产时间较短.借鉴页岩气开发理念,深入研究火山岩气藏体积压裂机理.根据缝内压力传导的力学模型,研究不同液体体系对压力传导的影响,分析无滤饼压裂液体系对体积压裂的作用,优选出压裂液体系;建立不同角度天然裂缝开启的力学模型,确立体积形成的关键力学条件,并针对火山岩气藏压裂目的层的地应力结构进行实际分析.从储层矿物角度出发,研究对比火山岩储层的脆性系数;根据力学条件,结合压裂工艺过程,建立相关模型,优化研究体积压裂关键工艺参数,包括排量、压裂规模等;分析降阻水、线性胶、浓胶液三种不同黏度液体对裂缝网络的作用.在上述研究基础上,针对新疆油田DX1413井实际地质条件,分析该井进行体积压裂的有利条件,并进行压裂设计与改造施工,对施工曲线、施工过程、施工结果进行分析,得到了一些有益的结论,这些结论对火山岩气藏的开发有重要的启迪作用.     

川西南乐山地区峨眉山玄武岩储层压裂改造技术探索

四川盆地主要发育溢流相及喷溢相两类火山岩,其中川西南乐山地区二叠系上统峨眉山玄武岩储层厚度大、分布广、埋深浅,勘探开发潜力大。以玄武岩为主的溢流相火山岩储层低孔、低渗,仅发育微裂缝,压裂改造是其“增储上产”的重要手段。基于室内评价实验,明确了储层非均质性强、岩石力学性质高、酸溶蚀率低、敏感矿物含量高、地层能量低是制约压裂改造工艺效果的主控因素。在此基础上,探索形成了“前置酸降破+两段式加砂+助排快排”的复合酸压技术,优化工作液黏土稳定剂浓度为0.5%、前置酸配方为12%HCl+2%HF、助排剂浓度为0.5%。采用前置酸解堵降破、降阻水造缝、胶液携砂、液氮助排的复合改造技术可进一步提高改造效果,通过优化黏土稳定剂用量、助排剂浓度形成的低伤害压裂液体系,可有效降低液体伤害,提高返排效率。     

徐家围子断陷兴城地区营城组火山岩旋回和期次的划分与对比

徐家围子断陷位于松辽盆地北部的东南断陷区,断陷形成于晚侏罗世到早白垩世早期,中生代火成岩较为发育,主要目的层段为营城组一段.在钻井取心研究基础上,根据火山岩的岩性、电性及地震反射特征,对研究区火山岩旋回和期次进行了划分与对比,建立了营城组火山岩旋回、期次模式,总结了旋回、期次的岩心标志、测井响应标志及地震反射标志.通过对研究区火山岩旋回、期次的对比发现,研究区营城组一段发育4个喷发旋回,旋回I为中基性岩浆喷发,规模小,旋回Ⅱ为流纹质酸性熔浆喷发,局部可见少量安山岩,火山岩发育厚度和范围比旋回I都有明显的增大,旋回Ⅲ为流纹质的酸性岩浆喷发,是本区火山喷发活动的高潮期,旋回Ⅳ以沉火山碎屑岩为主.通过对研究区火山岩地层的划分与对比,为下一步的火山岩勘探开发工作奠定了基础.     

多相干属性分析技术在断裂和裂缝识别中的应用——以松南气田营城组火山岩为例

火山岩油气藏储层岩性复杂,非均质性强.自2006年以来,松辽盆地南部长岭断陷相继钻探腰深1、腰深101、腰深102、腰平1等井,证实该区深层断陷地层的火山岩是深层天然气的重要储层之一.松南气田地质条件复杂,营城组火山岩储层非均质性强,孔、洞、缝是火山岩气藏的主要储渗空间,裂缝的发育程度是决定油气产能高低的主要因素.通过对松南地区营城组火山岩野外露头、岩心观察描述,结合测井测试等综合研究,认为营城组火山岩裂缝以构造成因裂缝为主.针对研究区目的层裂缝特点,采用多相干属性分析技术,对地震资料进行相关处理,获得倾角体、方位角体和相干体等多种属性数据体,通过对倾角体、方位角体和相干体的联合显示,落实了研究区的微断裂及裂缝发育带,为该区开发井位部署奠定了基础,钻井验证吻合程度高.     

欠平衡钻井技术在茨119井中的应用

茨119井是辽河油田茨榆坨采油厂的一口预探井,位于渤海湾盆地辽河坳陷东部凹陷茨榆坨潜山带茨110块,钻探目的是揭示太古界潜山内的含油气情况,控制茨110块的含油面积。为了更好地发现和保护油气层,减少对太古界潜山油气层的污染,施工中采用欠平衡钻井技术。通过对邻井施工情况进行调查,以及欠平衡技术的适应性研究和分析,制定出详细的施工预案。施工中严格落实欠平衡技术措施,茨119井欠平衡井控工作是重中之重,因此针对本井特点制定出合理的防喷预案。泥浆泵采用130mm×3的缸套,不仅实现了大排量携砂,而且有效地防止了沉砂卡钻。钻进至3621m时发现较好工业油气流,最高全烃值达到100%,为辽河油田东部凹陷茨110块的规模化开采提供了基础油气数据,同时也较好地保护了油气层。欠平衡施工有效提高了机械钻速,在19天内安全快速地打完了潜山段870m的进尺,三开平均机械钻速达到4.00m/h,比邻井机械钻速提高23.21%。     

An overview of the Awibengkok geothermal system,Indonesia

The Awibengkok (Salak) geothermal system is a liquid-dominated, fracture-controlled reservoir with benign chemistry and low-to-moderate non-condensable gas content. The geothermal system is hosted mainly by andesitic-to-rhyodacitic rocks, and floored by Miocene marine sedimentary rocks cut by igneous intrusions. The volcanic sequence is capped by an 8400-year-old phreatic explosion breccia, rhyolite fallout tuff (>8400 years and <40,000 years), rhyolite lavas, domes and related tuffs (≥40–120 ka), and dacite-to-rhyodate lavas and domes (185–280 ka) that were erupted across the eastern part of the field from NNE-trending vents controlled by a major fault. More regionally extensive basaltic–andesite to andesite volcanic centers are mostly between 180 and 1610 ka old.     

Geology of ascension Island, South Atlantic Ocean

Ascension Island is the exposed part of a large volcano located about 80 km west of the Mid-Atlantic Ridge axis in the notrhern South Atlantic Ocean. The volcanic rocks of the island form an alkaline suite with a compositional range of basalt-hawaiite-mugearite-benmoreite-trachyte-rhyolite. Trachyte and rhyolite compose approximately 14% of surface exposures. Petrochemical studies by other investigators have shown that the igneous suite was formed by fractional cyrstallization. The abundance of felsic volcanic rocks and the presence of granite and syenite blocks in pyroclastic deposits suggest that felsic magma chambers have formed and could provide the heat for a convective hydrothermal system. The felsic volcanic rocks form two eruptive centers that may be contemporaneous. The oldest rocks exposed on the surface are rhyolite with K---Ar ages of approximately one million years. Faults mapped on the island have four principal trends and appear to be related to regional structures that are apparent on the bathymetry of the island pedestal.     

Geochemical study of fluids on Lesbos island, Greece

Sixty-five water samples and seven associated gas samples have been collected on Lesbos island. The lithology and structural setting have resulted in two main types of hydrological circulation: a shallow circulation hosting low-salinity cold waters and a deeper one, hosting high-salinity hot waters that often emerge in thermal springs near the coast. The cold waters are characterized by Ca(Mg)-HCO₃(SO₄) composition, while the thermal waters generally have an Na-Cl composition. The chemical features of the former can be explained by their circulation in the ophiolite-bearing phyllitic basement and volcanic rocks. Waters circulating in the ultramafic layers of the basement are richer in Mg than the waters whose circulation is mainly within marble levels or volcanic rocks. The Na-Cl thermal waters are characterized by salinities ranging from 1910 to 35,700 mg/kg. As indicated by previous hydrogeochemical and isotopic studies, the Na-Cl composition of the thermal waters on Lesbos is the result of mixing between shallow meteoric waters and marine waters. While interacting with the minerals of the geothermal reservoir, the saline waters retain the Na/Cl sea water ratio but become enriched in Ca²⁺ and depleted in Mg²⁺ with respect to sea water.Processes of hydrothermal alteration at depth are activated by a gas phase enriched in CO₂, which reaches the geothermal reservoir by rising along the deep fractures of the basement. Thermodynamic calculations based on hydrothermal alteration processes occurring at the estimated temperatures of the geothermal reservoir (about 120 °C) indicate that the thermal waters of Lesbos are in equilibrium with talc and dolomite.     

Hydrothermal alteration and fluid inclusion geothermometry of los humeros geothermal field, Mexico

The Los Humeros geothermal field, located in Puebla State, Mexico, occurs in a caldera; drillholes to 3000 m depth encountered a sequence of Quaternary lavas and pyroclastic rocks that range in composition from rhyolite to basalt but are dominantly andesitic. These rest upon the local basement comprising limestone and siltstone of Cretaceous age, which was encountered below 2500 m in the northern part of the field and 1000 m in its southern part.Examination of 29 cores, mostly from below 900 m depth, from 14 wells show that the hydrothermal minerals that occur in the volcanic host rocks include quartz, calcite, epidote, amphibole, sericite, smectite, illite, chlorite, biotite, pyrite and hematite. Their distribution mainly reflects the prevailing hydrological and thermal regime where temperatures locally exceed 300°C. The limestone basement rocks, however, have altered to an assemblage that includes calcite, quartz, wairakite, garnet, wollastonite, parawollastonite, sericite and fluorite.The homogenization temperatures of 356 fluid inclusions were measured and the freezing temperatures of 200 determined. All except two sets of inclusions homogenized into the liquid phase and neither daughter minerals nor a clathrate phase were seen. The homogenization temperatures mostly match measured bore temperatures that range from 250 to 360°C and the apparent salinities are from 0.2 to 2.7 weight per cent NaCl equivalent, but some contribution to freezing point depression by CO₂ is likely.A preliminary model for the hydrology of the field based upon the hydrothermal alteration mineralogy and fluid inclusion data suggests that dilute hot water ascends via faults in the Central Caldera collapse area of the field and moves laterally outward to elsewhere within the caldera.     

Geothermal resources of Hachijojima

Hachijojima is a gourd-shaped volcanic island in the Pacific Ocean. Nishiyama and Higashiyama volcanoes consist of basalt lava and associated pyroclastic rocks. A promising geothermal resource was found in south Higashiyama, associated with an uplift of Tertiary rocks consisting of mainly andesite lava and related pyroclastic rocks, overlain by Quaternary volcanic rocks. Steep high-temperature (over 250°C) and high-pressure gradients occur in the deeper portion of the system near the Tertiary–Quaternary contact, indicating the presence of a cap rock. The cap rock formed by deposition of hydrothermal minerals. Geothermal fluid ascends from the deeper portions to shallow depths along vertical fractures through the cap rock. These vertical fractures form the geothermal reservoir in the Tertiary formation. Three wells were drilled into these vertical fractures, and approximately 30 t/h of superheated steam was obtained from each well during flow tests. The geothermal fluid is mainly a mixture of seawater and meteoric water in an approximate ratio of 1 to 2, based on chemical analyses, with a portion of volcanic gas included. At present a 3.3 MW_e, geothermal power plant is being constructed here.     

Hydrothermal activity in the Tulancingo–Acoculco Caldera Complex,central Mexico: Exploratory studies

Mineral alteration and fluid inclusion studies of drill cuttings and core samples indicate that the sedimentary basement rocks and the volcanic rocks associated with Tulancingo–Acoculco Caldera Complex have been the site of two distinct and major hydrothermal events. The complex, located in the eastern portion of the Trans-Mexican Volcanic Belt, is formed by the Pliocene Tulancingo Caldera and the younger (Pleistocene) Acoculco Caldera, which developed within the older depression. The volcanic rocks are underlain by Cretaceous sedimentary rocks of the Sierra Madre Oriental. The earliest important hydrothermal event occurred during the emplacement of Mid-Tertiary granitic intrusions that metamorphosed the sedimentary rocks; these intrusives are not exposed at the surface. However, granitic rocks were encountered at the bottom of exploratory borehole EAC-1, drilled within the Caldera Complex. The second main event occurred during the formation of the Tulancingo and Acoculco Calderas. Both episodes lead to secondary mineralization that reduced the permeability of the reservoir rocks. A possible third hydrothermal event may be associated with the recent magmatic activity within the Acoculco Caldera.Thermal logs from well EAC-1 display a conductive thermal gradient with maximum temperatures exceeding 300 °C at 2000 m depth. Although there are no active thermal springs in the area, there is extensive fossil surface hydrothermal alteration and cold gas discharges with high He³/He⁴ ratios.