扇三角洲前缘储层构型及对剩余油分布的影响研究

随着不断的深入开发,国内大部分油田已进入特高含水后期开发阶段,剩余油分布零散复杂,储层构型已经成为控制剩余油分布的主要地质因素。为了进一步提高开发效率,掌控剩余油分布规律,对储层构型进行精细解剖,明确储层构型对剩余油分布的影响关系尤为重要。本文以储层地质学、沉积学及储层层次分析理论为指导,综合利用钻井岩芯、测井及开发动态资料,以河南双河油田437区块核三段Ⅱ油组1、2层为例,对扇三角洲前缘储层内部构型及对剩余油分布的影响进行了精细研究。结果表明:目的层段扇三角洲前缘构型可划分为7级,并且复合砂体存在4种平面组合方式;基于3种砂体边界识别方法,得出单一辫状河道砂体在垂向上的3种叠置方式,即叠加式、切叠式和独立式。在此基础上,本文探讨了储层构型对剩余油分布规律的影响,分析可知复合砂体平面组合样式和单一砂体内部韵律性以及单一砂体之间垂向叠置样式是造成剩余油富集的主要因素,为指导研究区部署剩余油挖潜方案,以及类似沉积环境下构型解剖提供参考。     

MDT测压拟合方法及其在油藏开发调整中的应用

深水浊积水道沉积储层具有多期次水道垂向相互叠置的特点,砂体间连通关系极其复杂,各层砂体储量动用程度分析难度大,加剧了油藏历史拟合的不确定性及多解性,给剩余油分布规律及开发方案调整研究带来极大挑战。为此,展开了后续井MDT测压拟合指导深水浊积水道沉积储层油藏模型校正新方法的研究,其主要思路为利用后续井MDT测压资料作为拟合参数,通过拟合某一时刻下模型中各层压力和对应时间同一位置处新钻井MDT测压数据,不断修正模型中砂体的横向及纵向连通性,使模型砂体叠置关系及连通关系逐渐接近油藏实际,再结合常规开发指标拟合,最终完成剩余油分布规律研究以及开发方案调整研究。实际应用效果表明,后续井MDT测压拟合方法是一种拟合多期水道砂体连通关系的有效方法,显著降低了该类型油藏历史拟合的不确定性,为油田开发方案调整奠定了良好基础。     

致密油藏注水吞吐参数优化模拟——以吉林扶余油层为例

为了优选与注水吞吐开发效果有关的注水时机、注水量、注水速度等工程参数,以吉林扶余油层泉四段Ⅲ砂组致密油藏为研究对象,针对致密油藏不同尺度多重孔缝介质,采用非结构混合网格加密技术,利用有限体积数值模拟方法对压裂水平井的注水吞吐开发工程参数进行了优化计算,得到了注水时机、注水量、注水速度、闷井时间、吞吐周期这5个工程参数的最优范围。并对该吞吐条件下的吞吐开发效果进行了评价,评价结果表明,在进行11个吞吐周期后,产油量可以提高约7 000 m~3,提高采出程度为2.78%,吞吐效果较为明显。     

基于水平井信息的单砂体分布特征研究——以松辽盆地南部长岭凹陷乾安地区某水平井为例

目前中国致密砂岩油气开采通常选用水平井压裂的开发生产方式,这对地下储层砂体特征认识提出了更高的要求。针对直井距离远,地震资料品质差的地区,合理应用已有的水平井信息进行平面单砂体识别及边界厘定,可以有效提高储层内部单砂体分布特征描述的精度。该研究以松辽盆地南部长岭凹陷乾安地区X水平井开发区扶余油层为例,建立直井及水平井联动的单砂体识别方法,对该地区储层单砂体分布特征进行精细研究。研究结果表明:乾安地区扶余油层存在两种单砂体分布模式,其一是早期三角洲平原沉积的"河控带状体",其二为晚期三角洲前缘的"河控面状体"。该研究成果对同类型油田储层砂体分布预测和油田开发方案编制均具有指导意义。     

饶阳凹陷路27断块油水倒置成因分析

针对饶阳凹陷路27断块高孔高渗储层内油水倒置问题,以NgⅡ~1小层路27-18井区为例,从砂体组合与单一砂体2个层面入手,通过岩心观察、测井分析及高压压汞等手段对砂体内部结构进行解剖。研究表明:路27-18井区在NgⅡ~1小层发育心滩与辫状河道2种微相,位于高部位的心滩砂体沉积界面充分发育,砂体上部覆盖泥质沉积,构成与低部位河道砂体间的渗流屏障;河道砂体内部泥质纹层频繁发育,且在砂体上段倾斜砂层分布,形成砂体内部侧向渗流屏障。低部位油气在向上运移过程中分别受砂体内及砂体间两重屏障封阻,未能在高部位成藏,导致井区内油水倒置。     

鄂尔多斯盆地延长组深部长9油层组沉积微相研究

本文通过岩心观察、测井资料分析等手段,对延长组深部长9油层组沉积微相进行了系统分析。认为研究区主要发育三角洲前缘沉积微相,主要的储集砂体为三角洲水下分流河道和河口坝砂体,砂体展布受西北、东北、西南三个方向物源的影响。靠近与烃源岩的砂体是成藏的有利区域,对指导该区下步石油勘探具有重要意义。     

井间河道砂体的井震结合法精细解剖刻画

随着大庆油田萨北开发区开发程度的加深,储层非均质性矛盾日益严重,在密集的井网条件下如何有效预测井间河道砂体展布已成为提高采收率的关键问题。以大庆萨北开发区北二西区块为例,在多学科综合思想的指导下,充分利用井震结合的方法刻画河道砂体平面展布特征。在地震地质层位追踪的前提下沿参考层分别向上向下开取一定的时窗提取多种地震属性,以反距离加权平均法提取井点属性,利用某商业软件的二维聚类分析及作者研究的线性回归分析与聚类分析方法评价地震属性与井点处储层参数的相关性。研究认为,该方法可用于优选刻画河道砂体的地震属性。在此基础上,结合井数据的纵向优势与地震属性的横向优势编制了目的层段的河道砂体平面展布图。     

珠江口盆地白云北坡韩江组层序格架及富砂沉积体研究

通过钻井、测井、地震资料分析,并利用层序地层学、地震沉积学等方法,对珠江口盆地白云北坡韩江组的层序地层格架、体系域和富砂沉积体进行研究。结果表明:SQhj1层序体系域可四分为低位体系域(LST)、海侵体系域(TST)、高位体系域(HST)和下降体系域(FSST),SQhj2层序可划分出低位体系域、海侵体系域及高位体系域,其中低位体系域具有两期特征,可细分为LST1和LST2;SQhj1层序的FSST三角洲砂体和SQhj2层序的低位扇体是研究区重要的富砂沉积体,SQhj1层序FSST中的三角洲前缘近端坝、远端坝以及SQhj2层序LST1和LST2中的斜坡水道复合体、盆底扇以及低位楔三角洲前缘砂体等均为有利的富砂沉积体;SQhj1、SQhj2沉积层序发育演化受盆地古地貌、同沉积断裂及断裂坡折带、沉积物供以及海平面变化等因素的影响。     

砂页交互页岩油储层开采诱导应力场演化规律

页岩油储层立体开发中地应力演化规律复杂,影响邻井工程作业。本文以纵向砂页互层页岩油储层为研究对象,建立应力敏感模型,基于多孔弹性力学建立压裂储层开采诱导应力场演化预测模型,初步表征了页岩纵向非均质性条件下层内、层间开采诱导地应力动态演化规律。结果表明:多层合采时,水平井不同位置处的应力剖面演化规律不同,水平井中段近井处的层间水平应力差随时间减小,而端部的层间水平应力差随时间增大;随着生产进行,高渗层(砂岩)内有效最小水平主应力增大幅度和应力转向角度均大于低渗层(页岩);生产3年后,高渗层(砂岩)内最大应力转向角度达到79°。研究成果可为页岩油储层立体开发布井、压裂设计提供了理论支撑。     

五百梯长兴生物礁气藏储层连通性分析

五百梯长兴生物礁气藏储层岩性以白云岩为主,储层渗透性差非均质性很强。因此对该气藏连通性的研究是必要的。本文通过分析气藏的气体性质和折算地层压力在静态上来判断气藏是否连通,再通过井间干扰测试在动态上描述气藏连通性的好坏。连通性问题的研究能够直接指导五百梯长兴生物礁气藏生产,对于类似气藏也具有很好的借鉴和指导意义。     

Seismic Bearing Capacity of Piles in Liquefiable Soils

An investigation into the base capacity of piles in passing through loose, liquefiable sand and founded in underlying dense sand is presented based on the results of a series of dynamic centrifuge tests on instrumented model pile groups. Excess pore pressures equal in magnitude to the initial effective vertical stress were observed to be generated in the bearing layer of dense sand at both shallow (15 m) and deep (26 m) depths. This induced a dramatic reduction in base capacity and consequently, large settlements of the piles by as much as ~5D₀. A spherical cavity expansion solution for base capacity was validated against measured values showing good agreement, provided that excess pore pressure and dynamic shear stiffness in the bearing layer are known. A simple closed-form relationship, applicable to end-bearing piles, between the degree of liquefaction and the initial pile static safety factor was then developed against plunging failure at the pile base which can be used in design.     

Mobility of nanosized cerium dioxide and polymeric capsules in quartz and loamy sands saturated with model and natural groundwaters

The environmental and health risks posed by emerging engineered nanoparticles (ENPs) released into aquatic environments are largely dependent on their aggregation, transport, and deposition behavior. Herein, laboratory-scale columns were used to examine the mobility of polyacrylic acid (PAA)-coated cerium dioxide nanoparticles (nCeO₂) and an analogous nanosized polymeric capsule (nCAP) in water saturated quartz sand or loamy sand. The influence of solution ionic strength (IS) and cation type (Na⁺, Ca²⁺, or Mg²⁺) on the transport potential of these ENPs was examined in both granular matrices and results were also compared to measurements obtained using a natural groundwater. ENP suspensions were characterized using dynamic light scattering and nanoparticle tracking analysis to establish aggregate size, and laser Doppler electrophoresis to determine ENP electrophoretic mobility. Regardless of IS, virtually all nCeO₂ particles suspended in NaNO₃ eluted from the quartz sand-packed columns. In contrast, heightened nCeO₂ and nCAP particle retention and dynamic (time-dependent) transport behavior was observed with increasing concentrations of the divalent salts and in the presence of natural groundwater. Enhanced particle retention was also observed in loamy sand in comparison to the quartz sand, emphasizing the need to consider the nature of the aqueous matrix and granular medium in evaluating contamination risks associated with the release of ENPs in natural and engineered aquatic environments.     

沈161块S23亚段储层非均质性研究

沈161块S²₃亚段储层属于扇三角洲分流平原亚相沉积。各个沉积相的储层物性差异比较大,砂体横向连续性较差,其非均质性十分显著。垂直和水平的油层没有充分利用,回收率只有13%。油田开发仍具有潜力。文章阐明储层物性特征,认真研究储层非均质性,为下一步指导生产做好准备。     

Aerosol chemical composition over Istanbul

This study examines the chemical composition of aerosols over the Greater Istanbul Area. To achieve this 325 (PM₁₀) aerosol samples were collected over Bosphorus from November 2007 to June 2009 and were analysed for the main ions, trace metals, water-soluble organic carbon (WSOC), organic (OC) and elemental carbon (EC).PM₁₀ levels were found to be in good agreement with those measured by the Istanbul Municipality air quality network, indicating that the sampling site is representative of the Greater Istanbul Area. The main ions measured in the PM₁₀ samples were Na⁺, Ca²⁺ and non-sea-salt sulphates (nss-SO₄²⁻). On average, 31% of Ca²⁺ was found to be associated with carbonates. Trace elements related to human activities (as Pb, V, Cd and Ni) obtained peak values during winter due to domestic heating, whereas natural origin elements like Al, Fe and Mn peaked during the spring period due to dust transport from Northern Africa. Organic carbon was found to be mostly primary and elemental carbon was strongly linked to fuel oil combustion and traffic. Both OC and EC concentrations increased during winter due to domestic heating, while the higher WSOC to OC ratio during summer can be mostly attributed to the presence of secondary, oxidised and more soluble organics. Factor analysis identified six components/sources for aerosol species in PM₁₀, namely traffic/industrial, crustal, sea-salt, fuel-oil combustion, secondary and ammonium sulfate.     

RCP8.5情景下流域景观水文与泥沙 动态连通变化研究

在气候变化背景下,水文连通是风景园林学学科中 景观水文研究的热点和重点之一。目前的景观水文连通研究 多基于静态地表,而忽略地表演化过程,尤其是河底泥沙动态 变化。在总结现有水文连通研究的基础上,结合气候预测模 型、水动力地表景观演变模型及景观连通指数研究方法,以英 国赛文河凯尔苏斯流域为研究区,采用UKCP18气候模型预 测RCP8.5情景下未来10年间(2021—2030年)日降雨量, 运用凯撒二维水动力地表景观演变模型(CAESAR-Lisflood) 模拟10年连续河流演化及淹没模式变化,基于景观连通指数 评价流域景观水文的动态连通变化。结果表明：泥沙变化对淹 没模式和水文连通性产生影响,未来10年间整体连接度(IIC)与 可能连通性(PC)变低,雨季水文IIC与PC变化幅度较大,旱季 平稳。凯尔苏斯流域洪泛区域比河道的沉积作用更明显,流域 总沉积量是侵蚀量的4.6倍。泥沙输移作用使得淹没面积减少 0.25km2 、流域总水量减少40%,水文IIC与PC降低     

Effects of loading rate on rock fracture

By means of a wedge loading applied to a short-rod rock fracture specimen tested with the MTS 810 or SHPB (split Hopkinson pressure bar), the fracture toughness of Fangshan gabbro and Fangshan marble was measured over a wide range of loading rates, =10⁻²–10⁶ MPa m^1/2 s⁻¹. In order to determine the dynamic fracture toughness of the rock as exactly as possible, the dynamic Moiré method and strain–gauge method were used in determining the critical time of dynamic fracture. The testing results indicated that the critical time was generally shorter than the transmitted wave peak time, and the differences between the two times had a weak increasing tendency with loading rates. The experimental results for rock fracture showed that the static fracture toughness K_Ic of the rock was nearly a constant, but the dynamic fracture toughness K_Id of the rock ( ≥10⁴ MPa m^1/2 s⁻¹) increased with the loading rate, i.e. log(K_Id)=a log +b. Macroobservations for fractured rock specimens indicated that, in the section (which was perpendicular to the fracture surface) of a specimen loaded by a dynamic load, there was clear crack branching or bifurcation, and the higher the loading rate was, the more branching cracks occurred. Furthermore, at very high loading rates ( ≥10⁶ MPa m^1/2 s⁻¹) the rock specimen was broken into several fragments rather than only two halves. However, for a statically fractured specimen there was hardly any crack branching. Finally, some applications of this investigation in engineering practice are discussed.     

Deformability of water-saturated sands under cyclic loads

Conclusions 1. The additional plastic deformation in water-saturated sand under cyclic loading with a constant frequency increases nonlinearly with increase of the amplitude of the load and total value of the acting stress and decreases with increase of preliminary static compression.2. Secondary plasticity strains substantially depend on the initial sand density: in sands of average density and dense sands there exist critical parameters of the cyclic action, exceeding of which leads to the occurrence of secondary plasticity strains (additional to the strains during single loading); in loose sands, practically any cyclic action leads to the occurrence of additional strains.3. The amplitude of the vector of the cyclic load (in the plane of the invariants of the stress tensor, equal to _A ² + _1A ² ), leading to the occurrence of secondary plasticity strains, in addition to the dependence on the initial sand density, is proportional to the vector of the static stress state (equal to p²+q²) and depends on the degree of approach to the limit state (_i/_i*).Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 17–19, January–February, 1991.     

Influence of sand layer depth and percolate impounding regime on nitrogen transformation in vertical-flow constructed wetlands treating faecal sludge

Four laboratory-scale units of vertical-flow constructed wetlands (VFCW) were fed once a week with faecal sludge (FS) at a constant solids loading rate (SLR) of 250 kg TS/(m².year) (equivalent to 260-300 g N/(m².week)) for a period of 12 weeks to study: i) the nitrification and denitrification potential of the sand layer of VFCWs and ii) the effect of percolate impounding regime (permanent or batch-impounding) on nitrogen transformation. The TN content of raw FS was characterised by 65% org-N, 34% NH₄-N and 1% NO_x-N. After FS application and a six-day impounding period, 8-13% TN were recovered in the percolate exhibiting the following composition: 70-80% NH₄-N, 25-30% org-N and <1% NO_x-N. A large fraction of the influent organic N (55%) was filtered in the bed and 24-29% of initial NH₄-N were lost due to nitrification and volatilisation. In permanent impounding systems, 8-11% TN were recovered in the percolate versus 13% in batch-operated beds. N loss was increased with sand layer depth (20-40 cm) under permanent impounding regimes.     

Effects of loading rate on rock fracture: fracture characteristics and energy partitioning

By means of the Scanning Electron Microscope (SEM), an examination was performed of the fracture surfaces (including their vertical sections) of both Fangshan gabbro and Fangshan marble specimens fractured at the loading rates MPa m^1/2 s⁻¹. The results showed that one or more branching cracks near the fracture surfaces of dynamic rock specimens were clear and the cracks increased with increasing loading rates. However, such branching cracks were rarely seen near the static fracture surfaces. In addition, with the aid of the Split Hopkinson Pressure Bar (SHPB) testing system and a high-speed framing camera, the energy partitioning in the dynamic fracture process of a short rod (SR) rock specimen was analysed quantitatively. The total energy W_L absorbed by an SR specimen in the dynamic fracture process mainly consisted of the fracture and damage energy W_FD and the kinetic energy W_K of flying fragments. The energies W_L and W_K could be quantitatively calculated through stress wave measurement and high-speed photography in the SHPB testing system. Thus, the fracture and damage energy W_FD could be obtained. The results showed that: (1) the energy W_K increased with an increase in the impact speed of the striker bar or the loading rate; (2) the energy W_FD for dynamic rock fracture was markedly greater than that for static rock fracture, and the W_FD increased with an increase in the impact speed of the striker bar or the loading rate; and (3) the value W_L/W_B (W_B is the energy input into the loading system) in the case of dynamic fracture is much lower than that in the case of static fracture. In addition, the ratio decreases with an increase in the loading rate or the impact speed of the striker bar. This means that the energy utilisation decreases when the loading rate or the impact speed of the striker bar rises. Finally, some application problems are discussed in the paper.     

Deformation and cyclic resistance of sand in large-strain undrained torsional shear tests with initial static shear stress

This paper presents the findings from an experimental study focusing on the undrained cyclic behavior of sand in the presence of initial static shear stress. A series of undrained cyclic torsional shear tests was performed on saturated air-pluviated Toyoura sand specimens up to single amplitude shear strain ($\gamma$_SA) exceeding 50%. Two types of cyclic loading conditions, namely, stress reversal (SR) and stress non-reversal (SNR), were employed by changing the amplitude of the combined initial static shear and cyclic shear stresses. The tests covered a broad range of initial states in terms of relative density (Dr = 20–74%) and the initial static shear stress ratio (α = 0–0.30). The following five distinct modes of deformation were identified from the tests based on the density state, the transient undrained peak shear stress, and the combined cyclic and static shear stresses: 1) static liquefaction, 2) cyclic liquefaction, 3) cyclic mobility, 4) shear deformation failure, and 5) limited deformation. Of these, cyclic liquefaction and static liquefaction are the most critical. They occur in very loose sand (D_r ≤ 24%) under SR and SNR, respectively, and are characterized by abrupt flow-type shear deformation. Cyclic mobility occurs under SR in loose to dense sand with D_r ≥ 24%. Contrarily, shear deformation failure typically occurs under SNR in sand with 24 < D_r < 65%, and limited deformation may take place in dense sand with D_r ≥ 65%. In this paper, a stress-void ratio-based predictive method is proposed to identify the likely mode of deformation/failure in sand under undrained shear loading with static shear. Furthermore, the cyclic resistance is evaluated at three different levels of $\gamma$_SA (i.e., small, $\gamma$_SA = 3%; moderate, $\gamma$_SA = 7.5%; and large, $\gamma$_SA = 20%). The results show that, independent of the density state, the cyclic resistance continuously decreases with an increase in α at the small $\gamma$_SA level, while it first decreases and then increases for both loose and dense sand at the moderate and large $\gamma$_SA levels.