Characteristics of water alternating CO_(2)injection in low-permeability beach-bar sand reservoirs

Water flooding can be ineffective in highly heterogeneous low-permeability beach-bar sand reservoirs.The introduction of CO_(2)flooding helps boost the oil production of the reservoirs but only in an early stage.During the late stage of flooding,gas channeling would occur.Water alternating gas(CO_(2))(WAG)process can be used to delay gas channeling and improve the effect of CO_(2)injection,though its adaptability to beach-bar sand reservoirs remains unclear.In order to clarify CO_(2)injection characteristics in these reservoirs,experiments were carried out in high-temperature high-pressure NMR on-line displacement experiment apparatus to simulate different flooding modes on synthetic cores that can reflect the vertical heterogeneity of beach-bar reservoirs.Different CO_(2)injection modes were implemented on these cores and the displacement characteristics and residual oil distribution features during both WAG injection and continuous CO_(2)injection were analyzed quantitatively and qualitatively.The results show that the scheme of WAG injection after continuous CO_(2)injection can obtain better oil displacement efficiency than that of the scheme of continuous CO_(2)injection after WAG injection,but there is no significant difference in respect of oil displacement efficiency of WAG flooding between the mode of bar-injection e beach-production(injection into bar sand e production from beach sand)and the mode of beach-injection e beach-production(injection into and production from beach sand),with the former mode having a higher oil recovery rate.The wider pore-size distribution range of microscopic residual oil after WAG injection shows great potential of enhancing oil recovery from subsequent continuous gas injection.When WAG injection is implemented prior to continuous CO_(2)injection,the displacement effect of the latter is more significant.This research may provide a theoretical basis for CO_(2)EOR in this type of reservoirs.

Development,sand control mechanism and hydrocarbon accumulation of beach-bar sandstone in a saline lake basin:A case from the Neogene of southwestern Qaidam Basin,NW China

Based on the data of field outcrops,drilling cores,casting thin sections,well logging interpretation,oil/gas shows during drilling,and oil/gas testing results,and combined with modern salt-lake sediments in the Qinghai Lake,the Neogene saline lake beach-bars in southwestern Qaidam Basin are studied from the perspective of sedimentary characteristics,development patterns,sand control factors,and hydrocarbon accumulation characteristics.Beach-bar sand bodies are widely developed in the Neogene saline lake basin,and they are lithologically fine sandstone and siltstone,with wavy bedding,low-angle cross bedding,and lenticular-vein bedding.In view of spatial-temporal distribution,the beach-bar sand bodies are stacked in multiple stages vertically,migratory laterally,and extensive and continuous in NW-SE trending pattern in the plane.The stacking area of the Neogene beach-bar sandstone is predicted to be 3000 km^(2).The water salinity affects the sedimentation rate and offshore distance of beach-bar sandstone,and the debris input from the source area affects the scale and enrichment of beach-bar sandstone.The ancient landform controls the morphology and stacking style of beach-bar sandstone,and the northwest monsoon driving effect controls the long-axis extension direction of beach-bar sandstone.The beach-bars have a reservoir-forming feature of“one reservoir in one sand body”,with thick beach-bar sand bodies controlling the effective reservoir distribution and oil-source faults controlling the oil/gas migration and accumulation direction.Three favorable exploration target zones in Zhahaquan,Yingdong-eastern Wunan and Huatugou areas are proposed based on the analysis of reservoir-forming elements.

Diagenetic Evolution and Formation Mechanisms of High-Quality Reservoirs under Multiple Diagenetic Environmental Constraints:An Example from the Paleogene Beach-Bar Sandstone Reservoirs in the Dongying Depression,Bohai Bay Basin

The diagenetic environment, diagenetic responses, diagenetic transformation model and formation mechanisms of high-quality reservoirs（beach-bar sandstones of the Paleogene fourth member） in the Dongying depression were studied through the analysis of fluid inclusions, thin section and burial evolution history. The diagenetic fluids of the beach-bar sandstone reservoirs evolved from early high salinity and weak alkalinity to low salinity and strong acidity, late high salinity and strong alkalinity and late low salinity and acidity, which were accompanied by two stages of oil and gas filling. The fluids at the margins of the sandbodies were continuously highly saline and strongly alkaline. The western（eastern） reservoirs experienced early open（closed）, middle open, and late closed diagenetic environments during their burial history. The flow pattern was characterized by upwelling during the majority of the diagenesis（in the east, a non-circulating pattern transitioned into an upwelling current）. Due to the evolution of the diagenetic fluids, the diagenetic sequence of the beach-bar reservoirs was as follows： early weak carbonate cementation; feldspar and carbonate cement dissolution and authigenic quartz cementation; late carbonate and anhydrite cementation, authigenic feldspar cementation, and late quartz dissolution; and late carbonate cementation, feldspar dissolution, and authigenic quartz cementation. The diagenetic strength during these stages varied or was absent altogether in different parts of the reservoirs. Due to the closeness of the diagenetic environment and the flow pattern of the diagenetic fluids, the diagenetic products are variably distributed in the sandstones interbedded with mudstones and in the fault blocks. The evolution of multiple alternating alkaline and acidic diagenetic environments controlled the distribution patterns of the reservoir diagenesis and reservoir space, and the reservoir quality index, RQI, increased gradually from the margins to the centers of the sandstones. The closeness of the diagenetic environment and the flow patterns of the diagenetic fluids controlled the differences in the reservoir properties among the fault blocks. With increasing distance from the oil-source faults, the RQI values in the west gradually decreased and in the east initially increased and then decreased.

Genesis of reservoir heterogeneity and its impacts on petroleum exploitation in beach-bar sandstone reservoirs:A case study from the Bohai Bay Basin,China

Reservoir characteristics of beach-bar sandstone reservoirs in the 2nd member of the Shahejie Formation in Banqiao Sag are studied by means of well logging interpretation,thin section observation and physical property analysis.Further,the influence of deposition,diagenesis and internal architecture interface on reservoir quality are quantitatively analyzed.On this basis,the geneses of reservoir heterogeneity of beach-bar sandstone reservoirs are summarized.The following results are obtained.(1)Primary pores,secondary pores and micro-fractures are the main types of reservoir space in the study area,and the primary intergranular pore is the main pore type;the microscopic heterogeneity of reservoirs is strong,and the physical properties of beach-bar reservoirs in different regions vary widely.(2)Tectonicdeposition,diagenesis and reservoir internal architecture work in unison to cause the heterogeneity of beach-bar reservoir quality in the 2^(nd) member of the Shahejie Formation in Banqiao Sag;the locations and scales of beach-bar sand bodies are obviously different in different fault blocks in the study area,determining the macroscopic distribution of beach-bar reservoirs;differential diagenesis intensifies the degree of reservoir heterogeneity;the fine-grained argillaceous deposits between different architecture units of beach-bar reservoirs are critical to the quality of reservoirs.(3)The differential distribution of beach-bar reservoir quality parameters in the study area affects the spatial heterogeneity of reservoirs,which not only controls the original oil/gas distribution,but also has a significant influence on the effect of waterflooding and leads to the local enrichment of remaining oil.

Characteristics and mechanism of low permeability beach-bar sandstone reservoir of Es4 in Dongying sag

Core and cast sections observation and description,and logging,scanning electron microscope and core lab analysis data etc. were applied to the present research of the characteristics and mechanism of low permeability beach-bar sandstone reservoir of Es4 in Dongying sag. The results indicated the reservoir has the characteristics of middle-low pores,low-permeability,low compositional and structural maturity,and thin throat. The low-permeability is mainly due to sedimentation (fine particles and argillaceous inter beds) and diagenesis (compaction,cementation,and dissolution). The cementation reduced the physical property of the reservoir mainly by carbonate cementation,quartz autogeny and enragement,and autogeny clay. Clay minerals usually jam the pores by filling holes,close-fitting the wall of hole,bridging,wrapping grains,and separate attaching the pores and so on. The dissolution is insufficient so as not to improve the porosity and permeability of the reservoir obviously. So it is also an important factor of forming low-permeability reservoir.

胜利油田未动储量开发技术及实践

胜利油田未动储量规模大,是油田后续建产稳产的重要接替阵地。但多年的开发实践证实,这部分储量的整体动用存在很多问题,制约着油藏效益开发和建产。针对这部分油藏品位差、动用难度大和开发效果差的特点,系统梳理了胜利油田未动储量的类型及分布特征,明确了主要的未动储量类型和重点攻关目标。结合近年来在砂砾岩、滩坝砂和深层低渗透稠油等油藏类型方面的开发实践,分析了砂砾岩油藏大斜度井大规模压裂、低渗透滩坝砂油藏压驱和深层低渗透稠油油藏降黏复合压驱等3种主要的未动储量开发技术及实践。长井段大斜度井大规模压裂技术,通过地质工程一体化实现工程甜点与地质甜点的结合,在低品位砂砾岩油层中的应用大幅提高了油藏产能;压驱注水开发技术创新开发理念,实现了低渗透滩坝砂油藏补能增产的突破;降黏复合压驱开发技术通过转变开发思路,实现了深层低渗透稠油油藏效益开发的突破。这3种油藏类型从单井提产、油藏补能和低成本开发等方面实现了未动储量的有效动用,取得了良好的开发效果。开发技术的突破、开发理念的转变是未动储量有效开发的必由之路,对胜利油田其他未动储量的开发具有非常重要的示范和指导意义。

准噶尔盆地二叠系上乌尔禾组退覆式扇(辫状河)三角洲前缘-滩坝复合砂砾岩沉积特征及控制因素

近年来准噶尔盆地的油气勘探从源外常规圈闭逐渐走向源内岩性圈闭,二叠系上乌尔禾组是该盆地增储上产的主力层系,沉积体系展布对上乌尔禾组岩性油气藏分布具有控制作用。利用岩心数据、薄片资料等,并结合地震数据和钻测井资料,对准噶尔盆地二叠系上乌尔禾组的沉积相类型及沉积体系分布特征进行了识别和刻画,总结了大型退覆式扇(辫状河)三角洲-滩坝复合砂砾岩体的沉积模式,并分析了其控制因素。研究表明:(1)研究区发育扇三角洲、辫状河三角洲、滨浅湖滩坝等沉积相类型,扇三角洲平原亚相和扇三角洲前缘亚相主要发育在盆地西部,辫状河三角洲平原亚相和辫状河三角洲前缘亚相主要发育在盆地东部和北部,滩坝相叠置在扇三角洲和辫状河三角洲前缘之上或在其前端独立分布;(2)准噶尔盆地上乌尔禾组各段沉积体系是在整体湖侵的背景下发育的,乌一段沉积时期湖盆面积较小,沉积的砂体较厚,延伸距离近,靠近凹陷的中央;乌二段沉积时期物源持续供应,湖盆水体加深,湖盆面积增加,沉积砂体厚度薄,分布广;乌三段沉积时期湖侵作用增强,湖盆面积进一步扩大,湖盆内广泛发育湖泛泥岩;(3)扇三角洲与辫状河三角洲前缘在湖平面不断变化与湖浪的改造下,形成了扇(辫状河)三角洲前缘-滩坝复合砂砾岩体;(4)准噶尔盆地上乌尔禾组沉积时期,沉积体系的主要控制因素为气候、物源供给、湖平面变化和沉积时的古地形坡度和古地貌。该研究为上乌尔禾组油气勘探提供了地质依据。

典型海相砂质临滨坝沉积演化过程及成因机制

滩坝砂体是重要的油气储层,其形成的水动力机制复杂多变,受露头及现代沉积等资料的局限性影响,坝体的发育过程、几何形态、动态演化模式及构型叠置关系尚不明确。针对以上问题,利用沉积数值模拟与现代沉积相结合的方法,对典型正向线性临滨坝的沉积演化过程及成因机制进行了探讨。研究结果表明:典型海相临滨坝完整的发育阶段包括锥形坝形成期、弯月坝发育期、条带状复合坝形成期、条带状复合坝扩大生长期以及条带状复合坝停止发育期,现代沉积中可见不同发育阶段的坝体。不同演化阶段的坝体受向岸流、环流、沿岸流和底流等水动力控制。锥形坝及弯月坝为多个小规模、近等间距规则排列的坝体,受向岸流及沿岸环流不断冲刷,锥形坝演化为弯月坝。锥形坝及弯月坝间发育裂流凹槽,坝顶可发育回流沟槽,为典型的顶积式沉积过程。弯月坝坝体及坝间凹槽不断被沉积充填,形成相对整一的条带状复合坝,此阶段表现为典型的侧积式沉积过程。复合坝在向岸流及底流改造下变宽、变厚,最终出露水面形成障壁型滨岸。复合坝内部构型可由多个锥形坝、弯月坝及坝间凹槽构成,呈锥形坝-裂流凹槽-锥形坝或弯月坝-裂流凹槽-弯月坝的构型叠置关系,剖面上呈厚—薄—厚的叠置特征。

特低渗透滩坝砂油藏超前压驱技术及其应用

胜利油田在特低渗透滩坝砂油藏创新提出一种“超前压驱”的开发技术模式,并取得高产稳产的应用效果。针对高产稳产的致效机制,开展了物理模拟、数值模拟和矿场应用对比研究,分析高压力系数条件下油水井间压力剖面的建立和水井先压驱条件下储层应力场的改变及其对油井产能的影响。结果表明:高压力系数构建连续稳定的驱替压力剖面、超前压驱变应力场油井差异造缝是高产稳产的两大致效机制,在高压力系数条件下,有利于压力与介质协同传导,同时高压压头前移,有利于克服启动压力梯度,形成连续稳定的压力剖面;在超前压驱注水条件下,高油藏压力可有效降低储层的破裂压力,易形成复杂缝网,同时改变储层地应力场的大小和分布,进而影响油井压裂裂缝展布及产能。研究成果揭示了超前压驱高产稳产的致效机制,对特低渗透滩坝砂油藏的规模效益建产具有重要的指导意义。

渤海湾盆地黄河口凹陷SC7区块古近系东营组二段下亚段滩坝储集体构型特征

渤海湾盆地黄河口凹陷SC7区块滩坝是滨浅湖区的重要储集体,厘清其砂体内部结构特征对油气开发具有重要指导意义。根据现代沉积和岩心、录井、测井资料研究,对SC7区块古近系东营组二段下亚段(东二下亚段)砂体进行构型解剖,将厚泥-薄砂式滩坝划分为坝中心、坝侧缘、内缘滩、外缘滩和湖相泥5种沉积微相类型。基于厚泥-薄砂式滩坝成因和内部结构特征分析,研究了滩坝沉积特征、沉积模式和生长过程。将滩坝构型分为复合砂坝、单一坝和增生体3个级别,探讨各滩坝砂体构型单元空间展布特征。提出了单一坝坝间泥岩、测井曲线特征、相对高程差和单一坝侧向相变4种识别标志。用识别标志对密井网区单一坝进行划分,分析了单一坝规模、演化过程及连通性。在单一坝内部划分出4期增生体,最终确定了4级构型界面、单一坝侧向相变和单一坝内部增生体对油气分布的影响。

柴达木盆地尕斯地区水下古隆起滩坝成因机制及控藏模式

滩坝是重要的油气藏储集体,对油气成藏具有重要的控制作用。水下古隆起构造上的滩坝形成机制及其对油气藏的控制作用研究较少,尚待进一步揭示。通过岩心分析、镜下观察、井震解释等手段,重建了柴达木盆地尕斯地区水下古隆起滩坝的古沉积环境,明确了该地区的地质构造特征和沉积岩石特征,揭示了滩坝的形成机制,建立了滩坝成藏模式。研究结果表明,(1)尕斯地区上干柴沟组(N1)水下古隆起构造主要发育滨浅湖相沉积体系,地层岩性主要为泥岩、粉砂岩和细砂岩。(2)研究区古地貌西北高、东南低,滩坝主要接受来自砂西-红柳泉的阿拉尔物源沉积,同时受到波浪和沿岸流的作用,发育大面积的滩砂体。(3)尕斯古隆起发育于新生代之前,且产生了大量断层,其滩坝砂体在平面上分布较广,砂体厚度小;在垂向上为旋回叠置分布,呈弯曲的“条带状”。(4)尕斯地区油气藏为古隆起、断层、滩坝砂体共同控制的构造-岩性复合油气藏。

Sedimentary Characteristics and Formation Mechanisms of Lacustrine Beach-Bars in the Fourth Member of the Shahejie Formation in the Shubei Area, Western Depression of the Liaohe Oilfield, China

Beach-bars are well developed in the fourth member of the Shahejie Formation in the Shubei area, western depression of the Liaohe oilfield. The fourth member is composed of two three-order sequences, including a lower Sequence 1（SQ1） and an upper Sequence 2（SQ2）. SQ2, which is the focus of this study, comprises a lowstand systems tract（LST） and a transgressive system tract（TST）. Three types of beach-bars have been recognized： shallow-littoral lacustrine sandy beach-bars, semi-deep lacustrine storm-related sandy beach-bars and shallow-littoral lacustrine carbonate beach-bars. Paleo-environments during the deposition of SQ2, including the paleo-geomorphology, paleo-water depth and paleo-source have been reconstructed to determine the formation mechanisms of the different types of beach-bars. The shallow-littoral lacustrine sandy beach-bars formed mainly by waves and currents and were mostly deposited in the LST, where water depths ranged from 3 to 9 m and the terrestrial clast supply is sufficient. The storm-related sandy beach-bars developed in the TST in the southern part of the study area near previously massively deposited sand bodies where there was sufficient water depth to preserve them. The carbonate beach-bars formed primarily in the TST in the Shubei low buried hill belt where there was a lack of terrestrial clast supply and complex, uneven geomorphology that easily gave rise to a lagoonal environment.

Flume Tank Simulation on Depositional Mechanism and Controlling Factors of Beach-Bar Reservoirs

The beach-bar reservoir has become an important exploration target in China, but its depositional mechanism and controlling factors have not yet been fully modeled. They have become an inhibitory factor for the exploration and development of beach-bar reservoirs. The depositional mechanism of beach-bars and their controlling factors have been studied by means of a flume experiment including seven runs under controlled boundary conditions which were the water level（Run 1, Run 2 and Run 3）, wave parameters（Run 1, Run 4 and Run 5） and initial slope（Run 1, Run 6 and Run 7）. The experiment revealed that the development of beach-bar was controlled by water level, wave parameters and initial slope. The deposited locations of distal bar and nearshore bar were controlled by the water level. Two beach-bars were migrated downward when the water level falls（Run 1, Run 2 and Run 3）. The width and thickness of distal bar and nearshore bar were controlled by wave parameters, especially the wave height. They increased with the scale of wave. But, the maximum thickness is limited by the water level（Run 1, Run 4 and Run 5）. The distance between distal bar and nearshore bar was controlled by the initial slope. It became shorter with the steeper slope. Distal bar and nearshore bar changed into one bar when the initial gradient was greater than 1/20（Run 1, Run 6 and Run 7）. The results suggest formative mechanism and controlling factors related to beach-bars.

CO_(2)-EOR在低渗透滩坝砂油藏的应用初探——以高89为例

“双碳”愿景下,CO_(2)驱强化采油封存技术(CO_(2)-enchanced oil recovery, CO_(2)-EOR)因能在增强驱油的同时实现CO_(2)地质封存而愈发受到重视。当前,一是中国滩坝砂油气藏注不进采不出矛盾突出;二是对于较深埋藏、较高地层温度的低渗透滩坝砂油藏缺乏较成功的CO_(2)-EOR开发实践;三是中国对此领域系统归纳研究较少。开展滩坝砂油藏CO_(2)-EOR的应用研究需求较为迫切,在查阅文献的基础上,以高89为对象,借鉴国外CO_(2)驱项目实例,从地质条件、油藏工程、评价标准出发,在CO_(2)驱油机理研究基础上,开展了CO_(2)-EOR在低渗透滩坝砂油藏的适应性评价,并从技术工艺层面、经济政策层面,简要剖析了气源、混相压力高、气窜、伤害、产出CO_(2)气的收集等CO_(2)驱油的5大挑战和相应攻关方向,展望未来发展趋势,以期为类似滩坝砂油藏开展现场先导试验和工业化推广提供借鉴。

渤海湾盆地歧口凹陷歧北斜坡古近系沙二段滨浅湖滩坝沉积模式与勘探实践

近年来,滩坝砂体作为陆相滨浅湖重要的岩性油气藏勘探评价目标,增储作用愈发突出。针对渤海湾盆地歧口凹陷歧北斜坡古近系沙河街组二段(沙二段)分析滩坝砂体的形成机制和空间分布规律,指导油田滩坝砂体勘探。基于沉积古背景分析,认为沙二段滩坝砂体主要发育在基准面上升半旋回早期阶段,滨Ⅳ上、滨Ⅲ下油组沉积时期规模最大;在邻近物源供给充足、往复动荡的水动力及湖盆底形的影响下,水下古隆起控制厚层坝砂的沉积分布。利用地震模型正演技术,明确了厚层坝砂地震响应特征;根据频谱分析法,确定了厚层坝砂低频率—强振幅门槛值,采用低频率—强振幅属性融合技术,预测了厚层坝砂的有利发育区。通过滩坝砂体勘探实践研究,建立了构造宽缓浅水区圈定滩坝范围、水下古隆起锁定厚层坝砂、低频率—强振幅属性融合确定厚层坝砂有利发育区的勘探评价方法。优选出歧北斜坡沙二段3个坝砂有利发育区,钻探4口井获工业油气流,钻井成功率达到100%。勘探实践表明,歧北斜坡滩坝砂体发育,尤其是厚层坝砂产量高、油藏富集,是老油区增储建产的重要接替领域和方向。

济阳坳陷东营凹陷古近系隐蔽油气藏勘探实践及展望

东营凹陷经过60多年的勘探与开发,发现了盐家、滨南、纯化、博兴和金家等34个油田,截至2022年累计探明储量26亿吨,对中国能源供给与安全起到了举足轻重的作用。随着东营凹陷勘探程度不断提高,勘探对象已由构造油气藏向复杂隐蔽油气藏转变。基于隐蔽油气藏勘探理论与实践,对东营凹陷砂砾岩、滩坝砂及浊积岩等各类储集体发育控制因素及展布规律、油气成藏分布特征进行了分析总结,提出了油气成藏相似性、有序性、差异性等理论认识,极大推动了隐蔽油气藏的精细勘探。指出构造转换带、沉积结合部及地层突变带是现阶段重点勘探领域和方向,加强其综合研究是隐蔽油气藏勘探成功和规模增储的关键。紧密结合勘探实践,综合运用多手段、多学科、多方法是突破隐蔽油气藏勘探瓶颈的重要法宝,也将进一步指导隐蔽油气藏精细化和效益化勘探。

双向长短时记忆神经网络在滩坝砂储层岩性识别中的应用

研究区致密滩坝砂储层油气储量丰富,勘探开发潜力较高,但存在埋藏深、单层厚度薄、渗透率超低、孔隙结构复杂以及单井自然产能极低的特征,储层划分与岩性识别困难。针对测井数据具有纵向时序连续的特点,构建一个双向长短时记忆神经网络(BiLSTM)岩性识别模型,采用随机森林方法对常规测井数据等参数进行特征选择,将选择的参数作为输入变量训练BiLSTM模型。应用该模型对测试集的井资料进行验证,结果表明模型的岩性识别准确率为0.86,取得了良好的应用效果,证明了BiLSTM模型适用于滩坝砂储层岩性识别。

长江下游落成洲河段洲滩联动关系与航道浅滩碍航机制

航道浅滩演变与边心滩形态调整具有强关联性,叠加河道冲淤不均衡性、上游河段冲刷供沙等综合影响,使得航道浅滩碍航机制更趋复杂。本研究以长江感潮段内落成洲河段为对象,通过1959—2021年洲滩形态、河床冲淤特征、水动力环境与浅滩碍航特性等分析,明确边心滩—浅滩演变联动关系、上游河床冲刷供沙及对浅滩演变的影响机制。研究结果表明:①1981年以来落成洲河段所在的扬中河段由淤积转为1991年以来的持续冲刷,1981—2021年枯水河槽冲刷量为3.97亿m^(3),占洪水河槽冲刷量的95.9%;②三峡工程运行前嘶马弯道崩退—落成洲左缘淤积—三益桥边滩未发育,即嘶马弯道崩退是洲滩联动演变的主要诱因;③三峡工程运行后至航道整治工程实施前的来沙量减少引起洲滩整体冲刷,落成洲冲刷为三益桥边滩提供了发育空间,逐渐淤涨的三益桥边滩与水沙条件共同使得落成洲冲刷和右汊冲刷发展,即三益桥边滩形态变化逐渐由被动淤涨转为洲滩联动演变的主因;④1981—2010年三益桥边滩淤涨、落成洲洲头与左缘冲刷等决定着三益桥浅滩碍航程度,由于流域来沙量减少引起的河床冲刷使得碍航程度减弱,2011—2021年航道工程作用下的落成洲左缘边界逐渐稳定与下浅区航道条件得到改善,同时三益桥边滩面积由淤积转为小幅冲刷,航道碍航位置逐渐上提形成上浅区;⑤二期工程实施以来,流域来水过程条件、三益桥边滩冲刷和落成洲右汊相对发展等变化仍不利于落成洲河段前滩段航道条件的稳定,建议后续完善工程中采取稳定洲滩边界与限制右汊冲刷发展的工程措施。

非洲Muglad盆地Fula凹陷白垩系AG组岩性油气藏勘探潜力

借鉴国内断陷盆地岩性油气藏勘探理论与技术,运用层序地层学分析方法,对中非裂谷系Muglad盆地Fula凹陷开展多级次层序地层划分、烃源岩地化分析、油气成藏规律研究和有利区带划分与潜力评价。研究结果表明:①受基准面旋回发育控制,Fula凹陷AG组可划分为5个三级层序,湖泛面附近是岩性油气藏最有利分布位置。②研究区AG组主要发育三大物源体系,福西陡坡带为短轴近物源快速沉积,相带平面展布较窄;东北部发育辫状河三角洲沉积,展布范围较大,沉积持续时间长;AG组沉积晚期在东南部发育一套展布范围较小的辫状河三角洲沉积;三角洲前缘和滨浅湖滩坝是岩性油气藏发育的有利相带。③AG组AG2段(SQ4)暗色泥岩主要沉积于浅湖—半深湖环境,干酪根类型为Ⅰ—Ⅱ1型,TOC平均为3.41%,生烃潜量(S1+S2)多大于8 mg/g,为好—极好烃源岩,可为构造-岩性油气藏的形成提供充足的油气来源。④AG组可划分出7个岩性油气区带,其中Fula-Moga斜坡带北部成藏条件优越,勘探潜力大。

细粒碎屑岩储层基本特征及控制因素分析——以柴西茫崖地区新生代为例

采用岩心观察描述、样品薄片鉴定、激光共聚焦孔缝扫描、X衍射成分分析及扫描电镜观察等技术,对柴达木盆地新生代湖相细粒碎屑岩储层的沉积特征、储层特征、成岩作用及成岩阶段进行研究,明确了茫崖地区浅层和中深层两套细粒碎屑岩优质储层的成因及控制因素。结果表明:茫崖地区的细粒碎屑岩发育的沉积环境主要为滨浅湖滩坝和灰泥坪,具有相带变化快、岩石成分混杂、杂基含量高的特点。细粒沉积岩以低孔特低渗储层为主,浅层物性相对较好,发育残余粒间孔、粒间溶孔及黏土矿物晶间孔,具有分散分布以较粗孔喉为主和相对集中分布以连通微细孔喉为主两类孔喉组合;深层较致密,局部发育粒间溶孔,为相对集中分布的微细孔喉组合。影响储层发育的成岩作用主要为压实作用,两期碳酸盐岩胶结及溶蚀作用;其中压实作用控制浅层残余粒间孔的发育,早期的方解石胶结物抑制了压实作用,同时也是后期溶蚀发育的主要部位;溶蚀作用主要为浅层酸性流体在粒间孔基础上的溶蚀,是形成优质储层的关键。