加蓬G4-188区块钻井技术实践认识

加蓬G4-188区块是一个新的海外勘探区块,在钻井过程中遇到了井壁垮塌、气侵、井斜控制困难等诸多难题,影响了钻井施工的速度。针对这些难题,实施了解决G4-188区块钻井施工难点的各项技术措施,为G4-188区块后续钻井施工提供了有益的技术支持。     

高压气藏不动管柱分层压裂工艺研究与应用

川西低渗高压气藏具有多层系的特点,层间距离一般在十至百米左右。为了提高气井产量与开采经济效益,鉴于气井加砂压裂后压井会严重伤害储层,影响压裂效果,采用压裂管柱直接作为生产管柱,研究形成了以FCY211及Y241封隔器不同组合的两层不动管柱分层压裂工艺。同时,在成熟的两层分压工艺基础上,结合投球选压工艺,研究形成了以“工具分层＋投球选压”不动管柱三层分层的压裂工艺。现场应用实践表明,分层压裂极大地增加了单井的产能,取得了明显经济效益,对类似气藏的多层压裂与开采提供了有益参考。     

东海陆架两期沙脊的时空对比东海陆架两期沙脊的时空对比

基于高分辨率的单道地震和多波束测深数据,识别并对比了东海陆架中部同一海区相距20余万年的层U14和层U2两期沙脊群,其中层U14期沙脊属于埋藏沙脊,位于东海海底以下90 m深处,推测属于距今320~200 ka的海侵体系域(TST),沙脊顶界面是该期海侵的最大洪泛面(MFS);层U2期沙脊位于东海陆架,属于衰退沙脊,系末次盛冰期(LGM)以来的TST,顶界面是LGM以来的MFS。尽管两期沙脊形成年代相距20余万年,地层层位相距近90 m,但是沙脊群总体走向一致,表明距今2×105 a以来东海陆架潮波基本格局稳定。从层U2期可识别出4个亚期沙脊,通过多波束海底地形图可识别出4组走向的沙脊,多亚期、多走向沙脊是LGM以来海平面阶梯状波动在海底地形演变过程中的响应证据。     

Beach nourishments at Coolangatta Bay over the period 1987–2005: Impacts and lessons

Erosion of the southern Gold Coast beaches (SE Queensland, Australia) was exacerbated after the extension of the Tweed River training walls in the early 1960s. To achieve the objective of restoring and maintaining beach amenity, significant nourishment works have been undertaken in Coolangatta Bay over the past 30 years. Particularly, under the Tweed River Entrance Sand Bypassing Project (TRESBP) since 1995, a number of nourishment campaigns and the implementation of a permanent sand bypass system in 2001 have resulted in significant changes of Coolangatta Bay morphology. The present case study investigates the influence of both wave climate and nourishment works on the area extending from the updrift Snapper Rocks area to downdrift Kirra Beach. SWAN spectral wave model is implemented at Coolangatta Bay area and forced by the global wave model WW3 to estimate wave forcing and the potential natural longshore drift entering in Coolangatta. Specific transects extracted from accurate bathymetric surveys are used to investigate and quantify Coolangatta Bay sedimentation for the period 1987–2005. A network of Argus video stations provides high sample rate information on the shoreline evolution. Results show that, over the past 10 years, Coolangatta Bay has infilled rapidly. Sedimentation reached up to 6 m in some areas between 1995 and 2005, with beach width increasing by 200 m at Kirra Beach. Rapid seaward shoreline migration is consistent with the intense over-pumping of sand relative to the natural potential to move sand alongshore. The nourishment strategy used during this project has successfully delivered large amounts of sand to the southern Gold Coast embayment, although it has been up to now controversial from many community perspectives. The artificial sand bypassing process proved to be much more efficient than depositing the dredged sand in the nearshore area which requires a significant period of low energy condition in order for the deposited sediment to migrate shoreward and weld to the shore. This case study confirms that, when carefully undertaken, sand bypassing is a sustainable and flexible soft engineering approach which can work in concert with natural processes.     

Seismic geomorphology,architecture and genesis of Miocene shelf sand ridges in the Pearl River Mouth Basin,northern South China Sea

Multiple stages of large-scale shelf sand ridges, including the shoreface-attached and the offshore types, have developed in the Miocene successions on the mid-shelf region of the Pear River Mouth Basin, northern South China Sea. Utilizing a high-quality 3D seismic data set, accompanying 2D seismic profiles and well logs, the morphology, architecture and genesis of these shelf sand ridges have been systematically investigated in this study. The ridges are of very large scale, with the largest one having a maximum height of 64 m, a width of more than 20 km and a length of 37 km within the 3D survey area. Being mound-shaped, they also display obvious asymmetry character, with the ridge crest preferentially located on the SE side. Three main internal components, including the ridge front, central ridge and the ridge tail, have been recognized through careful anatomy analysis of the two most well-imaged ridges, each displaying distinct expressions on seismic amplitudes and geometries. In the plan view, most of the shelf sand ridges are generally NE–SW oriented and widening to the SW direction. Scouring features can also be clearly observed along the SW direction, including scour depressions and linear sandy remnants. On well logs, the shelf sand ridges are represented by an overall coarsening-upward pattern. Intervals with blocky sandstones are preferentially present on higher locations due to a differential winnowing process controlled by shelf topography.Plenty of evidence indicates that these ridges were primarily formed by the reworking of forced regressive or lowstand deltaic deposits under a persistent southwesterly flowing current during the subsequent transgression. This very current is a composite one, which is speculated to consist of winter oceanic current, SCSBK (South China Sea Branch of Kuroshio) intrusion onto the shelf and internal waves propagating from the Luzon Strait. Tidal currents might have contributed to the SE growth of the ridge. In response to the reglaciation of Antarctic ice-sheet and the closure of Pacific-Indian ocean seaway in the middle Miocene, the intensification of the North Pacific western boundary current was considered to have potential links to the initiation of the shelf sand ridges at ∼12 Ma. The development of shelf ridges was terminated and replaced by rapid deltaic progradation at ∼5.5 Ma.     

热带风暴过程中珊瑚礁坪示踪砂运移的现场实验研究

１９９５年１０月在小东海珊瑚礁海岸的礁坪上进行了示踪砂运动的现场实验。本次实验对浪,流以及示踪砂采样作了同步观测。根据所获的实验数据,分析在９５１６号热带风暴天气过程礁坪上示踪砂运移的基本规律。在一级近似下,测定并计算了泥沙在波生流作用下的漂移速度与流速比因子０．００２,混合深度小于２ｃｍ。这一结果与其它已往结果相比明显小得多。     

黄海辐射沙洲沉积物地球化学特征及其环境意义

对黄海辐射沙洲烂沙洋水道区域的3个钻孔共81个沉积物样品进行了微量、常量元素分析和^14C测年分析．化学元素质量分数的变化与当时沉积环境的变化相对应。突发事件(如风暴潮)的发生不但在沉积物的岩性上有所体现,而且在微量元素质量分数的变化上也有很明显的体现。微量元素Zr可作为沉积能量变化的地化指示剂,潮汐通道北部的西太阳沙区域的沉积动力环境在4000a以前是较弱的。潮流通道的上段沉积物是来自水深较浅的区域,由于潮流和波浪的作用使其能够保持稳定的水深。     

南黄海辐射沙洲主要潮沟的变迁

利用1966年和1977年海图、1995年和2000年合成孔径雷达影像,结合1980年以来的陆地卫星影像和2000年的岸滩实测剖面资料对南黄海辐射沙洲区主要潮沟的位置进行了解译与分析,得出上述4个时期研究区内主要潮沟深泓线位置图。对不同时期潮沟深泓线位置图进行几何校准与叠加,对比潮沟深泓线的迁移。结果表明：潮沟具有往返周期性摆动的特点,短期摆动速度明显快于长期摆动,主沟槽最大变动速度达127m／a,而支沟槽变动速度更大。潮沟摆动与沙洲变化有明显的相关性,但两者间的关系较为复杂。辐射沙洲目前处于破碎、萎缩阶段,除沙洲中心及陆岸岸滩仍有淤积外,大部分沙洲处于侵蚀状况,同时沙洲有整体向陆迁移的趋势。     

Ancient and modern cold-climate aeolian sand deposition: A review

Although partly active aeolian sand sheets and dunes cover large areas in the zones of (dis)continuous permafrost, little precise information is available about the influence of cold-climate conditions on modern aeolian processes. This means that palaeoenvironmental reconstructions in the stabilised, mainly Late Pleistocene dune fields and cover sand regions in the ‘sand belts’ of the European Lowlands and the Northern Great Plains of the USA and Canada, are necessarily still based on ancient evidence. Cold-climate wind deposits are typically derived from areas of abundant sediment supply like unvegetated flood plains, glacial outwash plains, till plains and lake shores. The common parabolic and transverse dune forms resemble those observed in temperate regions. Although a variety of periglacial features has been identified in Late Pleistocene dune and cover sands none of them indicate that permafrost is crucial to aeolian activity. Specific structures in aeolian strata permit tentative interpretation of the moisture content of depositional sand surfaces, the nature of annual sedimentation cycles and the processes by which strata were deposited and/or contorted. But surprisingly little is known about the role of vegetation in the process of sand accumulation. Dunes are most informative with respect to reconstructions of past wind regimes, which offer important data for verification of palaeoclimatic simulations.