正韵律厚油层剩余油的水平井开发技术研究

与直井相比,水平井开发具有缩短油井井距,扩大泄油面积,提高临界锥流量,更好地控制注入流体、改善波及效率等优势。在相同采液量的情况下,水平井可以降低采液强度,减缓含水上升速度。特高含水期河流相储集层的顶部是剩余油富集区,利用水平井技术挖掘正韵律厚油层顶部剩余油,取得了很好的开发效果,最终采收率较直井开发提高了14个百分点。     

老168平台海油陆采丛式井组关键钻井工艺

老168平台丛式井组是2009年中石化及胜利油田的重点产能建设项目之一,平台上共部署58口海油陆采定向井。该丛式井组的施工主要有以下难点：井网密集,防碰工作量大;造斜点浅、井斜大、造斜困难;位移大、裸眼稳斜段长,稳斜难度大;钻井液技术必须考虑环境保护问题,可借鉴经验非常少。因此钻井施工难度极大,通过实施优化井场布局及井眼轨道技术、大井眼松软浅地层定向技术、高精度轨迹控制技术、大位移井安全钻进技术,优质无污染海水钻井液技术,最终实现了老168钻完井一体化作业,节约了成本,提高了效率,为今后胜利油田丛式井组施工提供了宝贵经验。     

Characterisation and preliminary quantification of the methane reservoir in a coastal sedimentary source: San Simón Bay,Ría de Vigo,NW Spain

Ría de Vigo is a river valley flooded by the sea, with a bay (San Simón Bay) at its innermost part. The accumulation of Holocene sediment in San Simón Bay has been studied by the integration of 1) large scale high resolution seismic data, and 2) detailed geochemical analysis of a gravity core. In San Simón Bay the majority of the seismic records are obscured by acoustic turbidity which represents gassy sediments, but on records from Rande Strait it is possible to distinguish two Quaternary seismic sequences; an Upper Pleistocene sequence (SQ1) and a Holocene sequence (SQ2). Only SQ2 is recognized in San Simón Bay where it is comprised of two seismic units; the upper unit represents the HST sediment, i.e. the period of highest sea level. A gravity core taken within the gassy zone at 10 m water depth provided 3.55 m of fine-grained sediments (muds) from the youngest seismic unit (4 m thick). Geochemical analysis show high values (4 to 10%) of TOC. Sediment and porewater analyses indicate a distinct sulphate–methane transition zone (SMTZ) between 60 and 80 cm where sulphate is depleted (to <1.7 mM) and methane increases (to >0.4 mM). The top of the acoustic turbidity (the gas front) at 80 cm corresponds to the lower limit of the SMTZ. The methane cannot have been derived from the underlying metamorphic and granitic rocks, but was probably derived by microbial degradation of the organic matter in the Holocene sediments. We estimate that the sediments of the Bay contain approximately 1.8 × 10⁶ m³ of organic carbon and 275 ton of methane.     

南海中部和北部上层海水中溶存甲烷浓度及海气交换通量*

根据2010年4—5月国家基金委南海多学科综合航次在南海中部和北部的调查资料,利用抽真空气相色谱法测定海水中溶存甲烷浓度,分析了该海区上层海水中溶存甲烷的浓度、饱和度及海气交换通量。南海中部和北部表层海水中溶存甲烷浓度范围为1.15—5.6nmol·L?1,平均值为2.2nmol·L?1,饱和度范围为59.7%—298.8%,59%站位的溶存甲烷处于过饱和状态。甲烷海气交换通量范围分别为?17.7—61.3μmol·m?2·d?1(根据 LM-86方程计算)和?27.9—119.6μmol·m?2·d?1(根据 W-92方程计算)。南海是大气中甲烷的来源之一,年甲烷辐射量估算值为2.7×10?2—4.0×10?2Tg·a?1。     

Seasonal Study of Methane and Nitrous Oxide in the Coastal Waters of the Southern Baltic Sea

Atmospheric and dissolved methane (CH₄) and nitrous oxide (N₂O) were measured in the unique coastal ecosystem of theBoddenwaters, including the western Oder estuary, (southern Baltic Sea) during five campaigns between 1994 and 1997. The CH₄saturations, ranging from 105–15 500%, showed great spatial and temporal variability with maximum values in September and minimum values in December. The N₂O saturations were in the range of 91–312% with a maximum in March. Enhanced concentrations of both gases were observed only in the western Oder estuary near the mouth of the Peene River. Thus, we conclude that the distributions of CH₄and N₂O in the investigatedBoddenwaters are, directly or indirectly, linked to the Peene River runoff and not to the Oder River. Our estimate of the annual CH₄emissions from theBoddenwaters to the atmosphere indicates a significant contribution (c. 17%) to the overall CH₄emissions from the Baltic Sea. In contrast, theBoddenwaters represent only a small source for atmospheric N₂O.CH₄production rates estimated from sediment slurry experiments revealed a significant spatial variability and indicated that methanogenic activity was related to acetate consumption in the surface sediment layer. Sedimentary CH₄production might depend on different amounts of accumulation of organic material.     

南海北部流花碳酸盐岩储层频域属性分析

生物礁碳酸盐岩油气藏储层具有丰度大、产能高的特点,一直以来是油气勘探重点探索的目标。南海北部大部分的油气发现均位于新近系,生物礁油气田也是该区勘探发现最大的亮点。其中东沙隆起区LH11生物礁是我国近年来发现的最大规模的同类型油气田。但其作为复杂的一类岩性油气藏,其非均质性和隐蔽性,使得在常规地震剖面上往往难以识别。本研究从地震频域属性角度出发,通过提取地震剖面频域图谱并结合测井孔隙度数据,分析生物礁储层频域特征,并结合正演模拟加以验证,认为研究区生物礁碳酸盐岩储层总体偏薄,导致了频率和衰减的异常,另外也证实薄层调谐效应方法可以较准确地估计层厚。     

蒙特卡罗法在天然气水合物资源量计算中的应用

天然气水合物甲烷资源量的估算是天然气水合物研究中的热点问题。运用体积法计算含水合物沉积物中的甲烷资源量时,存在参数赋值不确定的问题,从而影响了计算结果的可信度。采用蒙特卡罗法,通过计算样本的频率可以较好地评价和描述计算结果的信度,弥补体积法的不足。对采用蒙特卡罗法估算甲烷资源量的原理进行了分析和探讨,并以麦肯齐三角洲和南海海域水合物为例,计算了水合物赋存区的甲烷资源量。     

Pore-water geochemistry in methane-seep sediments of the Makran accretionary wedge off Pakistan: Possible link to subsurface methane hydrate

Cold seeps are pervasive along the continental margin worldwide,and are recognized as hotspots for elemental cycling pathway on Earth.In this study,analyses of pore water geochemical compositions of one-400 cm piston core(S3) and the application of a mass balance model are conducted to assess methane-associated biogeochemical reactions and uncover the relationship of methane in shallow sediment with gas hydrate reservoir at the Makran accretionary wedge off Pakistan.The results revealed that approximately 77% of sulfate is consumed by the predominant biogeochemical process of anaerobic oxidation of methane.However,the estimated sulfate-methane interface depth is-400 cm below sea floor with the methane diffusive flux of 0.039 mol/(m~2·a),suggesting the activity of methane seepage.Based on the δ~(13)C_(DIC) mass balance model combined with the contribution proportion of different dissolved inorganic carbon sources,this study calculated the δ~(13)C of the exogenous methane to be-57.9‰,indicating that the exogenous methane may be a mixture source,including thermogenic and biogenic methane.The study of pore water geochemistry at Makran accretionary wedge off Pakistan may have considerable implications for understanding the specific details on the dynamics of methane in cold seeps and provide important evidence for the potential occurrence of subsurface gas hydrate in this area.     

冷泉系统甲烷气体渗漏的声学特征及潜在环境效应

The amount of methane leaked from deep sea cold seeps is enormous and potentially affects the global warming,ocean acidification and global carbon cycle. It is of great significance to study the methane bubble movement and dissolution process in the water column and its output to the atmosphere. Methane bubbles produce strong acoustic impedance in water bodies, and bubble strings released from deep sea cold seeps are called "gas flares"which expressed as flame-like strong backscatter in the water column. We characterized the morphology and movement of methane bubbles released into the water using multibeam water column data at two cold seeps. The result shows that methane at site I reached 920 m water depth without passing through the top of the gas hydrate stability zone(GHSZ, 850 m), while methane bubbles at site II passed through the top of the GHSZ(597 m) and entered the non-GHSZ(above 550 m). By applying two methods on the multibeam data, the bubble rising velocity in the water column at sites I and II were estimated to be 9.6 cm/s and 24 cm/s, respectively. Bubble velocity is positively associated with water depth which is inferred to be resulted from decrease of bubble size during methane ascending in the water. Combined with numerical simulation, we concluded that formation of gas hydrate shells plays an important role in helping methane bubbles entering the upper water bodies, while other factors, including water depth, bubble velocity, initial kinetic energy and bubble size, also influence the bubble residence time in the water and the possibility of methane entering the atmosphere. We estimate that methane gas flux at these two sites is 0.4×10~6–87.6×10~6 mol/a which is extremely small compared to the total amount of methane in the ocean body, however, methane leakage might exert significant impact on the ocean acidification considering the widespread distributed cold seeps. In addition, although methane entering the atmosphere is not observed, further research is still needed to understand its potential impact on increasing methane concentration in the surface seawater and gas-water interface methane exchange rate, which consequently increase the greenhouse effect.     

南海神狐海域沉积物自生黄铁矿和石膏S同位素特征及对甲烷渗漏强度的示踪

The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane(AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor(cmbsf) in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values(δ~(34) S) of pyrite vary greatly(from –46.6‰ to –12.3‰ V-CDT) and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction(OSR) and is influenced by AOM with depth.The relative high abundance and δ~(34) S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone(SMTZ).The sulfur isotopic composition of gypsum(from–25‰ to –20.7‰) is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO_2,iron(Ⅲ) and oxygen driven by the SMTZ location shift to great depths.The δ~(34) S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.