涠西南地区岩石特性及钻井液技术研究

北部湾盆地涠西南油田群是南海西部重要的原油产区，同时油田群紧邻众多国家级自然保护区，属于环境敏感区域。针对北部湾盆地涠西南地区环保要求，以及涠洲组和流沙港组钻井过程经常出现井壁失稳导致的憋卡、起下钻阻卡等问题，开展了涠西南地区地层泥页岩特性及环保钻井液技术研究。通过地层岩石黏土矿物分析、孔喉结构分析以及理化性能评价，明确了涠西南地区泥页岩井壁失稳的机理；提出以类油基的水溶性复合基基液为核心，构建了一套具有油基钻井液工程特性和水基钻井液环保特性的新型环保防塌钻井液技术，并进行了相关的现场应用。现场应用显示：应用井与邻井相比，12-1/4″井段阻卡划眼时间减少，井径扩大率大幅度降低，并且在128 h的长时间浸泡过程中没有复杂情况产生，有效地解决了涠洲组、流沙港组易失稳地层的井壁稳定问题；同时，钻井液环保性能达到一级海域环保要求，可以替代目前应用的油基钻井液体系，解决了海上使用油基钻井液存在配制成本高、含油钻屑需全回收及环境危害隐患大等技术难题。该研究对于涠西南油田环保、井壁失稳和钻井液技术发展具有较高的理论价值和借鉴意义。     

流体在岩浆型铬铁矿和铂族元素成矿过程中的作用及意义

镁铁- 超镁铁岩是揭示地幔物质组成和壳幔相互作用的重要窗口，也是Ni- Cu- PGE- Cr等金属矿产资源的重要载体。不同的镁铁- 超镁铁岩体赋矿特征明显不同：蛇绿岩以产出铬铁矿床为特征，阿拉斯加型岩体主要赋含铂族元素(PGE)矿床，大型层状岩体则可同时产出铬铁矿床、PGE矿床和Cu- Ni硫化物矿床。这种成矿差异显然与赋矿岩体形成的构造背景、母岩浆经历的岩浆演化过程有关，但缺少关键控制因素的研究。前人对上述不同种类矿床的研究工作主要集中于地幔源区的部分熔融、上升过程中或岩浆房内的围岩混染和结晶分异等岩浆过程，而极少关注流体作用。近年来，实验岩石学和岩石地球化学的研究均表明幔源岩浆演化过程中的流体活动可能对成矿元素的富集迁移起到至关重要的作用，同时这些成矿元素的赋存状态和分配系数也在不断更新。厘清Cr和PGE在熔体演化——尤其是流体出溶过程中的地球化学行为，刻画并揭示其迁移富集、分离和再富集的成矿过程及控制因素，已成为当前岩浆矿床研究的热点。本文围绕富水流体与铬铁矿和PGE成矿关系的科学问题，总结了不同镁铁- 超镁铁岩体的成矿差异以及铬铁矿和PGE矿床成矿过程中的流体活动记录，提出流体性质和组分对铬铁矿和PGE迁移富集的控制作用，强调有必要开展蛇绿岩、大型层状镁铁- 超镁铁岩体和阿拉斯加型岩体的对比研究。     

Seasonal variations of atmospheric sulfur dioxide and dimethylsulfide concentrations at Amsterdam Island in the southern Indian Ocean

Daily measurements of atmospheric sulfur dioxide (SO₂) concentrations were performed from March 1989 to January 1991 at Amsterdam Island (37°50 S–77°30 E), a remote site located in the southern Indian Ocean. Long-range transport of continental air masses was studied using Radon (²²²Rn) as continental tracer. Average monthly SO₂ concentrations range from less than 0.2 to 3.9 nmol m^-3 (annual average = 0.7 nmol m^-3) and present a seasonal cycle with a minimum in winter and a maximum in summer, similar to that described for atmospheric DMS concentrations measured during the same period. Clear diel correlation between atmospheric DMS and SO₂ concentrations is also observed during summer. A photochemical box model using measured atmospheric DMS concentrations as input data reproduces the seasonal variations in the measured atmospheric SO₂ concentrations within ±30%. Comparing between computed and measured SO₂ concentrations allowed us to estimate a yield of SO₂ from DMS oxidation of about 70%.     

Latitudinal variation of measured O3 photolysis frequencies J(O1D) and primary OH production rates over the Atlantic Ocean between 50° N and 30° S

The latitudinal variation of the photolysis frequency of ozone to O(¹D) atoms, J(O¹D), was measured using a filter radiometer during the cruise ANT VII/1 of the research vessel Polarstern in September/October 1988. The J(O¹D) noon values exhibited a maximum of 3.6×10^-5 s^-1 (2 sr) at the equator and decreased strongly towards higher latitudes. J(O¹D) reached highest values for clean marine background air with low aerosol load and almost cloudless sky. The J(O¹D) data, measured under these conditions and a temperature of 295 K, can be expressed by: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOsaiaacI% cacaqGpbWaaWbaaSqabeaaiiaacqWF8baFaaGccaqGebGaaeykaiaa% bccacqWF9aqpcaqGGaGaaeyzaiaabIhacaqGWbGaaeiiaiaabUhacq% GHsislcaaI4aGaaiOlaiaaicdacaaIYaGaeyOeI0IaaGioaiaac6ca% caaI4aGaaiiEaiaaigdacaaIWaWaaWbaaSqabeaacqGHsislcaaIZa% aaaOGaaeiiaiaabIhacaqGGaGaam4uaiabgUcaRiaaiodacaGGUaGa% aGinaiaacIhacaaIXaGaaGimamaaCaaaleqabaGaeyOeI0IaaGOnaa% aakiaadofadaahaaWcbeqaaiaaikdaaaGccaGG9bGaaeikaiaaboha% daahaaWcbeqaaiabgkHiTiaaigdaaaGccaGGPaaaaa!5EE9!\[J({\text{O}}^| {\text{D) }} = {\text{ exp \{ }} - 8.02 - 8.8x10^{ - 3} {\text{ x }}S + 3.4x10^{ - 6} S^2 \} {\text{(s}}^{ - 1} )\] where S represents the product of the overhead ozone column (DU) and the secant of the solar zenith angle. The meridional profile of the primary OH radical production rate P(OH) was calculated from the J(O¹D) measurements and simultaneously recorded O₃ and H₂O mixing ratios. While the latitudinal distribution of J(O¹D) and water vapour was nearly symmetric to the equator, high tropospheric ozone levels up to 40 ppb were observed in the Southern Hemisphere, SH, resulting in higher P(OH) in the SH.     

Trace gas exchange at the air/water interface: Measurements of mass accommodation coefficients

A liquid jet of 90 m diameter and variable length has been utilized to determine absorption rates and, hence, mass accommodation coefficients , of atmospheric trace gases. The compounds investigated are HCl (0.01), HNO₃ (0.01), N₂O₅ (0.005), peroxyacetyl nitrate (>0.001), and HONO (0.005). It is concluded that the absorption of these trace gases by liquid atmospheric water is not significantly retarded by interfacial mass transport. The strengths and limitations of the liquid jet technique for measuring mass accommodation coefficients are explored.     

Fluid sources for the La Guitarra epithermal deposit (Temascaltepec district, Mexico): Volatile and helium isotope analyses in fluid inclusions

The La Guitarra deposit (Temascaltepec district, South-Central Mexico), belongs to the low/intermediate sulfidation epithermal type, has a polymetallic character although it is currently being mined for Ag and Au. The mineralization shows a polyphasic character and formed through several stages and sub-stages (named I, IIA, IIB, IIC, IID, and III). The previous structural, mineralogical, fluid inclusion and stable isotope studies were used to constrain the selection of samples for volatile and helium isotope analyses portrayed in this study. The N₂/Ar overall range obtained from analytical runs on fluid inclusion volatiles, by means of Quadrupole Mass Spectrometry (QMS), is 0 to 2526, and it ranges 0 to 2526 for stage I, 0 to 1264 for stage IIA, 0 to 1369 for stage IIB, 11 to 2401 for stage IIC, 19 to 324 for stage IID, and 0 to 2526 for stage III. These values, combined with the CO₂/CH₄ ratios, and N₂-He-Ar and N₂-CH₄-Ar relationships, suggest the occurrence of fluids from magmatic, crustal, and shallow meteoric sources in the forming epithermal vein deposit. The helium isotope analyses, obtained by means of Noble Gas Mass Spectrometry, display R/Ra average values between 0.5 and 2, pointing to the occurrence of mantle-derived helium that was relatively diluted or “contaminated” by crustal helium. These volatile analyses, when correlated with the stable isotope data from previous works and He isotope data, show the same distribution of data concerning sources for mineralizing fluids, especially those corresponding to magmatic and crustal sources. Thus, the overall geochemical data from mineralizing fluids are revealed as intrinsically consistent when compared to each other.The three main sources for mineralizing fluids (magmatic, and both deep and shallow meteoric fluids) are accountable at any scale, from stages of mineralization down to specific mineral associations. The volatile and helium isotope data obtained in this paper suggest that the precious metal-bearing mineral associations formed after hydrothermal pulses of predominantly oxidized magmatic fluids, and thus it is likely that precious metals were carried by fluids with such origin. Minerals from base-metal sulfide associations record both crustal and magmatic sources for mineralizing fluids, thus suggesting that base metals could be derived from deep leaching of crustal rocks. At the La Guitarra epithermal deposit there is no evidence for an evolution of mineralizing fluids towards any dominant source. Rather than that, volatile analyses in fluid inclusions suggest that this deposit formed as a pulsing hydrothermal system where each pulse or set of pulses accounts for different compositions of mineralizing fluids.The positive correlation between the relative content of magmatic fluids (high N₂/Ar ratios) and H₂S suggests that the necessary sulfur to carry mostly gold as bisulfide complexes came essentially from magmatic sources. Chlorine necessary to carry silver and base metals was found to be abundant in inclusion fluids and although there is no evidence about its source, it is plausible that it may come from magmatic sources as well.     

Large eddy simulation of hydrocyclone—prediction of air-core diameter and shape

Hydrocyclones are widely used in the mining and chemical industries. An attempt has been made in this study, to develop a CFD (computational fluid dynamics) model, which is capable of predicting the flow patterns inside the hydrocyclone, including accurate prediction of flow split as well as the size of the air-core. The flow velocities and air-core diameters are predicted by DRSM (differential Reynolds stress model) and LES (large eddy simulations) models were compared to experimental results. The predicted water splits and air-core diameter with LES and RSM turbulence models along with VOF (volume of fluid) model for the air phase, through the outlets for various inlet pressures were also analyzed. The LES turbulence model led to an improved turbulence field prediction and thereby to more accurate prediction of pressure and velocity fields. This improvement was distinctive for the axial profile of pressure, indicating that air-core development is principally a transport effect rather than a pressure effect.     

Fracture analysis in the south-western Corinth rift (Greece) and implications on fault hydraulic behavior

This paper reviews the data concerning the fracture network and the hydraulic characteristics of faults in an active zone of the Gulf of Corinth. Pressure gap measured through fault planes shows that in this area the active normal faults (Aigion, Helike) act, at least temporarily and locally, as transversal seal. The analysis of the carbonate cements in the fractures on both the hangingwall and the footwall of the faults also suggests that they have acted as local seals during the whole fault zone evolution. However, the pressure and the characteristics of the water samples measured in the wells indicate that meteoric water circulates from the highest part of the relief to the coast, which means it goes through the fault zones. Field quantitative analysis and core studies from the AIG-10 well have been performed to define both regional and fault-related fracture networks. Then laboratory thin section observations have been done to recognize the different fault rocks characterizing the fault zone components. These two kinds of approach give information on the permeability characteristics of the fault zone. To synthesize the data, a schematic conceptual 3D fluid flow modeling has been performed taking into account fault zone permeability architecture, sedimentation, fluid flow, fault vertical offset and meteoric water influx, as well as compaction water flow. This modeling allows us to fit all the data with a model where the fault segments act as a seal whereas the relays between these segments allow for the regional flow from the Peloponnese topographic highs to the coast.     

Cross-formational hydrocarbon fluid flows in the Tertiary deltaic system of the Beaufort–Mackenzie Basin

Molecular and isotopic compositions of crude oils in the Beaufort–Mackenzie Basin confirm three genetic end-member oil groups and suggest extensive cross-formational hydrocarbon fluid flows in the Tertiary deltaic system. Inter- and intra-fractional variations in the geochemistry of the Tertiary-reservoired oils indicate that the oil source/maturity signatures were substantially masked by biomarkers that were picked up along migration pathways. Thus, many of the previously recognized “immature non-marine oils” are in fact thermally mature, probably derived from unpenetrated deeper marine source rocks. Although the effective source rock volumes have not been evaluated and their exact stratigraphic levels remain unknown, the relative timing of oil generation versus trap formation, rather than poor source quality, may be the cause of under-filled traps in the offshore area.