砂岩储层次生孔隙形成机制的研究进展

砂岩中次生孔隙的形成与长石在埋藏成岩过程中溶解或转化密切相关,形成有丰富的可溶矿物、酸性流体和水、有利的迁移条件。通过对砂岩中长石溶蚀的研究发现,相比钙长石和钠长石,钾长石的溶解速率最慢,也是次生孔隙得以保存的最主要矿物。而对于长石溶蚀的酸性流体来源中CO2主要来源为:是大气水中溶解的CO2、有机酸脱羧酸形成的CO2以及碳酸盐分解;有机酸的来源主要为:有机质热演化过程中形成的短链酸,泥质转变而来以及烃类氧化反应所产生。     

渤南洼陷北带沙四上亚段储层成岩流体演化

渤南洼陷北带沙四上亚段在埋藏过程中经历了多期酸碱流体演化,同时经历了多期油气充注作用,导致储层物性经历了复杂的演化过程。对渤南洼陷北带沙四上亚段埋藏演化史、有机质热演化、膏盐层脱水等综合研究,结合各种烃类和盐水包裹体特征分析,确定了渤南洼陷北带沙四上亚段成岩流体演化序列：(1)沙四上亚段沉积时期气候干旱,原始地层水呈弱碱性。(2)开始沉积至距今42.5 Ma,有机质尚未成熟,地层流体仍保持弱碱性,成岩作用主要为压实排水作用,形成早期球粒状黄铁矿胶结物。(3)距今42.5~30 Ma,为有机酸控制下的酸性环境,发生长石溶解、石英加大。(4)距今30~24.6 Ma,有机酸发生脱羧,同时沙四上亚段顶部膏盐层脱出大量碱性水,使地层水pH值呈碱性,发生碳酸盐胶结和石英溶解,其中距今28.8~24.6 Ma,发生第一期油气充注;距今24.6~6 Ma,地层经历抬升及再沉降,在抬升过程中有机质再次生成有机酸,使地层水pH值呈酸性,发生第二期酸性溶解、石英加大,其中距今10~6 Ma,发生第二期油气充注。(5)距今6 Ma至现今,沙四上亚段膏盐层发生脱水,地层流体呈碱性,发育少量晚期黄铁矿胶结等。     

煤系地层中储层基本特征与优质储层的形成与分布

通过对鄂尔多斯盆地和四川盆地煤系地层中发育的优质储层分布规律研究,发现优质储层主要受层序界面、有利沉积相带、有机酸性水的溶蚀作用等因素控制。一般来说,优质储层主要分布在三级层序的中下部、三角洲平原或前缘多期分流河道叠置的部位。它们在有机酸性水大量形成时期保留了较多的原生孔隙,酸性水容易进入并溶解其中易溶的碎屑颗粒,产生大量次生溶蚀孔隙,从而形成相对优质的有效储集层。因此,优质储层纵向上与不整合面或层序界面密切相关;平面上受沉积有利相带或断裂带的控制。     

柯克亚凝析气田石英的溶解现象及其成因

储层微观特征与成岩演化等的研究表明,柯克亚凝析气田西河甫组储层中广泛存在的石英溶解现象属于石英直接溶解。石英的直接溶解是长期干旱背景下形成的储层,在较深埋藏条件下碱性地层水活动的结果。成岩过程中碱性地层水的形成和原始沉积环境中有机质含量低有关,同时也受成岩演化的制约。早成岩B期一晚成岩期的早期储层中地层水的pH值最高,是研究区储层中石英溶解最强烈的时期,同时也是石英溶解型孔隙最主要的发育期。     

杭锦旗地区上古生界地层水成因及其与油气的关系

鄂尔多斯盆地北部杭锦旗地区上古生界地层水总矿化度为13 831 mg/L～89 445 mg/L,属于盐水和卤水的范畴,pH值在4.37～7.3,在强酸性一弱碱性之间,地层水水型基本为CaCl2型水.根据对鄂尔多斯盆地杭锦旗地区上古生界地层水矿化度、pH值及离子含量等的分析发现,泊尔江海子断裂带及其以南、以北地层水特征差异明显:泊尔江海子断裂带地层水矿化度最高(47 061 mg/L～89 445 mg/L)、pH值最低(4.37～6)及Mg2+离子含量最高.最高达7 024 mg/L;断裂带以南地层水阴离子主要为Cl-和HCO3-,不含SO42+离子;断裂带以北含SO42-离子,而且往北SO42-离子增加的趋势非常明显.采用Davission地层水Nadeficit与Caexcess之间关系及其作用过程的地层水成因模式和地质特征进行综合研究,认为泊尔江海子断裂带的地层水成因为混合作用,主要是由断裂带热液活动导致深部偏酸性的高温、高Mg2+含量、高矿化度水与上古生界地层水混合所致.现今实测表明断裂带地温梯度2.72℃/hm～2.9℃/hm,为研究区最高;断裂带以北地温梯度只有2.27℃/hm～2.36℃/hm,与后期地表水的渗入降温有关.断裂带以外主要的流体一岩石相互反应是斜长石的钠长石化过程.地层水特征变化与油气特征的关系显示热液活动有利于烃源岩的成熟;SO42-离子往北逐渐增加表明受大气淡水影响.保存条件逐渐变差;热流影响区可能成为油气有利聚集区.     

浅部流体对花岗岩储集空间改造作用实验研究

以渤海中生界花岗岩为研究对象,利用高压釜设备开展大气水、有机酸(地层水)、大气水+有机酸(地层水)3种不同流体与花岗岩进行相互作用实验。实验前后样品分析表明:3种流体在不同温度下与组成花岗岩的主要矿物碱性长石、斜长石发生相互作用,碱性长石、斜长石发生不同程度的溶蚀、溶解、次生作用,并形成次生孔隙和高岭石等次生矿物,提高了样品面孔率和喉道平均值;实验样品的重量在反应前后存在差异,具有温度越高样品重量损失越多的趋势。通过实验对比分析3种流体对花岗岩样品的改造结果可知,有机酸(地层水)溶液对花岗岩样品在提高储层物性上较其他2种溶液效果明显。     

贵州省遵义市降水中低分子有机酸对自由酸度的贡献

贵州省遵义市是我国酸雨高发地区,研究遵义降水中有机酸对自由酸度的贡献是认识遵义市有机酸地球化学循环和酸雨机制的重要内容。在遵义市中心城区进行了一年的降水采集,并利用离子色谱法和原子吸收光谱法对主要阴离子（包括无机和有机阴离子）和阳离子进行了测定。结果显示,年均pH值为4．11（范围3．12～6．04）,pH〈5．6的样品占93．1％,说明遵义市酸雨污染仍然严重;单因素方差分析显示四季的pH值存在显著差异（P〈0．05）,表明遵义市降水酸化程度具有显著的季节性特征;甲酸和乙酸的雨量加权平均值分别为9．29umol／L和6．47umol／L,检出率分别为98．68％和93．42％,表明有机酸在降水中广泛存在;应用热力学理论计算了有机酸对降水自由酸度的贡献量,发现在pH〈5的遵义降水中甲酸和乙酸对自由酸度的平均贡献量分别为14．79％和3．66％,表明有机酸对降水自由酸度具有重要贡献;对比显示,遵义市的有机酸贡献量低于边远地区,这与遵义市降水的低pH值和高无机酸度有关;四季的有机酸贡献量大小为：春季（31．95％）〉夏季（26．16％）〉冬季（11．17％）〉秋季（8．02％）,可见有机酸对自由酸度的贡献量存在明显的季节性变化。在低酸度和低水温的春季降水中,由于人类活动或有机物质的燃烧所释放的大量有机酸（如汽车尾气的排放、燃煤的燃烧）,促使有机酸对降水自由酸度的贡献量最高;其次是在低酸度和强降雨的夏季;而在低酸度的秋季和冬季,有机酸对酸度的贡献量相对最低。     

榆林北部气田山2段地层水化学特征与天然气聚集关系

通过对榆林北部气田山2段地层水样品测试结果的统计与分析,可知目的层段地层水以偏酸性为主,矿化度较高,以CaCl_2水型为主,总体反映了地层水封闭条件较好,处于还原的阻滞-停滞水文地质状态,有利于天然气的聚集与保存。地层水化学特征与天然气藏关系研究表明:地层水总矿化度高值区、CaCl_2型水分布区、rNa~+/Cl~-低值区(0.5)、rMg~(2+)/Ca~(2+)低值区(0.1)、r(Cl~--Na~+)/2Mg~(2+)高值区(10)等均与天然气富集区有较好的对应关系。     

地球化学模式在二连盆地中东部砂岩型铀矿床中的应用研究

文章采用PHREEQC模式程序,对研究区地下水的水文地球化学环境进行了模拟,确定水中铀的存在形式、水中沥青铀矿饱和指数(SI)和反应条件指数(RCI)等水文地球化学参数;分析了地层中铀所处状态与水中Eh值、pH值、铀浓度的关系;证明了水的Eh值是控制铀成矿作用的最主要因素;对砂岩型铀矿床的形成及其定位的水文地球化学条件进行了较系统研究和探讨;对砂岩型铀矿成矿水文地球化学机理进行了论证和计算;阐述了铀活化迁移、沉淀富集的本质规律;也为水文地球化学方法研究砂岩型铀矿的成矿预测和矿床定位提供了重要依据。     

莺歌海盆地乐东区储层碳酸盐胶结物成因机理及与流体活动的关系

乐东A区中新统黄流组是南海北部莺歌海盆地高温超高压天然气勘探的主力层系,发育重力流水道-海底扇沉积的细、中、粗粒砂岩,中、低、特低渗物性特征,多期次、多类型碳酸盐胶结。研究碳酸盐胶结物类型、期次、成因机理及其与流体活动的关系,对于储层评价预测有重要意义。研究结果表明,碳酸盐胶结物表现为早、中、晚三期方解石与早、晚两期白云石,由早期到晚期,方解石及白云石的δ¹³C、δ¹⁸O值负偏增大,MnO、BaO、SrO等含量增高,早—中期方解石的形成与生物碎屑、碳酸盐矿物溶解再沉淀有关;晚期铁方解石、(铁)白云石的形成与深部热流体、无机CO₂、有机酸脱羧有关。方解石的溶解-沉淀受地层压力及CO₂含量共同控制,地层压力与天然气组分中CO₂含量相对较高,溶解作用较强,(铁)白云石发育;反之则溶解作用较弱,(铁)方解石发育。     

Geochemistry of metal-rich brines from central Mississippi Salt Dome basin, U.S.A.

Oil-field brines are the most favored ore-forming solutions for the sediment-hosted Mississippi Valley-type ore deposits. Detailed inorganic and organic chemical and isotope analyses of water and gas samples from six oil fields in central Mississippi, one of the very few areas with high metal brines, were conducted to study the inorganic and organic complexes responsible for the high concentrations of these metals. The samples were obtained from production zones consisting of sandstone and limestone that range in depth from 1900 to 4000 m (70–120°C) and in age from Late Cretaceous to Late Jurassic. Results show that the waters are dominantly bittern brines related to the Louann Salt. The brines have extremely high salinities that range from 160,000 to 320,000 mg/l total dissolved solids and are NaCaCl-type waters with very high concentrations of Ca (up to 48,000 mg/l) and other alkaline-earth metals, but with low concentrations of aliphatic acid anions. The concentrations of metals in many water samples are very high, reaching values of 70 mg/l for Pb, 245 mg/l for Zn, 465 mg/l for Fe and 210 mg/l for Mn. The samples with high metal contents have extremely low concentrations (<0.02 mg/l) of H₂S. Samples obtained from the Smackover Formation (limestone) have low metal contents that are more typical of oil-field waters, but have very high concentrations (up to 85 mg/l) of H₂S. Computations with the geochemical code SOLMINEQ.87 give the following results: (1) both Pb and Zn are present predominantly as aqueous chloride complexes (mainly as PbCl₄²⁻ and ZnCl₄²⁻, respectively); (2) the concentrations of metals complexed with short-chained aliphatic acid anions and reduced S species are minor; (3) organic acid anions are important in controlling the concentrations of metals because they affect the pH and buffer capacity of the waters at subsurface conditions; and (4) galena and sphalerite solubilities control the concentrations of Pb and Zn in these waters.     

Generation of aliphatic acid anions and carbon dioxide by hydrous pyrolysis of crude oils

Two crude oils with relatively high (0.60 wt%) and low (0.18 wt%) oxygen contents were heated in the presence of water in gold-plated reactors at 300°C for 2348 h. The high-oxygen oil was also heated at 200°C for 5711 h. The compositions of aqueous organic acid anions of the oils and of the headspace gases were monitored inn order to investigate the distribution of organic acids that can be generated from liquid petroleum.The oil with higher oxygen content generated about five times as much organic anions as the other oil. The dominant organic anions produced were acetate, propionate and butyrate. Small amounts of formate, succinate, methyl succinate and oxalate were also produced. The dominant oxygen-containing product was CO₂, as has been observed in similar studies on the hydrous pyrolysis of kerogen. These results indicate that a significant portion (10–30%) of organic acid anions reported i be generated by thermal alteration of oils in reservoir rocks. The bulk of organic acid anions present in formation waters, however, is most likely generated by thermal alteration of kerogen in source rocks. Kerogen is more abundant than oil in sedimentary basins and the relative yields of organic acid anions reported from the hydrous pyrolysis of kerogen are much higher than the yields obtained for the two oils.     

Oilfield waters and sandstone diagenesis

The evolution of the organic geochemistry and carbonate alkalinity of oilfield waters is apparently regular and predictable; this evolution can be typified by five generalizations (1) at or near 80°C there appears to be an exponential rise in the concentration of organic acid anions; (2) the maximum concentration of organic acid anions occurs over approximately the 80–100°C temperature interval; (3) the highest concentrations of difunctional acid anions are associated with the other organic species maxima; (4) difunctional acid anions are the first to be decarboxylated, typically at temperatures of 100–110°C; (5) with increasing temperature (110–130°C) monofunctional acid anions begin to become decarboxylated, resulting in a fluid alkalinity dominated by bicarbonate. Dissolution experiments using artificial and natural oilfield waters demonstrate that mono- and difunctional carboxylic acid anions and hydroxybenzoic acid anions (present in both oilfield waters and the aqueous phase of hydrous pyrolysates) are capable of greatly enhancing Al, Si, Fe and Ca concentrations in solutions from dissolution of minerals by organometallic complexation. This enhancement of mineral solubility has been called upon to explain aluminosilicate dissolution porosity which is quantitatively important in many subsurface reservoirs; certainly, no other viable mechanism has been proposed to explain aluminum transport in the subsurface. When integrated into basin models, the regular evolution of organic and carbonate alkalinity in oilfield waters and the changing mineral stabilities that accompany that evolution help explain commonly observed diagenetic sequences in clastic systems.     

泥晶灰岩的成岩作用与微孔隙研究

本文用岩石学方法结合超微技术及现代测试手段研究泥晶灰碉的成岩作用微孔隙。结果表明，对泥晶灰岩微孔隙形成有得的主要成岩作用为压溶、溶解和一定程度的云化及去云化、硅和去硅化作用。这些作用可以扩大微孔主微裂隙，使之有可能具有储集性能。     

含有机质热水溶液与金、铜、汞相互作用的实验研究

本文用实验方法研究了含有机质(脂肪酸、腐植酸,氨基酸、原油、油田卤水等)热水溶液对岩石中Au、Cu、Hg的淋滤活化作用．结果表明,含一定有机质的水溶液对岩石中Au的淋滤能力超过含NaCl、KCl等盐类的卤水,含有机质和盐类的卤水的地球化学性质基本上取决于有机质的地球化学行为。原油、油田卤水对HgS有较强的溶解作用,腐植酸及低分子的脂肪酸、氨基酸对HgS的溶解基本上不起作用。丙氨酸是岩石中Cu的有效活化剂,常温下可使岩石中46%的Cu进入水溶液。     

柴达木盆地西部卤水水化学特征与找钾研究

柴达木盆地自中生代末-新生代初以来,四周山体不断抬升,形成"高山深盆"的沉积环境,为盆地带来了大量盐类物质,再加上晚第三纪干旱封闭的气候环境,使其西部沉积了广阔而厚层的盐岩.在对柴达木盆地西部第三系、第四系地层出露盐矿点实地考察的过程中,采集、分析了22件水样品的水化学组成,通过K+含量及一些水化学系数变化特征的研究,查明了卤水的水化学类型主要为氯化物型和硫酸镁亚型,其成因基本属溶滤岩盐卤水、深部循环水以及二者的混合水体,Br-、B3+、Sr2+、Li+等微量离子含量较高,区域差异性较大,出现显著水化学系数异常;相比之下,柴达木盆地西部南翼山坳陷Br-、B3、Sr2+、Li+含量值明显高于昆特依、察汗斯拉图、油砂山、开特米里克、油泉子、油墩子等坳陷区.Br×103/Cl、K×103/Cl等具找钾意义的水化学系数比其他地区高1～2倍,Br-、K+出现相对的富积,推测该坳陷成盐原始卤水曾浓缩达到较高析盐阶段或可能有大量深部富钾水体的补给,可作为寻找钾盐矿(富钾卤水)重点区域之一.     

含气岩系的组成及其形成环境

含气岩系是讨论天然气形成的地质基础，它的组成包括气源岩层、储集岩层和盖层三部分。不同地区、不同时代含气岩系的组合类型及其分布特点各异。含气岩系的形成与地质历史时期的沉积环境密切相关，最有利于形成含气岩系的气源岩层、储集岩层和盖层的沉积环境，应为海洋沉积相域的滨岸沼泽相至浅水台地相，少数在浅海开阔台地沉积环境中.陆盆沉积相域多在浅湖相，少数位于半深湖相环境中，它的生、储、盖层组合及其形成次序是形成天然气藏的决定因素。     

罗布泊盐湖承压卤水开采新技术及可采性研究

罗布泊罗北凹地承压卤水主要储集于钙芒硝层,钾含量高(>0.5％),是该区重要的后备钾盐资源之一.本文利用大气联通法及辅助孔注入卤水法,对罗布泊罗北凹地钾矿区富水性较差的3～11采卤井进行了改造.五次大规模、长时间段的抽水试验结果表明,上述技术手段改善了深部承压卤层的储集结构,有效增强了含水层水力联系,提高了含水层单位涌水量,增率达22.7％.由此证实大气联通法及辅助孔注水法,可以有效提高罗北凹地钾矿区承压卤水采卤率.同时,辅助孔与采卤井的距离以及辅助孔注水量对采卤率有较大影响.该成果可为矿区承压卤水大规模开采利用提供借鉴和指导.     

Do organic ligands affect calcite dissolution rates?

Steady state Iceland-spar calcite dissolution rates were measured at 25 °C in aqueous solutions containing 0.1 M NaCl and up to 0.05 M dissolved bicarbonate at pH from 7.9 to 9.1 in the presence of 13 distinct dissolved organic ligands in mixed-flow reactors. The organic ligands considered in this study include those most likely to be present in either (1) aquifers at the conditions pertinent to CO₂ sequestration or (2) soil/early diagenetic environments: acetate, phthalate, citrate, EDTA⁴⁻, succinate, d-glucosaminate, l-glutamate, d-gluconate, 2,4-dihydroxybenzoate, 3,4-dihydroxybenzoate, fumarate, malonate, and gallate. Results show that the presence of <0.05 mol/kg of these organic anions changes calcite dissolution rates by less than a factor of 2.5 with the exception of citrate and EDTA⁴⁻. The presence of 0.05 mol/kg citrate and EDTA⁴⁻ increases calcite dissolution rates by as much as a factor of 35 and 500, respectively, compared to rates in organic anion-free solutions. Further calcite dissolution experiments were performed in the presence of organic polymers similar to bacterial exudates, cell exopolysaccharides, and analogs of microbial cell envelopes: alginate, lichen extract, humic acid, pectin, and gum xanthan. In no case did the presence of <100 ppm of these organics change calcite dissolution rates by more than a factor of 2.5. Results obtained in this study suggest that the presence of aqueous organic anions negligibly affects calcite forward dissolution rates in most natural environments. Some effect on calcite reactivity may be observed, however, by the presence of organic anions if they change substantially the chemical affinity of the fluid with respect to calcite.