Petrographic and in situ geochemical analyses were carried out on cores of the fluvial sandstone (<50 to >4 mm; sublithic quartz arenite) dominated Tithonian Jeanne d’Arc Formation interval from wells C-09 and E-79 of the Terra Nova oilfield to understand diagenetic control on reservoir quality of the formation. Lithic clasts are dominantly carbonates and shales. Successively, early near-surface dolomite cementation, eogenetic dolomite dissolution, burial calcite cementation and its subsequent dissolution are the major diagenetic events that controlled the reservoir quality of the sandstone. Dolomite cement grades from mostly Fe-rich (FeCO₃ ca 12 ± 2 normalized mol.%) in the upper part of the formation to Fe-poor (<0.07 normalized mol.%) in the lower part of the formation in both wells. The dolomite and calcite cements generally have low Sr and Na; enriched Y and low δ¹⁸O and δ¹³C values relative to typical marine carbonates. Strontium is enriched in the Fe-poor (higher Mg) dolomite relative to the Fe-rich phase. Mineral liberation analyses of shale samples reveal common Fe-chlorite and minor glauconite. Furthermore, considerable amounts of solutes in the early diagenetic pore fluid were likely derived from water—rock interaction with underlying Oxfordian Rankin Formation marine carbonate that was also exposed in the watershed of the study area at the time. Together, these suggest that the dolomites were formed from an early diagenetic bicarbonate-rich pore fluid of mixed meteoric and seawater origin. The origin and distribution of early dolomite cementation and other successive diagenetic events have a depositional cycle control. Episodic post-deposition transgression of seawater and/or compactional fluid expulsion from shales into overlying sandstones led to formation of dolomite cement. Subsequent infiltration of organic acid-charged meteoric-water into underlying dolomite-cemented sandstones resulted in early dissolution. This porosity was mostly occluded by re-precipitation of calcite. Increase in the abundance of relic corroded dolomite crystals with depth in each cycle indicates that early dissolution was most effective at the top of the cycles. Iron depletion in the calcite cement with depth through the formation points to a local derivation of reactants from in situ dolomite species; implying a stratigraphic control. Calcite cementation was succeeded by continuous mesogenetic dissolution concomitant mechanical compaction. The responsible low-pH pore fluid attained its composition via enhanced H⁺ contribution from silicate burial diagenesis. The control of depositional settings on the major diagenetic processes makes it a key contribution to region-wide reservoir quality prediction for the formation.

中文翻译：

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纽芬兰 Terra Nova 油田 Tithonian Jeanne d'Arc 砂岩中的碳酸盐胶结：对储层质量演变的影响

对 Terra Nova 油田 C-09 井和 E-79 井以 Tithonian Jeanne d'Arc 组段为主的河流砂岩（<50 至 >4 mm；亚石器石英砂岩）岩心进行了岩石学和原位地球化学分析，了解成岩作用对地层储层质量的控制。岩屑碎屑主要为碳酸盐岩和页岩。先后早期近地表白云岩胶结、早生白云岩溶蚀、埋藏方解石胶结及其后溶蚀是控制砂岩储层质量的主要成岩事件。白云石水泥等级主要来自富铁（FeCO ₃ ca12 ± 2 归一化 mol.%) 在地层上部到两个井中地层下部的贫铁 (<0.07 归一化 mol.%)。白云石和方解石胶结物的Sr和Na一般较低；富集 Y 和低 δ ¹⁸ O 和 δ ¹³相对于典型海洋碳酸盐的 C 值。相对于富铁相，锶在贫铁（较高镁）白云石中富集。页岩样品的矿物释放分析揭示了常见的铁绿泥石和少量海绿石。此外，早期成岩孔隙流体中的大量溶质可能来自水-岩石与下层牛津兰金组海相碳酸盐的相互作用，当时该碳酸盐也暴露在研究区的分水岭中。总之，这些表明白云岩是由早期成岩富含碳酸氢盐的混合大气和海水的孔隙流体形成的。早期白云岩胶结作用等连续成岩事件的成因和分布具有沉积旋回控制。海水的间歇性沉积后海侵和/或压实流体从页岩中排出到上覆砂岩中导致了白云石胶结物的形成。随后，带有机酸的大气水渗入下伏白云石胶结砂岩中，导致早期溶解。该孔隙大部分被方解石的再沉淀所封闭。各个旋回中残蚀白云石晶体丰度随深度的增加表明早期溶解在旋回顶部最有效。方解石水泥中铁的消耗随着地层深度的增加表明反应物的局部衍生 该孔隙大部分被方解石的再沉淀所封闭。各个旋回中残蚀白云石晶体丰度随深度的增加表明早期溶解在旋回顶部最有效。方解石水泥中铁的消耗随着地层深度的增加表明反应物的局部衍生 该孔隙大部分被方解石的再沉淀所封闭。各个旋回中残蚀白云石晶体丰度随深度的增加表明早期溶解在旋回顶部最有效。方解石水泥中铁的消耗随着地层深度的增加表明反应物的局部衍生原地白云石物种；暗示地层控制。方解石胶结通过连续的中生溶蚀伴随机械压实而成功。负责任的低 pH 值孔隙流体通过提高硅酸盐埋藏成岩作用的H ^{+贡献来获得其成分。}对主要成岩过程的沉积环境的控制使其成为区域范围内地层储层质量预测的关键贡献。