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Journal of Petroleum Science & Engineering
Elsevier Science B.V.
Journal of Petroleum Science & Engineering

Elsevier Science B.V.

0920-4105

Journal of Petroleum Science & Engineering/Journal Journal of Petroleum Science & Engineering
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    Geochemical characteristics and depositional paleoenvironment of source rocks from the Lower Cretaceous Chijinbao Formation in Jiuxi Basin, China

    Ma, BoJi, LimingJin, PeihongZhang, Mingzhen...
    19页
    查看更多>>摘要：The Lower Cretaceous Chijinbao Formation is one of the primary source rocks in the Jiuxi Basin in Northwest China. However, it is poorly studied due to the lack of a complete stratigraphic sequence exposed by drilling. In this research, an integrated analysis of palynofacies, organic geochemistry, and element geochemistry was systematically conducted on samples with longitudinal continuity collected from the Chijinbao Formation in the Hanxia Section of the Jiuxi Basin to determine the distribution of source rocks and the source and type of organic matter and to reconstruct the depositional paleoenvironment of the Chijinbao Formation. The lower part of the sequence, which is governed by poor source rocks with Type III organic matter, is characterized by palynofacies A (woody tissue-charcoal assemblage) grown in a proximal alluvial fan-shallow lacustrine environment. The excellent source rocks with mostly Type II1 organic matter are considerable in the middle part of the sequence, which is marked by palynofacies B (amorphous organic matter assemblage), and occur in a distal semi-deep lacustrine-deep lacustrine environment. The upper part of the sequence is largely composed of poor and fair source rocks, represented by palynofacies C (amorphous organic matter-woody tissue assemblage), and a small amount of sporadically distributed good and excellent source rocks (approximately 1/3), which may be deposited in a proximal fan delta and a local semi-deep lacustrine-deep lacustrine environment. A semiarid-semi-humid climate and a freshwater-brackish water environment prevailed during the deposition of the Chijinbao Formation. The lower part of the sequence is characterized by the highest terrestrial detritus influx, strong weathering, humid paleoclimate, oxic water column conditions, and the lowest paleoproductivity. The middle part of the sequence has the lowest terrestrial detritus influx, relatively weak weathering, relatively arid paleoclimate, predominantly anoxic water environment, and the highest paleoproductivity. The climate became humid again during the deposition of the upper part, which is typified by an intermediate terrestrial detritus influx, strong weathering, fluctuations of oxic-anoxic bottom-water conditions, and moderate paleoproductivity. The correlation analysis of element proxies suggests that the increase in salinity during the deposition of the middle part is associated with an arid climate. Amorphous organic matter, which is derived mostly from aquatic organisms and degraded terrestrial higher plants, is the major hydrocarbon generation component in the source rocks of the Chijinbao Formation. It increases in abundance with an improvement in water reducibility and productivity, favoring the formation and preservation of excellent source rocks.
      原文链接:
    • NSTL
    • Elsevier

    Study on the penetration of strengthening material for deep-water weakly consolidated shallow formation

    Tian, LeijuBu, YuhuanGuo, ShenglaiLiu, Huajie...
    12页
    查看更多>>摘要：Unformed-rock silt and sand are the main components of shallow formations in deep-water oil and gas wells. The formations are different from the perspective of mechanical performance of the cement sheath and often causes brittle failure. Improving the cement system or cement-formation interface strength is not sufficient to solve this problem. This study tested solid and liquid strengthening materials to increase the mechanical performance of weakly consolidated shallow formations and to minimize the performance difference with cement stone. The test of the groutability of superfine slag, cement, and epoxy resin indicated that waterborne epoxy resin system is the best choice. An annular simulation core was used to evaluate the penetration of the epoxy resin system. The simulation cementing experiment indicated that the viscosity of the ER (epoxy resin) slurry and the compression degree of the core negatively correlated with the permeate depth, while the grouting pressure exhibited positive correlation. The permeate depth can reach 11.8 mm under 0.1 MPa while the maximum was 21.7 mm at 0.4 MPa. A thin ER layer was formed between the cement sheath and the core after the ER slurry was cured, which increased the cement-formation interface strength by 22.18 %. Standard blocks showed that 5% of ER can increase the strength of unconsolidated clay to 2.17 MPa. SEM indicates that the ER filled part of the space between the particles of clay and consolidated them. The difference between standard blocks and core samples after treatment in SEM was low. The difference in mechanical performance between the cement stone and the weakly consolidated formation was narrowed after the formation was reinforced.
      原文链接:
    • NSTL
    • Elsevier

    Electrical formation factor versus porosity coarse-scale transforms from microscopic digital images: Example-based study

    Hussaini, Syed RizwaahDvorkin, Jack PetrovichAl-Mukainah, Hani Salman
    10页
    查看更多>>摘要：The question posed in this work is whether and how elemental data obtained on small and often sub representative fragments of natural rock can be exploited to generate a physically valid transform between two physical properties useable at a coarser spatial scale, such as the reservoir scale. The pair of such properties targeted here is the porosity and electrical formation factor. We use the process-based upscaling to prove, by example, that a coarse-scale transform between these two variables can be obtained from a dataset computed on microscopic digital volumes of natural rock, including unconsolidated sand, medium-porosity sandstones, and low-and high-porosity carbonates. This upscaling method is based on constructing a coarse-scale (effective) rock volume from the elemental volumes with a subsequent simulation of a relevant physical process in this effective object, specifically the electrical current. A numerical simulation of Laplace equation governing electrical current is used to compute the effective resistivity. The effective porosity is simply the arithmetically averaged porosity of the elements. By using hundreds of random realizations of the effective object, we generate tight formation factor versus porosity transforms for each of the natural rock samples under examination. Because the proof offered here is by-example, it is not general. However, the method offered is general and, as such, can be used to address the same question as posed for various situations.
      原文链接:
    • NSTL
    • Elsevier

    Pore-scale characterization of CO2 front progress through a porous medium using a free energy model based on Phase-Field Lattice Boltzmann Method

    Moradi, BijanMoghadam, Amir HosseiniRasaei, Mohammad RezaPapi, Ali...
    13页
    查看更多>>摘要：Pore-scale simulation of CO2 front progression through a porous medium has been investigated by a free energy model based on phase-field lattice Boltzmann method. Visualization of the fluids distribution in the breakthrough time reveals a strong dependence of front pattern on viscous and capillary forces interaction. Therefore, the dominance of each force imposes a different front pattern on the system. According to the percolation theory, increasing the capillary number reduces the invading fluid saturation and, consequently, the sweep efficiency, because the viscous fingering regime will intensify. However, a uniform pattern is observed when the mobility ratio is high, whereas the front evolution is facilitated in the opposite case. Impressive results have also been obtained regarding the wetting conditions. Since an upward trend in the displacement efficiency from strong drainage to strong imbibition processes is expected, this trend has changed due to the capillary suction effects in the strong imbibition process. According to experimental studies, the viscous fingering phenomenon will be proportional to the capillary suction. Furthermore, new areas have also been introduced to predict the displacement regimes.
      原文链接:
    • NSTL
    • Elsevier

    Extraordinarily high organic matter enrichment during the late Guadalupian in northwestern Sichuan basin, China

    Chen, CongGao, ZhaolongShan, ShujiaoChen, Yangui...
    16页
    查看更多>>摘要：Shale with extraordinarily high organic matter content (EHOMC) formed in the margin of the Sichuan carbonate platform during the late Guadalupian in the eastern Paleo-Tethys. So far, not much consideration has been given to the enrichment of EHOMC. Here, integrated lithological and geochemical analyses of the top Maokou For-mation black shales in the northwest Sichuan basin were undertaken to investigate the EHOMC. The black shales were divisible into three units (i.e., Units 1 to 3 in ascending order); EHOMC occurred in Unit 2. Unit 1 was deposited during the early stage of the transgression under the small-scale upwelling in an anoxic environment with lower paleo-productivity than Unit 2, considering the moderate Cd/Mo ratios and the concentration of Mo, U, V, P, Cu, and Zn. Unit 2 exhibited high Cd/Mo ratios and high concentrations of elements (Mo, U, V, P, Cu, and Zn), suggesting that the shales with EHOMC were deposited through an intense upwelling in an euxinic-sulfidic environment with high paleo-productivity. Unit 3 demonstrated moderate paleo-productivity and anoxic-suboxic conditions, while the nutrient elements were derived through increased terrestrial detrital input. Unit 2 exhibited the highest total organic matter content (TOC) (17.72-32.58 wt%); it is inferred that the enrichment of EHOMC was mainly caused by a euxinic-sulfidic environment, while high paleo-productivity was another key factor. Besides, the euxinic-sulfidic environment and high paleo-productivity in Unit 2 occurred approximately during the intense upwelling, the occurrence of the high sea-level, and the biological extinction during the end of Guadeloupe. These factors together promoted the enrichment of EHOMC in Unit 2.
      原文链接:
    • NSTL
    • Elsevier

    Meteoric freshwater leaching and its significance to reservoir quality in a buried hill of lower-middle Jurassic fluvial sandstones: A case study from the Huanghua Depression, Bohai Bay Basin, China

    Wang, ZhukunCao, YingchangSwennen, RudyYuan, Guanghui...
    14页
    查看更多>>摘要：Within polycyclic sedimentary basins, meteoric freshwater leaching plays an important role in the formation of secondary porosity. Whereas, when superimposed by other late diagenesis processes, it is often difficult to identify its diagenetic indicators. The Jurassic clastic reservoirs in the "Wmy buried hill" of the Huanghua Depression testify from such meteoric freshwater diagenesis. The "buried hill" is named after a village called "Wmy" and nowadays buried deeply into a Paleogene lacustrine sag, which displays like a highland or hill. These reservoir sandstones were studied based on a variety of approaches including 3-D seismic interpretation, core and thin section observations, X-ray fluorescence analysis, Electron Probe Microanalysis and stable isotope analysis, combined with reconstruction of the burial and thermal histories. At last, the evolutionary model of reservoir quality was addressed. Difference of sedimentary fabrics in sand bodies leads to the heterogeneity of pores distribution, making the permeability in coarse-grained and fine-grained sandstones largely different. The meteoric water leaching caused the loss of Fe and Ti, leading to a zonation of core colors with white and red zones. In addition, the dissolution by meteoric water of biotite and volcanic fragments as well as feldspar grains produced large amounts of secondary porosity without formation of diagenetic by-products, which thus points to an open diagenetic system. The calcite cement of meteoric freshwater origin displays relatively low Fe and high Mn content exhibiting a low Fe/Mn ratio. The origin of Mn is probably dissolution of volcanic fragments. The evolutionary process of reservoir quality can be divided into four stages. The second stage is the crucial period for formation of secondary porosity whilst faults derived from the compressional stress during tectonic uplif associate coal-bearing source rocks with Jurassic reservoirs. Moreover, the last stage is the critical period for petroleum and/or gas migration and accumulation because the underlying coal-measures entered the hydrocarbon generation window and overlying Paleogene sealing rocks were intensely compacted. Scale of potential reservoirs in the whole well profile are evaluated by statistical methods, the total thickness of which can reach about 25 m. Reservoirs close to the unconformity surface between the Mesozoic and Cenozoic display more effective porosity than the deeper ones, which should be the target for the subsequent hydrocarbon exploration.
      原文链接:
    • NSTL
    • Elsevier

    Paleoenvironmental characteristics and evidence of subsag migration within the Laizhouwan Sag in the Bohai Sea

    Wang, FeilongTang, GuominWang, DeyingPan, Wenjing...
    10页
    查看更多>>摘要：The Laizhouwan Sag comprises many sets of source rocks, and their crude oil properties are complex and changeable. This research evaluates the quality of source rocks using mudstone samples of the Shahejie Formation from typical wells from northern and southern subsags by incorporating a detailed organic-inorganic geochemical, palynology and petrological analysis. Moreover, it analyzes the difference between the paleoenvironment and paleoproductivity. It also discusses the migration characteristics of the sag in combination with seismic data to reveal the fundamental reason for the complex oil source characteristics of the Laizhouwan sag. The results show there are two sets of effective source rocks in the northern subsag of the Laizhouwan Sag, (i) the third member of the Shahejie Formation(E2s3) (ii) the fourth member of the Shahejie Formation (E2s4). Additionally, the E2s4 is a high-quality, effective source rock in the southern subsag of Laizhouwan Sag. (2) During the sedimentary period of the E2s4 in Laizhouwan Sag, the water bodies of the southern and northern subsags were separated. The organic matter (OM) in the E2s4 of northern subsag mainly comes from lower algae, mainly amorphous, and deposited in a weak reducing environment of brackish water. The OM in the E2s4 of southern subsags mainly comes from terrigenous higher plants, mainly composed of terrigenous amorphous assemblages, and it was deposited in a strongly reducing environment of brackish water to saline water. (3) Moreover, the water bodies of the southern and northern subsags gradually changed to unified water bodies during the sedimentary period of the E2s3. During this period, OM comes from lower algae, mainly from amorphous material, and the water bodies were transformed to a weak oxidation-reduction environment from freshwater-brackish water. The subsidence center of the Laizhouwan sag continued to move southward during the sedimentary period of E2s4-E2s3. Gradually the southern subsag became a sedimentary center containing higher paleoproductivity and eutrophic lake settings. The differences in organic source, sedimentary environment and paleoproductivity of source rocks in different subsags lead to the complexity of crude oil generation features.
      原文链接:
    • NSTL
    • Elsevier

    Effects of wellbore irregularity on primary cementing of horizontal wells, Part 2: Small scale effects

    Sarmadi, P.Renteria, A.Thompson, C.Frigaard, I. A....
    20页
    查看更多>>摘要：Wellbore irregularities turn the narrow eccentric annulus of primary cementing into a fully three-dimensional (3D) flow geometry. Here we explore the effects of coupling the borehole geometry, reconstructed from high frequency caliper data, with 3D computations of the displacement flow. Displacement flows through circular boreholes with enlargements of varying depths and wavelengths tend to result in both enhanced secondary flows and in residual drilling mud. Short wavelength deep enlargements generally have larger percentage of residual mud. We then perform a frequency analysis of typical caliper data from Northwest Canada, showing that the borehole geometry may typically be reconstructed using the lowest 3-5 dominant frequencies. We present example computations of displacement flows through these geometries. Although the underlying dynamics are those of more uniform annuli, these computations do reveal in that small changes in geometric description can lead to noticeable changes in the displacement mechanics, especially in the fluid present at the walls of the annulus. The conclusion is that borehole irregularity can make a significant difference in cementing horizontal wells, which are anyway already troublesome.
      原文链接:
    • NSTL
    • Elsevier

    Geological storage of CO2 and acid gases dissolved at surface in production water

    Pearce, J. K.Khan, C.Golding, S. D.Rudolph, V...
    14页
    查看更多>>摘要：During geological CO2 storage traditionally CO2 is injected subsurface into a high permeability reservoir capped by a low permeability seal to trap the buoyant supercritical plume. Wastewater from oil and gas production is also currently disposed of by subsurface injection into suitable reservoirs, most notably in the USA and Canada. Injection of CO2 dissolved in water may both increase storage security by reducing vertical migration and enhancing dissolution and mineral trapping. There is potential for surface dissolution of CO2 into wastewater that is already being stored subsurface. CO2-water-rock reactions in different sandstone or limestone reservoir rocks with either saline coal production water or low salinity water were geochemically modelled. The geochemical potential for mineral trapping of CO2, and associated changes to pH for potential reservoirs is compared. For a mineralogically clean quartz-rich saline sandstone reservoir only 0.18 and 0.20 kg/m3 CO2 was mineral trapped as ankerite and calcite over 30 or 1000 years. Feldspars, clays and carbonate minerals were converted to kaolinite, calcite, ankerite and smectites, as pH increased to 5.65. The specific silicate minerals present controlled mineral trapping potential e.g. with an Fe-rich chlorite present rather than a clinochlore chlorite 6.3 and 6.8 kg/m3 CO2 was trapped at 30 and 1000 years respectively as siderite and ankerite. Disso-lution trapping dominated in the low salinity or limestone reservoirs with minor mineral trapping. The presence of small amounts of SO2 or H2S in the CO2 stream resulted in dissolved S sequestered as elemental S, pyrite, barite, and anhydrite. The effects of low CO2 content or potential reservoir cooling induced by injection fluids were also investigated. The low pH of the injection fluid could potentially corrode legacy wellbores, one solution is a form of amendment such as liming to neutralise pH.
      原文链接:
    • NSTL
    • Elsevier

    A modified nuclear magnetic model for characterizing the fluid signal response in hydrocarbon bearing rocks

    Wang, YuetianZhao, PeiqiangCui, YunjiangMao, Zhiqiang...
    11页
    查看更多>>摘要：The nuclear magnetic resonance (NMR) technique is a crucial means for formation evaluation. It can provide an accurate set of formation parameters in single-phase-flow reservoirs, such as porosity, permeability, and pore structure distribution; however, in most cases, there are hydrocarbon-water two-phase fluids in the reservoirs. The secondary change of the T2 distribution makes the accuracy of the evaluation a challenge. Hence, it is necessary to clarify the impact of changes in hydrocarbon content on the response of NMR signals before using the traditional evaluation methods. In this paper, we analyzed the response mechanism of NMR T2 distribution under different saturation conditions. Based on the theoretical derivation, we established a nuclear magnetic model that describes the relation among the T2 geometric mean value of water signal, hydrocarbon signal, and water saturation. The accuracy of each model part was verified by numerical simulation. In addition, the calculation results in core samples show that the proposed model is more effective and reliable than two existing models (the T2 saturation ratio model and the Xiao empirical model), especially in extreme conditions (irreducible water and hydrocarbon saturated samples). Finally, we applied the proposed model to field application in the Tertiary formation in the Bohai Bay Basin, China, which achieved good effects in the NMR fluid substitution and the NMR saturation evaluation.
      原文链接:
    • NSTL
    • Elsevier