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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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    An elemental and ~(87)Sr/~(86)Sr isotopic restitution of contaminated pore waters from sandy sediments of the Peciko gas field (Mahakam Delta, Indonesia)

    Norbert Clauer
    13页
    查看更多>>摘要：Pore waters of hydrocarbon-bearing sand layers from gigantic Peciko gas reservoir located to the South of the Mahakam Delta in Indonesia were reconstructed and studied by applying the restored pore-water technique. The method is based on the Sr isotopic compositions of rock chips leached with de-ionized water aided, here, by the associated contents of major, metal and rare-earth elements (REEs). The soluble minerals were also leached with dilute hydrochloric acid and analyzed for their Sr isotopic compositions. The main founding is that many of the recovered H2O leachates were most probably contaminated during coring, which induced abnormally high metal and REE contents. The leachates considered free of pollution yield ~(87)Sr/~(86)Sr ratios that increase progressively with depth, which suggests a recent supply of surface waters to the upper pore waters. It seems also that only a few sedimentary horizons are interconnected at intermediate depths. Furthermore, the minerals dissolved by dilute HCl yield quite systematically lower ~(87)Sr/~(86)Sr ratios than the associated pore waters, which suggests a crystallization earlier than the recent flushing of the upper sediments by surface-type waters.
      原文链接:
    • NSTL

    Examining performance of different two-phase fluid distributions simulation methods based on digital rock technology

    Jianmeng SunZhigang ChengWeichao Yan
    14页
    查看更多>>摘要：The accurate calculations of petrophysical properties are essential to evaluate oil/gas reservoirs. As an advanced non-destructive method, digital rock technology has been widely applied in simulating various rocks' petrophysical properties, such as the behaviors of resistivity and acoustic responses. Fluid distributions within the pore space are essential input data for such simulations. However, the 3D fluid distributions simulated by different methods may not be identical, leading to imprecise petrophysical interpretations. Therefore, it is necessary to compare the results of different methods on the same pore space to investigate their advantages and disadvantages. In our research, we used digital rock technology to compare different simulation methods of two-phase fluid distributions. We first adopted a sandstone core and acquired the actual oil and brine distributions in pores based on the micro-computed tomography scan images. Herein, a new simple and fast method was put forward to fix the rough connection between the oil and the brine phases. In the present study, five two-phase fluid distribution simulation methods were investigated including the steady-state pore morphology method, unsteady-state pore morphology method, network modeling method, steady-state lattice Boltzmann method, and unsteady-state lattice Boltzmann method. Then, we applied these methods on the same pore space and analyzed the results. Finally, the calculated resistivity indexes based on these methods were compared. It turns out that although the results of all different methods captured the main distribution characteristics of oil and brine phases, only the steady-state pore morphology method, unsteady-state pore morphology method, and steady-state lattice Boltzmann method provided the most useful two-phase fluid distribution and saturation exponent for our studied sandstone. These results can not only enhance our knowledge of different simulation methods' performance but also help to choose the best method for a desired petrophysical characterization task.
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    • NSTL

    Effect of formation strength anisotropy on wellbore shear failure in bedding shale

    Cao WenkeLiu WeiLiu Hailong
    12页
    查看更多>>摘要：The shale gas/oil is playing an important role in the current energy resources. However, the wellbore instability problems bring a high risk to drilling engineering especially in the formation with bedding planes. A normal wellbore stability analysis approach is based on elasticity, which is not enough to recognize the mechanisms. In this paper, the poroelasticity was adopted to present the hydro-mechanical coupling effect in shale formation, meanwhile, the permeability anisotropy which could affect the effective stresses around the well was considered. A three-dimensional finite difference model was developed to simulate arbitrary directional well in shale by the coordinate transformation method. The jointed material model was proposed to character the strength anisotropy and plastic behavior of bedding shale. Additionally, the effects of well trajectory, bedding plane orientation and mud weight on shale wellbore stability were discussed, thus some implications for improving wellbore stability in bedding shale formation were obtained from the proposed model.
      原文链接:
    • NSTL

    Fifty years of experience in rate of penetration management;; Managed pressure drilling technology, mechanical specific energy concept, bit management approach and expert systems-A review

    Mohammad NajjarpourHossein JalalifarSaeid Norouzi-Apourvari
    16页
    查看更多>>摘要：Rate of penetration (ROP) management is a matter of great importance in drilling operations, therefore it has been considered in different field management projects and research studies. In this way, several drilling technologies and concepts such as managed pressure drilling (MPD) and mechanical specific energy (MSE) have found their applications in this category. Moreover, some studies have used the bit management approach, while some other authors have developed special computer software and expert systems for this purpose. The history of ROP management studies reaches to more than half a century. In this article, some of these studies are reviewed to achieve a better understanding of this concept, its economic benefits and also its research capacities. Results indicate that among different methods which are discussed in this paper, bit management have the most field applications in ROP management studies.
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    • NSTL

    A generalized empirical expression for the collapse of worn tubulars with a crescent-shaped wear groove under combined loads

    Andreas TeiglandStein Inge DaleSigbjorn Sangesland
    10页
    查看更多>>摘要：As a large proportion of easily recoverable global hydrocarbon reserves is extracted and felds in operation are maturing, the oil and gas industry requires new methods of ensuring well integrity. Production of the remaining reserves may involve, for instance, extended-reach wells, multilateral wellbores, long horizontal sections and highly deviated trajectories. Moreover, wells in mature felds are being used to increase recovery through sidetracking. Casing wear has a signifcant infuence on the well integrity in such operations and the ability to assess its effects is crucial, both in terms of its impact on health, safety and environment, and in terms of enabling cost-effciency. This article utilizes the Finite Element Method (FEM) to analyze the stress distribution in worn tu-bulars with a crescent-shaped wear groove under external pressure. A model for tubular collapse is proposed using generalized empirical expressions for stress concentration factors in worn tubulars. The generalized expressions are based on 640 fnite element analyses of different geometries designed to represent typical dimensions used in the oil and gas industry. Comparisons with experimental data and existing models demonstrate improvement in both accuracy and precision using the developed approach.
      原文链接:
    • NSTL

    The hydrocarbon accumulation regularity and the model of hydrocarbon accumulation along the fault ridges in the slope zone of the continental fault basin

    Shijie ZhaoQiang FuWeifeng Luo
    17页
    查看更多>>摘要：The slope zone of fault basin has a large area and high hydrocarbon potential. Its relatively highly scattered reservoirs and vastly different accumulation characteristics make it difficult to accurately determine the main controlling factors of hydrocarbon accumulation. To solve this problem, we adopt the 3rd member of the Funing Formation (Ef3) in the slope zone of the Qintong Sag as an example to identify the main controlling factors of hydrocarbon accumulation in the slope zone of the Paleogene continental fault basin. The results reveal that there are two critical intervals for Ef3 in the Qintong Sag slope zone, namely, the Late Paleogene to the Early Neogene (23.2~(-2)0 Ma) and the Late Neogene to the Early Quaternary (2 Ma until now), and the crude oil comes from the source rock of the second member of the Funing group related to the slope barrier and the inner slope zone. Instead of migrating directly into the traps in the slope zone, three main paths of hydrocarbon migration were developed;; First from southwest to northeast and then from northeast to southwest;; From northeast to southwest;; From west to east directly. Oil and gas migrated along the sand body in the northeast and southwest directions and bypassed by the central antithetic fault terrace, thus forming the mode of accumulation along the fault edge.
      原文链接:
    • NSTL

    Origin and isotopic fractionation of shale gas from the Shanxi Formation in the southeastern margin of Ordos Basin

    Longfei XuYishan ChengJinchuan Zhang
    12页
    查看更多>>摘要：The Ordos Basin is abundant in natural gas resources, and the Shanxi Formation with the transitional facies is considered as a potential stratum for shale gas reservoir. However, the origin and geochemical characteristics of the Shanxi Formation shale gas remains unclear. In this study, 22 shale gas samples were collected from the SX~(-1) well in the southeastern margin of Ordos Basin, and tested for gas components and compositions of stable carbon isotope. Moreover, five rock samples were measured for total organic carbon (TOC), the vitrinite reflectance (Ro), kerogen type, porosity, permeability, and methane adsorption capacity. The shale gas in the Shanxi Formation has a high proportion of methane which is consistent with the high maturity of source rocks. The contradictory relationship between the carbon isotopes of ethane (δ~(13)C2) from the Shanxi Formation shale gas and kerogen types of rock samples may be caused by the complex sedimentary environment, multiple provenance systems, and high maturity. The carbon isotopes of methane (δ~(13)C1), δ~(13)C2 and alkane gas components indicate that the shale gas near coal seams is coal-derived gas, the gas at the bottom of the Shanxi Formation is oil-type gas and the gas in mudstones among the sandstone layer at the top of the Shanxi Formation may be mixed with natural gas migrating from other layers or mixed with gas generated in the later period. Meanwhile, the carbon isotopes of carbon dioxide (813 Cco2) suggest that the CO2 generated with hydrocarbons in the coal-measures is mainly of organic origin. The carbon isotopic fractionation of methane is commonly observed in shale gas samples. This fractionation is mainly controlled by the diffusion effect which can be promoted by high porosity and permeability. Furthermore, the positive correlation between the TOC values and the degree of fractionations may be attributed to the high TOC values in the samples, which can improve the development of organic pores and increase the content of adsorbed gas.
      原文链接:
    • NSTL

    Study on the effect of multiple non-breathable gangue occurrence on gas migration in coal seams

    Hongbao ZhaoYang LiJinyu Li
    10页
    查看更多>>摘要：As the mining environment gradually moves toward deep, the form and occurrence mode of gangue are more complex. The occurrence of non-breathable gangue seriously worsens gas migration conditions, which greatly reduces the gas extraction efficiency and increases the possibility of coal and gas outburst. Therefore, in order to explore the effect of multiple non-breathable gangue occurrence on gas migration in coal seams, the self-developed " the constant pressure coal and rock mass gas seepage test system" is used to systematically study the characteristics of coal seam gas migration under different layers of gangue and the differentiated occurrence of multiple gangue. The equivalent characterization of coal seam gas migration under the condition of multiple inclusions is proposed through theoretical analysis and numerical simulation. Research shows;; the permeability factor of the whole coal sample, sample containing a single layer gangue and sample containing double layers gangue exhibits a "V"-shaped variation law with the increase of the gas adsorption equilibrium pressure. There is a critical gas pressure point when the permeability factor is the lowest, and with the increase in the number of gangue layers, the greater the pressure value of the critical gas pressure point. According to the characteristics of gas pressure distribution, the sample containing gangue can be roughly divided into four influence areas;; gas expansion affected area, gas stable seepage area and upper and lower effective seepage area. The more the number of gangue layers and the larger the area of gangue layers, the upper and lower effective seepage area is smaller, the closer the positions of gangue are to the gas source, gas expansion affected area is smaller, both of them will cause more difficult in gas migration and the lower of the sample permeability factor. When different sizes of gangue are used at two positions of the gangue in the samples, with the increase of gas adsorption equilibrium pressure, the attenuation rate of permeability factor in the early stage of the sample is significantly higher than that of the sample with the same size of gangues in the front and at the back. The results of the paper have certain actual guiding significance for improving gas extraction efficiency and preventing mine gas disasters.
      原文链接:
    • NSTL

    A new approach to measure wettability by relative permeability measurements

    Abouzar Mirzaei-PaiamanMohsen Faramarzi-PalangarSofiane Djezzar
    13页
    查看更多>>摘要：Wettability is a key factor controlling the flow of fluids, solutes, heat and electrical current in porous media, and therefore it is important in studies of various processes including CO2 storage, secondary and tertiary oil recovery, as well as the displacement of water and nonaqueous phase liquid (NAPL). Although Amott-Harvey and USBM are conventional industry-standard techniques for measuring average wettability, they have some limitations. In this paper, we show that, in a plot of the relative permeability of a fluid, the area below the curve is closely related to the wettability. By using the areas below the water and oil relative permeability curves, we derive a new wettability index (called modified Lak). To demonstrate the applicability of this new index and testing other indices, we performed primary imbibition relative permeability, and primary imbibition and secondary drainage capillary pressure measurements on twenty carbonate reservoir samples. In general, all indices predicted oil-wet character of the tested rocks. USBM was associated with the broadest range of variation, whereas the new index corresponded to the smallest range of variation. Amott-Harvey and Lak, however, fell between USBM and the new index, with fairly similar ranges of variation. In addition, we report the correlations between different indices, and the change of wettability indices vs. reservoir depth. Advantages and limitations of different wettability indices are also discussed. Since each wettability index has some limitations in revealing the true state of wettability, none of these indices can be considered as an absolute measurement. Therefore, different indices should be regarded as complementary to each other, and determination of wettability should not be limited to only one method.
      原文链接:
    • NSTL

    Experimental study and modeling of final fracture conductivity during acid fracturing

    Hossein MehrjooSaeid Norouzi-ApourvariHosseinjalalifar
    18页
    查看更多>>摘要：Successful acid fracturing operation could reduce formation damage and increase production rate in a carbonate reservoir. Final fracture conductivity is a critical parameter that determines the success of the acid fracturing operation. A wide range of parameters could affect the fracture conductivity, making its prediction quite difficult. The effect of contact time, type of acid, and rock type has been evaluated before. In this study, however, the effect of concentration of hydrochloric acid (HCl), rock strength, injection rate, acid type, and rock type on the conductivity of the fracture was investigated. Based on our observations, for calcite rock types, greater fracture conductivities were achieved by using HCl 15% compared to HCl 7%. For dolomite, the result was completely different and lower concentration of HCl had better outcome. Depending on the type of acid that was used, different results achieved for rocks with different strength. When low concentration of HCl, HCl 7%, was used as an injection fluid, dolomite with higher strength had better conductivity. However, for strong acid, HCl 15% and emulsified acid, the best results were obtained for calcite with low strength. Injection rates resulted in two different outcomes. At low concentration, the injection rate of 4 ml/min created better fracture conductivity while at high concentration, the injection rate of 10 ml/min generated better results, when injection fluid was HCl. As for emulsified acid, higher injection rate resulted in proper conductivity. In most cases, emulsified acid had better final fracture conductivity. Based on experimental results obtained, three models for three different acid types were developed. The conductivity of rocks after acid etching was predicted based on injection rate, rock strength, and closure stress. Statistical and graphical analysis proved that developed models have a good performance.
      原文链接:
    • NSTL