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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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    Effects of bedding direction on brine imbibition in Lower Shaximiao tight sandstone: An NMR analysis

    Xu, LiangLi, QiMyers, MatthewTan, Yongsheng...
    11页
    查看更多>>摘要：Spontaneous imbibition phenomenon caused by capillarity plays an important role in the production of tight sandstone gas. Understanding the effects of bedding direction on liquid imbibition is important as it can give insights into water block phenomena that can negatively impact gas production. In this paper, four tight sandstone specimens were cored from Sichuan Basin, China with different bedding directions (i.e., the angles between the bedding plane and the horizontal plane of four specimens are 0 degrees, 45 degrees, 60 degrees and 90 degrees, respectively). Nuclear magnetic resonance (NMR) technique was used to monitor the fluid distribution changes during the spontaneous imbibition processes of these specimens. The results show that such tight sandstone exhibited strong hydrophilicity with the small pores dominating throughout the imbibition process. The T2 spectra for all four rocks specimens not only increased upward but also shifted to larger relaxation times due to brine intake along the minerals surface (further indicating the hydrophilic characteristics of this rock). For such tight sandstone, capillary force and friction resistance between the fluid (brine) and mineral surfaces controlled the imbibition processes. For the 0 degrees, 45 degrees and 60 degrees specimens, "stop illusion" phenomena which the imbibed brine volume had a tiny increase during a long period occurred. However, this was not observed in the 90 degrees specimen (where the bedding direction and fluid flow direction are parallel). This is largely attributed to the significant tortuosity in the flow for the 0 degrees, 45 degrees and 60 degrees specimens compared to the 90 degrees specimen, leading the smallest friction resistance existed in the 90 degrees specimen. Among these four specimens, the 0 degrees specimen had the slowest imbibition rate and lowest imbibition efficiency, while the 90 degrees specimen exhibited the fastest rate and highest efficiency. With the aim of maximizing gas production, this work provides some guidance for the selection of directional fracturing and injection-production methods in the exploitation and production of tight sandstone gas field.
      原文链接:
    • NSTL
    • Elsevier

    Testing rebound hardness for estimating rock properties from core and wireline logs in mudrocks

    Wang, YulunGrammer, G. MichaelEberli, GregorWeger, Ralf...
    22页
    查看更多>>摘要：Rebound hardness (RHN) has become a widely applied rock mechanical parameter in the petroleum industry due to economic and convenient testing procedures. However, the RHN data can be under-utilized when lacking detailed integration with other rock properties. Targeting the unconventional "Mississippian Limestone"/STACK play in north-central Oklahoma, USA, and outcrops of the Vaca Muerta Formation in Argentina, this study aims to test the value of RHN in predicting rock properties. RHN data from the "Mississippian Limestone"/STACK cores show correlative trends with mineralogy and porosity. All the correlations show clusters by facies groups with overlaps being present among different clusters. Within these correlations, mineralogy and porosity show variable significance levels in affecting RHN among different facies groups. Leverage analysis suggests that bulk clay content and porosity exhibits the most significant control on RHN for the MISS/STACK data, with variabilities being present in different facies groups. These partitioning patterns of data by facies groups imply that facies variability affects the statistical pattern and that RHN can assist in rock typing, and hence, sample selection for detailed laboratory analyses. Forward regression analysis reveals that the confidence level of predicting porosity and sonic velocity can be enhanced using RHN. In addition to the correlative trends between RHN and rock properties, results from forward regression analysis indicate that RHN can help estimate these properties in a faster, cheaper, and non-destructive way relative to conventional laboratory analyses. Correlative trends are also observed in Vaca Muerta data, suggesting the value of RHN in characterizing similar types of mixed carbonate-siliciclastic reservoirs.
      原文链接:
    • NSTL
    • Elsevier

    Determination of pores properties in rocks by means of helium-3 NMR: A case study of oil-bearing arkosic conglomerate from North belt of crude oil, Republic of Cuba

    Safiullin, KajumKuzmin, VyacheslavBogaychuk, AlexanderAlakshin, Egor...
    11页
    查看更多>>摘要：The developments of helium-3 nuclear magnetic resonance (NMR) technique to assess porous media properties such as porosity and pore size distribution (PSD) are reported. The method is suitable for use to characterize unconventional extra-heavy oil reservoirs, has a potential in application to tight shales and other unconventional formations, and has several advantages over conventional water NMR. It is based on He-3 nuclear magnetic relaxation measurements for different pore loadings and inverse Laplace transform of the data. The relation between different pore types as well as their mean radii are found within the models of spherical, cylindrical and planar pores. The method was applied to study porosity and PSD of rock samples acquired at the North belt of crude oil, Republic of Cuba, the unconventional formation known for its complexity. The obtained pore sizes and porosities are in a good agreement with conventional methods which validates the proposed He-3 NMR approach for porous media studies. Advantages of the He-3 liquid and gas as probes are discussed.
      原文链接:
    • NSTL
    • Elsevier

    Computational prediction of the drilling rate of penetration (ROP): A comparison of various machine learning approaches and traditional models

    Brenjkar, EhsanDelijani, Ebrahim Biniaz
    22页
    查看更多>>摘要：Rate of penetration (ROP) prediction, can assist precise planning of drilling operations and can reduce drilling costs. However, easy estimation of this key factor by traditional or experimental models is very difficult. This requires comparing available models for achieving the best prediction approach. In this study, four machine learning (ML) methods and two traditional ROP models were utilized to predict ROP. ML techniques include multilayer perceptron neural network (MLPNN), radial basis function neural network (RBFNN), adaptive neurofuzzy inference system (ANFIS), and support vector regression (SVR). MLPNN, ANFIS, and RBFNN methods were trained with four meta-heuristic algorithms including particle swarm optimization (PSO), ant colony optimization (ACO), differential evolution (DE), and genetic algorithm (GA). The backpropagation (BP) algorithm was also incorporated to train the ANFIS and MLPNN methods as a conventional method. For comparison purposes, the traditional ROP models of Bourgoyne and Young (BYM) and Bingham were also implemented in combination with four meta-heuristic algorithms. The required data were collected from the mud logging unit (MLU) and the final report of a drilled well located in southwestern of Iran. In the MLU, the information of different sensors is firstly collected through the data communications protocols and sent to a master unit to be processed into relevant dimensions (i.e. create operational variables). In order to accurately record information, the sensors are calibrated at regular intervals. After removing the outliers, the overall noise of data was reduced by SavitzkyGolay (SG) smoothing filter. Then, in order to simulate a drilling process in a realistic manner and also to evaluate the performance of the models in approximating the penetration rate at greater depth of hole, the available data were divided into 6 sections based on depth. After that, sections 2 to 6 were separately used as a test dataset and all previous sections were considered as a training dataset. Results indicated that PSO-MLPNN achieved the highest performance in comparing with other developed models. The concluding remark is that ML models are more efficient and reliable than traditional models. In addition, combining ML models with metaheuristic algorithms can achieve better results than conventional algorithms such as BP. The results of this study can be used as a practical guide for the management and planning of future well drilling.
      原文链接:
    • NSTL
    • Elsevier

    Spatial and temporal evolution of the Sinian and its implications on petroleum exploration in the Sichuan Basin, China

    Miao, ZhengshuoPei, YangwenSu, NanSheng, Shouzheng...
    13页
    查看更多>>摘要：In recent years, there have been significant discoveries of hydrocarbon resources with commercial value in the Dengying Formation of the central Sichuan Basin. However, the impact of tectonic evolution on hydrocarbon accumulation has not been appropriately documented. In this study, we employed multiple methods, including seismic interpretation, balanced cross-section restoration, deformation quantification, erosion calculation, and paleo-highs/lows reconstruction, to investigate the tectonic kinematics, erosion distribution, paleo-highs/lows evolution of the Sichuan Basin. The quantification of deformation reveals that the Sichuan Basin has experienced a complicated tectonic evolution, with two rounds of transition from tension to contraction since the Sinian. In the Late Ordovician, contraction caused by the Caledonian Orogeny resulted in a foreland basin being developed in the Sichuan Basin. Since the Late Triassic, the Sichuan Basin has experienced intense contraction, resulting in the development of its current structural pattern. By integrating the erosion distribution, the reconstructed paleo-highs/lows maps of Sinian strata indicate the development of inherited paleo-uplifts in the central and southwestern Sichuan Basin from the Early Cambrian to the present. The evolution of paleo-highs/ lows plays a critical control on the hydrocarbon accumulation of the Weiyuan and Anyue gas fields, indicating there could be high potential for hydrocarbon exploration in areas with high slope gradients in the paleo-uplifts.
      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

    Effect of temporary plugging agent concentration and fracturing fluid infiltration on initiation and propagation of hydraulic fractures in analogue tight sandstones

    Zhang, YinYu, RangangYang, WendongTian, Yong...
    15页
    查看更多>>摘要：Temporary plugging agent (TP) fracturing has been widely used in many cases as an efficient technology to improve well production performance. In particular, the initiation and propagation of hydraulic fractures are vital to the evaluation of fracturing effect. Hence, the research of its influencing factors and laws is crucial for successful design of fracturing operation. As a productive research method, TP fracturing laboratory experiments have been broadly applied by innumerable scientists. Despite of the great achievements, those experiments mainly focus on the plugging ability of TP in unconsolidated and high permeability reservoirs in order to promote initiation and refracturing. However, studies are limited in light of tight low permeability reservoirs, in which TP not only function in plugging but also achieves changing the induced stress field. Especially for tight sandstone reservoirs, TP concentration and fracturing fluid infiltration are key factors affecting the initiation and propagation of hydraulic fractures of tight sandstones, and the laws have not been fully mastered. In this work, we poured artificial analogue rock samples (AARS) according to physical and mechanical parameters of tight sandstone reservoir in Shengli Oilfield, China. And true triaxial TP fracturing experiments under different TP concentrations were carried out on AARS. Aided by nano-organoboron crosslinking agent (NBC) and sleeves, different fracturing fluid infiltrations were achieved with the acoustic emission (AE) system monitoring the initiation and propagation of hydraulic fractures. In addition, the injection pressure curves, the geometries, forms and propagation process of hydraulic fractures were investigated in detail. The results show that: TP accretion, fracturing fluid infiltration and hydraulic fractures generation can produce innumerable AE energy that matches with the fluctuating injection pressure. TP fracturing leads to extension pressure higher than initiation pressure and slow down fracturing rate at relatively low TP concentration. TP concentration is positively correlated with both initiation pressure and average pressurization rate, but negatively correlated with the time for initiation, and such regularity is better reflected in weaker infiltration. 1.2% is the optimal TP concentration to increase initiation pressure and shorten the time for initiation. On the middle cross section of AARS, single-wing fractures, bi-wing fractures and multiple fractures are formed. Inside AARS, the main and branch fractures are formed. The synergy of TP, NBC and sleeves generates a complex fracture system composed of main fractures and branch ones, which reduces the influence of sand on fracture propagation. In short, properly weakening fracturing fluid infiltration by using NBC and sleeves, combined with a reasonable selection of TP concentration, have proved to be a productive way of improving hydraulic fracturing effect of tight sandstone. The findings contribute to a more comprehensive understanding of the initiation and propagation laws of hydraulic fractures of tight sandstone and conduce to the optimization of fracturing parameters.
      原文链接:
    • NSTL
    • Elsevier

    Selective penetration behavior of microgels in superpermeable channels and reservoir matrices

    Zhao, YangBai, Baojun
    10页
    查看更多>>摘要：Gel treatment is an effective way to attack excessive water production in many mature oilfields around the world. Selective penetration is desired for successful gel treatments. That is, gel materials should easily penetrate the target zones (i.e., channeling features such as superpermeable channels) without entering/damaging the nontarget zones (i.e., reservoir matrices or oil zones). This study revealed that presence of threshold penetration pressure (Delta Pth) was responsible for selective penetration behavior of tested microgels. The concept of Delta Pth was utilized to figure out favorable working conditions for effective gel treatments. Microgel dispersions were injected into superpermeable (super-k) sandpacks (mimicking super-k channels in reservoirs, 60-221 darcies), heterogeneous models with super-k channels (79-230 darcies), and sandstone cores (mimicking reservoir matrices, 50-5000 md). The results demonstrated that a minimum differential driving pressure (i.e., threshold penetration pressure, Delta Pth) was required to push microgel particles to penetrate channels or matrices. The critical penetration behavior was closely related to the particle/pore size ratio. Low Delta Pth at smaller particle/pore ratios was beneficial to allow easy penetration of gel materials into the channeling zones. On the contrary, high Delta Pth at larger particle/pore ratios was desirable to prevent gel materials from massively invading and damaging the matrices. Instead, the gel particles accumulated at the inlet surface, and a gel cake was gradually formed. The cake further prevented the invasion of the gels. The cake could be removed by chemical breakers to resume the injectivity/productivity of the matrices. Correlations were developed to describe the relationship between Delta Pth and particle/pore ratio. A distinct transition was identified at the particle/pore ratio of about 3. This work could help identify the favorable conditions to achieve successful gel treatments. In an effective conformance treatment, the particle/pore ratio in the channel should be sufficiently low to allow easy penetration of gel materials into the channel (e.g., particle/pore ratio<2 in this study). Meanwhile, the particle/pore ratio in the matrix should be large enough to support a high Delta Pth and thus prevent massive gel invasion into the matrix. This study advances the current pore scale studies (a single particle passing through a single channel) to Darcy-scale characterization.
      原文链接:
    • NSTL
    • Elsevier

    Multi-solution well placement optimization using ensemble learning of surrogate models

    Salehian, MohammadSefat, Morteza HaghighatMuradov, Khafiz
    15页
    查看更多>>摘要：Well location optimization aims to maximize the economic profit of oil and gas field development while respecting various constraints. The limitations of the currently available well placement optimization workflows are their 1) high computational requirements, which makes them inappropriate for full-field applications where a large number of wells have to be optimized using a computationally expensive simulation model; and 2) providing a single optimal solution, whereas on-site operational problems often add unforeseen constraints that result in adjustments to this optimal, inflexible scenario degrading its value. This study presents a multi-solution, surrogate models (SMs)-assisted optimization framework to deliver diverse, close-to-optimum well placement scenarios at a reasonable computational cost. Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm is used as the optimizer while diversity in optimal solutions is achieved by multiple, parallel runs of the optimizer with different starting points. Convolutional Neural Network (CNN) is used as the SM, to partly substitute the computationally expensive reservoir model runs during the optimization process. A new, adjusted Latin Hypercube Sampling (aLHS) procedure is developed to generate initial training datasets with diverse well placement scenarios while respecting reservoir boundaries and well spacing constraints. An ensemble of CNNs is pre-trained using the generated dataset to enhance the robustness of the surrogate modeling as well as to allow estimation of the SM's prediction quality for new data points. The ensemble of CNNs is adaptively updated during the optimization process using selected new data points, to improve the SM's prediction accuracy. To the best of our knowledge, this is the first application of ensemble learning strategy to a well placement optimization problem. The added value of the framework is demonstrated by comparing three optimization approaches on the Brugge and Egg field benchmark case studies. The approaches are 1) 'no SM': using the actual reservoir model only, 2) 'Offline SM': the optimization is performed using SM-only that is pre-trained using initial training datasets generated by the actual reservoir model, and 3) 'Online SM': pre-trained CNNs are adaptively updated during the optimization process using new datasets generated using the actual reservoir model. The surrogate-assisted optimization approach substantially reduced the computation time, while a greater objective value was achieved by employing the adaptive learning strategy due to the enhanced prediction accuracy of the SMs. Multiple diverse solutions were obtained with different well locations but close-to-optimum objective values, which allows a more efficient exploration of the search space at a significantly reduced computational cost. The presented workflow integrates critical challenges that are correlated, yet often addressed independently, providing the much-required operational flexibility and computational efficiency to field operators when selecting from the optimal well placement scenarios.
      原文链接:
    • NSTL
    • Elsevier

    Petrophysical rock typing based on deep learning network and hierarchical clustering for volcanic reservoirs

    Wang, WeifangWang, ZhizhangLeung, Juliana Y.Kong, Chuixian...
    14页
    查看更多>>摘要：With the rebound of international oil prices, complex non-clastic volcanic rock reservoirs have been gaining much attention from the scientific community in recent years. However, due to the complexity of volcanic diagenesis and the intensity of tectonic activity at its development location, volcanic reservoirs generally exhibit strong heterogeneity. In particular, the volcanic rock reservoir in Block Jinlong 2 is a low-medium porosity, ultra low to low permeability reservoir with complex lithology and diverse storage spaces. Therefore, the author proposes a petrophysical rock typing method based on the VGG16 deep learning network and hierarchical clustering, which takes MCP curve images and physical data as input. First, the author uses the learning ability of the convolutional layer and max-pooling layer in the VGG16 network to extract the characteristics of each MICP curve. Second, through the PCA dimensionality reduction method, the feature of each picture is transformed into a low-dimensional feature vector. Then, the distance of the image feature vector and the distance of the physical point are combined into a new distance matrix, which is used as the input of hierarchical clustering. Finally, the scores of the Davies Boulding Index and Sillhouette Coefficient are used to determine the final clustering result. Comparing with the FZI and FZI* methods, this method has a better application effect in Jinlong-2 Block volcanic reservoirs. The volcanic rocks of Jinlong 2 are divided into 4 types. Type 1 has the best reservoir characteristics, type 4 is relatively compact, and type 2 and 3 are in the transition zone, but type 2 will develop some micro fractures to increase reservoir seepage capacity. Such petrophysical rock typing has laid a good foundation for the subsequent reservoir description and reservoir evaluation research of Jinlong-2 Block volcanic reservoirs.
      原文链接:
    • NSTL
    • Elsevier