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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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    Observations on the impact of displacement properties on mobility and relative permeability

    Andrew FagerGuangyuan SunRui Xu
    10页
    查看更多>>摘要：The accuracy of relative permeability and mobility data can strongly impact the uncertainty in predictions of production in reservoir models. It is of particular importance to identify the most practical conditions to perform relative permeability tests in order to mimic the difference between test and subsurface conditions. It is known that the details of a displacement test, such as capillary number, can immensely impact the characteristics of a displacement. Therefore, it is paramount to perform displacement tests representative of the reservoir conditions. To improve the general understanding and design of displacement tests this work presents an exploration of displacement parameters and their impact on results. A multiphase Lattice Boltzmann Method is used to digitally perform displacement tests for a range of relevant conditions. Direct simulations are performed on 3D models of pore spaces built from microCT images of rock. A parameter space consisting of capillary number, wetting condition, viscosity ratio and driving mechanism is explored on multiple sandstone rock images. Results showing the impact multiple displacement properties have on relative permeability and mobility are presented. Particular attention was paid to the role of capillary number on total mobility. A wide range of capillary numbers (l x 10~(-7) to 1 x 10~(-4)) was investigated. It was observed that a quantification of mobility, the minimum total mobility of both fluids, is largely constant for the lower most range of capillary numbers for a specific rock image. This plateau behavior holds when capillary number is below a critical threshold where capillary forces fully dominate the 2-phase flow topology. Above this threshold mobility increases monotonically with capillary number. The study also presents relationships for various wetting conditions, viscosity ratios and driving mechanisms. When using an alternate definition of capillary number which relates velocity and fluid properties at the point of minimum total mobility, broad similarity in mobility data was observed for the various viscosity ratios and driving mechanisms investigated. In contrast, the minimum total mobility was consistently higher for oil-wet displacements when compared to equivalent water-wet displacements.
      原文链接:
    • NSTL

    Characterization of meso-structure of glutenite reservoirs by ultrasonic characteristics and the velocity heterogeneity

    Jiantong LiuHongkui GeShanbo Mou
    12页
    查看更多>>摘要：Different from fine-grained sedimentary reservoirs such as sandstone and shale, glutenite reservoir is rich in gravel. Its physical and mechanical properties are affected by gravel content and gravel size and are related to the cementation and support pattern between the matrix and gravel. Characterizing the meso-structure of glutenite reservoirs and its influence on the physical and mechanical properties is of great significance for the evaluation, exploration and development of glutenite reservoirs. Thus, an experimental study on ultrasonic characteristics was conducted on glutenite of different meso-structures. Measurements were performed along different travel paths in each sample to study the effect of gravel. Combined with the meso-structure of samples, the scattering effect on ultrasonic waves by gravel was analyzed. The results show that (1) Gravel content, gravel size and the support pattern between the matrix and gravel have an important influence on the ultrasonic waveform, frequency spectrum and velocity. The higher gravel content or larger gravel size is, the more severe waveform disturbance is. And the wave velocity decreases with the increase of gravel content or gravel size. (2) In glutenite, the scattering of waves by gravel is responsible for the ultrasonic characteristics. The higher the gravel content or larger the gravel size is, the stronger the scattering effect is. (3) Because the gravel size and wavelength in glutenite are approximately the same, the effective medium theory does not work on ultrasonic propagation in glutenite. (4) Thus, we established the velocity heterogeneity model to evaluate the meso-structure of glutenite. The rise of the velocity heterogeneity reflects the increase of gravel content, gravel size and meso-heterogeneity, and the transition of support pattern from matrix-support to gravel-support. This approach is more concise and effective and may potentially realize downhole meso-structure characterization by logging.
      原文链接:
    • NSTL

    Stress distribution of cased elliptical hole with high fluid pressure;; Analytical expression

    Mian ChenKunpeng Zhang
    25页
    查看更多>>摘要：It's not uncommon that the high pressure fluid is injected within the cased wells, such as well test and hydraulic fracturing process. Recently, the circular model and numerical simulation are usually used to calculate the stress distribution in such circumferences. However, the interfaces of a cased hole are not circular but elliptical. Moreover, the numerical simulation method requires a large amount of computing and is not easy to generalize. Therefore, based on the complex stress function, this study obtained an analytical solution model of stress distribution in a cased hole with internal pressure. Consequently, the following conclusions are obtained;; (l)The elliptical model can describe stress distribution more accurately, and predict the occurrence of plastic damage in the cement sheath earlier. (2) As injecting pressure increases, the probability of casing collapse first decreases and then increases. Under the conditions of this paper, the turning point is 71 MPa (3) In formations with higher in-situ stress ratio and fracture pressure, cement sheath and casing being collapsed and interface debonding are more likely to occur. In formations with higher brittleness, the cement sheath is prone to be damaged. Other complex situations are more likely to occur in formations with lower brittleness. (4) The elastic modulus and Poisson's ratio of casing and cement sheath should be lower. And the wellbore diameter should be as large as possible. Moreover, under the conditions of this paper, the optimal casing thickness is 10.54 mm. The proposed analytical model will be useful for casing program design.
      原文链接:
    • NSTL

    An experimental study on steering response of PDC drill bits

    H. Murat Panayirci
    9页
    查看更多>>摘要：This paper presents the findings from an experimental study conducted to understand the steering response of PDC (polycrystalline diamond compact) bits. Various tests are carried out by drilling large limestone blocks with an actual size PDC bit and a highly sophisticated drilling machine. High resolution data acquired during the drilling process and 3D laser scans of the drilled holes are analyzed to assess the effect of drilling parameters and bit dynamics on steering response. The hole deviations measured during experiments are compared to a quasi-static FE (finite element) model, which utilizes a simplified bit-rock interaction formulated via a single bit steerability parameter. It is shown that, although this approach has its merits due to its computational efficiency, it can produce inaccurate prediction when the bit dynamics change. The experiments showed that the WOB (weight on bit) is a crucial parameter in this regard, dictating the stability of the drilling process, which in return affects the influence of the remaining parameters such as RPM (revolutions per minute) and side force.
      原文链接:
    • NSTL

    Automatic tracking for seismic horizons using convolution feature analysis and optimization algorithm

    Kai ZhangNiantian LinDong Zhang
    14页
    查看更多>>摘要：Seismic horizon tracking is a fundamental aspect of seismic data interpretation. However, seismic horizons are typically obtained using manual tracking or a combination of manual tracking and traditional auto-tracking techniques, either of which is a time-consuming and error-prone process. To improve the efficiency and the accuracy of seismic horizon tracking, we developed a convolution feature analysis method on the basis of the traditional coherent technology combined with the Viterbi algorithm, and proposed a method for auto-tracking seismic horizons in complex exploration areas. Firstly, the local seismic waveform data of the target horizon passing through the drilling area have been extracted as the convolution kernel (i.e. the standard seismic trace). Then, the waveform data of each seismic trace in the whole region have been treated with the convolution to obtain the convolution feature in a sliding time window (i.e, the similarity seismic attribute profile). Finally, the convolution feature data have been taken as the inputs, and constraint optimization is performed for the automatic tracking of the seismic horizon. It has the ability to search for the maximum value by integrating the maximum similarity forward and searching for the shortest path method on synthetic and real seismic data. The obtained results show that the proposed method performs effectively for seismic horizons auto-tracking of low signal-to-noise ratio seismic data in complex exploration areas, and also traces the seismic horizons with good continuity and high accuracy.
      原文链接:
    • NSTL

    Stochastic simulation of fan deltas using parallel multi-stage generative adversarial networks

    Ting ZhangZhonghao YangChaochao Sun
    17页
    查看更多>>摘要：The stochastic simulation of fan deltas has always been one of the significant problems in the numerical simulation of reservoirs. As one of the important numerical simulation methods of fan deltas, multiple-point statistics (MPS) obtains the statistical characteristics through the patterns in the training image (TI) to perform simulation. However, due to the non-stationarity of the TI of fan deltas, the traditional MPS cannot extract the non-stationary characteristics of the TI smoothly. Besides, traditional MPS mainly relies on CPU-based simulation, and the extracted probability information cannot be reused during simulation since the information only stored in memory instead of files on the storage medium, making the simulation process quite time-consuming if multiple simulations are performed successively. Thanks to the powerful feature extraction capability brought by deep learning, the fan delta simulation possibly will be largely improved. The generative adversarial network (GAN) is an important deep learning method for image generation, but it suffers from the lengthy simulation time and needs large-quantity training samples. Some variants of GAN, such as the single-image GAN (SinGAN), were proposed to reduce the amount of training data when realizing GAN. Based on SinGAN, a stochastic simulation method of fan deltas using parallel multi-stage GAN is proposed in this paper, through which the structural characteristics of fan deltas are learned from a single image of TI, and the stochastic simulation process can be parallelized for acceleration without lowering the simulation quality.
      原文链接:
    • NSTL

    Tight sandstone petrophysics and flow rate/water/alkali sensitivities variations;; A cross section of permian in the northeastern of Ordos Basin, China

    Yong LiShihu ZhaoYanbin Wang
    16页
    查看更多>>摘要：Tight gas is an important unconventional resource with continuous consumption demand, and co-production from multi-layers are becoming an inevitable choice for areas with low reserve abundance. The Ordos basin contain tight gas production from generally the whole Permian, recording sandstones deposited from transitional to terrestrial environments. In order to reveal the reservoir sensitivities of different layers, petrophysical and sensitivity experiments were conducted with samples from members of different sedimentary environment, i.e., Tai 2 Member (Pit2, coastal environment), Shan 1 Member (PiSi, deltaic environment), He 8 Member (P2X8, deltaic-fluvial environment), He 4 Member (P2S4, fluvial environment), and Qian 5 Member (P3S5, braided fluvial environment) of Permian. The results showed;; (1) The sandstones of P1t2, P1S1, P2X8, P2S4, and P3S5 are dominated by feldspathic litharenite, litharenite, lithic arkose, litharenite, and lithic arkose, respectively;; (2) From P1t2 to P3S5, the content of illite decreases, those of chlorite and illite/smectite (I/S) increase, and kaolinite firstly increases and then decreases (the trend changed in P2S4);; (3) The permeability of all the analyzed sandstones ranges between 0.2 and 0.6 mD, the average porosity between 5.7% and 8.2%, with mercury withdrawal efficiency between 32.8% and 42.1% and average median radius between 0.10 and 0.20 μm; (4) All the sandstones have medium-weak flow rate sensitivities, with medium-weak (P1t2), medium (P1S1), medium (P2X8), medium (P2S4), and medium-weak (P3S5) water sensitivities and weak (P1t2), medium-weak (P1S1), medium-weak (P2Xg), medium-weak (P2S4), and medium (P3S5) alkali sensitivities. The flow rate sensitivities are mainly influenced by pore structure and the quartz content, while water sensitivities are affected by pore structure, I/S and illite contents, and the alkali sensitivities are correlated with pore structure and kaolinite, I/S, and feldspar contents. The results can be beneficial for tight gas production engineering choices and strategies for improving gas production.
      原文链接:
    • NSTL

    A semi-analytical mathematical model for the pressure transient analysis of multiple fractured horizontal well with secondary fractures

    Bo WangQiushi ZhangShanshan Yao
    14页
    查看更多>>摘要：Over the recent years, several researchers have performed pressure transient analysis (PTA) of multi-fractured horizontal wells (MFHWs). However, most of these studies only considered hydraulic fractures (HFs), and the effect of secondary fractures (SFs) was ignored. To this end, in this study, a semi-analytical model is established based on the discrete coordinate method to examine the influence of SFs on the transient pressure characteristics of MFHWs. The mathematical model is solved using Laplace transform theory, source function theory, and superposition principle, and the actual pressure of the reservoir is obtained using the Stehfest numerical inversion algorithm. The efficacy of the model is verified through an industrial simulator (Ecrin-KAPPA). Further, sensitivity analysis is conducted to examine the impact of fracture parameters on the MFHW with and without SFs. The results indicate that the reservoir with SFs undergoes eight flow regimes in which the SF radial flow is a new flow process. The number of SFs mainly affects the SF radial flow regime and the bilinear flow regime, while the SF half-length also affects the first linear flow regime in addition to the above two regimes. The fracture conductivity mainly affects the SF radial flow regime, the bilinear flow regime, and the first linear flow regime. Overall, the proposed model facilitates accurate and effective analysis of the dynamics of unconventional multi-fractured reservoirs, and it can be potentially used to interpret the characteristics of actual reservoir pressures on site.
      原文链接:
    • NSTL

    An experimental study of the combination of smart water and silica nanoparticles to improve the recovery of asphaltenic oil from carbonate reservoirs

    Nima Sharifi RayeniMohammadreza ImanivarnosfaderaniAmin Rezaei
    11页
    查看更多>>摘要：Within recent decades, smart water (SW) injection has become an attractive approach to improve oil recovery from conventional oil reservoirs. However, less attention has been devoted to the application of this method to asphaltenic oil reservoirs. This study aims to evaluate the performance of the injection of SW + silica nanoparticles (SNPs) in improving oil recovery from such reservoirs. To this end, an extended series of measurements were conducted, including of oil-water interfacial tension (IFT), wettability, emulsion formation/stability, and core flooding tests. After the introduction of SNPs to formation brine (FB) and SW solutions, oil-water IFT was reduced by 17.5% and 52.5% respectively compared to their corresponding initial values. In addition, the SW + SNP solution could improve the wettability of the rock surface compared to FB + SNPs. Interestingly, we found that, due to its high asphaltene content, the crude oil used forms sludge in contact with FB, which will impose serious operational problems and production costs associated with the system. However, we observe that the presence of SNPs restrains sludge formation by breaking down asphaltene molecules as well as destabilizing oil-water emulsions. This is demonstrated by several centrifuge tests conducted to evaluate emulsion stability in the presence of FB + SNP and SW + SNP solutions. SARA analyses were also performed on the oil produced from core plugs after the injection of SW and SW + SNPs to better understand the role of SNPs in the deposition of complex structures like asphaltenes and resins groups in crude oil.
      原文链接:
    • NSTL

    Forecasting of the interaction between hydraulic and natural fractures using an artificial neural network

    Bruna Teixeira SilveiraDeane RoehlEleazar Cristian Mejia Sanchez
    16页
    查看更多>>摘要：In recent years, the increasing energy demand has led the oil and gas industry to explore unconventional reservoirs. The hydraulic fracturing technique (tracking) has been adopted in order to increase the reservoir drainage area. Nevertheless, there is an environmental concern about the contamination of aquifers due to this technique. The operation design requires predicting the induced fracture geometry to avoid hazards related to tracking. Hydraulic fracturing changes the state of stress at crack tip leading to more uncertainties in the definition of crack geometry, especially in naturally fractured formations. For such, analytical solutions and numerical simulations have been employed in recent decades. Nevertheless, the numerical models require high computational effort. This paper proposes an artificial neural network (ANN) to predict the interaction between hydraulic fracture and natural fractures. We performed over 800 simulations to build the training database varying the rock mechanical properties and model parameters, such as the approach angle between hydraulic fracture and natural fracture, in-situ stress magnitudes, friction angle, and fracture energy. The ANN results are compared against analytical solutions and numerical models, showing excellent agreement. These results show that the trained neural network can predict fracture interaction accurately. They also suggest that the most sensible parameters were taken into account in the proposed ANN.
      原文链接:
    • NSTL