Hasil untuk "Petrology"

Xiaoming Wang, Junbin Chen, Hao Wang et al.

Abstract The development of natural fractures can easily lead to horizontal wellbore instability caused by stress concentration after drilling in shale reservoirs, which is not conducive to the safe development of shale gas, but how different natural fractures impact the horizontal wellbore stability in shale reservoirs is still unclear. Therefore, the effect of single straight, intersecting, and T-shaped natural fractures on horizontal wellbore stability in shale reservoirs is studied. Then a stress distribution model around the horizontal wellbore in shale reservoirs considering natural fractures is established based on linear elasticity theory, the stress distribution around horizontal wellbores in shale reservoirs with single straight, intersecting, and T-shaped natural fractures is acquired through the finite element method (FEM), and the effect of different natural fractures on horizontal wellbore stability is analyzed finally. Results show that among three types of natural fractures, intersecting natural fractures relieve the maximum stress of 1.676 × 106Pa, and the horizontal wellbore is the most stable; T-shaped natural fractures have the largest effect on total stress around the horizontal wellbore, which is the largest and can reach 68.105 × 106Pa, which makes the wellbore the most unstable; single straight natural fractures and intersecting natural fractures can cause the maximum circumferential stress on the wellbore wall respectively in the two directions of the maximum horizontal principal stress and the vertical principal stress, and wellbore wall is prone to compression and tensile failure respectively; circumferential stress and total stress around horizontal wellbore are the largest in the direction of the maximum horizontal principal stress, the wellbore is the most unstable. This work will be helpful for a more reliable assessment of borehole instability and benefit the drilling design in shale reservoirs with single straight, intersecting, and T-shaped natural fractures.

Jianhua Guo, Yong Ma, Yatian Li et al.

Abstract Luzhou, in the southern Sichuan Basin, is one of China’s major shale-gas production areas; however, its extensive Permian carbonate formations frequently exhibit gas-logging anomalies and minor gas intrusion during drilling—both in carbonate and shale strata—severely impairing drilling efficiency. In this study, a two-pronged modeling strategy is introduced. First, based on porous–elastic coupling theory, a pore-pressure prediction model for carbonate and shale formations is established, subdividing the reservoir into high- and low-pressure zones to enhance precision. Second, the conventional Eaton model is applied across the full well section. Model performance is assessed against measured pressure data from the B and C wells. In the carbonate interval, the porous–elastic model achieved an average error of 6.02%, compared with 39.06% for the Eaton model. In the shale interval, the two approaches produced comparable errors of 8.75% for the fluid–solid coupling method and 3.30% for the Eaton method. The novel incorporation of stress-dependent zonal partitioning into the porous-elastic framework represents a significant advance beyond single-model approaches reported in previous literature. These findings demonstrate that the coupled model markedly improves pressure estimates in carbonate strata, while the Eaton model remains appropriate for shale. This hybrid methodology offers robust, quantitative support for guiding drilling design and risk mitigation in complex geological settings.

Sameeksha Mishra, Anup K. Prasad, Arya Vinod et al.

Abstract The ash yield resulting from the alteration of inorganic elements during the processes of combustion and gasification of coal stands as a crucial quality indicator for coal. Ash yield, along with calorific value, determines the commercial rating, ranking, and industrial usage of coal. Traditional methods of determining the ash yield in coal as per proximate analysis protocols are tedious and time-consuming as they involve the combustion of coal samples. A novel approach that uses mid-infrared Fourier Transform Infrared spectroscopy (FTIR) (optical technique) data in the range of 1450–350 cm-1 to identify spectrally sensitive zones (fourteen selective absorption bands) and to predict the ash yield in coal samples is presented. Multiple algorithms, including piecewise linear regression (PLR), artificial neural networks (ANN), partial least squares regression (PLSR), support vector regression (SVR), and random forest (RF), were utilized to predict the ash yield in coal. The present study suggests a multi-model estimation (MME) approach, using the average of the best three models (PLR, PLSR, and ANN) to achieve greater accuracy and robustness. This method outperforms individual models with a coefficient of determination – R-squared (R2) of 0.883, Root Mean Square Error (RMSE) of 3.059 wt%, RMSE in percentage (RMSE%) of 30.080, Mean Bias Error in percentage (MBE%) of 3.694, and Mean Absolute Error (MAE) of 2.249 wt%. The two-tailed t-test and F-test for mean and variance (99% Confidence Interval, CI) show no significant difference between the proximate analysis-derived ash yield and the multi-model estimated ash yield using FTIR data. FTIR spectroscopy data can accurately predict the ash yield in coal and perform well for coal samples from Johilla Coalfield, Umaria, Madhya Pradesh. The present model using FTIR analysis is a potential industrial tool for the quick determination of ash yield in coal and can be further improved by including data from other basins worldwide.

Alexandre Lavrov

Abstract Carter’s equation is routinely used to describe the leak-off rate and the cumulative fluid loss during deposition of solids on porous media from a suspension. According to this equation, the leak-off rate is inversely proportional to the square root of time. This creates an unphysical singularity at time equal to zero. To remove this singularity, a modification is made to Carter’s law in this contribution. Another modification to Carter’s law made herein accounts for dynamic loss conditions where cross-flow filtration leads to only partial deposition. The modified leak-off law provides a satisfactory fit to the experimental data as long as cross flow is not turbulent. The modified leak-off law is calibrated against experimental data of an earlier study, in both static and dynamic fluid loss tests. A static fluid loss test is used to calibrate the model for the filter cake porosity and permeability as well as spurt loss. Dynamic fluid loss tests are then used to calibrate the model for the particle adhesion probability for each shear rate value.

Mehdi Fadaei, Mohammad Javad Ameri, Yousef Rafiei et al.

Abstract During oil production, the reservoir pressure declines, causing changes in the hydrocarbon components. To ensure better separation of produced phases, separator dimensions should also be adjusted. It is not possible to change the dimensions of the separator during production. Therefore, to improve the separation of the phases, the level of the separator needs to be adjusted. An intelligent system is required to ensure that the liquid level is maintained at the desired level for optimal phase separation during changes in reservoir pressure. In this study, a novel correlation is presented to measure the desired liquid level using new separator pressures. For this purpose, an intelligent system was built in the laboratory and tested in different operational conditions. The intelligent system effectively maintained the desired liquid level of the separator through a new correlation technique. The system accomplished this by acquiring new separator pressure readings collected by installed sensors. This approach helped mitigate the negative effects of the slug flow regime and minimized issues such as foam formation and over-flushing of the separator. It could achieve a 99.1% separation efficiency between gas and liquid phases. This was possible during liquid and gas flow rates ranging from 0 to 2.35 and 8–17 m3/h, respectively. The system could operate under bubble, stratified, plug, and slug flow regimes. Then the intelligent model obtained from lab experiments was integrated into the production model for the southern Iranian oil field. The smart model increased oil production by 13% and prevented the separator from over-flushing in 840 days.

Penny E. Wieser, Adam J. R. Kent, Christy B. Till et al.

Abstract The iconic volcanoes of the Cascade arc stretch from Lassen Volcanic Center in northern California, through Oregon and Washington, to the Garibaldi Volcanic Belt in British Columbia. Recent studies have reviewed differences in the distribution and eruptive volumes of vents, as well as variations in geochemical compositions and heat flux along strike (amongst other characteristics). We investigate whether these along‐arc trends manifest as variations in magma storage conditions. We compile available constraints on magma storage depths from InSAR, geodetics, seismic inversions, and magnetotellurics for each major edifice and compare these to melt inclusion saturation pressures, pressures calculated using mineral‐only barometers, and constraints from experimental petrology. The availability of magma storage depth estimates varies greatly along the arc, with abundant geochemical and geophysical data available for some systems (e.g., Lassen Volcanic Center, Mount St. Helens) and very limited data available for other volcanoes, including many which are classified as “very high threat” by the USGS (e.g., Glacier Peak, Mount Baker, Mount Hood, Three Sisters). Acknowledging the limitations of data availability and the large uncertainties associated with certain methods, available data are indicative of magma storage within the upper 15 km of the crust (∼2 ± 2 kbar) beneath the main edifices. These findings are consistent with previous work recognizing barometric estimates cluster within the upper crust in many arcs worldwide. There are no clear offsets in magma storage between arc segments that are in extension, transtension or compression, although substantially more petrological work is needed for fine scale evaluation of storage pressures.

Petros Petrounias, Panagiota P. Giannakopoulou, Aikaterini Rogkala et al.

This study focuses on the use of petrology as a useful tool in construction applications (i.e., concrete). More specifically, this study investigates how the petrogenetic characteristics of ultramafic rocks derived from ophiolite complexes (Veria–Naousa, Gerania) can act as a key tool for the prediction of the final behaviour of ultramafic aggregates as concrete aggregates. For this reason, their petrographic, chemical and mineralogical characteristics were examined and correlated with their engineering properties for evaluating their suitability as concrete aggregates. This study had come up, for the first time, that the genesis environment of the ultramafic rocks is the determinant factor for their physico-mechanical characteristics. Their suitability is relevant to the impact of their mineralogical and structural characteristics both from the two different ophiolite complexes (Veria–Naousa and Gerania). Except serpentinization, the basic alteration process-index of ultramafic rocks, there are also other chemical indices which can be used for ultramafic rocks that may determine their properties. In this context the term ‘fertility rate’ (FR) was introduced which may characterize ultramafic rocks as fertile or not. Furthermore, the Ultramafic Rock Health Index (U.R.H.I.) as well as the Normalized U.R.H.I. (U.R.H.I._N) was also introduced and correlated with the engineering properties of the investigated aggregate rocks. The last index aims to assess and quantify the overall health conditions, encompassing the two major modifying factors that include removal of primary mineral phases, as well as the extent of serpentinization. The main conclusion of this paper is that the genesis environment of the ultramafic rocks is the critical factor that determines their mineralogical, petrographic and chemical characteristics which consequently determines the basic engineering properties of rocks that determine their suitability or not as concrete aggregates.

Nancy Hui-Chun Chen, Peter A. Cawood, Yoshiyuki Iizuka

AbstractThe Ortosuu and Uchkuduk regions of the Tianshan orogen contain a volumetrically small series of basaltic rocks erupted primarily during the late Mesozoic-Paleogene. Petrology, chemical composition, and P-T geotherm data from xenoliths within the basalts characterize the nature of the lithospheric mantle beneath this orogenic belt. Two groups of clinopyroxene can be identified from the studied xenoliths based on their Mg# and trace element patterns. Group 1, primitive clinopyroxenes, has lower Mg# (86–90) and LREE-depleted patterns than group 2, depleted clinopyroxenes, which are characterized by a relatively high Mg#, 91–92, and LREE-enriched patterns. The REE distribution in group 1 clinopyroxenes suggests that they were controlled by partial melting, whereas group 2 clinopyroxenes are far more complex involving partial melting degrees of 6–11%, and later metasomatism by carbonatite and/or silicate melts. Coupled P-T estimations from geothermobarometry indicate that the more fertile group 1 xenoliths were probably derived from the uppermost mantle, and the more depleted group 2 xenoliths were likely derived from a depth close to the crust mantle boundary.

Yuryi L. Rebetsky

In the article by N.A. Sycheva and L.M. Bogomolov, the authors proposed to combine the interrelated data on the stress drop in the earthquake sources, ∆σ, and reduced seismic energy, ePR, to analyze the dependence of these parameters on earthquake scale along with expansion of the measurement statistics (assessments). The dependence of these parameters of a source on the seismic moment or on the earthquake magnitude within 2.2 ≤ М ≤ 4.0 magnitude range has been determined using the example of the Northern Tien Shan (Bishkek geodynamic polygon with the KNET network). The author of the letter to the editor notes the article conclusions to be limited, because such relationship is only manifested within the more or less narrow range of the magnitudes. Attention is also drawn to the semantic difference between the ∆σ and ePR parameters. It is the reduced seismic energy that reflects the mean strain in the source area, and its appliance to the analysis of scale dependences of earthquake sources is more informative.

Moustafa Oraby

Abstract The determination of the formation water saturation, S w, is a continuous process throughout the life of the fields. Multiple water saturation models are developed to increase the accuracy of calculating this critical parameter for both open-hole and cased-hole wells. All current open-hole water saturation models require prior knowledge of some field parameters namely; formation water resistivity, R w, clay volume, V c and rock electrical properties (m, n). It is normally assumed that those reservoir parameters as either constant for the entire reservoir section or change by zones. This is obviously an impractical assumption especially for the (m) and (n) parameters. Also, when a reservoir is under water injection for enhanced oil recovery, the water salinity may change throughout the reservoir, based on the distribution of the reservoir permeability and the salinity of the injected water, resulting in a variable R w. This case represents a real challenge to the existing water saturation models. In this paper, a methodology to determine water saturation without the need for prior knowledge of the formation water resistivity or the rock electrical properties is developed. This approach is a generalization of the Passey total organic carbon, TOC, model which is developed to determine the organic richness of the unconventional reservoirs. The scientific basis of the method, the modification required to be applied in conventional reservoirs, the proof of concept using forward modeled cases and actual field applications in sandstone and carbonate reservoirs are performed to examine the theoretical and the practical applications of the methodology. Excellent results are obtained and discussed.

Artem V. Degterev, Marina V. Chibisova

The Ebeko volcano located in the northern part of Paramushir Island (Northern Kuril Islands) is currently the most active volcano of the Kuril Island arc: since 2016, next explosive eruption has continued, proceeding in the form of regular ash-gas explosions of moderate force. In the period from January 2018 to October of 2020 a total of at least 1834 emissions were recorded (during daylight hours and under good weather conditions). In May–July 2020, the intensification of the eruptive activity of the volcano was observed, that manifested in a sharp increase of the emissions frequency and height. During this period, 296 emissions were recorded, 90 of which were at an altitude of 3 km or more.

LUCIA CAPRARA, EDUARDO GARZANTI, MARIO GNACCOLINI et al.

During Serravallian time, a shallow—water shelf mantled by northward migratine sand waves occupied the eastern part of the Tertiary Piedrnont Basin (Serravalle Sandstone, Gavi area). Towards the west, the shelf graded into a basinal zone through a series of steps probably controlled by synsedimentary faults. The autochthonous sediments of the shelf—basin transition were sandy siltstones, which are interbedded in the stratigraphical column with sands carried from near—shore arcas by tectonically—triggered sediment gravity flows. On the Proxima] "steps traction currents could rework these sands and re—form sand waves, while in deeper water they were buried without further reworking. Finally, at the western edge of the study area (Cassinasco), "high—dcnsity" turbidity currents flowing towards the ENE depositcd the sands of the Cassinasco Fm. onto the deep bottoni of the basmal zone. Riv. IC. Paleont. Strat. 90   pp. 545—564 Marzo 1985 Two distinct petrofacies characterize the Serravalle hybrid arenites (bioclastic lithic arkoses) and the Cassinasco sandstones (litharenites), pointing to different source terranes. The Cassinasco Fm. was fed by the Alpine fold—thrust belt, comprising Carboniferous metasediments, Permlan igneous rocks, Mesozoic sediments and the Ligurid Allochthon. The paragencsis of lithic fragrnents and the heavy mineral assemblage show that the source rocks bave undergone blueschist facies (eoalpine) and greenschist facies (rnesoalpine) polyphase rnetarnurpllism. The Serravalle arenites bave a similar "aphanite" rock fragment population, but detritus frorn granitoid bodies is prominent and the detrital modes are closer to the Tertiary clastic units of the Apennines.

Silvya Dewi Rahmawati, Steven Chandra, Prasandi Abdul Aziz et al.

Abstract Gas lift optimization has been a classic problem since its inception. The problem with currently practiced optimization, the gas lift performance curve (GLPC), was the sole requirement for exhaustive calculation that has to be performed every time changes to the reservoir are acknowledged. The approach of mechanistic modeling has been proven to be a powerful tool to complement the analysis of GLP curves, especially in complex, multi-well gas lift system. This publication offers a new approach in modeling the progression of flow pattern map (FPM) in case of reservoir pressure decline. The findings presented in this publication encourage the hypothesis that FPM can be used with minimum alteration should there be any changes in reservoir pressure.

Rana M. El-Saghier, Mahmoud Abu El Ela, Ahmed El-Banbi

Abstract Bottom-hole flowing pressure and pump intake pressure (PIP) are important parameters to optimize the performance of oil wells. In recent years, downhole sensors are becoming widely used in electrical submersible pump systems to measure these pressures. However, it is still rare to use downhole sensors in sucker rod and progressive cavity pumped wells. In this study, two correlations were developed to calculate bottom-hole flowing pressure and PIP from readily available field data. The two correlations do not require measurements of buildup tests, but they rely on measuring the dynamic fluid level and estimating fluid gradient correction factor using either (1) the tubing gas flow rate or (2) the annular gas flow rate. Then, the PIP is calculated by the summation of either (1) the tubing pressure plus the tubing gaseous liquid column pressure or (2) the casing pressure, annular gas column pressure and the annular gaseous liquid column pressure. The correlations were developed using 419 field data points (389 points for training and 30 for testing) of wide range for each input parameter. Using the training data, the mean absolute percentage deviation (MAPD) between the calculated and measured PIPs is 25% and 20% for the first and second correlations, respectively. However, the testing data showed MAPD of 33% and 12% for the first and second correlations, respectively. The accuracy of these correlations is significantly higher than that of the previously available methods, and the correlations require simpler input. Such study is an original contribution to calculate the PIP with improved accuracy and without downhole pressures sensors.

Tereza Neuma de Castro Dantas, Andrey Costa de Oliveira, Tamyris Thaise Costa de Souza et al.

Abstract Enhanced oil recovery (EOR) techniques play an essential role in the maintenance of petroleum production worldwide. These techniques are receiving special attention due to the continuous decline in availability of oil resources. The study of surfactants and correlated systems have been considered due to their capacity to alter the wettability and interfacial proprieties, consequently reducing residual oil saturation and increasing oil production. In this context, heterogeneity becomes one of the main challenges to overcome, for it makes the fluid flow preferably thought the highest permeability regions, affecting sweep efficiency. It is also known that acids react with carbonate formations promoting matrix dissolution. However, few works in the literature report the use of reactive fluids in EOR. Therefore, this work analyzes the effects of reactive acid flow on porous carbonate media and its impact on advanced oil recovery operations. It presents an experimental study of the effects of acid microemulsion flooding in the enhancement of oil recovery in carbonate reservoirs. Acid microemulsions studied were characterized by surface tension, droplet diameter, viscosity, and corrosiveness. Flooding experiments demonstrated that the reactive flow of acid microemulsions in porous media increases oil recovery, achieving up to 30% additional recovery of the total oil in place. However, by increasing the reactivity of the systems, severe dissolution of the porous matrix can occur. The results presented open a new path on the use of low reactive fluids in enhanced oil recovery.

Shaine Mohammadali Lalji, Javed Haneef, Muhammad Arqam Khan et al.

Abstract Drilling in Barents Sea proves to be a challenging task, as this region is situated in auroral zones having high geomagnetic latitude, where magnetic interferences develop from magnetic field and magnetic materials inside subsurface are quite common. For this region, monitoring of magnetic field is utterly significant as any fluctuations can distort the tool sensor performance with ultimately enlarging the uncertainty in azimuth. To guide a well to its desire location, measurement while drilling (MWD) tool needs to be operated with utmost precision; however, its accuracy compromises as a result of magnetic interferences from drill string and nearby magnetic material. The performance of this tool depends upon its sensors. Any distortion in sensor performance can lead to problems such as multiple sidetracking and increase in overall project cost. Furthermore, the same BHA was also placed in a region of Pakistan and the impact drill string interference was observed. It was discovered that the interferences that had tremendous impact on magnetometer Z-component in Barents Sea had a drastic reduction in the region of Pakistan as it is situated in low latitude, where uncertainty in azimuth is low. In this work, an exemplary bottom-hole assembly (BHA) was analyzed and the impact of individual drill string components interferences was observed on the MWD sensors. It was perceived that the bit was responsible for creating the major distortion in MWD sensor. Apart from that, it was also investigated that the location of the well also plays a vital role in this distortion. This intervention in the sensors is created by a vast difference between the used actual length and the recommended length of nonmagnetic drill collar in the BHA. Numerically, it was investigated that if the physical distance between the sensors and bit is increased, then this interference is reduced. It was also apparent that the Z-component of the magnetometer was utterly distorted because of this interference, while the X- and Y-components were proved to be independent of these interferences. It was further examined that the effects of latitude and longitude play a significant role in the course of changing the impact of these errors on magnetization.

M. G. Best

M. Teichmüller

R. Ingersoll, C. Suczek

Jie-Hui Yuan, Sheng Zhou, Tian-Duo Peng et al.

Abstract This study develops a bottom-up model to quantitatively assess the comprehensive effects of replacing traditional petroleum-powered vehicles with natural gas vehicles (NGVs) in China based on an investigation of the direct energy consumption and critical air pollutant (CAP) emission intensity, life-cycle energy use and greenhouse gas (GHG) emission intensity of NGV fleets. The results indicate that, on average, there are no net energy savings from replacing a traditional fuel vehicle with an NGV. Interestingly, an NGV results in significant reductions in direct CAP and life-cycle GHG emissions compared to those of a traditional fuel vehicle, ranging from 61% to 76% and 12% to 29%, respectively. Due to the increasing use of natural gas as a vehicle fuel in China (i.e. approximately 28.2 billion cubic metres of natural gas in 2015), the total petroleum substituted with natural gas was approximately 23.8 million tonnes (Mt), which generated a GHG emission reduction of 16.9 Mt of CO2 equivalent and a CAP emission reduction of 1.8 Mt in 2015. Given the significant contribution of NGVs, growing the NGV population in 2020 will further increase the petroleum substitution benefits and CAP and GHG emission reduction benefits by approximately 42.5 Mt of petroleum-based fuel, 3.1 Mt of CAPs and 28.0 Mt of GHGs. By 2030, these benefits will reach 81.5 Mt of traditional petroleum fuel, 5.6 Mt of CAPs and 50.5 Mt of GHGs, respectively.