bluuebunny/crossref_metadata_2025 huggingface dataset:
Pendidikan Karakter Remaja Gen Z Terhadap Pembelajaran Di Sekolah Pada Era Globalisasi
Authors: Nadia Sa’bani
Published: January 2025

Pemerintah telah membuat program gerakan Penguatan Pendidikan Karakter (PPK) demi meningkatkan karakter anak sekolah. Generasi Z memiliki tantangan yang memerlukan pendidikan yang lebih berkelanjutan dan berfokus pada pembentukan moralitas agar mereka tidak terpengaruh secara negatif oleh gelombang globalisasi dan kemajuan teknologi dan ilmu pengetahuan. Penelitian ini menggunakan pendekatan kualitatif dengan metode tinjauan pustaka dengan mengumpulkan literatur yang valid dengan topik pembahasan yang dibutuhkan. Dengan adanya pendidikan Islam, karakter siswa dapat berkembang dengan berbagai cara dan pendekatan. Pendidikan karakter dan pendidikan akhlak mempunyai korelasi yang sangat bagus, karena sama-sama bertujuan untuk menempa individu ke arah hidup yang sejahtera. Pendidikan karakter terbentuk karena adanya generasi muda yang terkena berbagai permasalahan pada era globalisasi ini. Pada saat ini, bila dilihat dari gaya pergaulan anak muda dan gaya hidup serta rendahnya motivasi belajar dan banyak permasalahan lainnya yang terlihat seperti hal lumrah yang sedang terjadi menyebabkan rasa keprihatinan yang tinggi terhadap negeri ini. Oleh karena itu, untuk mempertahankan negara dan bangsa perlu dilaksanakan pendidikan karakter. Karakter merupakan unsur penting dalam membentuk sifat-sifat seseorang dan menjadi pribadi yang berakhlak mulia. Apabila kualitas diri seseorang baik dan berkembang, maka setiap orang dapat menjadi pribadi yang memberikan dampak positif terhadap lingkungan dan pembangunan negara.
Penerapan Model Pembelajaran problem Based Learning (PBL) Berbantuan Media Audio Visual Terhadap Kemampuan Menyimak Cerita Fiksi Siswa Di Sekolah Dasar
Authors: Azeera Azeera , Wulan Neneng Sri , Sari Nadia Tiara Antik
Published: January 2025

Penelitian ini bertujuan untuk mengetahui: (1) proses pembelajaran menyimak dengan menggunakan model pembelajaran Problem Based Learning (PBL) berbantuan media audio visual pada siswa kelas V SDN 01 Karangmekar. (2) kemampuan menyimak siswa kelas V SDN 01 Karangmekar dengan menggunakan model pembelajaran Problem Based Learning (PBL) berbantuan media audio visual. Desain yang digunakan dalam penelitian ini adalah desain penelitian tindakan kelas model Kemmis & Mc. Taggart yang terdiri dari perencanaan, tindakan, observasi, dan refleksi. Penelitian ini berlangsung selama 2 siklus yang diawali dengan prasiklus. Metode pengumpulan data yang digunakan adalah observasi dan tes. Hasil penelitian menunjukkan bahwa penerapan model pembelajaran berbasis masalah berbantuan media audio visual dapat meningkatkan kemampuan menyimak cerita fiksi siswa kelas V SDN Karangmekar 01. Hasil penelitian menunjukkan bahwa penerapan model pembelajaran berbasis masalah berbantuan media audio visual dapat meningkatkan kemampuan menyimak cerita fiksi siswa kelas V SDN Karangmekar 01. Pada siklus I diperoleh rata-rata 64% dan pada siklus II sebesar 81%, peningkatan yang diperoleh sebesar 17%. Dapat disimpulkan bahwa model pembelajaran problem based learning berbantuan media audio visual dapat meningkatkan kemampuan menyimak cerita fiksi siswa di sekolah dasar.
Pengaruh supervisi terhadap kinerja guru PNS Rayon A Kota Bandunh
Authors: Saprudin Asep , Lisdianty Eka
Published: January 2025

Penelitian ini bertujuan mengetahui pengaruh supervisi terhadap kinerja guru SMA di rayon A Kota Bandung. Metode penelitian yang digunakan adalah metode deskriptif kuantitatif. Sampel dalam penelitian ini diambil menggunakan rumus slovin sebanyak 64 orang dari total populasi sebanyak 177 guru PNS SMA Rayon A Kota Bandung tahun Pelajaran 2017/2018. Teknik pengumpulan data menggunakan angket/quisiner.
Guru memiliki peran terhadap keberhasilan pembelajaran dengan keterampilan dan pengetahuan yang cukup diharapkan guru dapat mentransfer pengetahuan pada siswa, serta mengajak siswa untuk berfikir. Untuk meningkatkan kualitas Sumber Daya Manusia (SDM) tersebut hanya dapat dilakukan oleh seorang guru yang kompeten, professional dan memiliki kinerja yang optimal. Kualitas kinerja guru akan sangat menentukan pada kualitas hasil pendidikan, karena guru merupakan pihak yang paling banyak bersentuhan langsung dengan siswa dalam proses pendidikan/pembelajaran di lembaga pendidikan Sekolah.
Hasil penelitian menunjukan terdapat pengaruh positif dan signifikan antara supervisi terhadap kinerja guru PNS SMA Negeri Rayon A Kota Bandung. Pelaksanaan supervisi dilakukan Kepala Sekolah di SMA Negeri Rayon A Kota Bandung sudah berjalan dengan baik didahului dengan penyusunan program supervisi yang dipersiapkan pada awal tahun ajaran. Selanjutnya dilanjutkan dengan pelaksanaannya yang dilakukan setiap awal semester dan akhir semester pada saat berlangsungnya kegiatan proses belajar mengajar untuk melihat keberhasilan sejauh mana program yang telah dipersiapkan dapat terealisasi.Kegiatan supervisi secara kontinyu dan berkelanjutan sangat diperlukan untuk membantu kelancaran tugas sehingga kinerja guru meningkat.
Peningkatan Motivasi Belajar Siswa Kelas IX-E Melalui Layanan Bimbingan Kelompok
Authors: Aminah Siti
Published: January 2025

Tujuan dari penelitian ini adalah untuk mengetahui gambaran motivasi belajar siswa sebelum mendapatkan layanan bimbingan kelompok, untuk mengetahui gambaran motivasi belajar siswa setelah mendapat layanan bimbingan kelompok, dan untuk mengetahui apakah motivasi belajar dapat ditingkatkan melalui layanan bimbingan kelompok. Jenis penelitian yang digunakan dalam penelitian ini adalah Penelitian Tindakan Bimbingan dan Konseling dengan melaksanakan dua siklus. Subyek penelitian ini yaitu 10 siswa kelas IX-E MTsN 14 Jakarta yang terdiri atas 8 siswa bermotivasi belajar rendah dan 2 siswa yang memiliki motivasi belajar tinggi, agar terjadi dinamika kelompok. Metode pengumpulan data yang digunakan yaitu wawancara, skala motivasi belajar dan observasi. Sedangkan teknik analisis  datanya menggunakan analisis deskriptif persentase dan kualitatif. Hasil penelitian menunjukkan bahwa motivasi belajar siswa sebelum memperoleh perlakuan berupa bimbingan kelompok, sebesar 44,4% kategori rendah. Setelah diberi layanan bimbingan kelompok pada sikus I, motivasi belajar siswa meningkat menjadi kategori sedang sebesar 65%. Sedangkan pada siklus II motivasi belajar siswa terus meningkat menjadi kategori tinggi dengan perolehan sebesar 74%. Hal ini menunjukkan layanan bimbingan kelompok dapat meningkatkan motivasi belajar pada siswa kelas IX- E di MTs Negeri 14 Jakarta. Berdasarkan hasil penelitian yang telah dilakukan, dapat disimpulkan bahwa sebelum diberikan layanan bimbingan kelompok motivasi belajar siswa sebesar 44,4% kategori rendah. Setelah diberikan layanan bimbingan kelompok pada siklus I motivasi belajar siswa sebesar 65% kategori sedang dan pada siklus II motivasi belajar siswa sebesar 74%. Sehingga terjadi peningkatan motivasi belajar yang signifikan setelah diadakan layanan bimbingan kelompok. Saran yang dapat diberikan yaitu hendaknya guru pembimbing lebih mengembangkan layanan bimbingan kelompok untuk membantu dalam meningkatkan motivasi belajar siswa.
Edukasi Digital Sebagai Strategi Media Pembelajaran
Authors: Karinah Junita , Salman Salman
Published: January 2025

Dengan berkembangnya media sosial, kinerja menjadi lebih cepat, tepat dan akurat, yang pada akhirnya meningkatkan produktivitas.. Salah satu pengguna media sosial saat ini adalah pelajar. Pasalnya, media sosial memungkinkan pelajar dengan mudah berkomunikasi dalam jarak dekat maupun  jauh tanpa harus bertatap muka atau bertatap muka. Media sosial  tidak hanya penting bagi mahasiswa untuk tetap mendapat informasi, namun juga dapat meningkatkan pemikiran kritis dan mengembangkan keterampilan dan kreativitas terkait pekerjaan. Tujuan penelitian ini adalah untuk mengetahui pemanfaatan media sosial sebagai media pembelajaran.Penelitian ini menggunakan metode analisis data yang berfokus pada penelitian kepustakaan dengan cara membaca, mempelajari, dan mensurvei buku-buku dan bahan-bahan sastra yang berkaitan erat  dengan pertanyaan penelitian. Pemanfaatan media sosial dalam media pembelajaran dapat lebih meningkatkan kualitas pembelajaran bila digunakan sekomprehensif mungkin. Namun, bukan berarti media sosial akan memberikan dampak negatif jika penggunaannya tidak dikontrol dan informasinya tidak disaring. Kesalahan mungkin saja terjadi pada saat proses pembelajaran apabila guru tidak menggunakan media sosial sebagai media ajar dengan baik..
Kata kunci: Manfaat, Media Sosial dan Pemberajaran
Impact of Gas Hydrate Dissociation on Wellbore Stability: Utilizing a Temperature Simulator Approach
Authors: Hamid Osman , Abdalrahman Eslam M. , Al-Ramadan Mustafa
Published: January 2025

This study had two primary objectives: first, to develop a sophisticated temperature simulator capable of predicting gas hydrate dissociation, and second, to assess how this dissociation impacts wellbore stability. The simulator design incorporated key heat transfer principles (such as Fourier's law), pressure-volume-temperature (PVT) relationships for gas hydrates, and the Mohr-Coulomb failure criterion for evaluating wellbore stability.

The methodology involved simulating various gas hydrate dissociation scenarios using the temperature simulator and analyzing their effects on wellbore stability. The simulator accounted for different drilling fluid temperatures and pressure conditions to replicate the actual conditions encountered during offshore drilling.

Findings indicated that gas hydrate dissociation, induced by drilling activities below the mud line, significantly affects wellbore stability. This effect is pronounced in high-pressure, low-temperature environments, where gas hydrate dissociation leads to a notable decrease in sediment shear strength, potentially resulting in wellbore failure.

The innovation of this study lies in integrating temperature simulation with wellbore stability assessment to evaluate the impact of gas hydrates. This method improves the predictability of gas hydrate behavior and their implications for wellbore stability, contributing to safer and more efficient drilling operations in gas hydrate-rich offshore areas.

The study concludes that understanding gas hydrate behavior beneath the mud line, as provided by temperature simulation, is crucial for maintaining wellbore stability during offshore drilling operations. It underscores the need for detailed drilling plans that incorporate the dynamic nature of gas hydrates in their preparation stages.

Introduction:

Gas hydrates are a class of clathrate compounds, forming solid crystalline phases where guest gas molecules, primarily methane, are encased within a host framework of hydrogen-bonded water molecules. These structures are thermodynamically stable under high-pressure and low-temperature conditions. Suboceanic sedimentary deposits, particularly below the mud line, often contain these hydrates, making them significant due to their impact on the geomechanical integrity of hydrocarbon extraction operations.

Drilling in deep-water and onshore Arctic environments can disrupt the existing pressure-temperature equilibrium, causing a phase transition from solid hydrates to free gas and water, accompanied by volumetric expansion. This phenomenon can lead to various geomechanical destabilization issues within the wellbore structure, necessitating careful consideration during subsurface operational planning and execution.
Well Orientation and Fracture Turning
Authors: Han G. , Elisabeth F.
Published: January 2025

Horizontal wells and hydraulic fractures are key enablers for developing unconventional fields. Horizonal wells are normally drilled in the direction of minimum horizontal stress to develop transverse fractures perpendicular to wellbores. However, wells are sometimes drilled at angles off in-situ stress to accommodate lease boundaries, operational limitations, and geological uncertainties. Following a comprehensive study of US unconventional field data, a series of Finite Element and Discrete Element (FEDEM) simulations have been developed to capture and confirm fracture turning for a cased-and-perforated horizontal well, with various alignment angles between wellbores and in-situ stress. Fracture geometries, fracture apertures, breakdown pressures, and net pressures are calculated and compared to quantify the impacts of turning. In addition, different stress anisotropies are applied to clarify their roles in initiating, turning, and propagating fractures. These findings clarify the significance and control of fracture turning when wells are not aligned with in-situ stress to optimize well and fracture designs and improve stimulation efficiency in unconventional fields. These insights and workflows can also be applied to other hydraulic fracturing applications such as enhanced geothermal systems (EGS) and mining.

1. INTRODUCTION: FIELD AND LABORATORY OBSERVATIONS

When developing unconventional fields, horizontal wells are normally drilled in the direction of minimum horizontal stress so that hydraulic fractures can be initiated transversely and perpendicular to the wellbore. This design maximizes the reach of hydraulic fractures and stimulated rock volume. However, sometimes wells are drilled at angles off the direction of in-situ stress to accommodate lease boundaries, operational limitations, and geological uncertainties. The misalignment of well trajectory and in-situ stress can significantly affect stimulation efficiency and well productivity.

Based on the data from more than 71,000 wells in multiple US unconventional plays, a recent study determined that majority of fields showed strong and sinusoidal correlation of production with well-stress alignment (Gabry et al., 2024).

For example, the production from Eagle Ford wells declined more than 30% when they were oriented 20 degrees away the minimum horizontal stress (Shmin) direction (Fig. 1). Similar trends were observed in other unconventional plays such as the Utica, Bakken, Marcellus, and Granite Wash. Meanwhile no significant production effect was observed in the Barnett, Haynesville, and Wattenberg/Niobrara, where reservoir properties and completion qualities are more dominant.
Application of a 4D Geomechanical Model to Reduce the Risks of Offshore Field (Russian Federation) Development Throughout the Entire Life Cycle
Authors: Yusupov Yan , Zaglyadin Yaroslav
Published: January 2025

Based on the results of the 3D/4D geomechanical modeling, the influence of the static mud weight on the degree of shear failures of the borehole was shown. Recommendations were made to increase the mud weight to avoid clay shear failures, but at the same time control the equivalent circulation density (ECD) during drilling to avoid fault reactivation. Also the reservoirs layers have experienced a decrease in pore pressure associated with development. As a result, the minimum total horizontal stresses in the far field are reduced due to the "stress-path" effect. Design safe mud weight windows for wells of different orientations for different cases were obtained. Based on the completed 3D/4D geomechanical modeling, several design horizontal wells were successfully drilled. This geomechanical model used in the construction of wells takes into account work with problematic wells of previous years. Thanks to this model, well drilling happened faster and was accompanied by much fewer emergency situations. The predrill model agreed with the postdrill one. The seafloor subsidence and the degree of reservoir compaction are predicted. With the remaining 70% of the total depletion expected over the next 25-30 years, the final subsidence, according to the baseline case, could reach 0.55–0.65 m.

1. INTRODUCTION

At the studied offshore field, geomechanical drilling support is an important support for trouble-free oil and gas production. It is used to solve various problems in the process of field development and operation. The objective of this work is to apply the geomechanical model to prevent risks during the construction of inclined and horizontal wells. The main problems is borehole instability of well walls, manifested in the presence of overpulls, tightening, collapsing cuttings on vibrating screens and sticking, were observed in clay intervals with a drilling mud density of 1.18 to 1.33 g/cc (Fig. 1).

Most successful wells were drilled in 340 mm and 244 mm sections with a higher drilling mud density exceeding 1.33-1.37 g/cc. In the 178 mm section, elevated gas readings (up to 50%), tightening and landings were mainly observed at a density of 1.13–1.18 g/cc. The number of caverns is smaller than in the upper parts of the section, since the 178 mm section usually exposes sandstones, which are more stable than siltstones and mudstones. To display all drilling events that accompanied the construction of the well, a "stick chart" diagram is used, shown in Fig. 2.
Laboratory Assessment of High-Power Ultrasonic Tools for Well Stimulation and Drilling Operations
Authors: Alfaraj Rima T. , AlTammar Murtadha J. , Mierez Jesus , Alruwaili Khalid M. , Oluyemi Gbenga , Liu Chao , Shaikh Aijaz A. , Alhamad Luai A.
Published: January 2025

This proof of concept study explores ultrasound technology applications in the oil and gas industry, focusing on its impact on permeability in core samples damaged by drilling fluids and its ability to break down drill cuttings. Laboratory experiments utilized a 20 kHz sonotrode to assess the effects of ultrasound power (500 and 1,000W) and exposure times (25 and 45 minutes) on tight sandstone cores. Initial permeability was measured before inducing drilling fluid damage, followed by ultrasound treatment. Post-treatment permeability results indicated significant permeability recovery of up to 40%, with enhancements exceeding initial rock permeability by up to 12%. Scanning electron microscopy (SEM) showed reduced deposits in pore throats, confirming treatment effectiveness. A notable shift in particle size distribution (PSD) of up to 14% was observed at 1,000W, indicating partial breakdown of drill cuttings, while no changes occurred at 500W. Computed tomography (CT) scans showed no induced micro-fractures. This study supports the potential use of ultrasound for stimulating low permeability reservoirs and improving hole cleaning during drilling operations.

1. INTRODUCTION

As the oil and gas industry moves towards more sustainable solutions in drilling operations and optimizing production of hydrocarbons, it still faces significant challenges when it comes to traditional techniques of chemical-based well stimulation methods that often come with substantial environmental impact and high operational cost. Drilling operations can cause formation damage due to infiltration of drilling fluids into formation rock, leading to overall lower permeability and well productivity (Mierez et al 2023).

Innovative and sustainable technologies are essential to overcome these challenges related to oil and gas production. One such emerging technology is ultrasound, which offers promising solutions for various oil and gas applications due to its ability to deliver energy effectively through media with less environmental impact. Significant advancements in ultrasound applications have demonstrated over 90% enhancement in oil recovery rates while simultaneously reducing viscosity by more than 80% (Mierez et al, 2024).
Lateral Variations in Geomechanical Properties of Mudstones: An Outcrop Analogues of Caprocks for Geological Carbon Storage
Authors: Iijima Yasutaka , Nifuku Ko , Watanuki Shunsuke , Kobayashi Yuki , Yamamoto Kazune , Suzuki Manabu , Sekine Kotaro , Ito Makoto
Published: January 2025

A better understanding of geomechanical properties of mudstone caprocks over a targeted storage area is crucial for effective geological carbon storage. However, it is difficult to evaluate lateral variations in geomechanical properties in detail because primary subsurface information obtained through appraisal wells is limited in most cases. Utilization of onshore outcrops as an analogue of subsurface geology enables us to overcome limitation of primary subsurface data. The present study investigated lateral variations in geomechanical properties of semiconsolidated mudstones collected from outcrops with precise lateral correlation. Triaxial compression tests of the mudstone samples revealed that both deformation and strength-related parameters do not show remarkable lateral variation in a spatial range in which pressure disturbance is induced by CO2 injection. It is also inferred from the present study that outcrop samples can be used to evaluate lateral variations in geomechanical properties with precise lateral correlation and the triaxial compression tests under the same confining pressure condition.

1. INTRODUCTION

For effective geological carbon storage (GCS), a better understanding of geomechanical properties of caprocks over a targeted storage area is crucial. Considering spatial range of pressure disturbance induced by CO2 injection, lateral variation of geomechanical properties in a few to tens of km need to be assessed in detail, whereas primary subsurface information obtained through appraisal wells is limited in most cases.

Variations in geomechanical properties, such as Young's modulus and Poisson's ratio, have been evaluated in some case studies for the characterization of shale gas reservoirs that targeted tight mudstones (e.g., Rickman et al., 2008). On the other hand, regarding GCS, a few case studies have only been conducted. Especially, it is pointed out that studies targeted the Neogene–Quaternary soft sedimentary rocks regarding GCS are very limited (Fujii et al., 2024), although GCS projects targeting these rocks are extensively planed in regions such as Southeast Asia and Japan.
Mineralogical Impact on CO2-Rock-Fluid Interactions in High-Temperature Carbonate Reservoir: Case Study from Offshore Malaysia
Authors: Kashim M. Z. , Md Shah S. S. , Tewari R. D. , Giwelli A. , Esteban L. , Clennell M. B. , Noble R. , Vialle S.
Published: January 2025

Understanding the evolution of rock porosity and permeability due to geochemical interaction is vital for assessing the impact on CO2 storage performance in identified geological formations. This study focused on the influence of rock mineralogy on CO2-rock-fluid interactions and their effects on rock porosity and permeability for S field, which is high temperature, high in-situ CO2 content (∼70%) offshore carbonate field located in Malaysian waters. Two representative core samples, one from gas interval and another from the aquifer interval, were selected from the S field for unsteady-state core-flooding experiments conducted at reservoir conditions (35 MPa/5076 psi and 150° C). Pre- and post-flooding core characterization was carried out using Nuclear Magnetic Resonance (NMR), X-Ray CT-imaging and porosity-permeability measurement to examine any petrophysical alteration resulting from the experiment. The results show that the gas interval sample exhibited a dissolution fingering pattern at the inlet face, induced by CO2 flooding, whereas the aquifer interval sample showed very limited changes. These observations were supported by increased gas porosity-permeability in the gas interval, as indicated by NMR porosity measurements and X-ray CT images showing fingering features, whereas no significant changes were detected in the aquifer interval sample.

1. INTRODUCTION

CO2-rock-fluid interaction could result in alterations of the petrophysical properties (Hao et al., 2013; Zekri et al., 2013; Garing et al., 2015; Khather et al., 2017; Khather et al., 2020) and the multiphase flow characteristics (El-Maghraby and Blunt, 2013; Bennion and Bachu, 2020; Seyyedi et al., 2020) of both rock formation and the subsurface system. The rates of surface reaction are very high in carbonate reservoirs, where calcite reaction rate is 1 × 10−5 mol/cm2/s and for dolomite is 1 × 10−7 mol/cm2/s, which usually lead to greatly uneven rock minerals dissolution (Wellman et al., 2003; Egermann et al., 2005). Even though the rock porosity and permeability are expected to increase due to the dissolution of rock minerals, the change in temperature/pressure conditions at downhole conditions could result in rock minerals precipitation, counteracting the dissolution mechanism. The net effect of this process will result in reduction of rock effective porosity and permeability (Oomole and Osoba, 1983; Izgec et al., 2005).
State of the Art Technology Development for Hydrocarbon and CCS Caprock In-Situ Stress Testing
Authors: Achourov V. , Bautmans P. , Reitan H. , Thompson N.
Published: January 2025

Until recently the measurement of reservoir caprock and shale in-situ stress has mainly been limited to extended leak off tests (XLOTs) performed during drilling operations at casing or liner shoes. Whilst the wireline formation tester tool has been used for in-situ stress data acquisition for many years, the technique's application has been restricted to particular environments constrained by the fracture initiation, propagation & closure capabilities of the tool. Although many hardware & operational practice improvements have enhanced the technique's success rate, these solutions have not always been successful in shallow and non-conventional formations such as the caprocks that are present in frontier exploration areas of the Norwegian Continental Shelf (NCS). Two flowback solutions were developed to improve the reliability of the wireline formation tester tool. These allow fluid to flow out of the fracture across a fixed choke or at a controlled rate and thereby provide suitable conditions for interpretable fracture closure processes. The technology permits repeated measurements due to its ability to conduct multiple flowback cycles with downhole fluid recycling. These two independent flowback techniques have been deployed in several exploration and development projects on the NCS over several recent years. These developments, together with other operational practice & hardware optimizations, have made it possible for the wireline formation tester to measure fracture closure in low and non-permeable open hole environments.

1. INTRODUCTION

Rock stress measurements in low permeable formations such as caprocks and shales provide critical input to hydrocarbon field developments as well as to carbon capture utilization and storage (CCUS) projects. The industry has traditionally acquired this data by performing (extended) leak-off tests (XLOTs) at casing shoes, which unfortunately aren't necessarily located there where the rock stress data is needed. Other stress testing methods, such as DFITs and minifrac tests, measure rock stress at the depth of interest by perforating a cemented casing, but these often require a tailored well design with associated time and cost implications.
Coupled Wellbore-Reservoir-Geomechanical Modelling of Uneven Depletion and Induced Stress Responses in Shale Oil Reservoirs with Heterogeneous Hydraulic Fractures
Authors: Guo Xuyang , Song Hongwei , Liu Junfeng
Published: January 2025

The production in horizontal wells with multi-stage hydraulic fractures causes pressure drop and depletion-induced in-situ stress state changes at both near-well and far-field locations. Multi-stage hydraulic fractures are usually heterogeneous with various widths, heights, half-lengths, and conductivities. The pipe flow in wellbores is also affected by multi-stage fractures connected through perforations. This study proposes a numerical model that simultaneously considers the coupled behaviors of pipe flow, depletion in heterogeneous fractures and reservoirs, and induced in-situ stress state evolutions. In this numerical model, the three physical fields mentioned above are modeled and fully coupled. Heterogeneous hydraulic fractures are assigned with uneven fracture widths, fracture half-lengths, and fracture conductivities. Simulation results indicate that dominant flow paths are observed and they are usually associated with hydraulic fractures with greater sizes and better conductivities. Within the reservoir, dominant fractures lead to greater and faster depletion and stress reorientation, while inferior fractures result in slower and insignificant stress responses. Another observation captured by the coupled wellbore-reservoir-geomechanical simulation is the effect of productivity competition between superior and inferior hydraulic fractures during production. Fractures with greater sizes and higher productivities draw fluids from adjacent fractures and intensify uneven flow distribution and induced stress changes. Increasing cluster spacing can help to obtain more uniform stress state changes during horizontal well production and to avoid excessive local stress reversals around dominant fractures. The study helps to improve the representation of wellbore-reservoir interaction in the simulation of horizontal well depletion-induced reservoir stress responses. It also provides a numerical modeling reference to the optimization of hydraulic fracturing design and production schedules.

1. INTRODUCTION

During the development of shale oil reservoirs, horizontal wells and hydraulic fracturing techniques are widely used. In certain scenarios, re-fracturing and infill well fracturing techniques are involved due to the limited recovery efficiencies of hydraulically fractured legacy wells (Gupta et al., 2013). To optimize hydraulic fracturing parameters and fracturing timings in these scenarios, it is very important to understand depletion-induced stress evolutions in the reservoirs (Morales et al., 2016; Jacobs, 2017). Due to this effect, local stress magnitudes and stress orientations can be different from the original in-situ stress state prior to any shale oil production (Roussel et al., 2013; Chen et al., 2021; Zhi et al., 2021). In such complex and heterogenous stress fields, the propagation behaviors of new hydraulic fractures caused by infill well fracturing and re-fracturing can be hard to predict.
Field-Based Mud Design Optimisation for Mitigating Time-Dependent Wellbore Instability in a Shale Formation in Gulf Region
Authors: Tan C. P. , Zainudin W. N. S. W. M. , Idris I. H. , Razak M. S. A. , Devadass L. , Ariffin M. S. M.
Published: January 2025

It is estimated that time-dependent shale instability accounts for up to 20% of the wellbore instability problems in Field X, Gulf region which are related, at least in part, to incorrect mud salinity and mud type. While drilling the Shale X formation, severe time-dependent instability problems due to shale sloughing have led to invisible lost time associated with hard back-reaming and stuck pipe. However, conventional method of handling time-dependent shale instability in using offset well drilling experience and practice in the field has not been robust and effective in mitigating the problems. Hence, a study was conducted to deploy the field-based Optimal Mud Salinity Design Tool to eliminate time-dependent wellbore instability problems related to improper mud salinity design in the field. Petrophysical and chemical properties of the shale formation were characterised on sizeable cuttings. End of Well reports of the offset wells were reviewed, and numerous time-dependent wellbore instability-related drilling events in the shale formation were identified. The integrated back-analysis of the identified instability events showed the instability was attributed to insufficient salinity in the drilling fluid which resulted in pore pressure increase due to the mud pressure penetration mechanism not being counteracted by the chemical potential mechanism. The output from the back-analysis were subsequently used to develop two optimal mud design criteria for the shale formation based on breakout mud weight and mud weight used. The tolerable upper limit hole enlargement and lower limit chloride concentration required for optimal mud salinity design were determined based on the invisible lost time for offset wells together with chloride concentration used and associated hole enlargements. Following that, the optimal mud design criteria were used with input from mechanical wellbore stability analysis to develop optimal mud salinity design for drilling the shale formation with water-based mud in two planned wells. As the required mud activity is approximately 0.85 and as excessive high KCl concentration could be detrimental to some shales with generation of microfractures, combined KCl and NaCl salinities with KCl limited to 5% are recommended as optimal mud design for the two wells.
Transforming Subsurface Insights: A Rock Physics Atlas for Enhanced Seismic and Geomechanical Analysis
Authors: Ambati Lokesh , Tiwari Upendra , Bt Abdullah Irmawaty , Rajput Sanjeev
Published: January 2025

Wireline log data is essential for subsurface characterization, but incomplete data, such as missing shear sonic logs, can limit our understanding of rock properties. In this study, we developed a rock physics model to predict shear sonic logs in wells with missing data. The predicted logs were then used to estimate geomechanical properties, which showed excellent agreement with measured values. To further explore the implications of our results, we conducted fluid and lithology substitution modeling using the predicted elastic logs. This allowed us to investigate how different fluid types and saturations affect seismic responses. Additionally, we constructed a rock physics template to integrate all relevant information for subsurface analysis, making it accessible to geologists, geophysicists, and geomechanical engineers. The predicted elastic logs can be applied to various subsurface characterization studies, including seismic reservoir characterization, 4D analysis, stress estimation, and wellbore stability assessment. Our research demonstrates the value of rock physics modeling in addressing data gaps and providing valuable insights into subsurface properties.

1. INTRODUCTION

Rock physics has historically been crucial in linking geological characteristics with elastic and seismic parameters, enabling the precise interpretation of well logs and seismic data. This pilot study in the Sarawak Basin, Malaysia, advances the field by integrating rock physics with geomechanical principles. By developing and applying rock physics techniques, we significantly enhance subsurface modelling and prediction. We created a pilot rock physics atlas over the study area, incorporating geological, geophysical, well log, and reservoir engineering data. This atlas offers geoscientists detailed, accessible analyses, dramatically improving exploration and production efforts.

One of the most discussing challenges in geophysics is tracking the most accurate relationship between elastic properties and pore structure of porous rocks. It is important to find the relations between fluids, pore space and rock, and how they modify the rock properties. The elastic bounds give the narrows of such a system without considering the interconnectivity details, pore shape, and size. Several analytical methods have been suggested to describe the dry rock/porous saturated elastic bounds. These methods depend on stress-strain investigation or are accurately based on the microstructural information. Recently, several elastic bounds such as Voigt-Reuss Bounds, Voigt-Reuss-Hill (VRH) approximation, and Hashin-Shtrikman (HS) Bounds etc.
Field Cases for Back-Analysis of Maximum Horizontal Stress of Oil Fields from Breakout Formations
Authors: Al Sabri M. , Al Ajmi A. , Al-Hadrami H. , Al Aamri M.
Published: January 2025

Efficient in-situ stress prediction in oil fields is a vital step in wellbore stability and drilling optimization. In many cases, the lack of accurate prediction of in-situ stresses is the key issue in borehole instability problems; consequently, drilling issues with high severity often occur, leading to non-productive time periods and significant increases in drilling costs. Three-dimensional geomechanical models have improved the prediction of the maximum horizontal stress of the fields from the formed breakouts. This 3D model is based on poroelastic constitutive law in conjunction with Mogi-Coulomb shear failure criterion. However, the classic Mohr-Coulomb failure criterion has been also used to verify the effect of the intermediate principal stress on the back analysis of the maximum horizontal stress. In all the field cases, the Mogi-Coulomb failure criterion was able to accurately predict the maximum horizontal stress that was well compatible with the actual field.

1. INTRODUCTION

When a well is drilled, the removal of rock mass will result in a redistribution of stress around the wellbore. The redistribution of stresses near the wellbore may lead to shear or tensile failure at the borehole wall, resulting in wellbore instability. These changes in stress distribution are functions of the magnitude of the far-field in-situ stresses, their orientation relative to the wellbore, rock properties, formation fluid pore pressure, and the annular mud pressure inside the wellbore. Far-field stresses are natural earth stresses prior to drilling, away from the wellbore, and are not affected by the borehole. In contrast, wellbore stresses are near-wellbore stresses and are affected and controlled by far-field stresses, mud density, and the corresponding equivalent circulating density (ECD). Far-field stresses are normally described in cartesian coordinates, with one vertical stress σV and two horizontal stresses orthogonal to each other. They are known as minimum horizontal stress σh and maximum horizontal stress σH. The wellbore stresses are described in cylindrical coordinates, with one radial stress σr and two orthogonal stresses, which are the axial stress σz and the tangential or hoop stress σθ, as illustrated in Figure 1.
Transfer Learning: A Key Approach to Fault Prediction and Extraction in Deep Learning
Authors: Khan Muhammad , Bery Andy Anderson , Ali Syed Sadaqat , Aldossary Saleh
Published: January 2025

Faults are key subsurface features that significantly influence geomechanics, affecting stress fields and playing a crucial role in hydrocarbon exploration, production, and CO2 storage. The redistribution of stress around faults depends on factors like fault size, orientation, and the mechanical properties of surrounding rocks. Seismic data is commonly used to interpret faults, but the process can be labor-intensive and subjective. Structural attributes such as variance, curvature, fault likelihood, and ant-tracking have improved fault detection, but still require substantial manual editing to create a comprehensive fault framework. To overcome these challenges, we propose a novel approach using 3D deep convolutional neural networks (DCNN) with transfer learning from six dip lines to incorporate local structural knowledge. This method generates fault probability volumes with high training and validation accuracies (0.98 and 0.965). Ant-tracking is used as a post-processing step to enhance fault discontinuities both vertically and horizontally, allowing for the automatic extraction of fault planes ranging from 58 km to 1.25 km in length with minimal manual intervention. We successfully applied this approach to the Poseidon 3D dataset, detecting major and minor discontinuities, demonstrating its robustness and effectiveness in complex fault systems.

1. INTRODUCTION

The interpretation of faults has traditionally represented a fundamental aspect of subsurface characterization within the fields of geomechanics, hydrocarbon exploration, geothermal and assessments of CO2 storage and sequestration. Initially, the identification of faults was accomplished through manual interpretation techniques, wherein skilled geoscientists visually analyzed seismic sections for structural discontinuities. This process required the identification of abrupt changes in reflector continuity, displacements within stratigraphic layers, or other geophysical indicators that implied fault activity. However, manual interpretation is inherently laborious and subjective, leading to variability in results that depend on the interpreter's proficiency and understanding of the geological framework. Despite these limitations, manual interpretation laid the groundwork for the advancement of more refined fault detection techniques by establishing criteria for fault recognition in complex structural settings.
Comprehensive Post-Fracturing Analysis of a Typical Deep Shale Gas Reservoir Pad
Authors: Zeng Bo , Huang Haoyong , Xu Ersi , Feng Jiangrong , Guo Lingkong , Yu Wei , Liu Chuxi
Published: January 2025

This study presents an integrated approach combining hydraulic fracture simulation, production history matching, and Estimated Ultimate Recovery (EUR) prediction to optimize well performance in a deep shale gas pad located in the Sichuan Basin, China. The boundary element method was employed to simulate fracture propagation, incorporating key reservoir properties such as in-situ stress variations, natural fracture networks, and rock brittleness. The model's accuracy was validated by comparing the simulated hydraulic fracture geometry with microseismic data and pumping pressure curves, revealing a strong correlation and confirming the model's reliability. Following the fracture simulation, production history matching was conducted, using gas flow rate constraints to match bottom hole pressure data, successfully capturing reservoir heterogeneity with an average porosity of 4.2%. EUR predictions demonstrated variability across the four wells, with Well-1, Well-2, Well-3, and Well-4 showing EUR values of 1.24×108 m3, 1.08×108 m3, 1.86×108 m3, and 1.50×108 m3, respectively. The results highlighted the impact of reservoir heterogeneity on production potential and provided critical insights for optimizing future well planning and stimulation strategies.

1. INTRODUCTION

The development of shale gas reservoirs has emerged as a critical component in the global energy mix, particularly in regions with vast unconventional resources such as the Sichuan Basin in China. Shale gas extraction requires complex hydraulic fracturing techniques to unlock the potential of tight, low-permeability formations. This process involves creating fractures in the reservoir rock to enhance gas flow, but the heterogeneity of the rock properties, natural fracture networks, and in-situ stress variations can significantly impact fracture propagation and overall well productivity. Recent advancements in hydraulic fracturing technologies, combined with sophisticated simulation models, have provided deeper insights into fracture behavior and enabled better optimization of fracture designs for improved production outcomes (Liu et al., 2024; Pearson et al., 2024). However, the challenges posed by reservoir complexity continue to demand advanced modeling techniques and field data integration to ensure the economic viability of shale gas operations.
A Consistent Approach for Stress Field Orientation Determination from Multiple Measurements: Calipers, Images and Sonic
Authors: Gaede O. , Karpfinger F. , Donald A.
Published: January 2025

A method is presented to qualify the maximum horizontal stress direction on basis of dipole shear sonic anisotropy in near-vertical wellbores. The proposed scheme follows a similar qualification standard to that used for stress observations on the basis of image logs and caliper logs in the World Stress Map Project. Image log analysis and shear wave anisotropy analysis will often complement one another and add confidence when both are observed. The combination of geological setting and rock properties, together with drilling practices, does not always result in clear borehole failure, limiting the ability to quantify stress direction from images alone. Shear sonic anisotropy is often able to identify horizontal stress imbalance where borehole failure has yet not occurred. Herein, we review the methodology to determine stress direction on the basis of dipole borehole sonic data, including examination of the effect of hole ovality. The use of slowness frequency dispersion curves is particularly important, as dispersion curve analysis is essential for distinguishing shear sonic anisotropy due to horizontal differential stresses from that caused by lithological fabric and natural fractures. A new machine-learning-based analysis of the dispersion data is used to uniquely identify the crossover characteristics of stress-sensitive zones.

1 INTRODUCTION

Stress field characterization is an important input for all subsurface geomechanics applications. Improved understanding of the stress direction and the stress regime will help to reduce the risk of drilling operations and enhance the success of hydraulic fracturing (Fjaer et al., 1992; Zoback, 2010).

Over the last 30 years four-arm caliper (Plumb and Hickman, 1985) and borehole image data (Zoback et al., 1985) have been established as the industry standard measurements to interpret the in-situ horizontal stress direction.

The interpretation of the stress direction is closely linked to the near-wellbore stresses that are a function of the far-field stresses and the borehole pressure. Breakouts (BO) can be observed when compressive stresses on the bore-hole wall exceed compressive shear strength of the formation (usually the case when borehole pressure is too low).
Role of Negative Pore Pressure in Injection-Induced Post-Slip of Rock Fractures
Authors: Fang Z. , Wu W.
Published: January 2025

Negative pore pressure induced during unconventional energy production may provide new insights into assessing and mitigating injection-induced post-slip of rock fractures. Using triaxial experimental setup in the laboratory, we sheared sawcut, filled, and natural fractures in granite under zero, positive, and negative pore pressures and measured the evolution of fracture permeability. The results suggest that negative pore pressure increases the peak strength in the sawcut and filled fractures, while reducing their permeability and post-peak stressing rate. The reduction in post-peak destressing rate is most closely related to negative pore pressure in the sawcut fracture with the lowest fracture permeability, whereas in the natural fracture, the reduction in post-peak destressing rate is associated with increased hydraulic aperture following consecutive shear tests. Moreover, in the sawcut fracture, the decay in post-peak stressing rate is more rapid under negative pore pressure, corresponding to a rapid reduction in post-slip frequency during injection-induced seismicity. This rapid decay inhibits post-slip events after the shut-in of fluid injection.

1. INTRODUCTION

Injection-induced post-slip is commonly observed during unconventional energy production and is driven by pore pressure diffusion, shear stress redistribution, and slip-stress transfer (Cebry and McLaskey, 2020; Kim and Avouac, 2023; Guglielmi et al., 2015). Post-slip events are characterized by a declining frequency over time since the peak strength, resulting from an exponential reduction in post-peak stressing rate after the mainshock perturbation (Dieterich, 1994). A rapid decay represents swift re-sealing of fractures after the peak strength (Miller, 2020).

According to available data of post-slip frequency versus time since peak strength (Table 1), the decay rate exponent from natural earthquakes varies more widely and is generally lower than that from induced seismicity of lower seismic magnitudes. The normalized post-peak stressing rate, calculated as the normalized post-slip frequency (Dieterich, 1994), drops more rapidly to nearly zero for induced earthquakes. Field observations indicate that the decay rate exponent increases with deeper post-slip events (Shebalin and Clément, 2017), contrasting with the higher exponents of the shallower induced seismicity. Fluid extraction during energy production has been demonstrated to result in fracture compression and inhibit post-slip events (Segall, 1985), which potentially increases the decay rate exponent. Thus, understanding the post-peak stressing rate during unconventional energy production may uncover the rapid decay of injection-induced post-slip events.