Improving the oil production from nonmain oil layers is crucial for the complex fault block oilfields during the late stage of high water cut development to ensure stable production and capacity expansion. However, the developing characterization of the nonmain layers and their remaining oil distribution is still inadequate. Developing an efficient mode of development remains a challenge. This paper presents a detailed characterization of the sedimentary microfacies and architecture of a nonmain reservoir based on core and logging data analysis. A flexible injection-production development strategy model was designed and applied in the Hetan oilfield, located in the southeast of Zhanhua Depression of Bohai Bay Basin as an example. The results show that the nonmain oil layer of the Hetan oilfield is composed of estuary bar microfacies sand bodies. Deposits of various shapes are formed on the side or in front of the main body of the estuary dam, which constitutes the nonmain oil reservoir. The lithology is fine, the sand body thickness is small, and the plane heterogeneity is strong. The distribution is banded, potato-shaped, and fragmented. The nonmain oil layer has a small oil-bearing area of 0.1-1.0 km2 and a high oil saturation of over 58%. The Hetan oilfield has a significant amount of remaining oil enrichment and considerable potential for production digging. To optimize production, a flexible injection and production adjustment scheme is proposed, which includes designing multitarget horizontal wells and utilizing various methods such as optimizing well spacing, coupled injection, and cycle injection. Field tests conducted in the area have shown an increase in the recovery factor of nonmain oil layers from 16.7% to 28.5%. This indicates that identifying and characterizing nonmain oil layers through detailed analysis of sedimentary microfacies and reservoir architecture is useful in the late-stage development of complex fault block reservoirs to maintain sustainable and efficient oilfield development.

Lei Xu

Xiutian Yao

Sen Yan

Zhang Wen

Jimei Xue

Geofluids

Fine Characterization of Nonmain Oil Layer Distributions in Complex Fault Block Oilfield and Its Development Model

复杂断块油田非主力油层分布精细表征及其开发模式

The management of rock mass deformation in high-stress roadways is a pivotal aspect of deep geotechnical engineering. Given the fruitful outcomes of research in rock mechanics regarding traditional confining pressure control methods, scholars have increasingly turned their attention to exploring pressure-relieving techniques, including borehole pressure relief and blasting pressure relief. However, there is limited research on pressure relief methods for deep-buried hard rock tunnels. This article commences with an overview of pressure relief in the roadway and conducts a detailed study on the parameters and methods of pressure relief in the roadway. To address safety and mining efficiency challenges, such as severe deformation leading to support failures, this study conducted a parameter analysis using the Sanshandao Gold Mine as a case study. Based on existing support methods, a strategy for arranging pressure relief roadways at varying distances from the main roadway is proposed, significantly enhancing the stress environment there. Numerical simulation software was employed to model two scenarios: (1) excavating the pressure relief roadway, main roadway, and maintenance roadway simultaneously and (2) first excavating the pressure relief roadway, followed by the main roadway and the maintenance roadway simultaneously. Simulation results indicated that the first pressure relief approach outperforms the second. The optimal position for both pressure relief roadways is 15 m from the main roadway, resulting in maximum deformation of the main roadway within 100 mm. These findings align with on-site stress monitoring data and satisfy safety production criteria. The research offers a theoretical foundation for similar pressure relief techniques in deeply buried, high-stress roadways.

MingWei Jiang

YuYun Fan

WeiWei Su

Jincheng Wang

Ming Lan

Qibin Lin

Optimization of Support and Relief Parameters for Deep-Buried Metal Mine Roadways

深埋金属矿山巷道支护与卸压参数优化

Gas flaring (GasF) is an important aspect of the combustion mechanisms in the burning of related, undesirable, or surplus fluids (gases in particular) that are released during the ordinary or unexpected overpressuring process in several industrial activities, specifically in the petroleum resource (PTR) industries. It is also one of the major sources of greenhouse gas emissions which cause climate change (CMC). In addition to the generation of noise and heat, it makes substantial adjacent areas uninhabitable and, hence, causes detrimental consequences to the entire ecosystem as well as waste energy and results in economic losses. Reducing GasF is a critical issue due to its ensuing complications; consequently, there is a tenacious need to measure GasF via the study of its composition, distribution, and capacity, as well as the utilization of appropriate GasF recovery/removal procedures. The present review study will, thus, attempt to assess the impacts of GasF on the environment vis-à-vis the possible nexus between GasF/CMC using the perspective of the Niger Delta region of Nigeria which is rich in PTR, with relevant information drawn from existing publications. The roles of government, policymakers, and relevant stakeholders as well as suggestions and recommendations that will assist in the extenuation approaches and technologies of the influence of GasF on the environment are also discussed.

Kingsley Eghonghon Ukhurebor

Uyiosa Osagie Aigbe

Robert Birundu Onyancha

Hussain Athar

Benedict Okundaye

Paul Atagamen Aidonojie

Benita Ebindu Siloko

Ismail Hossain

Heri Septya Kusuma

Handoko Darmokoesoemo

Environmental Influence of Gas Flaring: Perspective from the Niger Delta Region of Nigeria

天然气放空的环境影响：尼日尔三角洲地区的视角

Gas migration incidents, particularly stream contamination cases, have been rarely investigated and gone through the peer review process, with the exception of three sites in northeast Pennsylvania (Dimock and two Sugar Runs in Lycoming and Bradford counties, respectively) where air emission surveys, dissolved methane measurements, and structural (hydro)geologic interpretations have been used to demonstrate potential environmental impacts due to shale gas operations. In addition to reviewing previously published work from these three sites, we report and analyze unpublished new data trying to determine if a direct relationship between methane migration, stream contamination, and air emissions exists at those sites. Our analysis indicates that subsurface methane migration, stream methane contamination, and air emissions might not be all present or detectable at a faulty/leaky shale gas well. Which of these signs of contamination, if any, exist is largely controlled by the local (hydro)geologic conditions. In each case, the most likely migration pathway was from gas charged zones up well annular spaces to confined permeable formations, then laterally to a direct discharge or by vertically controlled joints to streams, water wells, and the atmosphere. The confining units act as barriers to the buoyant movement of stray gases, allowing subsurface travel of gas for 1–4 km from a leaky gas well. The knowledge we learn from these three sites can guide the future investigations of methane contamination cases in other regions.

Patrick A. Hammond

Tao Wen

Josh Woda

David Oakley

Pathways and Environmental Impacts of Methane Migration: Case Studies in the Marcellus Shale, USA

甲烷迁移的路径与环境影响：美国马塞勒斯页岩的案例研究

The red-bed soft rocks in South China have obvious creep characteristics and are prone to engineering geological disasters such as landslide and foundation settlement under the action of rainfall, groundwater, and load. In order to reveal its creep characteristics and mechanism under complex conditions, a step-loading creep test was carried out under chemical-stress-seepage coupling, and the energy evolution law of the whole creep process was analyzed based on linear energy storage and energy dissipation theory. The results also show that the acid chemical solution has the greatest influence on the triaxial strength and creep strength, and the creep damage and energy evolution of red-bed soft rock are universal. The creep damage and total strain increase with the increase of acidity, the decrease of confining pressure, and the increase of seepage pressure. The evolution law of creep damage shows the characteristics of slow-acceleration-rapid growth, and with the increase of load level, it has obvious transfer and accumulation. After entering the constant velocity creep stage, the damage rate begins to accelerate. The proportion of instantaneous strain and creep strain in the total strain increment is about 50%, and confining pressure has little influence on their respective proportions. The instantaneous strain is more sensitive to the acidity of the chemical solution, and the proportion of creep strain increases gradually with the increase of seepage pressure. The relationship between elastic energy density and total energy density is linear. The elastic energy density and dissipated energy density in the loading stage and creep stage all increase nonlinearly with loading time. The density of dissipated energy in the creep phase is lower than that in the loading phase, but the opposite is true in the higher stress phase, and the law of energy dissipation can explain the hardening damage effect in the creep process of soft rock samples. The research results provide a new perspective for us to reveal the mechanical properties and failure mechanism of red-bed soft rocks and provide an important theoretical basis for predicting and evaluating the creep instability and long-term stability of such rocks.

Shuguang Zhang

Fanyao Peng

Yingbo Li

Zhifeng Liu

Wenbo Liu

Creep Energy Evolution of Red-Bed Soft Rocks in South China under Chemical-Stress-Seepage Coupling

华南红层软岩在化学-应力-渗流耦合作用下的蠕变能量演化

Unlike conventional single-phase seepage monitoring methods, monitoring multiphase flow in porous media is more complex. This paper addresses this complexity by analyzing the heat transfer in porous media models under multiphase seepage conditions. It introduces a set of theories, methods, and devices to effectively monitor the flow velocity in multiphase seepage processes. Utilizing a self-developed single-point self-heating temperature-sensing device combined with saturation testing at monitoring points, we establish a method to determine the relationship between different saturation and resistivity, as well as the saturation and thermal conductivity of the reservoir model, which provides essential parameter support for the calculation of results during flow velocity monitoring. The effectiveness of the flow velocity monitoring method was confirmed through a one-dimensional constant velocity multiphase seepage experiment. Furthermore, oil-water two-phase seepage simulation experiments were conducted based on the sandpack model. By comparing the real oil-water flow velocity with the monitored velocity, the accuracy can reach over 95%, validating the accuracy and reliability of the method proposed in this paper. The seepage flow velocity monitoring theory and technology established herein offer corresponding theories and methods for obtaining fluid seepage velocity in porous media with multiphase fluids.

Cuo Guan

Xianjie Li

Ke Hu

Chen Liu

Hong Du

Ruokun Xian

Development and Application of a Percolation Velocity Monitoring Method in Multiphase Percolation Physical Experiments

多相渗流物理实验中渗流速度监测方法的开发与应用

Retaining wall is essential for stopes mining in two steps, for it can prevent the instability and collapse of backfill. In this study, taking the retaining wall of backfilled stope as the research object, a stability analysis method of retaining wall based on the close coupling of catastrophe theory and numerical analysis was proposed. First, by extracting the unit failure rate of the retaining wall from the numerical simulation results and fitting it with the mining depth, the functional expression between them was established. Second, the function relation was transformed into the normal form according to catastrophe theory, and the instability criterion of retaining wall was deduced. Furthermore, an effort was made to analyze the changing law of the state of retaining wall and calculate the critical span of stope, under different thickness conditions. On this basis, the application test of retaining wall was carried out by using this method. The results show that with the thickness decreasing, the values of splitting variables <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1"><mi>a</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" id="M2"><mi>b</mi></math> show a reverse trend, which leads to the discriminant of instability criterion decreasing and turning from positive to negative, resulting in the collapse. Meanwhile, in order to ensure the stability, the wider the span of the stope, the thicker the retaining wall is required, and conversely, the thicker the retaining wall, the higher the adaptability to the span of stope. In addition, it can be found from the application test that instability was bound to occur with a thickness of 3 m, but the retaining wall with a thickness of 4 m maintained stable, which tended to be consistent with the analysis. Therefore, the stability analysis method proposed in this study provides a way to accurately evaluate the stability of the retaining wall and calculate the critical thickness of that, and its application value is expected to be further explored.

Chang Liu

Kui Zhao

Peng Zeng

Cong Gong

Liangfeng Xiong

Jinbo Xiong

Rongsen Pan

Stability Analysis of Retaining Wall in Backfilled Stope Based on Catastrophe Theory and Numerical Analysis

基于突变理论和数值分析的充填采场挡墙稳定性分析

After the rupture of pressurized water supply pipes in urban underground areas, seepage-induced ground subsidence becomes a severe geological hazard. Understanding the permeation and diffusion patterns of water in soil is crucial for deciphering the mechanisms underlying soil settlement and damage. Notably, the pressure within water supply pipes significantly influences the settlement and damage of the soil. Therefore, this study simulated experiments on soil settlement and damage caused by water seepage from a preexisting damaged pipeline under various internal pipe pressure conditions using an indoor model apparatus. The results indicate that the internal pressure of the pipe significantly influences the settlement of the soil. High-pressure seepage causes noticeable erosion in the soil, forming cavities within it. In contrast, low-pressure seepage results in water diffusing in an ellipsoidal pattern, leading to the formation of circular surface cracks. The degree of surface settlement increases with higher pipe pressure. The onset of subsidence at a specific point on the ground is not directly related to whether the moistening front within the soil has reached that point horizontally. Instead, it is associated with the moisture content below the subsidence point within the soil. The research results further illustrate the water diffusion and moisture content increase processes after water seepage from pipes with different pressures, revealing the influence of pipe pressure on the degree and form of soil settlement damage and clarifying the relationship between water diffusion and settlement in the soil.

Jingyu Cui

Fengyin Liu

Ruidi Chen

Shuangshuang Wang

Cheng Pu

Xu Zhao

Effects of Internal Pressure on Urban Water Supply Pipeline Leakage-Induced Soil Subsidence Mechanisms

内部压力对城市供水管道泄漏引发土壤沉降机制的影响

This study presents a novel perspective for improving the understanding of permeable structures at geothermal prospects by jointly diagnosing the responses of conventional pressure transient and tracer testing. The pressure and tracer responses individually yield apparent porosity–thickness products. The difference between them implies the existence of unknown dead-end features involved in a reservoir model. Laboratory experiments and numerical simulations validate this concept. Potential application to hypothetical exploration demonstrates that the logarithmic ratio of the porosity–thickness products, determined based on pressure and tracer responses, indicates the accuracy of the reservoir model to be successively updated with the progress of the exploration. The reservoir model successfully reproduced the synthetic observations regardless of the accuracy of permeable structure if different porosity–thickness products were allowed to be assumed to individually reproduce pressure and tracer responses. These porosity–thickness products coincided only if the reservoir model correctly captured the permeable structure. This novel perspective will provide strategic guides for successful exploration and development at the prospects of geothermal and, potentially, general geofluid resources.

Mitsuo Matsumoto

Kazuki Sawayama

Joint Diagnostic Approach to Pressure and Tracer Responses from Reservoirs: An Experimental and Theoretical Study to Estimate the Accuracy of Reservoir Models

联合诊断方法研究储层压力和示踪响应：实验与理论研究储层模型精度估计

In the process of long-term water flooding in the Gaoqian Southern Area with an average porosity of 30% and an average permeability of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1"><mn>1333.5</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></math> μm2, the fluid-solid interaction among oil, water, and rock has a great influence on the pore structure. It has resulted in changes in reservoir parameters with the extension of time. This paper used electron microscopy scanning, mercury injection, X-ray diffraction, physical properties, and oil-water relative permeability curves to study the variation of clay mineral content, pore throat structure, porosity, permeability, and relative permeability curves of high-permeability sandstone after high-pressure water flooding. The results showed that clay minerals such as montmorillonite and kaolinite were dissolved, hydrated, and migrated after long-term water flooding, which resulted in the decrease of clay mineral content in fine sandstone and medium sandstone, the increase of pore throat radius, and the decrease of displacement pressure, median pressure, and separation coefficient. The saturation of the isotonic point of the oil-water relative permeability curve was obviously shifted to the right, the hydrophilicity was significantly enhanced, and the porosity and permeability were effectively improved, but there was a blockage of the throat less than 2 μm in the fine sandstone. In addition, this paper established the equations of water injection, permeability, irreducible water saturation, residual oil saturation, and oil-water relative permeability curve coefficient and establishes the initial permeability model with the well data before water flooding. The logging interpretation results of development wells in the process of water flooding as verification data were used, and the relative error of permeability far lower than the general requirement of permeability error within an order of magnitude was less than 30%, which verified the rationality of the method.

Hui Xu

Guofeng Cheng

Nannan Liu

Lizhi Wang

Zhenghuai Guo

Xiang Wang

Xiangji Dou

Juan Li

Shangping Chen

Xing Shi

Numerical Simulation of Time-Varying Characteristics in a High-Permeability Sandstone Reservoir: A Case of Gaoqian Southern Area

高渗透砂岩储层时间变化特征的数值模拟：以高迁南区为例

GEOFLUIDS 是一份经过同行评审的开放获取期刊，为与流体在地壳的矿物学、化学和结构演化中的作用相关的原创研究和评论提供了一个论坛。其明确目标是在开展地流体研究的各个子学科范围内传播思想。为此，鼓励作者强调其研究的跨学科相关性和国际影响。还鼓励作者尽可能让其他子学科的读者能够访问他们的工作。GEOFLUIDS 强调整个地壳中地下流体的化学、微生物和物理方面。 GEOFLUIDS 涵盖地下水、陆地或海底地热流体、盆地盐水、石油、变质水或岩浆流体的研究。

GEOFLUIDS is a peer-reviewed open-access journal that provides a forum for original research and reviews related to the role of fluids in the mineralogy, chemistry, and structural evolution of the Earth's crust. Its explicit aim is to disseminate ideas across various sub-disciplines involved in geofluid research. Authors are encouraged to highlight the interdisciplinary relevance and international impact of their work, and to present their findings in a manner accessible to readers from other sub-disciplines. GEOFLUIDS emphasizes the chemical, microbial, and physical aspects of subsurface fluids throughout the crust, covering studies on groundwater, terrestrial or submarine geothermal fluids, basin brines, petroleum, metamorphic waters, and magmatic fluids.

GEOFLUIDS 是一本经过同行评审的开放获取期刊，专注于流体在地壳中的矿物学、化学和结构演化方面的原创研究和评论。期刊的目标是传播与地流体研究相关的各个子学科的思想，鼓励作者强调其研究的跨学科相关性和国际影响力。同时，作者也被鼓励以便于其他子学科的读者理解的方式呈现他们的工作。GEOFLUIDS 强调地下流体在整个地壳中的化学、微生物和物理特性，涵盖地下水、陆地或海底地热流体、盆地盐水、石油、变质水和岩浆流体等研究。

Journals	Geofluids
ISSN	1468-8115, 1468-8123
h-index	68
Journal Impact	1.08
Quartiles(Global)	GEOLOGY(Q2)
Quartiles(China)	地球科学(4区)地球科学地球化学与地球物理(4区)地球科学地质学(4区)