bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on Early Warning and Controlling of Water Invasion in Gas Reservoirs
Authors: Fan Hairun , Zhang Xiaoyan , Zhao Xurong , Dong Zhanmin , Tang Lei , Li Hao , Dou Yugang , Sun Chaochao , Zhou Yicheng 
Published: March 2023

Abstract
Warning and controlling the water invasion in water-driving gas reservoirs is significant because water invasion will seriously hamper well productivity and gas recovery. Unfortunately, there are few comprehensive methodologies to control water invasion. In this paper, firstly, a water invasion model of reservoir scale is established and verified. Then a new workflow for Warning and controlling the water invasion is developed by the numerical simulation method in this paper. This paper takes the water-gas ratio corresponding to the turning point of the water invasion rate as the water invasion identification signal. Then, the method of water control after water invasion is studied by turning off the perforation of the primary water production. Finally, the optimal water control scheme is obtained by comparing water and gas production.
The results show that the reserve accuracy of the established water invasion model is 99%, and the model has a good pressure-fitting result. After studying the warning method of water invasion, it is found that the water-gas ratio of about 10-2 m3/104m3 is the signal of water breakthrough under the well produced at fixed production. The water-gas ratio in the range of 10-3 to 10-2 m3/104m3 signals water breakthrough in the well producing at a fixed pressure. The water-gas ratio as a signal of water breakthrough will increase with the increase of gas production rate and decrease with the fixed bottom hole pressure increase. The water-gas ratio chart of the early warning under the different producing models is drawn in this paper for applications in the field. A study of the water control method found that there will be a success in controlling the water cut after closing the perforation of the primary water production. Water production has been reduced by 90.9%, and gas production has been reduced by only 9.7% after using the technique in the field.
Effective Logging Identification of Chang 2 Low-Resistivity-Low-Contrast Pay Zones in a Sandstone Reservoir, Ordos Basin
Authors: Wang Yang , Yao Yuedong , Chen Jieyi , Yang Jian , Wang Lian 
Published: March 2023

AbstractAs one of the subtle reservoirs, low-resistivity-low-contrast (LRLC) pay zones are crucial potential exploration objective in Ordos basin. However, since its resistivity similarity to the adjacent water zones, and the genetic mechanism is complex, thence, LRLC pay zones still produce hydrocarbon at minimum resistivity contrast between hydrocarbon-bearing intervals and water-wet or shaly zones. So, if LRLC pay zones could be accurately identified only by conventional logging curves, it would bring new reserves to the development of Yanchang Oilfield.Focusing on the difficulties in well logging identification of Chang 2 LRLC pay zones in Zhidan area of Ordos basin, the work on logging identification of low resistivity pay zones in this area is carried out by processing field data such as drilling coring, well logging curves, oil testing and daily production data. Meanwhile, combined with the experimental data such as NMR experiments, rock electrical experiments, laser particle size and cation exchange capacity experiments, we form an integrated workflow based on petrography, rock typing and petrophysical methods, and deal with the identification, characterization and evaluation of LRLC pay zones.This study indicates that under the deposition environment of delta plain subfacies, Chang 2 reservoir is dominated by medium-fine-grained feldspar sandstone, and the pore structure is extremely complex due to the strong compaction. Therefore, the key cause for LRLC pay zones is the high salinity of formation water, accompanied by secondary reasons such as complex pore structure, and additional electron conductivity of the clay. In order to effectively identify the pay zones, we establish a set of suitable logging curve interpretation models based on the "four properties" relationship and test them with oil testing data, which could improve the accuracy of these models. Finally, the "apparent formation water resistivity - deep induced resistivity" cross-plot, the adjacent water zone comparison and the multivariate discriminant methods are selected to be suitable for Chang 2 low resistivity pay zones in the area. And these methods could help engineers to better estimation of water saturation in the low resistivity pay zones and accurately determine the target layer by using only limited set of well log data (conventional well logging data).In this work, three effective logging identification methods have been proposed to determine the advantaged pay zones from qualitative or quantitative perspectives. Through real block verification, these methods could effectively improve the coincidence rate of logging identification, and would provide bases for selecting the target layers in original development areas. More importantly, the results may offer new perspectives for risk assessment and target layer determination of other similar low resistivity reservoirs exploration and development.
Solving Processing and Imaging Challenges in a Southern Caspian Sea Complex Structure through Modern OBN Acquisition
Authors: Lyu Xiaolin , Hu Xin , Wang Wei , Khdhaouria Mourad , Rouis Lamia , Rondon Aldrin , Ameish Giamal , Qi Qunli , Zhao Min 
Published: March 2023

AbstractThe Greater Cheleken Area (GCA) developed by Dragon Oil, situates on a complex NW-SE dextral transcurrent zone which separates the Northern from the Southern Caspian Basin (SCB). Numerous hydrocarbon accumulations were discovered in highly faulted Pliocene-Pleistocene flower structures of different types. Shallow gas has been identified vastly distributed in this region via numerous site surveys, that creating slow-velocity and high-absorption dimming zone on the seismic imaging. It poses great challenges on seismic processing and imaging.In 2022, an OBN seismic campaign was carried out aiming to resolve the imaging problems that exist in a legacy dataset. The main objectives for the 3D OBN seismic survey are: proper imaging of structures, faults and fractures characterization, stratigraphy, petrophysical properties, Gas columns and clouds mitigation and fluid contacts in clastic reservoirs cited between1500-4700m depth. The implementation of the seismic acquisition is successful by delivering high quality data on schedule and within the predetermined budget at the full satisfaction of all involved parties and stakeholders. Strong commitment to HSSE Standards and working as an integrated One-Team with full collaboration and a continuous and close communication between all the Team members are among the main Success Factors.A fast track 3D data cube is being produced at the time of writing this manuscript. The preliminary results of the 3D seismic data processing and interpretation are very encouraging and showing a clear improvement compared to the legacy 3D seismic data set.
Well Placement Design for Enhancing Heat Recovery from Geothermal Systems: Sensitivity Analysis using Thermo-Poro-Elastic Effects
Authors: Abdel Azim Reda Rabiee , Hamada Ghareb 
Published: March 2023

AbstractGeothermal energy is considered one of the most promising energy to replace oil and gas. In order to enhance this type of energy from the geothermal reservoirs, an appropriate design and evaluation tool is required to assess the stimulation treatment for improving the reservoir permeability. This paper presents an innovative approach to evaluate the well placement and designed stimulation program under thermo poroelastic coupling process using momentum, mass and energy conservation. The proposed approach is applied on a selected volume of Soultz reservoir to assess the permeability enhancement over stimulation period of more than 3 month and fluid circulation period of 14 years. In this method, the change in fracture is caused by shear slippage. The proposed stimulation model evaluates different scenarios of well placement, hydraulic fracture geometry and injection program with an objective of economic heat recovery using different fracture parameters. Results show that the thermal stress led to decreasing the produced fluid temperature across the reservoir. This is due to the fact that distributed 3-D thermal stress support in increasing the fracture opening which leads to creation of flow channeling between the injectors and producers. In addition, the result show that the presented model is capable of evaluating simulation parameters such as well placement and induced fracture geometry. This has also allowed us reducing the risk of short circulating due to excessive permeability enhancement.
High Resolution Discrete Fracture Network Application for Polymer Flooding Design in a Naturally Fractured Carbonate
Authors: Corbo Diego Nicolas , Lathion Rodolphe , Games Federico , Martinuzzi Vincent 
Published: March 2023

AbstractDespite their higher complexity (Juri et al., 2015) and usually more challenging commercial development, naturally fractured reservoirs account for a significant portion of oil and gas reserves worldwide (Sun et al., 2021). Typically, natural fractures tend to enhance the productivity of the wells, yet they also tend to accelerate reservoir depletion, often leading to sub-optimal field production and leaving significant volumes of hydrocarbons behind (Aguilera, 1995). In this work, we propose a specific polymer injection design that can provide the conditions for fracture-matrix counter-current flow to develop in a naturally fractured carbonate reservoir. In turn, this flow could trigger a virtuous cycle where the displacement front is progressively slowed down, increasing the efficiency of the displacement process and the oil recovery. This study focused on the integration of multiple sets of data to characterize karstic and tectonic fractures in a discrete fracture network (DFN) model and its posterior use in a dual medium simulation model to determine polymer flooding optimal spacing and injection strategy in a complex, naturally fractured carbonate system.An innovative and integrated approach combining 3D seismic data, bore-hole imagery (BHI), cores, and production data was applied to characterize and represent karstic features. The applied workflow consisted of (1) identification and manual picking of karstic features on BHI, (2) deterministic picking of karstic features as geobodies on the 3D seismic (enhanced similarity volume), (3) integrated implementation of the karstic features into the geological model using advanced geostatistical methods (Multi-Points Simulation, or MPS), and (4) implementation of resulting enhanced reservoir properties on a fit for purpose high-resolution dynamic model (dual porosity/dual permeability).Multiple simulations were run to evaluate different sensitivities including injection rates, injection strategy, completion approach, and producer-injector pattern spacing. Particularly for the latter, a robust karst/fracture system characterization was critical to propose optimal pattern sizes which aim to simultaneously avoid early polymer breakthrough -in shorter than optimal designs and minimize potential shear thickening degradation effects tied to higher polymer throughput required by excessive producer-injector distancing. In terms of the completion interval, the DFN-derived properties were also strongly conditioning the selection of the injection interval with noticeable effects and contrasting results. Because of the superposed features constituting the total fracture system and their different origins, a field-level comprehension of anisotropy and local intensity of the fractures is critical for selecting both the wells for the injectivity test and the potential area for the pilot in the next stage of the project.
Implications of Wellbore-Fracture Separation on Temperature Log Interpretation Studied Through Numerical Modeling and Field Measurements and Observations
Authors: Khan Abdul Muqtadir , Binziad Abdullah , Alsubaii Abdullah 
Published: March 2023

AbstractTemperature logging is an old technique that quantifies fracture height based on cooldown anomalies. Warm anomalies are very frequently observed in post-fracturing measurements. One of the reasons for these anomalies is misalignment of the wellbore with the fracture, which depends on the geometry of wellbore and preferential fracture plane. A systematic study is presented here to avoid misinterpretation of fracture height.Two mathematical tools were coupled: (1) a geometrical resolution of the 3D space around the wellbore and (2) a numerical scheme solving the heat transfer partial differential equation (PDE) in dimensionless form to simulate temperature evolution around the wellbore. Finally, the findings were tested and corroborated with a few field cases in deep, hot, clastic reservoirs. The temperature log was conducted with three passes and was used for interpretation in deviated wellbores.The first tool utilized the wellbore deviation, wellbore azimuth, and fracture azimuth to resolve the relative positions and detailed geometry in 3D space. The tool yielded the fraction of total fracture height that will be coincident with the wellbore for a given set of inputs. The outputs were then coupled with the numerical tool with an explicit finite difference code to solve the relevant PDE with appropriate boundary conditions for the given geometrical space for the angled/separated fracture. The results showed that the further the fracture separates from wellbore, the more difficult it is to observe cooldown if the temperature logging is conducted soon after fracturing. Delaying the temperature passes allows the cold front from fracture to move towards wellbore and is a viable solution to capture cooldown, as seen from field measurements and validated by the model. The field cases demonstrated some complicated temperature behaviors, and the understanding developed from the modeling tools aided in interpreting the anomalous trends. The possibility of constructing pseduo temperature logs, lowering the number of passes, and extending the approach for multiple applications is discussed.The innovative approach avoids pitfalls of false indications of fracture containment in deviated wells. It can be used to improve the utility of high-resolution temperature logging data to enhance efficiency.
Critical Review of Interfacial Tension of CO2-brine Systems: Implications for CO2 Storage
Authors: Mouallem Johny , Raza Arshad , Mahmoud Mohamed , Arif Muhammad 
Published: March 2023

AbstractCarbon capture utilization and storage (CCUS) constitute promising underground storage techniques to address the challenge of climate change. Subsurface storage of carbon dioxide depends on several factors like injectivity, formation characteristics, sealing integrity etc. One critical parameter is the interfacial tension (IFT) of the fluid-fluid system in question e.g., CO2-brine IFT for CO2 geo-storage. Importantly, the IFT influences the capillary pressure of the seal, which, in turn, controls fluid leakage. In addition, different fluid-fluid IFTs give rise to distinct relative permeability curves and residual saturations of the fluids, thereby impacting residual trapping characteristics. Successful application of EOR techniques is also dependent on the IFT of the carbonated water (CO2+water/brine) and the oil in place given that the IFT controls fluid miscibility and flow.Numerous researchers investigated the IFT of fluid-fluid systems and its effect on capacity estimates for CO2/H2 storage as well as the expected performance EOR techniques. Associated trends, however, have not been critically analyzed before. Thus, this paper presents a critical review of published data sets on CO2-brine IFTs. The significance of IFT for underground gas storage and EOR applications is detailed. IFT depends primarily on pressure, temperature, and salinity. The influence of pressure, temperature, and salinity on IFT and associated trends are analyzed. In addition, latest developments pertaining IFT measurements for sequestration purposes are discussed from a risk managing perspective. Finally, this study elucidates research gaps and presents a future outlook.
Well Testing Analysis Methodology and Application for Complex Fault-Block reservoirs in the Exploration Stage
Authors: Liao Changlin , Wang Ruifeng , Zhang Juntao , Huang Qizhi , Li Xiangling , Zheng Xuerui , Lin Zimo 
Published: March 2023

AbstractA complex fault-block reservoir usually has large layer span, many thin layers and oil-water systems. The available data are limited in the exploration stage. One of the biggest advantages is that each well is tested several times. Based on comprehensive geological study, this paper proposed a well testing analysis methodology to carry out reservoir evaluation, and the results are applied to the oilfield development plan. Well testing can reflect the static and dynamic characteristics of reservoir at the same time. It shows high application value in the exploration stage. The analysis methodology of well testing in complex fault-block oilfield mainly includes three aspects: (1) Establish a novel calculation method to obtain crude oil parameters of all tested intervals, which are necessary in well test interpretation. (2) Build reliable interpretation models to evaluate wellbore, formation property, productivity and boundary according to pressure derivatives curves. (3) Propose a concise evaluation process to show reservoir characteristics in both vertical and plane. This methodology is applied in Doseo Oilfield and proved to be a great methodology in complex fault-block reservoirs. The calculated crude oil parameters are good matched with limited PVT data. The errors are less than 10%. The formation characteristics obtained from the models including permeability, faults and aquifer energy are well verified by seismic and well-logging interpretation. The reservoirs in middle area on the plane and Zone K in the vertical show high productivity and permeability. They can be selected as the key oil regions for the first production. Similar formation characteristics are reflected by the analogous shape of pressure derivatives. They can be put into production with the same development methods to obtain higher benefits. The innovation is that this paper proposes an analysis methodology of well testing to calculate right crude oil parameters, identify formation characteristics and key oil regions, and find similar reservoirs. It can decrease the errors which are caused by parameter uncertainties and multi-solution of interpretation models.
Phase Field Simulation of Immiscible CO2 Flooding EOR Mechanisms in Porous Media
Authors: Fu Hongtao , Dang Sisi , Yang Kena , Zhao Yu , Guo Chunping , Fu Hong , Guo Hu , Song Kaoping 
Published: March 2023

AbstractCO2 flooding technology for EOR not only meet the needs of oilfield development, but also solve the problem of carbon emission, which has become a global research hotspot. CO2 flooding includes miscible and immiscible flooding. The advantage of immiscible CO2 flooding is the ability to achieve high recovery in different reservoirs or fluid conditions compared with miscible flooding. But there are no reports about quantitative analysis of immiscible CO2 flooding at the micro level due to the expense and complexity of the experiments.In this paper, the process of immiscible CO2 flooding was simulated based on the Navier-Stokes equation in porous media by COMSOL Multiphysics. An ideal homogeneous rock structure model was established to study the influence of interfacial tension, injection velocity, injection viscosity and gravity on immiscible CO2 flooding. The porosity of the model is 34.7% and the permeability is 36.9mD. The simulation of pressure is 10 MPa and the temperature is 80 ℃.It was found that with the injection of CO2, the contact interface of two phases gradually changes from near-piston flow to non-piston flow under immiscible condition. Decreasing the interfacial tension and increasing the injection velocity significantly change the flow paths of CO2 and increase the sweep area of CO2. The difference between CO2 and oil viscosity is one of the factors influencing the occurrence of fingering. Increasing the viscosity of CO2 injection effectively suppress viscous fingering and improve the sweep effect. Gravity is one of the factors affecting the effect of immiscible CO2 flooding.Phase field simulation was used to study immiscible CO2 flooding for the first time. It was found that increasing the viscosity of CO2 injection could significantly enhance recovery. In order to increase the viscosity of CO2, a thickener can be added to the supercritical CO2. This study provides micro-level theoretical support for the development of process parameters in oilfield, and further provides new ideas for CO2 EOR.
Breaking Dogma on the Single-Stress-Gradient Based Mechanical Earth Modeling – Wireline Formation Testers Micro-Frac, Not Just an Input… It's a Fact!
Authors: Akham Abderrahmane , Berranen Chems-Eddine , Kelkouli Mohammed 
Published: March 2023

AbstractMeasuring in-situ stresses in unconventional formations constitutes a cornerstone for reservoir-quality and completion-quality evaluation. Challenges of succeeding these tests are related to difficulties to break these formations and propagate the created fracture allowing fracture gradient estimation. Moreover, formation heterogeneities and properties anisotropy, often lead to model inaccuracies and expose drilling or fracking operations to "avoidable" failures. Hence earlier in unconventional reservoir exploration, successful in-situ stresses become a must have for geomechanical model and Fracturing design calibrations.While cross-discipline integration is key to building a representative and comprehensive MEMs, since the early 2000's, Wireline Formation Testers are used to collect localized in-situ stress measurements that constitute a valuable input to fine-tune MEMs. However, with limited knowledge and inadequate planning, these operations known as "Micro-Frac/Stress Testing" are often challenged with high failure rate, especially with legacy tools physical limits. A combination of a novel stochastic planning approach involving the multidomain integration of Petrophysics, Borehole-Images and Geomechanics, coupled with Cutting-Edge WFTs technologies significantly increases the success likelihood for Stress Testing providing thereby an unfailing calibration source for MEMs.This new approach allowed first to define the depths to test with higher rate of success to break the formations and then, to communicate to drillers and client supervisor the test duration and potential adjustment such as mud weight, to break the rock and propagate the created fractures in the formations.The above enables, from operational standpoint, successful risk-free stress test measurement, allowing the calibration of the Mechanical Earth Model and Frac Design in the hydrocarbons embedded Source Rocks across South Algerian Basins.Furthermore, stress mapping allowed the identification of a lateral variability of stress gradients within the same field, confirming the unreliability of single-stress-gradient based models and highlighting the importance of multi-well modeling of mechanical earth properties.By using a well calibrated MEMs leading to a keen understanding of stress state, chances of stimulation operations success were significantly increased.The benefit of utilizing this new method with advanced logging technologies among which the new generation of WFTs, combined with a multidomain data integration as well as a novel planning approach based on stochastic simulation enabled the achievement of a failure-free Stress Testing operations, yielding fine-tuning of MEMs in the challenging South Algerian Hot Shale. Through a keen knowledge of stress state, stimulation operations success was significantly increased.