bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discontinuous Chemical Flooding: An Effective Approach to Achieve Sustainable Oil Production for Mature Reservoir
Authors: Zhang Jian , Jin Yi , Tang Engao , Yu Fanghao , Zhou Wensheng , Zhang Zenghua , Huang Bo 
Published: October 2023

Abstract
The offshore oilfields in China have entered the mature stage with high water cut and recovery rate. Oilfield Q has an oil viscosity of only 5 cp, with a water cut of 95% and a recovery rate of more than 40%. It is challenging to maintain sustainable oil production with only waterflooding. The field production is close to the economic limit. Therefore, finding an effective and economical EOR technique is crucial to mature oilfield development.
In this paper, we proposed a new EOR method, called discontinuous chemical flooding (DCF) for mature oilfield development with a case study of oilfield Q. Four types of chemical slug, which are primary slug, main slug, secondary slug, and supplementary slug are designed. Primary slug injection well is determined based on the interwell connectivity analysis model and tracer test. The CMG CMOST module is applied to determine the optimal slug size and concentration of primary and main slug. According to the predicted produced agent concentration and water cut curve trend from numerical simulation, the implement criteria of secondary slug, and supplementary slug are provided.
The interwell connectivity analysis indicates that the permeability between injector I3 and producers A1, I1 as well as A5 are relatively high, which is an indication of a potential thief zone. Primary slugs of gel injection are designed for all injectors with channeling effects. The CMOST evaluation results show that the optimal formula of strong primary slug is polymer with a concentration of 5000 mg/L plus cross-linker with a concentration of 4000 mg/L. As for weak primary slug, the optimal formula is polymer with a concentration of 3000 mg/L plus cross-linker with a concentration of 2000 mg/L. The optimal main slug concentration for injectors, I1, I6, and I9 is 1400mg/L. The optimal main slug concentration for injectors, I5, I7, I8, and I11 is 1000mg/L. The optimal main slug concentration for the rest of injectors is 1200mg/L. The optimal main slug size is 5 years. The final reservoir simulation results yield a maximum water cut reduction of 6.7%, and an incremental oil production of 53.2×104 m3 compared with the optimal waterflooding scheme.
The scheme of oilfield Q is the first DCF scheme for mature offshore thin oil reservoir in China. It gives the approach of further enhance oil recovery for mature oilfields with ultra-high water cut and recovery rate. It also promotes the application of chemical flooding in offshore reservoir.
Simulation of Heterogeneous Geomechanical Damage in Tight Reservoir Based on Projection-Based Embedded Discrete Fractured Mode l
Authors: Li Hong , Tian He , Mei An'xin , Wu Yongchun , Peng Yu , Shi Lihua , Cao Nai 
Published: October 2023

Abstract
An advanced numerical simulation method was developed to accurately characterize the heterogeneous geomechanical damage of heterogeneous matrix, hydraulic fractures, and natural fractures during production. The proposed model can automatically obtain the geomechanical damage correction coefficient according to the physical property differences of the reservoir, which reveals the heterogeneous geomechanical damage law of the spatial domain and the time domain so that the simulation results are more realistic. The heterogeneous geomechanical damage laws of multi-scale fractures are obtained. Due to the uneven pressure drop during the production process, each fracture is subjected to different geomechanical damage, and the permeability drops are not uniform. Particularly, we set the physical properties of each fracture differently in the model, which fully reflects the heterogeneity of the actual reservoir. Therefore, the geomechanical damage law of each fracture is different. The K/K0 distribution of each fracture can be seen in the simulation results. At the same time, the porosity and permeability are coupled based on the classification theory. Therefore, the whole model is dynamic. In unconventional reservoirs, the physical properties of the matrix are poor and the heterogeneous geomechanical damage has little effect on productivity. However, if natural fractures or hydraulic fracturing are developed, the heterogeneous geomechanical damage will have a significant impact on productivity, particularly during early production stages. If the natural fractures and hydraulic fractures are connected, productivity will be more affected. The novelty of the new numerical models that it can characterize the heterogeneity of heterogeneous matrix, natural fractures, and hydraulic fractures in both the time domain and the spatial domain.
Assessing the Value of Reservoir Surveillance Data from Gas Fields Producing to LNG Plants Using VoI (the Value of Information)
Authors: O'Reilly Daniel Ian , Xia Zhi Qui , House Andrew Richard 
Published: October 2023

Abstract
A set of examples will be shared for calculating the value of reservoir surveillance conducted in gas fields tying into LNG plants. This includes such measurements as transient pressure, rate and temperature changes, fluid chemistry or diagnostic information related to well integrity. These data are typically gathered during production operations, but their value is rarely quantified. The objective of this paper is to use existing VoI methods to provide a means to justify this reservoir surveillance. The results will be useful for justifying routine surveillance activities to other departments in the upstream organisation, e.g. Operations and Facilities Engineering.
Established VoI methods will be applied to common surveillance problems occurring in production operations. In operating fields, gauges and metering equipment are already installed so there is no additional cost. However, surveillance may incur either personnel labour costs (when wells are still flowing) or lost production caused by shutting in wells (e.g. pressure transient tests). This is compared against the calculated value of a more reliable production forecast incorporating the new surveillance data. This value is realised when the future supply to a gas plant is ensured – i.e. avoiding future ullage or penalties from missed cargo deliveries.
Discussion is provided on the degree of uncertainty for which interpreted production data (pressure, rate flow and time) resolves reservoir parameters and forecasting metrics. This is known as imperfect information.
It is concluded that VoI is a powerful method with application in two areas. Firstly, it can be used in daily reservoir management and to increase production forecast reliability. Secondly, the surveillance data are used to inform future decisions such as infill drilling or compression projects (gas plant ullage). It is observed that management of operating companies are more inclined to agree to reservoir surveillance when its value is clearly calculated.
Several generic and non-specific case studies are given that could be applied to gas fields on the North West Shelf in Australia.
Most commonly, the VoI method is used prior to field development during the appraisal stage. The main difference for operating fields is that there are usually minimal material/service costs for these tests, but the cost relates to foregone production when the well is offline or curtailed. Few papers, if any, discuss its application to producing wells. However, in the upstream organisation the question of the value of surveillance arises and should be addressed.
Effects of Permeability Anisotropy and High Angle Completions on Non-Darcy Skin in Gas Wells
Authors: Xia Zhi , Terziev Ivaylo , Vasilyev Denis , Kazanov Dmitry , O’ Reilly Daniel Ian , House Andrew Richard 
Published: October 2023

Abstract
High-rate gas wells can be significantly impacted by the effects of non-Darcy skin. Since the prediction of well deliverability is affected, there are implications for production forecast reliability, reserves bookings, worst-case discharge modelling and relief well planning.
In this paper, adjustments are proposed to the inputs of conventional analytical equations for estimating D-factor. These proposals are applicable to gas wells penetrating formations with permeability anisotropy (kx/kz) at high angles.
Sensitivity analysis was performed using the Forchheimer pseudopressure inflow equation to evaluate the effects of varying the terms ‘permeability’ and ‘height’ on the predicted sandface drawdown. In textbook examples, the assumption is for a fully penetrating vertical well in a homogenous reservoir, where these two parameters are readily definable. For the more complex case considered here, the appropriate definitions for these two terms are less obvious.
Given that turbulence and inertial effects are most pronounced near the wellbore, it was postulated that use of the geometric average permeability and contributing completion length would result in more accurate estimations of D-factor. Spreadsheet calculations were performed to determine the impact of these changes for a range of scenarios. Verifications were subsequently performed using a numerical simulator.
It was observed that drawdown pressures are affected more as well angles and the vertical to horizontal permeability ratio increased. Generic examples are presented to help illustrate these dependencies, along with a brief discussion such changes can have on production forecasts and worst-case discharge estimates.
These proposed clarifications to the gas inflow equations were found to be undocumented in a survey of the literature, indicating a lack of published research in this area.
Enhancing Fracturing of Tight Carbonate Using Plug and Perf Technique- Case Study
Authors: Awad Mohamed Omar , Sajer Abdulaziz Ali , Qamber Anood Mohammad , Ibrahim Hamdi Saber , Robles Fernando , Song Quek Khang 
Published: October 2023

Abstract
The 1st oil in Kuwait was discovered in Bahrah in 1936. However, it was found uneconomical to develop this field due to complicated geological structure, formation tightness, cost and lack of technology at that time. In 2016, KOC has accomplished subsurface evaluation study to re-develop Bahrah field utilizing advanced fracturing technique. In last 5 years, the outcome of this study was applied successfully and resulted in remarkable production incremental from from ~3 MBOPD to more than 40 MBOPD. Multi-stage fracturing helped to unlock potential in most tightness carbonate formation in North Kuwait fields. Nevertheless, more studies was conducted to optimize the fracturing and completion design to improve well productivity as well as uniform production profile through well bore.
Multi stage fracturing in open hole was the common technique since new development plan started. Although this technique had positive impact on overall field production, but it was observed uneven flow through wellbore. An approach using Plug and Perforation technique was implemented successfully to reduce dissipate of fracturing energy during pumping and improve acid propagation.
Multi-stage fracturing completion in open hole horizontal wells has negative impact on acid propagation in comparison to the same for Plug and Perforation (PnP) Technique. The production logs was run in both cases and proved uniform production contribution in Plug and Perforation (PnP) technique.
The paper will discuss results of applied cases with two different fracturing techniques. In addition, it will share practical operation experience including upsides and downsides of each technique to reduce risk of execution.
Unconventional Fields Recovery Enabled By Large-Scale Green Power Supply Based on Multi Micro-Grids and Energy Storage Sharing with National Data Centers
Authors: Tong Zheng , Wang Xiaoqi , Weng Dingwei , He Chunming , Yang Rui , Zhang Zhigang , Qiang Sun 
Published: October 2023

Abstract
Unconventional oil and gas reserves have drawn considerable attention for petroleum companies over the last two decades. Eco-friendly electric-powered drilling rigs and fracturing fleets have been commercially available instead of diesel-powered equipment. However, Operators were often confronted with challenges of the great demand on electrical power especially fracturing operation. Fossil-energy-powered electricity and existing expensive high-voltage power grids have negative effect on Environmental-Social-Governance (ESG) initiatives and CAPEX of shale-oil developing projects. Additionally, although operators concern multi-energy complementary with regard to green energy such as solar energy and wind power, economic and efficiency drawbacks of green electricity caused by power uncertainties could not be ignored.
Unconventional reserves have been proved in Western China full of abundant green energy. As demonstrated in the national project of "Channels computing resources from east to west", computing-power data centers are constructed with electrochemical Energy-Storage System (ESS) in Western China and power source mainly stem from local green energy. In this paper one novel green-power supply solution based on capacity leasing and energy storage sharing with data centers was proposed due to electrical power surplus. One hybrid power network, combining 35kV grid with Multi Micro-grids (MMGs) between green-power stations and oil field pads, was planned to be constructed by operators. One ESS-based system integrating MMGs was set up in one case demonstration. Some mobile energy-storage units were used for cost-effective power supply and peak shaving on certain pads due to poor load curves. The solution feasibility was verified and compared with the traditional power supply mode. ESS-based system with MMGs is qualified for affordable green-powered well construction and sustainable development of unconventional oil fields.
Multicomponent Fluid (H2/CO2-CH4-H2O) Occurrence Characteristics in Shale Nanopores: Insights from MD Simulations
Authors: Zhao Yulong , Guan Bowen , Hu Haoran , Wang Shuolong , Wang Suran , Wu Jiayi , Huang Yishu , Zhang Tao 
Published: October 2023

Abstract
Due to the emissions of greenhouse gasses, the climate change has greatly threatened people's living environment, urging to reduce CO2 in the atmosphere and promote carbon-free energy structures. Large-scale underground H2/CO2 storage emerges as a promising technology for H2 seasonal supply and CO2 reduction. The depleted shale gas reservoir presents a favorable site due to its abundance of nanopores, which inherently prevents leakage and ensures long-term storage. However, the coexistence of H2/CO2 with the original water in the nanopore results in the formation of a ternary mixture system (H2/CO2-CH4-H2O), as water is ubiquitous within organic-rich shale. This transformation leads to the primary CH4-H2O binary mixture interaction evolving into a H2/CO2-CH4-H2O ternary mixture interaction, introducing complexity to the intermolecular interactions within the nanopores and rendering the occurrence characteristics of multicomponent fluids uncertain. In this study, we constructed a shale organic nanopore using a realistic kerogen model and conducted molecular dynamics (MD) simulations to gain insights into the occurrence characteristics of multicomponent fluids within the organic nanopore. The results reveal that, due to their inherent affinities towards the kerogen, these two ternary mixture systems exhibit distinct occurrence characteristics. In the H2-CH4-H2O system, H2 predominantly exists near the pores without the formation of an adsorption dense layer near the walls, resulting in a relatively high diffusion capacity. However, in the CO2-CH4-H2O system, CO2 tend to occupy adsorption sites and strips CH4 into the bulk free region due to the more attractive interaction upon kerogen, greatly restricting CO2 diffusion capacity due to limited vacancies along the dense layer. Our work is expected to provide a deeper insight into multicomponent fluid occurrence characteristics within shale organic nanopores, which could serve as a guideline for large-scale underground H2/CO2 storage evaluations.
Applying Downhole Wireless Telemetry System to Water Flooding Operation
Authors: Chen Qiang , Jia De-li , Sun Fu-chao , Hao Zhong-xian , Huang Shou-zhi , Zhu Shi-jia 
Published: October 2023

Abstract
Water flooding had proved its value in oil recovery enhancement. Generally downhole data was obtained through electric cable which increased the cost significantly, meanwhile the communication was often interrupted due to sealing issues in the cable system.
This paper focused on theoretical modeling of electromagnetic waves as it propagated across different downhole mediums, including casing, cement, and reservoir with varied electrical resistivity. The preparedness of the telemetry system was presented from the perspective of field operation, finally the case study of water flooding operation with telemetry system equipped was described in details.
Based on the attenuation model, 6.25Hz electromagnetic wave could reach 3000m deep underground with residual strength of 0.1mV, provided the average electrical resistivity exceeded 10Ω·m which was not too demanding. The telemetry system comprised of three parts which are signal sender, metal connector and decoding device on the ground. Viability tests were carried out to optimize the frequency and power setup, making it adaptable for water flooding operations. The system was integrated with water injector and trialed in the oilfield, while electric cable was used to verify the wireless system. According to the feedback, the pressure and flowrate data were received through 5Hz electromagnetic waves in a real-time manner from 1025m deep underground, its accuracy was approved by the data obtained via electric cable, the flowrate control instruction was also passed through wireless system and the nozzle downhole responded correctly. The system could replace cable in the future popularization of water flooding operation, reducing the risk and the capex.
Intelligent oilfield has been the objective and pursued constantly, matured downhole wireless telemetry system was an integral part of this process. This study has expand our horizons the knowledge on this lucrative subject, successful application of wireless telemetry system in the water flooding operations gave us more insights in how to reach the goal.
Application of Proxy Model and Reservoir Simulation for CO2 Injection Optimization in Multi-Layer Depleted Reservoirs: A Case Study of CCS Project in Gulf of Thailand
Authors: Tripoppoom Sutthaporn , Doungprasertsuk Chonlada , Pongthunya Potcharaporn , Prasertbordeekul Taweewat 
Published: October 2023

Abstract
PTTEP has committed to achieve net zero greenhouse gas emission in 2050 and the CCS project in the gulf of Thailand is the first CCS planned by PTTEP to achieve this goal. To evaluate the feasibility of the project, the reservoir simulation study was extensively performed from the geological, petrophysical, seismic inversion and reservoir engineering input. One of the keys in CCS project is the CO2 injection strategy and CO2 storage volume. Therefore, the objective of the study is to determine the optimized injection strategy and storage volume for CO2.
Normally, the CO2 injector locations were targeted at the high permeability-thickness (KH) location based on reservoir simulation model. However, the optimization of injection with many layers in depleted reservoirs is cumbersome and required up to millions of simulation runs which is not possible to be performed. Therefore, this study proposes the new workflow to optimize the injection strategy by integrating reservoir simulation and proxy model or surrogate model simplified from actual simulation model results as pre-screening. First, we identify well location candidates based on KH map, pressure and shale thickness. Then, we construct the creaming curves scenario from reservoir simulation model and input them to train proxy model.
With this workflow, instead of evaluating millions of injection scenarios by reservoir simulation, consisting of which well location and which reservoirs to be injected as separate target or commingle, we instead optimized the time required to obtain the injection strategy firstly from proxy model as pre-screening. Then, we run these possible optimized scenarios from proxy model to be run with reservoir simulation model. Finally, we obtain the most optimized injection strategy from simulation model including selected injector locations, number of injectors and sand targets for each injector. This can be obtained by evaluating the cumulative CO2 injection volume per number of injectors. To conclude, the optimized scenario of CO2 injection strategy and volume were determined and ready to be coupled with the integrated model including geomechanics, geochemistry and thermal simulation.
With the proposed workflow, the study is the first CCS project in Thailand that adopts the injection strategy optimization based on the integration of dynamic reservoir simulation and proxy model. The proposed workflow can be used as the practical and robust injection optimization workflow used in any future CCS project in depleted reservoirs with multi-layers.
A Novel Inter-Porosity Flow Model for Multi-Scale Shale Reservoirs with Nonuniform Laminated Fractures
Authors: Zhang Qian , Wang Wengdong , Su Yuliang , Yu Wenfeng 
Published: October 2023

Abstract
In shale reservoirs, the presence of nano-scale pores and natural fractures leads to various phenomena, such as micro-scale effects and media deformation. Further studies are necessary to better understand the flow mechanisms occurring within nanopores and micro-fractures. Moreover, the flow relationship among organic pores, inorganic pores, and laminated fractures is not well understood and the existing methods for evaluating shale oil productivity do not adequately account for the heterogeneous distribution of laminated fractures. Therefore, the primary objective of this paper is to develop a comprehensive mathematical model that encompasses multi-scale and multi-mechanism coupled flow for shale oil reservoirs, with a specific emphasis on characterizing the inter-porosity flow occurring between different media. The apparent permeability model has been established coupling adsorption, slip, and stress sensitivity characteristics of matrix. By utilizing fractal theory, the non-uniform characteristics of aperture, density, and tortuosity in laminated fractures have been characterized, and finally, an inter-porosity flow model that is applicable to stress-sensitive multi-porosity media has been developed. The accuracy of the model is validated using numerical solution and actual production data with excellent agreement. Notably, the semi-analytical model significantly reduces the computation time. The study investigates the permeability loss of multi-porosity media during production. The results show that the permeability loss of matrix is less than 4%, and that laminated fractures exhibit a significant permeability loss around 30%, while hydraulic fractures suffer a substantial permeability loss exceeding 90%. Oil production varies across media and the contribution of laminated fractures to oil production can reach as high as 80%. Analysis of the heterogeneity of laminated fractures indicates that fractal dimension has a significant effect on the density, aperture, and tortuosity, especially near hydraulic fractures, where density and aperture decrease rapidly with distance. Sensitivity analysis has shown that longer hydraulic fracture can make the single well maintain higher production for a long time.