Theoretical and experimental study of the pulling force of jet bits in radial drilling technology

Radial drilling technology,of which the jet bit is the key device,is a research focus in the field of oil drilling and production.This paper establishes mechanical equations for jet bits and analyzes the hydroseal of backward jets in bottom holes.Meanwhile this paper establishes a mechanical equation for a high pressure hose and analyzes the axial force distribution.Laboratory experiments indicate that the flow rate,the angle between the backward nozzle axis and the jet bit axis,and the hole diameter are the major influencing factors;the generation of the pulling force is mainly due to the inlet pressure of the jet bit;the backward jets can significantly increase not only the pulling force but also the stability of jet bits.The pulling force would reach 8,376 N under experimental conditions,which can steadily pull the high-pressure hose forward.

Intelligent Drilling and Completion:A Review

The application of artificial intelligence(AI)has become inevitable in the petroleum industry.In drilling and completion engineering,AI is regarded as a transformative technology that can lower costs and significantly improve drilling efficiency(DE),In recent years,numerous studies have focused on intelligent algorithms and their application.Advanced technologies,such as digital twins and physics-guided neural networks,are expected to play roles in drilling and completion engineering.However,many challenges remain to be addressed,such as the automatic processing of multi-source and multi-scale data.Additionally,in intelligent drilling and completion,methods for the fusion of data-driven and physicsbased models,few-sample learning,uncertainty modeling,and the interpretability and transferability of intelligent algorithms are research frontiers.Based on intelligent application scenarios,this study comprehensively reviews the research status of intelligent drilling and completion and discusses key research areas in the future.This study aims to enhance the berthing of AI techniques in drilling and completion engineering.

Editorial for the Special Issue on Unconventional and Intelligent Oil and Gas Engineering

A key global challenge in the 21st century is how to secure sustainable access to energy for a growing global population—set to reach 10 billion by 2035—while coping with the threat of dangerous climate change.The oil and gas industry will still play an essential role in the energy transition by providing affordable and reliable energy to improve living conditions.Meanwhile,producing this energy with decreasing emissions supports a net-zero world.

Bottom hole pressure prediction based on hybrid neural networks and Bayesian optimization

Many scholars have focused on applying machine learning models in bottom hole pressure (BHP) prediction. However, the complex and uncertain conditions in deep wells make it difficult to capture spatial and temporal correlations of measurement while drilling (MWD) data with traditional intelligent models. In this work, we develop a novel hybrid neural network, which integrates the Convolution Neural Network (CNN) and the Gate Recurrent Unit (GRU) for predicting BHP fluctuations more accurately. The CNN structure is used to analyze spatial local dependency patterns and the GRU structure is used to discover depth variation trends of MWD data. To further improve the prediction accuracy, we explore two types of GRU-based structure: skip-GRU and attention-GRU, which can capture more long-term potential periodic correlation in drilling data. Then, the different model structures tuned by the Bayesian optimization (BO) algorithm are compared and analyzed. Results indicate that the hybrid models can extract spatial-temporal information of data effectively and predict more accurately than random forests, extreme gradient boosting, back propagation neural network, CNN and GRU. The CNN-attention-GRU model with BO algorithm shows great superiority in prediction accuracy and robustness due to the hybrid network structure and attention mechanism, having the lowest mean absolute percentage error of 0.025%. This study provides a reference for solving the problem of extracting spatial and temporal characteristics and guidance for managed pressure drilling in complex formations.

Large-Scale Underground Storage of Renewable Energy Coupled with Power-to-X:Challenges,Trends,and Potentials in China

1.Introduction Promoting the green and low-carbon transition of energy systems and constructing a new renewable-dominated power system is essential to achieving carbon neutrality in China[1,2].Furthermore,implementing electrification and hydrogenation strategies to address energy consumption is necessary for a successful energy transition.China’s share of electricity in its total energy consumption is estimated to increase from 26%in 2021 to more than 70%by 2060.

超疏水材料的研究进展

近年来,油水分离技术越来越受到人们的重视,而具有特殊润湿性的油水分离材料成为研究热点。文中综述了超疏水材料在油水分离领域的研究进展。简单地介绍了构建超疏水材料的基本原理,归纳总结了超疏水材料的制备方法如水热法、刻蚀法、静电纺丝技术、自组装技术、溶胶-凝胶法和沉积法等方法,并且讨论了不同方法的优缺点及前景,为今后超疏水材料的发展提供理论建议。

Performance Analysis of Composite Magnetic Circuit Permanent Magnet Wind Generator

In order to reduce the starting wind speed of the wind wheel and improve the efficiency of the wind wheel, this paper proposes a new type of composite magnetic circuit permanent magnet generator, which changes the relationship between the magnetic induction intensity and the air gap by changing the structure of the main magnetic circuit. The structure greatly improves the air gap sensitivity of the generator, which makes the structural design of the permanent magnet generator easier to implement. Finally, the effectiveness and feasibility of the method are verified by simulation.

陆相中低熟页岩油富集与原位转化科学问题及关键技术

围绕第281期双清论坛主题,本文回顾了陆相中低熟页岩油富集与原位转化研究现状,从陆相页岩油概念与类型、富有机质页岩形成机理、原位转化反应与传热机制、原位转化流动机制与原位开发技术五方面总结归纳了近年来的主要研究进展。从陆相有机质超量富集的环境响应与地质模型、陆相有机质超富段母质结构、能量场与产出物构成和固、液、气相有机质多相态、多场耦合流动机理三个方面归纳了关键科学问题与技术需求,并提出了五方面研究面临的难点和挑战,梳理了未来研究重点方向和国家自然科学基金资助的目标。

Settling behavior of non-spherical particles in power-law fluids:Experimental study and model development

Solid-particle settling occurs in many natural and industrial processes, such as in the transportation of drilling cuttings and fracturing proppant. Knowledge of the drag coefficient and settling velocity of cuttings and proppant is of significance to hydraulics design, wellbore cleanout, and fracture optimization. We conducted 553 tests to investigate the settling characteristics of spherical and non-spherical particles in power-law fluids. Three major particle shapes (spherical, cubic, and cylindrical) and eight different particle sphericities were used to simulate cuttings and proppant, and power-law fluids were applied to simulate drilling and fracturing fluids. Based on the data analysis, a new drag coefficient-particle Reynolds number correlation was developed to determine the drag coefficient in a power-law fluid for spherical and non-spherical particles. The drag coefficient increases as the sphericity decreases for the same particle Reynolds number. For a specific particle shape, the drag coefficient decreases as the particle Reynolds number increases, but the decreasing trend is reduced at high particle Reynolds number conditions. An explicit settling-velocity equation was proposed to calculate the settling velocity of spherical and non-spherical particles in power-law fluids by considering the effect of sphericity. A suitable range for the proposed model is 0.0001 < Re <200, 0.471 <φ< 1, and 0.505 < n < 1. An illustrative example is presented to show how to calculate the drag coefficient and settling velocity in power-law fluids with given particle and fluid properties.

Settling behavior of spherical particles in vertical annulus:Experimental study and model development

Coiled tubing(CT)drilling technology offers significant advantages in terms of cost and efficiency for exploitations of unconventional oil and gas resources.However,the development of CT drilling technol-ogy is restricted by cuttings accumulation in the wellbore due to non-rotation of the drill string and limited circulating capacity.Cuttings cleaning becomes more difficult with the wall resistance of pipe-wellbore annulus on the cutting transport.Accurate description of particle transport process in the pipe-wellbore annulus is,therefore,important for improving the wellbore cleanliness.In this study,high-speed cam-era is used to record and analyze the settling process of particles in the transparent annulus filled with power-law fluids.A total of 540 tests were carried out,involving dimensionless diameters of 0.10-0.95 and particle Reynolds Numbers of 0.01-12.97,revealing the effect of the dimensionless diameter and particle Reynolds number on the annulus wall effect,and the wall factor model with an average relative error of2.75%was established.In addition,a dimensionless parameter,Archimedes number,independent of the settling velocity,was introduced to establish an explicit model of the settling velocity of spherical particles in the vertical annulus,with the average relative error of 7.89%.Finally,a calculation example was provided to show how to use the explicit model of settling velocity in annulus.The results of this study are expected to provide guidance for field engineers to improve the wellbore cleanliness of coiled tubing drilling.

Expulsive force in the development of C02 sequestration:application of SC-C02 jet in oil and gas extraction

With the rapid development of global economy,an increasing amount of attention has been paid to the emission of greenhouse gases,especially CO2.In recent years,dominated by the governments around the world,several significant projects of CO2 sequestration have been conducted.However,due to the huge investment and poor economic effects,the sustainability of those projects is not satisfactory.Supercritical CO2(SC-CO2)has prominent advantages in well drilling,fracturing,displacement,storage,plug and scale removal within tubing and casing,which could bring considerable economic benefits along with CO2 sequestration.In this paper,based on physicochemical properties of SC-CO2 fluid,a detailed analysis of technical advantages of SC-CO2 applied in oil and gas development is illustrated.Furthermore,the implementation processes of SC-CO2 are also proposed.For the first time,a recycling process is presented in which oil and gas are extracted and the CO2 generated could be restored underground,thus an integrated technology system is formed.Considering the recent interests in the development of enhancing hydrocarbon recoveries and CO2 sequestration,this approach provides a promising techni?que that can achieve these two goals simultaneously.

Predicting wall drag coefficient and settling velocity of particle in parallel plates filled with Newtonian fluids

The hindrance of boundary to particle transport exists widely in various industrial applications.In this study,the wall drag force of parallel plates on settling particles was revealed through settling experiment.High-speed camera was used to record and analyze the settling process of particles in parallel plates that are filled with Newtonian fluids.A total of 600 experiments were carried out,involving the range of relative diameter and particle Reynolds number of 0.01-0.95 and 0.004-14.30,respectively.The wall drag coefficient was defined to quantitatively analyze the wall drag force of the parallel plates.The influence of relative diameter,particle properties,rheological properties,and the settling dynamic process on the wall drag coefficient was revealed,and the wall drag coefficient model with mean relative error of 5.90% was established.Furthermore,an explicit settling velocity model with mean relative error of 8.96% for the particle in parallel plates was developed by introducing a dimensionless variable independent of settling velocity,the Archimedes number.Finally,a calculation example was provided to clarify the using process of the explicit model.This research is expected to provide guidance for optimizing water hydraulic fracturing in the oil and gas industry.

Research advances in multi-field coupling model for geothermal reservoir heat extraction

As a kind of clean renewable energy,the production and utilization of geothermal resources can make a great contribution to optimizing the energy structure and energy conservation and emission reduction.The circulating heat extraction process of working fluid will disturb the equilibrium state of physical and chemical fields inside the reservoir,and involve the mutual coupling of heat transfer,flow,stress,and chemical reaction.Revealing the coupling mechanism of flow and heat transfer inside the reservoir during geothermal exploitation can provide important theoretical support for the efficient exploitation of geothermal resources.This paper reviews the research advances of the multi-field coupling model in the reservoir during geothermal production over the past 40 years.The thrust of this paper is on objective analysis and evaluation of the importance of each coupling process and its influence on reservoir heat extraction performance.Finally,we discuss the existing challenges and perspectives to promote the future development of the geothermal reservoir multi-field coupling model.An accurate understanding of the multi-field coupling mechanism,an efficient cross-scale modeling method,as well as the accurate characterization of reservoir fracture morphology,are crucial for the multi-field coupling model of geothermal production.

Key problems and solutions in supercritical CO2 fracturing technology

Supercritical CO2 fracturing is considered to be a new method for efficient exploitation of unconventional reservoirs,such as shale gas,coal bed methane,and tight sand stone gas.Supercritical CO2 has many special properties including low viscosity,high diffusion coefficient,and lack of surface tension,which brings about great advantages for fracturing.However,these properties also cause several problems,such as difficulty in proppant transportation,high friction loss,and high pump displacement.In this paper,the above problems were analyzed by combining field test with laboratory study and specific solutions to these problems are given.The high frictionloss in the pipeline could be reduced by developing a new drag reducing agent and selecting large-size casing.Besides,for the problem of poor capacity in proppant carrying and sand plug,the methods of adding tackifier into supercritical CO2,increasing pump displacement and selecting ultralow density proppants are proposed.Moreover,for the problem of fast leak-off and high requirement for pump displacement,the displacement can be increased or the pad fluid can be injected into the reservoir.After solving the above three problems,the field test of supercritical CO2 fracturing can be conducted.The research results can promote the industrialization process of supercritical CO2 fracturing.

Throttle characteristics of multi-stage circumfluence nozzle during the separate-layer injection of CO_(2)

Separate-layer injection of CO2 is an important method to improve oil and gas production and recovery.Conventional single-stage nozzle is usually blocked by impurities,and the ice-barrier phenomenon is very common.To solve this problem,large-diameter multi-stage circumfluence nozzle was designed to release pressure stage by stage.In order to illuminate the throttle characteristics of the CO2 multi-stage circumfluence nozzles,numerical simulation was performed to test several nozzles with different diameters and stage numbers.Furthermore,we tested the throttle characteristics through laboratory experiments and obtained the effects of several critical parameters such as nozzle diameter,number of stage and pressure drop on the throttle characteristics.The results show that the flow rate decreases as the nozzle stage increases on the condition of constant pressure and nozzle diameter.And pressure difference increases as nozzle stage number increases under the constant flow rate.The throttle capability of multi-stage circumfluence nozzles was much better than the concentric nozzles.Large-diameter multi-stage nozzle is recommended rather than small-diameter single-stage nozzle during the process of separate-layer injection,which can efficiently prevent impurities and ice blocking.The results are expected to provide a theoretical support for the nozzle choice of separate-layer injection of CO2.