Comparative Study of Yield-Power Law Drilling Fluids Flowing Through Annulus

An exact solution for calculating the frictional pressure losses of yield-power law (YPL) fluids flowing through concentric annulus is proposed. A solution methodology is presented for determining the friction factor for laminar and nonlaminar flow regimes. The performance of the proposed model is compared to widely used models as well as the experimental results of 10 different mud samples obtained from the literature. The results showed that the proposed model could estimate the frictional pressure losses with an error of less than 10% in most cases for both laminar and nonlaminar flow regimes, more accurately than the widely used models available in the literature.     

A Mechanistic Model for Predicting Frictional Pressure Losses for Newtonian Fluids in Concentric Annulus

Abstract

A mathematical model is introduced estimating the frictional pressure losses of Newtonian fluids flowing through a concentric annulus. A computer code is developed for the proposed model. Also, extensive experiments with water have been conducted at Middle East Technical University, Petroleum and Natural Gas Engineering Department Flow Loop and recorded pressure drop within the test section for various flow rates. The performance of the proposed model is compared with computational fluid dynamics (CFD) software simulated annulus flow section and various criteria such as crittendon, hydraulic diameter and slot flow approximation as well as experimental data. The results showed that the proposed model and experimental results are in good agreement for almost all cases when compared with the other criteria and CFD software. Also, the proposed model could estimate the frictional pressure losses for both laminar and turbulent flow regimes within an error range of ±10%.     

Modelling of Two-Phase Flow Through Concentric Annuli

Abstract

A mathematical model is introduced in order to predict the flow characteristics of multiphase flow through an annulus. Flow patterns and frictional pressure losses estimated using the proposed model are compared with the experimental data of a wide range of liquid and gas flow rates recorded at a flow loop consisting of numerous circular pipes and annulus. The results showed that the model predictions for flow patterns and frictional pressure losses are reasonably accurate. Moreover, it is observed that geometry and liquid phase viscosity have a significant influence on flow pattern transitions and frictional pressure losses.     

内管旋转的垂直同心环形管内单相流动特性的试验研究

分别以空气、油、水为工作介质对内管旋转的垂直同心环形管内的单相流动特性进行了系统的试验研究。首先在100 Re 70000的范围内对内管不转的环形管内的摩擦阻力进行了试验测定,并与几种摩阻关系式进行了比较,得出同心环形管内紊流摩擦系数比圆管摩擦系数约高6%~10%,Sadatomi的关系式可用于4000 Re 70000的范围内的紊流计算。采用测量轴向摩擦压降的方法,对内管旋转的环形管内的流动离心不稳定性以及摩阻进行了试验研究,得出了直径比小于0.8时,层流向层流+Taylor涡旋的转换边界及紊流+Taylor涡旋向紊流的过渡边界,并针对不同流型给出了适用于较大环形间隙环形管的摩阻关系式。     

Modelling of Two-Phase Flow Through Concentric Annuli

A mathematical model is introduced in order to predict the flow characteristics of multiphase flow through an annulus. Flow patterns and frictional pressure losses estimated using the proposed model are compared with the experimental data of a wide range of liquid and gas flow rates recorded at a flow loop consisting of numerous circular pipes and annulus. The results showed that the model predictions for flow patterns and frictional pressure losses are reasonably accurate. Moreover, it is observed that geometry and liquid phase viscosity have a significant influence on flow pattern transitions and frictional pressure losses.     

The Investigation of Vertical Wells' Optimum Two-phase Flow Empirical Correlation for the Ab-Teymour Reservoir

Abstract

There are different procedures for predicting pressure drop in two-phase flow pipelines. However, for each reservoir one or two correlations or mechanistic models give more accurate results. The authors investigated various correlations and mechanistic models in order to match fluid pressure losses considering all parameters such as friction, liquid holdup, superficial velocities, densities, viscosities, and interfacial tension. Commercial software, Pipesim, was used to simulate the fluid pressure losses. Drift flux modeling for predicting pressure profile was also investigated. A program for calculating pressure drops and average deviation of calculated pressures using this drift flux model was developed and the results were compared with other correlations.     

Mathematical Model For Bubbly Water-Heavy Oil-Gas Flow in Vertical Pipes

Abstract

In this work a unidimensional, time-dependent homogeneous mathematical model is presented. The model is able to predict pressure, temperature and velocity profiles of the flow known as bubbly-gas—bubbly-oil, which can be present when water-heavy oil and gas flow simultaneously in vertical pipes. The mathematical model consists of mass, momentum, and energy conservation equations and its numerical solution is based on the finite difference technique in the implicit scheme. The thermodynamic and transport properties of the fluids are estimated by correlations reported in the literature. The effects of different water-gas and water-oil shear stress correlations on the prediction were evaluated. As a result, some correlations are recommended to simulate the bubbly-gas—bubbly-oil flow. A new correlation for water-heavy oil-gas friction factor is suggested. A comparison of the model with existing experimental data shows a satisfactory agreement.     

Pressure Loss at the Bit While Drilling with Foam

Abstract

Foam is one of the most frequently used drilling fluids at underbalanced drilling operations. As foam flows, due to the pressure drop, a volumetric expansion is observed, which causes the foam quality to increase in the same direction with flow. Flow of foams through circular pipes and annular geometries are well studied. Interestingly, although one of the major sources of pressure drop is at the bit, there have been few studies of this subject for foams. Many drilling parameters including hole cleaning capacity, volumetric requirements of liquid and gas phase, and backpressure are out of control if the pressure drop at the bit is not accurately determined, even though pressure drops inside the pipes and wellbore are properly determined. This article introduces a more accurate model for estimating the pressure drop of foam flowing through the bit. The major difference between the proposed and the existing models is that the proposed model includes the effect of foam expansion and velocity change as a function of pressure. Pressure drop has been observed to increase significantly as the upstream pressure and foam average velocity increases when compared with the existing models. For the same flow conditions, pressure drop decreases as the foam quality increases, and as the upstream pressure increases, pressure drop also increases. The existing models cannot detect this event at all. In some cases, the pressure drop at the bit can be 10 times greater than the pressure drop predicted from existing models.     

Surge Analysis of Multiphase Flow in a Gathering Manifold

Abstract

Analysis of pressure transients in multiphase flow in a real flow line upstream of a manifold in an oil-gathering station in the presence of slug flow is presented. The transient analysis is based on the solution of the partial differential equations governing the pressure transients using the method of characteristics. The analysis permitted the identification of pipe material and valve closure time combinations that could lead to unacceptable pressure levels in the flow line and the combinations that represented a safe configuration. The results revealed that pressure surge could be responsible for a glass reinforced epoxy (GRE) pipe installed in one oil-gathering station.     

基于锥形层流元件的气体微小流量测量研究

目的 常规毛细管层流流量测量技术因层流传感元件结构而存在进出口压损等非线性问题。因此,须改进层流传感元件,解决非线性问题。方法 提出了一种锥形结构的层流元件,利用在层流充分发展段直接取压的优势,有效解决层流起始段非线性压损问题,能直接反映流量与差压之间的线性关系。设计并加工了3种不同间隙的锥形层流元件,搭建了空气微小流量测量系统。结果 在0.015 0～2.348 1 kg/h气体流量范围内,3套装置的测量误差均小于±2%,其中,基于间隙为0.7 mm的锥形层流元件装置的测量误差最小,小于±1%。结论 锥形层流元件用于天然气等气体微小流量测量方面具有良好性能。     

水平井井筒变质量流动压降计算新模型

为了使水平井变质量流压降模型更具合理性和准确性,更有效地分析油井产能和生产动态,通过回顾和分析以往关于水平井筒压降模型的计算理论与方法,利用现有实验数据回归分析建立了一种新的射孔完井压降计算回归模型,该模型能够实现射孔完井孔密、相位角连续变化时综合摩擦系数的求取和井筒压降的计算。通过实例对比分析可以看出,该模型和目前常见模型的计算精度较为接近、计算结果较为合理。该模型的提出可以为进一步改进油藏渗流与井筒流动耦合模型的理论研究提供参考。     

Hydrochloric acid diffusion coefficients at acid-fracturing conditions

The reaction of a 15% HCl solution with Indiana Limestone was investigated at 93 °C and 34.5 MPa using an annular flow reactor that was erected vertically. The laminar flow conditions were such that both free and forced convections contributed to the overall mass-transfer rate. The experimental results correlated well with theory when the forced and free convections were in the same direction (assisting flow) and when free-convection mass transfer dominated the mass-transfer process. Deviation from theory, however, occurred when free convection was in the opposite direction to forced convection (opposing flow). Correlating the experimental results with theory provided a method for the determination of the effective diffusion coefficient of HCl at the high temperature, pressure and acid concentrations encountered in acid-fracturing treatments. An HCl effective diffusion coefficient of 5.25 × 10⁻⁵ cm²/s was found from correlating the present experimental results with theory.Recent trend in designing acid-fracturing treatments is to use computer models to predict and optimize the etched length of the created fracture. The accuracy and reliability of such computer model predictions depend heavily on the accuracy of the values used for physical parameters such as reaction rate and diffusion coefficient of HCl. The annular flow reactor and the correlations discussed here provide a way to obtain reaction rates and diffusion coefficients at practical conditions for use in computer models and design of acid-fracturing treatments.     

垂直上升管内油水乳状液流动特性的研究

在石油、化学工业中,经常会遇到油水两种互不相溶的液体共同流动的情况.由于油水乳状液的广泛存在,以及采出液含水率的不断提高,导致油气集输过程中输液量的大幅度增加,给油气集输工艺和设备带来了新的困难.文中对垂直上升管内油包水型(W/O)和水包油型(O/W)油水乳状液的流动特性进行了实验研究.实验参数范围:含水率εw=0.0～1.0;压力p=0.1～0.6MPa;流量Q=0.14～1.7kg/s;温度T=10～45℃.实验结果分析得出了一个新的油水乳状液表观粘度的表达式,此表达式优于文献中别的预测模型,其计算值和实验结果吻合良好;同时得出一个新的油水乳状液发生相转变的判别式,分析了在相转变点附近油水乳状液在垂直上升管内的流动状态以及发生相转变和流量、含水率的关系;提出了采用Re和摩擦阻力系数的关联式计算摩擦阻力的方法,得到判别油水乳状液为牛顿流体和非牛顿流体的方法.该研究结果对管道输送系统的设计有一定的参考价值.     

计算流体力学方法模拟规整填料塔内流体流动行为的研究进展

对采用计算流体力学(CFD)方法模拟规整填料塔内流体流动行为的研究进展进行了综述,分别介绍了单相流模型和两相流模型。单相流模型可预测气相或液相在规整填料塔内轴向、径向的扩散行为及气相的压头损失等;两相流模型主要研究规整填料塔内气液相流动行为,利用该模型可计算液体在规整填料表面的流动过程及气液相间的传质行为,其模拟结果比单相流模拟更接近实际。随流体力学学科和计算机技术及现代测量技术的进一步发展,将会促进CFD技术在化工过程中的应用。     

A homogeneous model for gas–liquid flow in horizontal wells

Radial influx or outflux stands for the major difference between fluid flow in a pipe and fluid flow in a well. A homogeneous model for gas–liquid flow in a horizontal well is presented in this paper. In addition to frictional and gravitational components of total pressure drop, accelerational pressure drops due to fluid expansion and radial influx or outflux are considered. Effect of radial influx or outflux on wall friction is also taken account for. With a segmented approach, the new model and several existing pipe flow models have been applied to predict pressure drop along a wellbore, and predictions are compared with experimental data. It is found that the new homogeneous model outperforms existing models for gas–liquid flow in horizontal wells.     

四参数流变模式及其水力计算模型

提出了一种四参数流变模式,该模式能够精确地描述各种无时间依存关系的钻井液体系。利用多组测量数据评价了四参数流变模式对不同流体的拟合效果。根据管流特性参数法,并扩展应用到环空中,推导了管内与环空的层流压降计算公式,同时给出了紊流计算的半经验公式。通过引入广义流性指数的方法,给出了流态判别模型,使层流与紊流计算一致。根据四参数水力计算模型编制了计算机程序,利用一组不同来源的实验数据(包括管内与环空各种钻井液下的层流和紊流流动),验证了四参数模式的水力计算模型。与实测数据的对比表明,该模型计算结果与测量数据吻合得很好。说明该模式的水力计算模型要优于当前可用的流变模式。     

Friction Factor Determination for Horizontal Two-Phase Flow Through Fully Eccentric Annuli

Abstract

In this study, empirical friction factor correlations were developed for two-phase stratified- and intermittent-flow patterns through horizontal fully eccentric annuli. Two-phase flow hydraulics were investigated, and a flow pattern prediction model is proposed. The friction factor correlations were validated using experimental data collected at the multiphase flow loop METU-PETE-CTMFL. Two different geometrical configurations were used during experiments—that is, 0.1143 m inner diameter (ID) casing, 0.0571 m outer diameter (OD) drillpipe; and 0.0932 m ID casing, 0.0488 m OD drillpipe. The eccentric annuli has been represented by representative diameter d _r . A new mixture Reynolds number based on liquid holdup is proposed for friction factor determination.     

Estimation of oil and gas properties in petroleum production and processing operations using rigorous model

Wellhead chokes are widely used in the petroleum industry. Owning to the high sensitivity of oil and gas production to choke size, an accurate correlation to specify choke performance is vitally important. The aim of this contribution was to develop effective relationships among the liquid flow rate, gas liquid ratio, flowing wellhead pressure, and surface wellhead choke size using the support vector machines (SVMs). The accurate data set was gathered from the 15 different fields containing 100 production samples from the vertical wells at wide ranges of wellhead choke sizes. This computational model was compared with the previous developed correlations in order to investigate its applicability for subcritical two phase flow regimes through wellhead chokes. Results confirmed amazing capability of the SVM to predict liquid flow rates. The value of R² obtained was 0.9998 for the SVM model. This developed predictive tool can be of massive value for petroleum engineer to have accurate estimations of liquid flow rates through wellhead chocks.     

产水气藏气液两相管流动态规律研究

由于气液两相流流型的多变性和流动机理的复杂性,需要建立适用于任何流动条件的压降模型。目前工程常用的两相流压降模型主要是基于圆管流动实验数据得到的,其适用条件均具有一定的局限性。对于含水气井,其气水比一般比油井高得多,而且水和油物性差异大,气水两相流液体滑脱严重。现有的两相流压降模型用于气井压降预测时误差较大。因此对其进行了修正,给出了修正曲线。依据气水两相流实验,深入研究了气水两相上升流流动机理及特性参数变化规律,在现有气液两相流压降模型基础上探讨了适用于产水气井的H-B修正模型,应用现场资料对该模型进行的评价和验证表明,提高了预测产水气井压降分布的准确性,更符合实际情况。