Estimating Flow Patterns and Frictional Pressure Losses of Two-Phase Fluids in Horizontal Wellbores Using Artificial Neural Networks

Underbalanced drilling achieved by gasified fluids is a very commonly used technique in many petroleum-engineering applications. This study estimates the flow patterns and frictional pressure losses of two-phase fluids flowing through horizontal annular geometries using artificial neural networks rather than using conventional mechanistic models. Experimental data is collected from experiments conducted at METU-PETE Flow Loop as well as data from literature in order to train the artificial neural networks. Flow is characterized using superficial Reynolds numbers for both liquid and gas phase for simplicity. The results showed that artificial neural networks could estimate flow patterns with an accuracy of 5%, and frictional pressure losses with an error less than 30%. It is also observed that proper selection of artificial neural networks is important for accurate estimations

Pressure Loss at the Bit While Drilling with Foam

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

PHPA as a Frictional Pressure Loss Reducer and Its Pressure Loss Estimation

This article analyzes the performance of a liquid polymer emulsion containing partially hydrolyzed polyacrylamide/polyacrylate (PHPA) copolymer as a circulating system pressure loss (drag) reducer. Straight cylindrical pipe flow experiments were performed at different concentrations of solutions for measuring frictional pressure losses. Comparison of measured and theoretical frictional pressure loss values showed that as the PHPA concentration increased, considerable drag reduction (as high as 60%) was achieved and the optimum PHPA concentration for drag reduction purposes was estimated as 0.0020 (v/v). A friction factor is developed as a function of PHPA concentration and Reynolds number, and the results show that the pressure losses can be estimated with an error less than 15% by using the proposed friction factor

Heat Distribution within the Wellbore While Drilling

Analysis of the drilling fluid temperature in a circulating well is the main objective of this study. Initially, different analytical temperature distribution models were studied. Variables that have significant effect on temperature profile are observed. Since the verification of the analytical model is not probable for many cases, a computer program that uses a finite element method is employed to simulate different well conditions. Three different wells are modeled by using rectangular elements with four nodes. Maximum drilling fluid temperature data corresponding to significant variables are collected from these models. These data are then used to develop an empirical correlation in order to determine maximum drilling fluid temperature. The proposed empirical correlation can estimate the temperature distribution within the wellbore with an average error of less than 16%, and maximum drilling fluid temperature with an average error of less than 7%

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

PHPA as a Frictional Pressure Loss Reducer and its Pressure Loss Estimation

This article analyzes the performance of a liquid polymer emulsion containing partially hydrolyzed polyacrylamide/polyacrylate (PHPA) copolymer as a circulating system pressure loss (drag) reducer. Straight cylindrical pipe flow experiments were performed at different concentrations of solutions for measuring frictional pressure losses. Comparison of measured and theoretical frictional pressure loss values showed that as the PHPA concentration increased, considerable drag reduction (as high as 60%) was achieved and the optimum PHPA concentration for drag reduction purposes was estimated as 0.0020 (v/v). A friction factor is developed as a function of PHPA concentration and Reynolds number, and the results show that the pressure losses can be estimated with an error less than 15% by using the proposed friction factor

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

Predicting Frictional Pressure Loss During Horizontal Drilling for Non-Newtonian Fluids

Accurate estimation of the frictional pressure losses for non-Newtonian drilling fluids inside annulus is quite important to determine pump rates and select mud pump systems during drilling operations. The purpose of this study is to estimate frictional pressure loss and velocity profile of non-Newtonian drilling fluids in both concentric and eccentric annuli using an Eulerian-Eulerian computational fluid dynamics (CFD) model. An extensive experimental program was performed in METU-PETE Flow Loop using two non-Newtonian drilling fluids including different concentrations of xanthan biopolimer, starch, KCl and soda ash, weighted with barite for different flow rates and frictional pressure losses were recorded during each test. This study aims to simulate non-Newtonian fluids flow through both horizontal concentric and eccentric annulus and to predict frictional pressure losses using an Eulerian-Eulerian computational fluid dynamics (CFD) model. Computational fluid dynamic simulations were performed to compare with experimental data gathered at the METU-PETE flow loop and previous studies as well as slot flow approximation for the annulus. Results show that the computational fluid dynamic model simulations are capable of estimating frictional pressure drop with an error of less than 10% in most cases, more accurately than the slot equation

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

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%

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

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