A New Model for Predicting Dynamic Surge Pressure in Gas and Drilling Mud Two-Phase Flow during Tripping Operations

Xiangwei Kong,Yuanhua Lin,Yanchao Chen,Hongjun Zhu,Long Dong,Yijie Qiu

doi:10.1155/2014/916798

Abstract

Investigation of surge pressure is of great significance to the circulation loss problem caused by unsteady operations in management pressure drilling (MPD) operations. With full consideration of the important factors such as wave velocity, gas influx rate, pressure, temperature, and well depth, a new surge pressure model has been proposed based on the mass conservation equations and the momentum conservation equations during MPD operations. The finite-difference method, the Newton-Raphson iterative method, and the fourth-order explicit Runge-Kutta method (R-K4) are adopted to solve the model. Calculation results indicate that the surge pressure has different values with respect to different drill pipe tripping speeds and well parameters. In general, the surge pressure tends to increase with the increases of drill pipe operating speed and with the decrease of gas influx rate and wellbore diameter. When the gas influx occurs, the surge pressure is weakened obviously. The surge pressure can cause a significant lag time if the gas influx occurs at bottomhole, and it is mainly affected by pressure wave velocity. The maximum surge pressure may occur before drill pipe reaches bottomhole, and the surge pressure is mainly affected by drill pipe operating speed and gas influx rate.

Highlights

Prospects of petroleum industry are the exploration and development of high pressure, formations pressures uncertainties, and abnormal permeability reservoirs [1, 2]
Tripping is a constant operation in the Managed pressure drilling (MPD), and moving drill pipe is accompanied by a displacement of the drilling mud in wellbore [6], so the movement of drill pipe in a wellbore filled with drilling mud can generate an additional pressure
The pressure produced by the downward movement of drill pipe is called surge pressure, while the pressure that decreased in the upward movement of drill pipe is called swab pressure

Summary

Introduction

Prospects of petroleum industry are the exploration and development of high pressure, formations pressures uncertainties, and abnormal permeability reservoirs [1, 2]. The models of laminar flow velocity profile and surge pressure of Newtonian and power law liquid in the wellbore are developed, and the drill pipe operating speed and drilling mud properties controlled for the safety of operation. The coefficients of surge pressure under different conditions are plotted These results are useful in the control of drill pipe operating speed and the design of drilling mud properties. Crespo and Ahmed [30] reported recently the results of an experimental study aimed at investigating the effects of drill pipe speed, drilling mud properties, and wellbore geometry on surge pressures under laboratory conditions. The object of the present work is to present a new calculation model for predicting surge pressure during tripping operations, which is applicable for gas drilling mud two-phase fluid. The model can be used to predict the change of the surge pressure at any well position at different influx rate, drill pipe operating speed, and drilling parameter

The Mathematical Model

Physical Equations

Boundary Conditions and Initial Conditions of the Model

Solution of the United Model

Analysis and Discussion

Conclusions