فهرست مطالب saeed ghobadpouri

Well conditions during drilling operation can be predicted using numerical simulation. During under-balanced drilling (UBD) operation, controlling the bottom-hole pressure (BHP) in a suitable range and also appropriate hole-cleaning is essential. In this paper, numerical simulation of gas-liquid-solid three-phase flow in the annulus is used to study the effects of annulus geometry and also liquid properties on the BHP and hole-cleaning during UBD operation. To validate the numerical simulation, the results are compared with the experimental data from a laboratory study. Also, the gain results from developed code are compared with the actual field data from a real well, several mechanistic models from WellFlo software, and gas- liquid two- fluid numerical simulation. Due to the significance of controlling the BHP and hole-cleaning during UBD operation, the effects of annulus geometry and liquid phase properties on BHP and the solid volume fraction distribution are investigated. According to the results, changing the hydraulic diameter and cross-sectional area of the annulus can affect BHP and hole- cleaning in UBD operation. In other words, increasing the hydraulic diameter at a constant cross- sectional area improves hole-cleaning and decrease BHP. Also, decreasing the cross-sectional area at a constant hydraulic diameter improves hole-cleaning and increase BHP. The results show that the liquid viscosity affects hole-cleaning through two contrary mechanisms. In fact, by increasing the liquid viscosity, carrying capacity of the liquid phase is increased and cutting transfer velocity is decreased.

In this research, gas-liquid-solid three-phase flow in the annulus during under-balanced drilling operations is simulated numerically. One-dimensional form of steady-state governing equations including mass and momentum conservation equations for each phase, gas equation of state, and saturation constraint equation in the Eulerian frame of reference are solved by a proposed algorithm. The computational code is validated by using experimental data from a real well, gas-liquid two-fluid numerical simulation, and also some mechanistic models of WellFlo software. Moreover, the results are compared with the experimental data from a laboratory study. The numerical code succeeds in predicting bottom hole pressure and obtaining the characteristic flow behavior during under-balanced drilling. Due to the importance of controlling flow characteristics during the drilling operations, the effects of change in the injected liquid flow rate, gas injection flow rate, choke pressure on the gas, liquid, and solid volume fractions, as well as gas, liquid, and solid velocity distributions along with the annulus, are investigated. According to the obtained results, the effects of liquid injection flow rate and injected gas flow rate on the flow characteristics are decreased along the annulus in the flow direction, but the effects of choke pressure on the flow characteristics are increased along the annulus in the flow direction. Consequently, to change the flow characteristics in the wellhead area, it is better to change the choke pressure and to affect the flow characteristics in the bottom-hole area, it is preferred to change the gas and liquid injection flow rate. In other words, depending on the required situation of flow characteristic changes, the appropriate operational parameter can be used.

The accurate prediction of wellbore temperature distribution helps to accurately estimate well pressure profile and bottom-hole pressure (BHP) which is important in the under-balanced drilling (UBD) operation. In this paper effect of temperature variation due to heat transfer of drilling fluid with the formation and also oil and gas production from the reservoir into the annulus in under-balanced drilling condition were investigated. Gas-liquid two-phase flow model considering thermal interaction with the formation is used to numerically simulate a well with real dimensions. Based on drilling fluids flow and heat transfer characteristics in wells, conservations of mass and momentum and energy equations have been developed to compute BHP and wellbore temperature and pressure profile. After temperature and pressure validation of the numerical model, the effect of heat transfer between drilling fluid inside the well and the formation was considered on the pressure distribution and bottom-hole pressure. The results of two-phase flow, considering thermal effect gives better results compared to two-phase flow with geothermal temperature distribution analysis and better accuracy in comparison with other models.

In this paper, gas-liquid two-phase flow in the annulus of a real well during under-balanced drilling operations is simulated numerically. Oil and gas flow from the reservoir in to the annulus is considered due to under-balanced drilling condition. A numerical code based on one-dimensional form of steady-state single pressure two-fluid model in the Eulerian frame of reference is developed and its results are validated using experimental data from two real wells. The results of numerical simulation show better accuracy in comparison with other researches. Given the importance of prediction and control of the bottom-hole pressure and the amount of oil and gas production during the drilling operations, the effects of controlling parameters such as liquid and gas injection flow rate and choke pressure are discussed. Also, the effects of different controlling parameters on the characteristics of two-phase flow pattern, including liquid and gas void fractions, liquid and gas velocities and pressure distribution along with the annulus are discussed. According to the results, the effects of choke pressure and injected liquid flow rate on the production of the oil from the reservoir are independent of the values of each other and are dependent on the injected gas flow rate.