Modeling of yield-power-law fluid flow in an eccentric annulus with fixed horizontal cuttings bed

ABSTRACT

Inclination and horizontal wells are commonly used to develop petroleum and natural gas reservoirs. Cuttings bed buildup is inevitable in an eccentric annulus because of the high inclination angle (>60°), which affects the drag and torque as well as the downhole pressure. To accurately and conveniently predict the pressure gradient in an eccentric annulus with fixed horizontal cuttings bed, a simplified model was established in this study to predict the pressure gradient by using the effective hydraulic diameter. In addition, simulation experiments were carried out to investigate the pressure gradient in the eccentric annulus with a cuttings bed using the computational fluid dynamics (CFD) software ANSYS Fluent. The simplified model was validated by comparing the results with those obtained from CFD simulations. The results show that the average shear stress of the cuttings bed wall first decreases and then increases with increasing cuttings bed height. The simplified is in good agreement with the results of existing numerical and CFD simulations (within an error of ±10%). The proposed simplified model provides a shortcut for the prediction of the pressure gradient in an eccentric annulus with a cuttings bed.

KEYWORDS:

• Cuttings bed
• eccentric annulus
• YPL fluid
• pressure gradient
• simplified model

Additional information

Funding

This research was supported by an open fund [No. PLN201734] of the State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Southwest Petroleum University), Scientific Research Starting Project of Southwest Petroleum University [No. 2017QHZ001], and the National Natural Science Foundation of China [Nos 51574202, 51774247, and 51904260].

Notes on contributors

Ming Tang

Ming Tang an associate professor at Southwest Petroleum University of China, and a visiting scholar at the Mewbourne School of Petroleum and Geological Engineering at the University of Oklahoma, Norman. He specializes in underbalanced drilling, wellbore stability, well control, and other areas concerning drilling technologies. He holds a PhD in oil and gas drilling technology from Southwest Petroleum University.

Lang He

Lang He is a graduate student majoring in oil and gas well engineering at Southwest Petroleum University.

Richun Ma

Richun Ma is a graduate student majoring in oil and gas well engineering at Southwest Petroleum University.

Shiming He

Shiming He is a professor at Southwest Petroleum University of China and the vice director of the Oil and Gas Well Drilling Technology Center at Southwest Petroleum University, Chengdu. He specializes in underbalanced drilling, wellbore stability, well control, and other areas concerning drilling technologies. He holds a PhD in oil and gas drilling technology from Southwest Petroleum University.

Genghua Yao

Genghua Yao is a graduate student majoring in oil and gas well engineering at Southwest Petroleum University.