Two methods for simulating mud discharge after emergency disconnection of a drilling riser

Dynamic recoil response of tensioner and riser coupled in an emergency disconnection scenario

The flow of cement-based slurry within concentric annular geometry is a major problem of study in the field of engineering, especially regarding the prevention of water ingress in an annulus formed during shaft construction utilizing the artificial freezing technique in China. In this study, an analytical governing equation of motion for the axial flow of an incompressible Newtonian fluid in a long concentric annulus is derived under the condition of high groundwater pressure. A stepwise calculation method is proposed to describe the grouting process based on two injection modes, namely, flow rate control and pressure control. The injection time is divided into a series of time segments; correspondingly, the grouted zone is subdivided into infinitesimal elements. Some key parameters, such as the location, dimension, slurry viscosity, and pressure gradient of each element, can be obtained using the developed MATLAB program. On this basis, the distribution of pressure and slurry viscosity in the grouted zone and the variations in injection pressure at the grouting point and grouting flow rate are determined. Two injection mode cases are investigated to reveal the grout propagation in the concentric annulus. Finally, numerical simulations are conducted and employed to validate and calibrate the calculated results. The results obtained by the present stepwise calculation method show good agreement with the numerical results.

https://downloads.hindawi.com/journals/ace/2019/2587035.pdf

Grouting Mechanism of Cement-Based Slurry in a Concentric Annulus under High Groundwater Pressure

A Simplified Method of Hydraulics Analysis for Riserless Drilling System

Fluid dynamics study of the flow and pressure drop analysis of a non‐Newtonian fluid through annular ducts with unusual cross‐sections

A new utility approach that is independent of the rheological model is presented for the flow of non-Newtonian fluids in concentric annulus. The novel model was developed without assuming that the generalised flow index remains constant over all shear rate ranges. Based on the slot model, the flow rate expressions for all common rheological models flowing in annuli were obtained, such as the Herschel–Bulkley model, the Robertson–Stiff model, and the Four-parameter model, and they all can be solved numerically to obtain accurate wall shear rate and shear stress. Following Metzner and Reed's study, we defined a generalised flow index for non-Newtonian fluid flow in annuli. Through a theoretical analysis, we also defined a new effective diameter for non-Newtonian fluid flow in annuli, which accounts for the effects both of annulus geometry and fluid rheology but which is different from that was proposed by Reed and Pilehvari. Through the generalised effective diameter we linked non-Newtonian annular flow with Newtonian pipe flow. A general annular Reynolds number expression was derived from this method for conditions under which the generalised flow index is variable. A theoretical calculation method for the generalised flow index and a uniform pressure loss calculation model for non-Newtonian flow in concentric annuli were developed, which are applicable to all time-independent non-Newtonian fluid. The predictions of this model have been compared with an extensive set of data from the literature. The comparisons of different fluids in different size annuli show very good agreement over the entire range of flow types.

Zhou Haobo

Papers

A new utility calculation model for axial flow of non-Newtonian fluid in concentric annuli