Effect of Buried Depth on Steady-State Heat-Transfer Characteristics for Pipeline-Flow Assurance

Abstract

Pipeline embedment into the seabed is a key consideration for offshore oil and gas developments with high-temperature fluids. To date, the mechanism of steady-state heat transfer from partially and fully buried pipes has been modeled predominantly through analytical and numerical approaches. The current study focuses on making detailed measurements of heat-transfer characteristics. A laboratoryscale experimental apparatus imitating a subsea pipeline partially or fully buried into the seabed is created. Hot flow of hydrocarbons inside oil and gas offshore pipelines and the cold external flow of seawaters are simulated by means of 70 C and 5 C water flows from two separate water tanks, respectively. The experiments are carried out for seven different burial depths representing a range of various burial configurations, from fully exposed to fully buried pipes. The temperatures measured on the external surface of the pipe are analyzed, and the overall heat-transfer coefficient of the pipe is calculated. The effect of burial depth on the overall heat-transfer coefficient is compared with analytical formulae.

Numerical Simulation for Preheating New Submarine Hot Oil Pipelines

“…Thusyanthan [14] presented a novel laboratory setup using the thermal imaging technique to simulate the heat loss of offshore pipelines and determine the thermal conductivity of offshore clay. Oh [15] created a laboratory-scale experimental apparatus to imitate a submarine pipeline partially or fully buried into the seabed. By analyzing the temperature of a pipe's external surface, the effect of buried depth on the steady-state heat transfer coefficient was investigated.…”

Numerical Analysis of Thermal Mixing in a Swirler-Embedded Line-Heater for Flow Assurance in Subsea Pipelines

“…At high Re of 1011, axial flow dominates the heat transfer thus most region of the cross-section could not be heated uniformly, though the radial advection effect can be observed as increases. Thermal mixing of each case is compared quantitatively in terms of the standard deviation (see (8)) in Figure 13. In general, the standard deviation decreases as the swirl number increases, which indicates that the swirler enhances the thermal mixing as expected from the mixing analysis results of Figure 11.…”

“…There are several approaches to prevent hydrate plug formation [1,[3][4][5][6][7][8]. By injecting chemical inhibitors such as methanol and glycol at the well head, hydrate formation can be basically prevented.…”

“…Pipe-in-pipe (PiP) and buried pipe are representative examples of this approach and heat transfer characteristics of the buried pipe has been investigated analytically and numerically [7]. In addition, recent experimental investigation has shown that the heat transfer characteristics of the subsea pipeline is significantly affected by the buried depth [8]. Running cost of this approach is considerably lower than that of inhibitor approach.…”

An Overview of Flow Assurance Heat Management Systems in Subsea Flowlines

“…Some other merits of flowlines burial system include more option on installation vessels and contractors, more options on the vendor for the fabrication of flowline, when compared to PIP system gives a slower cooldown time during shutdown and a likelihood of single flowline repair [49], and also provide a reduced time and enhanced schedule for first oil [49,105,106]. Oh et al [107] carried out laboratory experiments to ratify some numerical and analytical models [50,[108][109][110][111]. Figure 6 shows the comparison between burial depth and U-value for both bared and a coated polypropylene foam flowline [51].…”