Numerical Simulation Of The Spread-Diffusion Process Of Oil Released From Seabed In Penglai19-3Oilfield Area

As the offshore oil and gas field operations into the era of deepwater and ultradeepwater, its engineering equipment also gradually turn to the subsea productionsystem with the characteristics of large-scale, intensive, complex and automatic. Andthe risk of oil release in underwater oil and gas exploration is persistent. Theconstantly improving of the emergency response and countermeasures in underwateroil release accident sets higher demands for the accuracy of underwater oil releasesimulation and prediction. Making timely and accurate forecast about the oil releasetrajectories and range in the early accident has the extremely vital significance toeffectively control the oil release and reduce the environmental and economic damage.Due to the depth and marine environment, the oil release accidents’ emergencyresponse and countermeasures in the Bohai Sea area has lower difficulties than whichin deep-water,but has more obvious and effective control effect. Therefore, to carryout the three-dimensional simulation of underwater oil release in the Bohai Sea isboth necessary and urgent.Necessary background and current research situations at home and abroad on theunderwater oil release has been stated in this paper. Related content and conclusionsare as follows:1. Using the finite-volume coastal ocean numerical model FVCOM, this paperestablished a three-dimensional hydrodynamic model of the Bohai Sea to simulate thehydrodynamic field under the M2, S2, K1, O1four constituents’ control, and madecomparisons between observed and calculated data include tidal elevations andsurface and vertical tidal currents in several stations. This hydrodynamic field is usingas the background flow field input of the submarine oil release model.2. A seabed oil release numerical model is established: in a deepwater blowout ofoil, there can be a momentum driven stage in near zone and a buoyancy driven stage in far region of the mix. In the momentum driven stage this paper using Lagrangiancontrol volume integral method while in the buoyancy driven stage using anintegrated formulation to calculate the buoyant velocity of oil droplets.,and discussesthe transition from plume dynamics stage to advection diffusion stage. Whats more,we make comparisons between the two calculate methods mentioned in the buoyancydriven stage with the experimental data given in the literature.3. The model is applied to the seabed oil release in the central Bohai Penglai19-3oilfield. We calculate the buoyant velocity of oil droplets in different size, andsimulate the oil trajectory, diffusion range, time to the sea and locations on the surfacein different particle sizes and size range without momentum driven. What’s more, thecases whether there have momentum-driven stage in the oil release accident aresimulated. The conclusions are listed as follows:①The larger oil droplets particle size, the larger buoyant velocity. The oilparticle’s buoyant velocity as the particle size increases when it’s less than7mm, butthe growth rate is gradually reduced; But the oil droplets buoyant velocity notincrease as the particle size increases all the time. When the particle size is great than7mm, the buoyant velocity is no longer increases.②The larger oil droplets particle size,accordingly the shorter underwater transportdiffusion, and the less impact by the horizontal motion of the flow field.Thedifferences in oil droplets’ arriving time are no longer significant when the particlesize is fall in between3mm and10mm;③The level at which the dynamics of the plume is no longer dominant isdecided by the initial momentum. The greater the momentum, the deeper the terminallevel for plume dynamics; It takes less time for the oil to reach to the surface frombelow when the momentum increases, accordingly the less offset distance on thesurface and less pollution under the water;④The momentum driven stage can’t be ignored when the initial momentum isgreat for it has great impact on the arriving time and offset distance; When themomentum driven stage is quite short,such as the slow oil release from pipelines, oilwells, and sunk ships, there are suitable applications for ignore the initial momentum in the simulation.Through the study of this article, the underwater oil release transport diffusionprocess can be more clear understanding. And this paper tries to make a littlecontribute for the further research.