Method for detecting hydrate dynamic decomposition position of natural gas hydrate reservoir drilling well shaft

Abstract

The invention discloses a method for detecting hydrate dynamic decomposition position of a natural gas hydrate reservoir drilling well shaft, and particularly relates to a method for detecting the hydrate dynamic decomposition position of the natural gas hydrate reservoir drilling well shaft, which belongs to the field of exploration drilling or production drilling of ocean natural gas hydrates. The method for detecting the hydrate dynamic decomposition position of the natural gas hydrate reservoir drilling well shaft has the advantages that the real-time collection of data is realized, the detection accuracy is high, and the dynamic change can be dynamically detected. The method comprises the following steps of A, dividing nodes according to the drilling depth position range; B, substituting parameters into a multi-phase model, and calculating the density distribution of mixed slurry and the annulus pressure loss; C, calculating the pressure of a vertical pipe; D, comparing the calculated pressure of the vertical pipe and the monitored pressure of the vertical pipe. The method has the characteristics that by monitoring the change of vertical pressure on ground, the dynamic decomposition position of the hydrate can be calculated and predicted in real time, the drilling risk of the ocean natural gas hydrate reservoir is effectively decreased, and the loss is reduced.

Description

technical field [0001] The invention relates to a method for detecting the dynamic decomposition position of hydrate in a drilling wellbore of a natural gas hydrate layer, in particular to a method for detecting the dynamic decomposition position of hydrate in a drilling wellbore of a natural gas hydrate layer in the field of exploration drilling or production drilling of natural gas hydrate . Background technique [0002] Natural gas hydrate, also known as "combustible ice", is an unconventional energy source with high density and high calorific value (1m 3 Gas hydrates can release 164m 3 methane gas and 0.8m 3 Water), which mainly exists in the form of layers between the seabed rock layers, and is extremely rich in resources. During the drilling process of marine gas hydrate layers, the hydrate particles return to the drilling platform with the drilling fluid. The pipe flow in this process is different from the conventional oil and gas drilling process: during the upwar...

AI Technical Summary

Problems solved by technology

In the existing methods, some scholars use the natural gas hydrate phase equilibrium curve, combined with the temperature and pressure changes in the annular wellbore, to predict the change of the natural gas hydrate decomposition position, but the existing natural gas hydrate phase equilibrium curve is mainly used under steady-state conditions, and The position of hydrate dissociation is the result of theoretical calculation, which cannot fully reflect the real-time change of the dynamic dissociation position of hydrate in the drilling of the actual offshore gas hydrate layer

Patent CN102865066A discloses a deep-water wellbore multiphase flow experimental device and method for phase transition of natural gas hydrate, which can realize the simulation of the influence of natural gas hydrate decomposition on wellbore law in deep-water wellbore, but it does not propose a real-time and effective Prediction method of natural gas hydrate decomposition position

Patent CN104198674A discloses an online early warning device and method for pipeline natural gas hydrate formation, which can calculate the concentration of hydrate inhibitors and salt in the water phase at the monitoring point, and realize early warning in combination with the collected gas phase pressure, composition and temperature parameters. However, it requires a complex online data acquisition module, which cannot be effectively applied in offshore drilling

Therefore, there is no method in the prior art that can collect data in real time, is simple to operate, has high detection accuracy, and can detect dynamically changing hydrate decomposition positions in real-time in natural gas hydrate layer drilling.

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