Self-feedback three-phase-system well drilling liquid mixing system and method for mixing well drilling liquid

Abstract

The invention relates to a self-feedback three-phase-system well drilling liquid mixing system which comprises a mixing device, a seawater pool, a basic mud pool and an additive pool. The seawater pool is connected with the mixing device through a first pipeline, the basic mud pool is connected with the mixing device through a second pipeline, and the additive pool is connected with the mixing device through a third pipeline. The seawater pool contains seawater and is used for supplying seawater raw materials to the first pipeline, the basic mud pool contains basic mud and is used for supplying basic mud raw materials to the second pipeline, and the additive pool contains additives and is used for supplying additive raw materials to the third pipeline. The seawater, the basic mud and the additives enter the mixing device to be mixed and then enter a mud pool or a mud pump manifold through a density self-feedback module. By additionally arranging the density self-feedback module of theself-feedback well drilling liquid mixing system, the density of well drilling liquid can be more accurate, a flowmeter can further be corrected through comparison of the detected density and the setor designed density, and the system can achieve mixing of the raw materials of various proportions under the situation that the pump power is not controlled.

Description

technical field [0001] The invention belongs to the technical field of drilling, and in particular relates to a self-feedback three-phase drilling fluid mixing system and a drilling fluid mixing method. Background technique [0002] Drilling fluid balanced drilling is a mature drilling technology in the world at present. The balanced drilling technology uses the static pressure of drilling fluid to balance the bottom pressure to ensure the normal drilling. However, deepwater surface drilling faces shallow geological disaster risks such as shallow flow and shallow gas, as well as drilling difficulties such as narrow pressure windows caused by weak formations: [0003] 1. The safe density window is narrow, the design of the well body structure is difficult, and the casing cannot be lowered to the predetermined depth. In deepwater drilling, the overburden pressure exerted by seawater is much lower than that exerted by rock on land because the density of seawater is lower than ...

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Problems solved by technology

Therefore, since the fracture pressure gradient of deep-sea formations is smaller than that of land formations with the same well depth, the safety margin between the formation pressure gradient and the fracture pressure gradient is very small, and the safety density window becomes narrower as the water depth increases. It is more difficult, and the casing cannot be lowered to the predetermined depth

[0004] 2. Drilling encountered high-pressure shallow flow, it is difficult to effectively implement well control

[0006] There is no self-feedback device in the prior art, and it is impossible to re-test and adjust the mixed liquid that does not meet the requirements. The long-term use of the system will lead to deviations in the readings of the flowmeter, which will cause the ratio of the base slurry, seawater and additives to be different from the preset parameters. Or the design parameters deviate, which eventually leads to the failure of the mixed fluid density to meet the requirements, which is very fatal in the implementation of this technology; there is no pump pressure protection device in the prior art, and it is impossible to achieve various mixing ratios Mixing, or the safety and reliability of the pump cannot be guaranteed

[0007] The existing mixer has problems such as complex structure, large volume, and difficult installation

Moreover, the high-speed fluid ejected from the nozzle will produce inelastic collision in the cabin, especially when the inlet flow rate of the two-phase fluid is close, the collision of the two-phase fluid will form a radial flow, which will directly flow out of the mixer, and the collision will also cause the loss of momentum of the high-speed fluid. The high-speed and low-speed shear is an important factor for mixing, and the loss of momentum will also affect the efficiency of mixing, and it cannot ensure uniform mixing under various displacements and mixing ratios.

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