A kind of low density oil well cement

Abstract

Belonging to the technical field of oil-gas well cementing, the invention discloses a low-density oil well cement. The oil well cement comprises the following raw materials by weight percentage: 82-90% of cement clinker, 1-8% of gypsum, 5-10% of hollow glass beads, 0-0.3% of a dispersant, and 0.5-0.8% of a retarder. The cement clinker is one of sulphate aluminium cement clinker and high belite sulphoaluminate cement clinker. The sulphate aluminium cement clinker has a specific surface area of 470-520cm<2> / g; and the content of anhydrous calcium sulfoaluminate C4A3Sbar in the sulphate aluminium cement clinker is 50-75%. The cement provided by the invention is mainly used for offshore drilling operations of shallow strata, has high early strength and long thickening time, and can meet the requirements of pressure stability before cementing, during cementing and after cementing.

Description

technical field [0001] The invention relates to a low-density oil well cement, which belongs to the technical field of oil and gas well cementing. Background technique [0002] During the drilling operation, if a shallow gas blowout occurs, it will bring more serious results, especially in offshore drilling operations, when the blowout is severe, it will cause bowl-shaped subsidence at the surface, loss of ships and platforms, etc. The shallow lithology is loose and the pressure bearing capacity is low, resulting in a narrow pressure window and difficult pressure stability control. The shallow formation temperature is low, the cement slurry hydration rate is slow, and the early strength of cement stone is low, which intensifies the risk of gas channeling. The surface annulus The cement slurry with large volume, low displacement efficiency, and isolation of upper shallow gas is seriously damaged by drilling fluid, so it is difficult to ensure good cementation of cement stone....

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