Retardation cement mortar

Abstract

The invention discloses retarded cement slurry. The retarded cement slurry comprises the following components in percentage by weight: 15 to 35 percent of urea, 0.01 to 0.1 percent of suspending agent, 30 to 65 percent of cement, and 19 to 35 percent of water. In the components of the cement slurry, the urea has the following functions: (1) the urea changes the nature of pure water as the urea molecules and water molecules form hydrogen bonds; and (2) the existence of the urea in the water reduces the chance of the contact between cement particles and water molecules which both have the function of settling retardation. The function of the suspending agent in the retarded cement slurry is to reduce the sedimentation and aggregation speed of the cement in the water for convenient inject via a pump. The retarded cement slurry can make the thickening time of the G-grade cement slurry at 40 DEG C reach 10 to 48 hours. The main technical indexes of the retarded cement slurry are as follows: the thickening time at 40 DEG C is between 10 and 48 hours; the compressive strength after solidification is between 4 and 27MPa; and the temperature resistance after solidification is more than or equal to 300 DEG C.

Description

technical field [0001] The invention relates to a slow-setting cement slurry, in particular to a slow-setting cement slurry used for water shutoff of oil wells, profile control of water injection wells, sand prevention and sealing of heavy oil thermal recovery wells, etc., and belongs to the field of chemical water shutoff and profile control of oil fields. Background technique [0002] At present, the cement slurry used in domestic and foreign oilfield oil wells for water plugging and sand consolidation, heavy oil thermal recovery wells for sand control, channel sealing, oilfield water injection well profile control, and coal seam permeation plugging generally has the disadvantage of fast thickening. Less than 2 hours (the thickening time of G-grade cement slurry with a water-cement ratio of 0.44 is about 90 minutes at 40°C), while using cement slurry for water plugging and sand consolidation in oil wells, sand control and channel sealing in heavy oil thermal recovery wells,...

AI Technical Summary

Problems solved by technology

[0003] The object of the present invention is to provide a retarded cement slurry with a long retarding time, so as to solve the problem of cement slurry in construction operations such as water plugging, sand prevention and sealing of heavy oil thermal recovery wells, profile control of water injection wells, and plugging of coal seams. The existing wellbore is sealed, and the tubing and downhole tools cannot be pulled out.