Method for evaluating integrity of well cementing barrier

Abstract

The invention relates to a method for evaluating the integrity of a well cementing barrier. The method includes the following steps that 1, a simulated formation of a tubular structure with the open upper end and the closed lower end is manufactured; 2, the manufactured simulated formation is put in a barrel; 3, a casing pipe coated with a drilling fluid layer is put in the simulated formation; 4, an ultrasonic probe is arranged in the middle in the casing pipe, and the ultrasonic probe is electrically connected with an oscilloscope, a pulse generation receiving instrument and a high-speed transient signal acquisition instrument, wherein the oscilloscope, the pulse generation receiving instrument and the high-speed transient signal acquisition instrument are arranged outside; 5, water is injected into the barrel till the water surface reaches an upper end opening of the simulated formation, and the casing pipe is filled with water; 6, cement paste is prepared; 7, the cement paste is injected between the casing pipe and the inner wall of the simulated formation, after injection is completed, water is injected into the barrel till the water surface is flush with the upper end face of the casing pipe, and waiting on cement setting is carried out; 8, the ultrasonic probe is started, the pulse generation receiving instrument is used for measuring and acquiring a well cementing acoustic amplitude curve of a to-be-measured time point, and the peak value of the first wave of the well cementing acoustic amplitude curve is read out; 9, whether the cell cementing integrity is qualified or not is judged according to the well cementing barrier integrity criterion.

Description

technical field [0001] The invention relates to a method for evaluating the integrity of a cementing barrier, belonging to the field of oil and gas exploration and development. Background technique [0002] After cementing, the casing-cement sheath-formation will form a cemented body, which plays the role of protecting the casing and supporting the formation, which is called the cementing barrier. How to improve the sealing quality of the cement sheath between the well wall and the casing is a long-term concern in cementing engineering. The mechanical properties of the cement sheath are related to the quality of the cementing barrier and the life of the oil and gas well. During the production and service of oil and gas wells, the cementing barrier is subject to various loads, such as the internal pressure transmitted through the casing, the confining pressure of the formation rock, the temperature strain caused by the temperature change of the wellbore, and the high pressure...

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Problems solved by technology

During the production and service of oil and gas wells, the cementing barrier is subject to various loads, such as the internal pressure transmitted through the casing, the confining pressure of the formation rock, the temperature strain caused by the temperature change of the wellbore, and the high pressure shock of the gas well. etc. During the entire life cycle of oil and gas wells, multiple loads often act and change at the same time. The action and changes of these loads will lead to changes in the stress state of the cementing barrier system, and in severe cases will cause the sealing of the cementing barrier. If the system fails, the phenomenon of annular air leakage and formation fluid crossing occurs. The cement sheath loses its protective effect on the casing, which accelerates casing damage and shortens the life of the oil and gas well. In severe cases, the well may be scrapped and cause serious economic losses

For a long time, there have been many studies on the prediction and digital simulation of the sealing integrity of the cementing cement slurry ring. There are few experimental methods, which make the evaluation of the integrity of the cement barrier very limited

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