Well cementation method for high-temperature oil-gas well

Abstract

The invention relates to a well cementation method for a high-temperature oil-gas well. The well cementation method sequentially comprises the following steps that (1) a casing string is placed in a well hole; (2) a cement head is installed on a top joint, and a rubber plug is arranged in the upper portion of the cement head; (3) drilling fluid is fed into an inner cavity of a casing, ascends along the annulus of the well hole and flows back to the ground, and rock debris is cleaned; (4) prepad fluid is injected into the casing string; (5) cement paste is injected into the casing string until the cement paste reaches the well cementation design amount; (6) the rubber plug is released, a cement truck injects tamponade fluid through a tamponade fluid inlet, and the tamponade fluid pushes the rubber plug to move downwards; (7) the drilling fluid is injected for paste replacement, the drilling fluid pushes the tamponade fluid to move downwards, the rubber plug pushes the cement paste to move downwards, the cement paste enters the annulus of the well hole from a float shoe and then pushes the prepad fluid to ascend, and the prepad fluid pushes the drilling fluid to ascend; and (8) the rubber plug stops moving downwards when moving downwards to a spoiler of a float collar, collision pressure is generated, a mud pump is turned off immediately, and at the moment, the cement paste returns to a preset well section and enters a waiting-for-cement state. The well cementation quality is good, and well logging of an electrical logging instrument can be smoothly carried out after well cementation.

Description

technical field [0001] The invention relates to oil and gas well cementing, in particular to a cementing method for high-temperature oil and gas wells, and belongs to the technical field of oil and gas well cementing. Background technique [0002] Well cementing is an indispensable and important link in the process of drilling and completion operations, which includes casing running and cementing; the main purpose of well cementing is to protect and support casings in oil and gas wells, and to isolate oil, gas and water formations. In recent years, with the continuous deepening of oil and gas exploration, more and more cementing operations have been performed in deep wells and ultra-deep wells in order to reveal the geological reserves of deeply buried reservoirs. For example, the CT-1 well, the first deep well in the Bohai Bay of Dagang Oilfield, has a vertical depth of nearly 6,000 m, a bottom-hole static temperature (BHST for short) of over 190°C, and a circulation temper...

AI Technical Summary

Problems solved by technology

[0007]However, when the temperature at the bottom of the well is high, the functions of various plugging fluid systems commonly used at present are limited, and there are the following defects and problems: 1. At room temperature, it can reach dripping In the downhole high temperature state, especially when the BHST>80℃, the plugging fluid is severely diluted, and after contacting with the drilling fluid, the drilling fluid is fully diluted, and the weighted material in it precipitates, forming a plug

2. The density of the plugging fluid is low, 1.00-1.05g / cm³, the density of the general drilling fluid is 1.10-1.50g / cm³, the plugging fluid and the drilling fluid are replaced, and the effect of suspending the upper drilling fluid cannot be achieved

[0008]In short, when the BHST>80℃ of the plugging fluid system currently used for cementing operations, the stability of the plugging fluid becomes poor, and it cannot effectively suspend the weight of the displacement fluid. Materials and solid particles can no longer meet the needs of cementing construction in deep and ultra-deep wells

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