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Drilling liner cementing method for controlling annulus equivalent density of pressure-sensitive stratum

A technology of equivalent density and liner cementing, which is applied in earthwork drilling, sealing/isolation, wellbore/well components, etc. It can solve problems such as lost circulation, affecting oil and gas recovery, easily induced well kick, blowout, etc.

Active Publication Date: 2018-07-03
CHINA NAT PETROLEUM CORP CHUANQING DRILLING ENG CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When cementing oil and gas wells, the probability of encountering pressure-sensitive formations is increasing. The formation pore pressure of these formations is close to the formation fracture pressure. Contradictions are prominent, and the design of the annular slurry column structure and injection displacement is difficult. If the annular pressure is higher than the formation pore pressure, it may cause well loss in a small range. Once well loss occurs, it is very easy to induce well kick, blowout and other accidents , threatening downhole and well control safety, if the cement filling effect is poor, annular channeling may occur, affecting later operation and production safety, and cementing is extremely difficult
[0003] For liner cementing operations in pressure-sensitive formations, the conventional method is to reduce the construction displacement to reduce the risk of lost circulation or to take technical measures such as "forward injection and reverse extrusion". However, the above methods may be difficult to guarantee the cementing quality and affect the later stage Drilling and completion operations may cause pollution to the reservoir and affect the oil and gas recovery rate, neither of which can achieve the purpose of cementing, nor can it solve the problem of cementing in pressure-sensitive formations

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0063] A liner cementing method for controlling the equivalent density of annulus in a pressure-sensitive formation, comprising the following steps:

[0064] a. Determine the minimum equivalent density ρ to keep the wellbore stable through the hydraulic parameters, leakage and oil, gas and water display during the drilling process min , and the highest equivalent density ρ without leakage in the formation max ;

[0065] b. Carry out cementing construction design, cement slurry density ρ c , spacer fluid density ρ s , Drilling fluid density ρ 1 The relationship is: ρ c >ρ s >ρ 1 , to obtain the rheological data of the slurry entering the well at the circulating temperature at the bottom of the well, and calculate the displacement Q of the injection replacement s , Formulate replacement construction parameters;

[0066] c. Adjust the density of the drilling fluid to ρ before the last drilling trip before running the casing 0 , this density drilling fluid will produce hy...

Embodiment 2

[0116] The key to cementing in pressure-sensitive formations is to stabilize high-pressure formations while avoiding leakage in weak pressure-bearing formations. The invention provides a liner cementing method for controlling the equivalent density of annulus in pressure-sensitive formations. The method contains the following steps:

[0117] 1. Accurately calculate the annular pressure and determine the minimum equivalent density ρ to keep the wellbore stable through the hydraulic parameters, leakage and oil-gas-water display during the drilling process min , and the highest equivalent density ρ without leakage in the formation max :

[0118] ρ min =ρ m (1)

[0119] P max =ρ m '×g×H b ×10 -6 +P f (2)

[0120] (3)

[0121] (4)

[0122] In the formula

[0123] ρ m Minimum drilling fluid density to maintain wellbore stability, kg / m 3 ;

[0124] g is the acceleration of gravity, take 9.81m / s 2 ;

[0125] h b is the middle completion depth, m;

[0126] P ...

Embodiment 3

[0157] After drilling to the medium completion depth, the minimum equivalent density ρ to keep the wellbore stable is obtained through hydraulic calculation according to the actual drilling tool assembly, drilling fluid rheological parameters, drilling fluid density, mud pump displacement and pump pressure min , and the highest equivalent density ρ without leakage in the formation max ;

[0158] Adjust the drilling fluid density of the whole well to ρ before lowering the liner 0 , under this condition, the drill can be tripped normally without leakage or oil, gas and water display;

[0159] Send the tailpipe down to the position of the upper pipe shoe to circulate the drilling fluid, and lower the drilling fluid density to ρ 1 , the density of the drilling fluid above the position of the upper pipe shoe after adjustment is ρ 1 , the drilling fluid density in the open hole section is still ρ 0 ;

[0160] Continue to run the liner to the design well depth. During this proce...

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Abstract

The invention discloses a drilling liner cementing method for controlling the annulus equivalent density of a pressure-sensitive stratum. Based on the minimum equivalent density for keeping shaft stability and the maximum equivalent density for avoiding formation leakage, the density of a drilling fluid is decreased before cementing, accordingly, the leakage risk is reduced, and the cement slurrydisplacement efficiency is improved; and after finishing drilling, on the basis of hydraulic parameters and leakage and the oil-gas-water display situation in the drilling process, the annulus pressure is calculated, and the minimum equivalent density phimin for keeping the shaft stability and the maximum equivalent density phimax for avoiding formation leakage are determined. Cementing construction designing is conducted based on phimin and phimax, and for the purpose that the annulus cement slurry displacement efficiency is larger than 90%, the pressure stabilizing and leakage preventing effects are achieved by decreasing the density of the drilling fluid, applying back pressure to a wellhead and reasonably designing injection displacement.

Description

technical field [0001] The invention relates to a liner cementing method for controlling the equivalent density of annulus in a pressure-sensitive formation, and belongs to the field of petroleum and natural gas engineering. Background technique [0002] With the gradual deepening of exploration and development, offshore and deep oil and gas reservoirs have entered a period of rapid development, and drilling and completion projects have become more and more difficult. When cementing oil and gas wells, the probability of encountering pressure-sensitive formations is increasing. The formation pore pressure of these formations is close to the formation fracture pressure. Contradictions are prominent, and the design of the annular slurry column structure and injection displacement is difficult. If the annular pressure is higher than the formation pore pressure, it may cause well loss in a small range. Once well loss occurs, it is very easy to induce well kick, blowout and other ...

Claims

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Application Information

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IPC IPC(8): E21B33/14
CPCE21B33/14
Inventor 冯予淇陈敏鲜明余才焌聂世均刘洋吴朗赵常青杨向宇
Owner CHINA NAT PETROLEUM CORP CHUANQING DRILLING ENG CO LTD
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