Drilling fluid density determination method capable of controlling creep shrinkage of boreholes in frozen earth stratum

A technology for determining the density of drilling fluids and methods, applied in special data processing applications, instruments, electrical digital data processing, etc., can solve problems such as sticking, shrinkage, hindering oil and gas development, etc., achieving creep protection and strong engineering practicability Effect

Active Publication Date: 2018-11-27
CHINA UNIV OF PETROLEUM (EAST CHINA)
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Problems solved by technology

In the process of oil drilling, creep phenomenon will lead to diameter shrinkage, stuck pipe, and mo...

Method used

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  • Drilling fluid density determination method capable of controlling creep shrinkage of boreholes in frozen earth stratum
  • Drilling fluid density determination method capable of controlling creep shrinkage of boreholes in frozen earth stratum
  • Drilling fluid density determination method capable of controlling creep shrinkage of boreholes in frozen earth stratum

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Embodiment Construction

[0062] In conjunction with the accompanying drawings, a method for determining the density of drilling fluid for controlling borehole creep shrinkage in permafrost formations comprises the following steps (such as figure 1shown):

[0063] (1) Several cores of different depths in permafrost strata were drilled to make standard rock samples with a height of 50 mm and a diameter of 25 mm. Select a core at a certain depth and use a low-temperature triaxial tester to perform frozen soil creep experiments at a certain temperature and calculate the creep parameters A, α, m; the constitutive model for frozen soil creep is: σ=Aε m t -α ;

[0064] Among them, A represents the strain coefficient dependent on the temperature, properties and creep action time of the soil, α and m are the experimental fitting parameters; σ is the stress difference, MPa; ε is the strain.

[0065] (2) Change the test temperature, carry out creep experiments under different low temperature conditions for th...

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Abstract

The invention discloses a drilling fluid density determination method capable of controlling creep shrinkage of boreholes in a frozen earth stratum. The method includes the following steps of drillingrock cores at different depths in the frozen earth stratum, selecting one rock core at a certain depth under a certain temperature to carry out a frozen earth creep experiment, and calculating creepparameters; creating a correlation between the creep parameters and the temperature; conducting a mechanical test of the rock core to obtain elasticity modulus, a Poisson's ratio and rock density; creating a correlation between the creep and the depth of the stratum and a relation between the rock density and the depth of the stratum; creating a correlation between the temperature of the stratum and the depth; according to stress performed on surrounding rock of a well wall, obtaining a balance equation, a geometric equation and boundary conditions and figuring out simultaneous equations to obtain a drilling fluid density equation; determining drilling liquid density for controlling the shrinkage rate of the boreholes in all well sections of the frozen earth stratum under different workingconditions and drawing a drilling fluid density graph. On the basis of creep mechanical behaviors of frozen earth, the drilling fluid density graph for drilling of the frozen earth stratum after viscoelasticity is taken into account is provided, and the method has an extremely significant engineering meaning.

Description

technical field [0001] The invention relates to a method for determining the density of drilling fluid in the field of petroleum development in polar regions, in particular to a method for determining the density of drilling fluid for controlling the creep diameter reduction of permafrost formations. Background technique [0002] Today, as the oil and gas energy situation is becoming increasingly severe, unconventional oil and gas has become the focus in the energy industry. In 2008, the US Geological Survey issued a report confirming that the Arctic region has rich oil and gas resources. As a result, the oil industry of various countries in the world has also begun to focus on the polar regions. In my country's Qinghai-Tibet Plateau, Jungar Basin and other permafrost areas, there are also huge potentials for oil and gas development, so the study of drilling fluid density in permafrost formations has great engineering significance. [0003] Compared with conventional terres...

Claims

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Application Information

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IPC IPC(8): G06F17/50
CPCG06F30/20
Inventor 李阳闫传梁程远方韩忠英周晓辉宋本建
Owner CHINA UNIV OF PETROLEUM (EAST CHINA)
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