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A quantitative evaluation method for wellbore instability risk based on reliability theory

A technology for wellbore instability and quantitative evaluation, applied in earthwork drilling, data processing applications, wellbore/well components, etc., can solve problems such as narrow adaptability and wellbore instability, and achieve the effect of effective decision-making basis

Active Publication Date: 2022-07-22
SOUTHWEST PETROLEUM UNIV
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Problems solved by technology

However, this technical solution can only solve the problem that the current traditional evaluation method has narrow adaptability and is not enough to solve all wellbore instability problems

Method used

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  • A quantitative evaluation method for wellbore instability risk based on reliability theory
  • A quantitative evaluation method for wellbore instability risk based on reliability theory
  • A quantitative evaluation method for wellbore instability risk based on reliability theory

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specific Embodiment

[0096] Taking Xujiahe Formation in Well CW-101X in an oilfield in the Sichuan Basin as an example, the burial depth of Xujiahe Formation is 2500-3500 m. Stress 52.10-69.52MPa, maximum horizontal in-situ stress 42.55-59.47MPa (N37.86°E), minimum horizontal in-situ stress 35.63-49.68MPa, pore pressure 26.95-33.24, rock cohesion 12.15-18.63MPa, rock internal friction angle 33.54- 36.67°, the tensile strength of the rock is 3.47-5.63MPa, the Poisson's ratio of the rock is 0.23-0.27, and the porosity is 0.05-0.16. After statistical analysis, a statistical table of uncertainty of input parameters is constructed. The input parameters include vertical stress, maximum level In-situ stress, minimum horizontal in-situ stress, porosity, Poisson's ratio, cohesion, internal friction angle, well inclination angle, well inclination azimuth, Biot coefficient, permeability coefficient and caving width parameters mean and variation coefficient statistics are shown in the following table:

[0097...

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Abstract

The invention discloses a method for quantitative evaluation of wellbore instability risk based on reliability theory, which comprises the following steps: S1, according to the basic data of the drilled stratum; S2, according to the input parameter uncertainty statistical table established in step S1 S3, establish the limit state model of wellbore collapse and wellbore fracture instability; S4, according to the wellbore instability limit state model described in step S3, respectively solve the wellbore collapse pressure value and wellbore fracture limited by the basic random variables Pressure value; S5. Given the mean value and coefficient of variation of wellbore pressure, and use Monte Carlo simulation to generate the value of wellbore pressure under the given mean value and coefficient of variation; S6, Statistical calculation results to obtain the quantification of the risk of wellbore collapse and rupture instability Evaluation results. The beneficial effects of the invention are that the risk of wellbore instability under the influence of parameter uncertainty can be quantitatively evaluated, and more accurate and effective decision-making basis can be provided for drilling technicians and construction personnel.

Description

technical field [0001] The invention relates to the technical field of wellbore stability evaluation in oil drilling, and a quantitative evaluation method for wellbore instability risk based on reliability theory. Background technique [0002] At present, with the depletion of conventional oil and gas resources, unconventional oil and gas resources such as tight oil and gas, coalbed methane, shale oil and gas, and deep-water marine oil and gas have gradually attracted attention. In order to effectively develop such unconventional oil and gas resources, more and more directional wells, horizontal wells, extended-reach wells and other deviated wells are widely used. For example, the use of extended-reach wells to develop beach-sea oil and gas can avoid the construction of offshore drilling platforms; the use of directional wells to develop offshore oil and gas can reduce the number of drilling platforms required; the use of horizontal wells to develop tight oil and gas, coalbe...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F30/20G06Q10/06G06Q50/02E21B49/00G06F119/14
Inventor 马天寿祝功升陈平范翔宇夏宏泉桂俊川白杨高佳佳
Owner SOUTHWEST PETROLEUM UNIV
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