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Well wall instability risk quantitative evaluation method based on reliability theory

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

Active Publication Date: 2019-06-07
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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  • Well wall instability risk quantitative evaluation method based on reliability theory
  • Well wall instability risk quantitative evaluation method based on reliability theory
  • Well wall instability risk quantitative evaluation method based on reliability theory

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specific Embodiment

[0096] Taking the Xujiahe Formation strata in well CW-101X of an oilfield in the Sichuan Basin as an example, the Xujiahe Formation stratum is buried at a depth of 2500-3500 m. Stress 52.10-69.52MPa, maximum horizontal stress 42.55-59.47MPa (N37.86°E), minimum horizontal 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 rock tensile strength is 3.47-5.63MPa, the rock Poisson's ratio is 0.23-0.27, and the porosity is 0.05-0.16. After statistical analysis, a statistical table of uncertain 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 are shown in the following table:

[0097] No.

Random Variables

average

s...

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Abstract

The invention discloses a well wall instability risk quantitative evaluation method based on a reliability theory. The well wall instability risk quantitative evaluation method comprises the followingsteps: S1, according to basic data of a drilled stratum andS2, according to the input parameter uncertainty statistical table established in the step S1; S3, establishing a well wall collapse and well wall fracture instability limit state model; S4, according to the well wall instability limit state model in the step S3, respectively solving a well wall collapse pressure value and a well wall rupture pressure value under the limitation of a basic random variable; S5, giving a wellbore pressure mean value and a variable coefficient, and adopting Monte Carlo simulation to generate a wellbore pressure value under the given mean value and the variable coefficient; and S6, counting calculation results to obtain a quantitative evaluation result of the risk of borehole wall collapse and fractureinstability. The method has the beneficial effects that the well wall instability risk under the influence of parameter uncertainty can be quantitatively evaluated, and more accurate and effective decision basis can be provided for drilling technicians and constructors.

Description

technical field [0001] The invention relates to the technical field of wellbore stability evaluation in petroleum drilling, and relates to a method for quantitatively evaluating the risk of wellbore instability 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 marine deepwater oil and gas are gradually being paid attention to. In order to effectively develop such unconventional oil and gas resources, more and more deviated wells such as directional wells, horizontal wells, and extended-reach wells are widely used. For example, the use of extended-reach wells to develop offshore 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 required drilling platforms; the use of horizontal wells to deve...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/50G06Q10/06G06Q50/02E21B49/00
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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