Calculation method of borehole sloughing pressure applicable to the bedding fractured stratum

A technology of borehole collapse and calculation method, which is applied in earthwork drilling, wellbore/well components, measurement, etc.

Inactive Publication Date: 2017-01-25
CHINA PETROLEUM & CHEM CORP +1
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  • Abstract
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  • Claims
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Problems solved by technology

[0005] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art, to provide a calculation method for wellbore collapse pressure suitable for bedding fractured formations, to overcome the deficiencies of existing wellbore collapse pressure determination methods, and to quantitatively analyze bedding weak surfaces , drilling fluid density, drilling fluid invasion time, in-situ stress, wellbore trajectory and other factors on the stability of the borehole wall, and calculate the borehole wall collapse pressure coefficient after the drilling fluid invades

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  • Calculation method of borehole sloughing pressure applicable to the bedding fractured stratum
  • Calculation method of borehole sloughing pressure applicable to the bedding fractured stratum
  • Calculation method of borehole sloughing pressure applicable to the bedding fractured stratum

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Embodiment approach

[0038] According to one embodiment of the present invention, a method for calculating borehole wall collapse pressure suitable for bedding and fractured formations is provided, which includes the following steps: in a simulated environment, after the drilling fluid is immersed in the experimental core at different times, measure the strength of the weak surface of the core parameters to determine the strength change curve of the weak surface of the core under the action of drilling fluid seepage; based on the measured strength parameters of the weak surface of the core, the wall collapse pressure is calculated. The simulation environment can adopt the drilling fluid system used on site, according to the designed drilling fluid density ρ 0 and the well depth to set the experimental fluid pressure P i , set the confining pressure of the indoor experiment according to the pressure of the overlying rock formation, and simulate the state of drilling fluid intruding into the core at...

specific Embodiment

[0081] Refer below Figure 2-6 A specific embodiment of the present invention is described as follows:

[0082] (1) The target well depth is 3600m. According to the logging data, the vertical stress=83.9MPa, the maximum horizontal principal stress=76.3MPa, the minimum horizontal principal stress=71.3MPa, Poisson’s ratio=0.3, Biot’s effective stress coefficient=0.8, and the porosity Degree = 0.1, pore pressure = 46.4MPa;

[0083] According to the imaging logging observation, the direction of the weak bedding plane of the formation is Azim=0°, and the dip angle Dip=60°;

[0084] (2) The designed wellbore trajectory is a vertical well, the azimuth = 0, the inclination angle = 0, the angle between the wellbore and the formation bedding is 30°, and the core used for the experiment is drilled. figure 2 Explain the angle relationship between the wellbore and the weak bedding surface, where X 0 Y 0 Z 0 is the earth rectangular coordinate system, X 0 is the direction of the maxi...

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Abstract

The invention provides a calculation method of borehole sloughing pressure applicable to the bedding fractured stratum which belongs to the technical field of oil and natural gas exploitation and well drilling. The method comprises the steps of: in the simulated environment in different time after the drilling fluid soaking into the rock core, calculating the strength parameter of the weak side of the core, calculating the borehole collapsing force, setting the experimental liquid pressure based on the design density of the drilling fluid and the well depth, simulating the infiltration status of the rock core caused by the drilling fluid in different time, and measuring the cohesive force and internal friction angle of the core weak side after different moments of drilling fluid infiltration, by calculation obtaining the curve of collapsing force relative to the time under the condition of drilling fluid infiltration, determining the stability of the borehole, thereby optimizing the drilling fluid density of different moments. The method solves the problem of the reliance on experiences to regulate the drilling fluid density, can guarantee the drilling safety and reduces the drilling costs.

Description

technical field [0001] The invention belongs to the field of petroleum and natural gas exploration and development drilling, and in particular relates to a calculation method for well wall collapse pressure applicable to bedding and fissure formations. Background technique [0002] Borehole wall collapse and instability can easily lead to drilling accidents, and even lead to the scrapping of the wellbore. Therefore, the stability of the wellbore wall is one of the important factors affecting the success or failure of drilling and the speed of drilling. Wellbore instability in shale formations with well-developed bedding is a worldwide problem, and wellbore instability in shale formations with weak bedding planes accounts for more than 70% of the total. For a long time, on-site drilling fluid density adjustment methods are mostly based on empirical prediction methods or remedial methods for collapse. In terms of theoretical research, it is mainly based on the elastic theory ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): E21B49/00E21B47/06
Inventor 陈曾伟王怡林永学张凤英李大奇刘四海刘金华
Owner CHINA PETROLEUM & CHEM CORP
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