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A Method for Predicting the Equivalent Density Window of Collapse Pressure in Weak Face Formation

A technology of collapse pressure and equivalent density, which is applied in the direction of earthwork drilling and production, wellbore/well components, etc., can solve problems such as field operation restrictions, wellbore instability, and inability to fully predict the formation collapse pressure window, so as to prevent complex downhole situations , The effect of preventing the instability of the well wall

Active Publication Date: 2018-02-23
CHINA UNIV OF PETROLEUM (BEIJING)
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Problems solved by technology

Whether it is the technical solutions of the above two patents or other existing technical solutions, although they have achieved certain technical effects, they only consider the state of wellbore instability when the drilling fluid density is low, while ignoring the drilling fluid density. Higher values ​​can also lead to wellbore instability issues, so the formation collapse pressure window cannot be fully predicted, limiting field operations

Method used

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  • A Method for Predicting the Equivalent Density Window of Collapse Pressure in Weak Face Formation
  • A Method for Predicting the Equivalent Density Window of Collapse Pressure in Weak Face Formation
  • A Method for Predicting the Equivalent Density Window of Collapse Pressure in Weak Face Formation

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Embodiment 1

[0130] In this embodiment, combined with the actual situation of a fractured tight sandstone formation in a certain block, the equivalent density window of the collapse pressure of the weak plane formation is predicted. The formation is 100-400m thick and is a set of red clastic rocks, mainly exposed in the northern part of a depression. The formation is divided into three lithological sections, from top to bottom are the first section, the second section and the third section. The first section is 20-70m thick, mainly composed of pebble-bearing sandstone and sandstone, with no fractures, and is a tight sandstone section; the second section is 40-260m thick, mainly composed of fine sandstone interbedded with thin mudstone, and relatively pure mudstone Thin layers appear; the thickness of the third section is 45-100m, mainly composed of maroon conglomerate, glutenite interbedded with pebble-bearing sandstone, and siltstone. Fractures are well developed in the second and third ...

Embodiment 2

[0244] In this embodiment, combined with the actual situation of a fractured tight shale formation in a certain block, the collapse pressure equivalent density window of the formation with weak planes is predicted. Its prediction method, principle, beneficial effect, etc. are the same as those in Example 1, except that the parameter values ​​of shale weak plane formation are shown in Table 2.1.

[0245] Table 2.1 Parameter values ​​of shale weak plane formation

[0246]

[0247] Substituting the parameter values ​​in Table 2.1 into the model for calculation, the calculation results are as follows Figure 8 and Figure 9 Shown: If the allowable borehole expansion rate is given as 13%, the lower limit of the equivalent density of the collapse pressure of the tight shale section is 1.1g / cm 3 ; The lower limit of the collapse pressure equivalent density of the fractured shale section is 0.95g / cm 3 , the upper limit is 1.35g / cm 3 . Therefore, the collapse pressure equivalen...

Embodiment 3

[0249] In this embodiment, combined with the actual situation of a fractured tight carbonate formation in a certain block, the collapse pressure equivalent density window of the formation with weak planes is predicted. Its prediction method, principle, beneficial effect, etc. are the same as those in Example 1, except that the parameter values ​​of shale weak plane formation are shown in Table 3.1.

[0250] Table 3.1 Values ​​of various parameters in weak carbonate formations

[0251]

[0252]

[0253] Substituting the parameter values ​​in Table 3.1 into the model for calculation, the calculation results are as follows Figure 10 and Figure 11 Shown: If the allowable diameter enlargement rate is given as 12%, the lower limit of the collapse pressure equivalent density of the tight carbonate formation is 1.45g / cm 3 ; The lower limit of the collapse pressure equivalent density window of fractured carbonate formations is 1.5g / cm 3 , the upper limit is 1.6g / cm 3 . The...

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Abstract

The invention discloses a method for forecasting a weak plane formation collapse pressure equal yield density window. The method sequentially includes the steps: dividing a weak plane formation into a compact section and a crack section according to characteristics of the weak plane formation; testing the strength of a rock body and the strength of a weak plane of a rock by the aid of the triaxial compression test of the rock; inverting stress distribution and pore pressure distribution of surrounding rocks of a compact formation well by the aid of a fluid-solid coupling model, and determining the lower limit of the collapse pressure equal yield density of a compact formation according to Mohr-coulomb failure criteria; analyzing the failure state of the surrounding rocks of the weak plane formation well according to the rock weak plane failure criteria, and determining the lower limit and the upper limit of the collapse pressure equal yield density window of a crack formation; building a weak plane formation collapse pressure equal yield density window calculation model, substituting parameter values into the model and then determining the weak plane formation collapse pressure equal yield density window. The weak plane formation collapse pressure equal yield density window can be forecasted before drilling, so that drilling fluid density is reasonably selected, and wellbore instability is effectively stopped.

Description

technical field [0001] The invention belongs to the technical field of oil and gas drilling engineering, and relates to a method for predicting a formation collapse pressure window, in particular to a method for predicting a weak surface formation collapse pressure equivalent density window. Background technique [0002] Most of my country's oil and gas resources are concentrated in fractured reservoirs, and drilling in such formations is a key technical problem restricting my country's oil drilling. Due to the impact of structural extrusion and deformation in the formation, multiple sets of fracture systems are formed, and the regional structural stress difference is large, and there is a high-pressure water layer, which leads to frequent wellbore instability during drilling. When the drilling fluid density is low, it cannot support the surrounding rock of the wellbore wall, resulting in the instability of the wellbore wall; Wall instability. This shows that there is an e...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): E21B49/00
CPCE21B49/00
Inventor 卢运虎金衍陈勉刘铭
Owner CHINA UNIV OF PETROLEUM (BEIJING)
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