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Managed pressure drilling method for geological conditions of narrow safe density window

A technology of managed pressure drilling and geological conditions, applied in drilling equipment and methods, drilling equipment, earthwork drilling and production, etc., can solve problems affecting the application of managed pressure drilling, bottom hole overflow, pressure difficulties, etc., and achieve extended length, The effect of increasing drilling speed and improving safety

Active Publication Date: 2014-12-17
BC P INC CHINA NAT PETROLEUM CORP +1
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  • Summary
  • Abstract
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  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, for the near-zero density window (narrow window), the bottom of the well shows strong overflow and leakage phenomena, which brings difficulties to the control of the wellbore pressure of the existing pressure management drilling
For example, the Tazhong carbonate formation in the Tarim Oilfield is a typical zero-density window type formation. During the process of MPD, overflow or lost circulation accidents occurred in many wells, resulting in multiple conventional well control operations during the process of MPD. , which seriously affects the application of managed pressure drilling in formations with narrow safe density windows
That is, there is a lack of a managed pressure drilling method and system for geological conditions with a narrow safe density window in the prior art

Method used

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  • Managed pressure drilling method for geological conditions of narrow safe density window

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Embodiment approach

[0035] According to an embodiment of the present invention, when the downhole condition is judged to be underbalanced, it means that when drilling into the reservoir, the bottomhole pressure is always kept lower than the formation pressure, and there is an underpressure value at the bottomhole. Formation gas enters the drilling wellbore to keep the gas entering the wellbore constant, thereby maintaining the stability of the underbalanced managed pressure drilling. According to Darcy's law, as the thickness of the drilled reservoir increases continuously, in order to keep the gas entering the wellbore constant (that is, the gas flow rate Q sc remain unchanged), it is necessary to continuously increase the wellhead back pressure to reduce the bottom hole negative pressure value, so the following steps can be used to adjust the wellhead back pressure, the specific process is as follows:

[0036] (a) Calculate the bottomhole pressure P at the current moment according to the follow...

example

[0053] 1. The designed drilling depth of a well in Tarim Oilfield is 5355m, the designed horizontal section is 998m long, the maximum inclination angle is 87.99°, and the drilling fluid density is 1.16g / cm 3 , the displacement is 10L / s, and the pump pressure is 20MPa. In the 4248-5355m well section, the complex situation of lost circulation and overflow occurs, and the safe density window of the drilling fluid is close to the zero safe density window. The managed pressure drilling method provided by the present invention is used to carry out zero Safe Density Controlled Pressure Drilling. Since the formation is a gas-bearing section reservoir with high formation energy, gas invasion is prone to occur in conventional drilling, so underbalanced managed pressure drilling is adopted in managed pressure drilling. In the process of managed pressure drilling, it is necessary to keep the bottom of the well in a stable underbalanced state. Since the outlet flowmeter cannot normally ref...

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Abstract

The invention discloses a managed pressure drilling method for geological conditions of a narrow safe density window. The method comprises the following steps: determining down-hole conditions according to the outlet flow Qout and the inlet flow Qin of drilling fluid; in case that the down-hole conditions are under-balanced, performing under-balanced managed pressure drilling, or in case that the down-hole conditions are over-balanced, performing over-balanced managed pressure drilling. According to the managed pressure drilling method for the geological conditions of the narrow safe density window, the complicated problems such as overflow or loss easily caused to a stratum with the narrow safe density window (a zero safe density window for instance) can be solved, the target depth can be effectively drilled, and the cognitive level of reservoir geology and the safety of the whole drilling process are improved.

Description

technical field [0001] The invention relates to the technical field of petroleum drilling engineering, in particular to a managed pressure drilling method for geological conditions with a narrow safe density window. Background technique [0002] The drilling safety density window refers to the range of drilling pressure (density) that can maintain the stability of the well wall without causing drilling accidents such as blowout, leakage, collapse, and sticking during the drilling process. When the bottom hole pressure is lower than the formation pressure, the formation fluid will enter the wellbore, forming overflow; The bottom pressure should be controlled within the formation pressure and fracture pressure density window. [0003] With the continuous exploration and development of deep and complex formations, the problem of narrow safe density window becomes more and more prominent, and even zero safe density window appears, that is, formation pressure and leakage pressur...

Claims

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Application Information

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IPC IPC(8): E21B7/00
Inventor 石林张兴全郭庆丰周英操方世良王瑛刘伟王一博赵丽萍
Owner BC P INC CHINA NAT PETROLEUM CORP
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