Borehole wall stabilization method applicable to underbalanced drilling and experimental device

Abstract

The invention relates to a borehole wall stabilization method applicable to underbalanced drilling and an experimental device. The method comprises the following steps: (1) determining stratum water activity of mud shale; (2) determining the pore pressure of a stratum to be drilled; (3) calculating the temperature of the stratum; (4) measuring the membrane efficiency of the stratum by using a membrane efficiency test experiment device; (5) determining the density of drilling fluid according to the liquid column pressure of the drilling fluid and borehole depth; (6) determining a difference value as an underbalanced value between the liquid column pressure of the drilling fluid and the pressure of the stratum if the density of the drilling fluid is determined, obtaining chemical potential difference by using the underbalanced value according to the principle that the total potential energy is balanced, and determining the activity of the drilling fluid according to the chemical potential difference and the stratum water activity; (7) adjusting the density or activity of the drilling fluid according to determined results so as to keep a borehole wall stable. The method has the beneficial effects that the action of chemical potential is taken into full consideration, the density of the drilling fluid at the time when the total potential energy of the stratum is kept balanced is given accurately, a drilling fluid filtrate is effectively prevented from invading the stratum, the stability of the borehole wall is improved, and the application and popularization of an underbalanced drilling technology are enhanced.

Description

technical field [0001] The invention relates to an oil field drilling method, in particular to a well wall stabilization method and an experimental device suitable for underbalanced drilling. Background technique [0002] Underbalanced drilling refers to the drilling technology in which the circulating pressure of the drilling fluid (including liquid column pressure and circulating back pressure) is lower than the pore pressure of the formation during the drilling process, so that the formation fluid enters the wellbore in a controlled manner and circulates it to the surface. The use of underbalanced drilling technology can increase the mechanical penetration rate, prolong the life of the drill bit, reduce or eliminate leakage and differential pressure sticking, improve drilling efficiency, and reduce the direct cost of drilling; it can also discover new production layers, reduce oil and gas layer soaking time, reduce or Eliminate the invasion and damage of drilling flui...

AI Technical Summary

Problems solved by technology

Since 2007, the number of underbalanced drilling wells completed in the United States has been more than 12,000 per year, accounting for about 26% of the total number of wells drilled each year. It has become the preferred technology for opening reservoirs; , China has completed 1,017 underbalanced wells, and the application effect is remarkable; however, the wellbore stability of underbalanced drilling has not been effectively resolved, and has become the main obstacle restricting the development of underbalanced drilling technology

[0005] In summary, the traditional underbalanced drilling fluid density design method is not applicable, and a simple and practical underbalanced drilling borehole stability design method based on the total potential energy balance theory is very important for underbalanced drilling borehole stability

[0006] The semi-permeable membrane membrane efficiency tester announced by the utility model patent of China Patent Application No. 200720187488.9 and the shale membrane efficiency tester announced by the utility model patent of 200420089356.9 all adopt the conductivity of the semi-permeable membrane liquid in the equilibrium state with the known Conductivity comparison, an indirect measurement method converted into semi-permeable membrane membrane efficiency, only considers the changes in the properties of the semi-permeable membrane fluid in equilibrium, ignoring the influence of shale properties and pore structure on osmotic pressure and membrane efficiency; Chinese patent The utility model patent application number 200620034702.2 discloses a drilling fluid semipermeable membrane measurement device that can only be tested at room temperature, and cannot measure the membrane efficiency at the actual formation temperature. The flow of drilling fluid in the wellbore; the development of the shale film efficiency tester, oil drilling and production technology, 2010, No. 11, author, Zhang Yan, Xiang Xingjin, Yan Jienian, Wu Bin, Zhao Lei; The change of the resistivity of the end solution, and the film formation efficiency of different drilling fluid systems were compared and evaluated, which can only be analyzed qualitatively, and the measurement results of the shale film efficiency cannot be given quantitatively.

Shale Hydration-Mechanics Coupling Simulation Experimental Device and New Pressure Transfer Experimental Technology, and Journal of Petroleum, Volume 26, Issue 6, November 2005 Xu Jiafang, Qiu Zhengsong, Lu Kaihe Mud Shale Membrane Efficiency Test Device and Testing Technology Although Lu Kaihe, Qiu Zhengsong, and Xu Jiafang directly measured the osmotic pressure and membrane efficiency, they can only use regular standard cores to carry out experiments, and cannot use irregular cores and dropped blocks to carry out experiments. Moreover, the experimental device is complicated and inconvenient for on-site operation and use

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