An all-round three-dimensional fracturing method for vertical wells in ultra-low permeability reservoirs

Abstract

The invention provides an all-dimensional three-dimensional fracturing method for a vertical well of a reservoir with ultra low permeability. The method comprises the following steps that firstly, a shaft of the target reservoir is subjected to first volume fracturing to form a main crack extending in the direction of the maximum principal stress and secondary net-shaped cracks around the main crack, and the main crack is temporarily blocked; secondly, the shaft of the target reservoir is subjected to second volume fracturing, since the maximum principal stress field within a certain range around the shaft turns over at almost 90 degrees after first volume fracturing, a secondary main crack perpendicularly intersecting with the main crack generally can be constructed through second volumefracturing, and net-shaped cracks are formed around the secondary main crack. By means of the method, the all-dimensional three-dimensional net-shaped cracks can be constructed in the vertical well through fracturing, the transformation volume of an oil well is greatly increased, and the productivity of the oil well is improved.

Description

technical field [0001] The invention relates to the field of oil production, and relates to an omnidirectional three-dimensional fracturing method for vertical wells in ultra-low permeability reservoirs. Background technique [0002] Fossil energy has been one of the important energy sources for our survival for many years, and people pay more and more attention to oil and gas resources. With the further development of oil and gas resources, the newly proven reserves of ultra-low permeability oil and gas reservoirs are increasing year by year, and the fracturing of ultra-low permeability oil and gas reservoirs will become the main position for increasing oil and gas production. The ultra-low permeability reservoir refers to: the average permeability of the oil layer is (1.1~10.0)×10 -3 μm 2 . The difference between this kind of oil layer and normal oil layer is obvious. Generally, the irreducible water saturation increases, the logging resistivity decreases, and the norma...

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Problems solved by technology

[0006] Therefore, people began to look for new fracturing methods, and two technologies were introduced and applied to the ultra-low permeability mining in my country. One was multi-stage staged fracturing of horizontal wells, which did increase the productivity of a single well, but The cost of drilling and subsequent fracturing is expensive, and it is difficult to achieve the purpose of economic exploitation; one is volume fracturing, which builds network fractures through reconstruction, thereby avoiding the unfavorable factors of poor matrix seepage and increasing production capacity. However, An important condition for realizing volume fracturing is that the difference between the maximum horizontal principal stress and the minimum principal stress should be small. However, oil wells in my country are generally buried deep, and the difference in horizontal principal stress is relatively large, so it is difficult to form all-round three-dimensional network fractures. Therefore, There is no wider application in vertical well mode mining operations

The multi-stage staged fracturing + volume fracturing mode of horizontal wells can achieve good results, but the cost problem is still an important factor restricting its wide application

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