Method for calculating permeability of matrix after acid fracturing of carbonatite

Abstract

He invention discloses a method for calculating the permeability of a matrix after acid fracturing of carbonatite. The method comprises the steps that 1) basic parameters are collected; 2) a viscositydynamic change equation of natural gas in the matrix flowing process is set up; 3) a dynamic change calculation model of the tubular billet aperture and the secondary microfissure width considering stress sensitivity is set up; 4) the starting pressure gradient and a irreducible water film are considered, and flow equations of the natural gas in a tubular billet and a crack are set up; and 5) a fractal theory is introduced, a total flow calculation equation of the tubular billet and the crack is set up, the face, close to the crack, of the carbonatite obtained after acid fracturing is treatedinto a tubular billet-crack dual pore medium seepage model, and a model for calculating the permeability of the matrix after acid fracturing of the carbonatite is set up. The method for calculating the permeability of the matrix after acid fracturing of the carbonatite is provided based on the actual flowing process of the natural gas under the conditions of stress sensitivity, crack width dynamic changes, multiple pore media and the starting pressure gradient.

Description

technical field [0001] The invention relates to the field of exploration and development of carbonate rocks, in particular to a calculation method for matrix permeability after acid fracturing of carbonate rocks. Background technique [0002] Acid fracturing is a key technology for the development of carbonate gas reservoirs. The pores in carbonate rock reservoirs are mainly capillaries. After acid fracturing, the matrix near the main fractures will produce secondary micro-fractures, thus forming capillary-fractures. In double-porous media, because the fracture permeability is much greater than the capillary permeability, the gas permeability will increase when it flows into the artificial main fracture, and the residual acid will also enter the secondary micro-fracture to form a bound water film. Since the capillary-fracture size is extremely small, These pore structures can be regarded as capillary-fracture dual porosity. [0003] After the acid fracturing construction, t...

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Problems solved by technology

The experimental research method uses nitrogen as the medium to simulate the seepage law of natural gas in carbonate reservoirs, which has the following shortcomings: (1) The experiment cannot completely simulate the opening and extension of secondary micro-fractures formed after acid fracturing; (2) It is impossible to consider the real gas effect and stress sensitivity in the process of gas flow under high temperature and high pressure; (3) It is difficult and expensive to make experimental cores

This method has the following disadvantages: (1) The modeling process is complicated and the calculation is difficult; (2) It cannot fully consider the irreducible water, the starting pressure gradient, the dynamic change of fracture width, and the real gas effect and stress sensitivity of the gas under high temperature and high pressure. (3) It is impossible to characterize the seepage characteristics of multi-porous media

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