A cutting-core-wellbore-reservoir multi-scale 3-D fracturing evaluation method for shale reservoirs

Abstract

The invention relates to a debris-core-borehole-reservoir multiscale shale reservoir three-dimensional fracturing evaluation method. The method comprises the steps of: (S1) calculating mineral content brittleness indexes in a shale coring position; (S2) building relations among an internal friction angle, I type and II type fracture toughness and rock mechanical parameters; (S3) building shale fracturing evaluation models comprehensively considering a mineral content, elastic parameters, the internal friction angle, a critical strain energy release rate and the rapture toughness; (S4) applying a support vector machine algorithm to obtain a cluster analysis mode between a reservoir fracturing performance and the elastic parameters; and (S5) applying the cluster analysis mode and a reservoir three-dimensional elastic parameter data body to obtain a debris-core-borehole-reservoir multiscale shale reservoir three-dimensional fracturing model. The method can be applied to obtain the fracturing performance of any space position in a shale reservoir, so that the well position selection blindness is prevented, and the fracturing modification effect and the after-pressing yield are improved.

Description

technical field [0001] The invention belongs to the technical field of shale oil and gas development, and in particular relates to a three-dimensional fracturing evaluation method for shale reservoirs with multiple scales of cuttings-core-wellbore-reservoir. Background technique [0002] With the continuous and rapid growth of my country's national economy, the demand for energy has increased sharply, and the contradiction between supply and demand of oil and natural gas resources has become prominent. my country's shale gas resources are very rich. According to the latest research results of the Oil and Gas Center of the Ministry of Land and Resources in 2012, the recoverable resources of shale gas in my country are 25 trillion cubic meters, and the development potential is huge. With the successful development of typical shale gas fields such as Barnett and Eagle Ford in the United States and Fuling in my country, shale gas is expected to become an important alternative en...

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Problems solved by technology

However, due to the severe geological structure and complex geological conditions of reservoirs in Sichuan area, the internal physical properties and heterogeneity of shale reservoirs are quite different. The existing brittleness index evaluation methods only belong to the wellbore scale and cannot realize the prediction of the brittleness of the entire reservoir. , if the wellbore trajectory of the horizontal well is located in a reservoir with poor brittleness or encounters a brittle interlayer with a high elastic modulus and a small Poisson's ratio, it will be difficult to achieve volume fracturing with the perforation position and fracturing interval optimized by the existing method. Due to the required fracture network, the production capacity of shale gas wells cannot reach the expected target, and even part of the well pressure does not see gas, which makes it difficult to return the huge investment in early drilling and large-scale hydraulic fracturing

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