Method for evaluating compressibility of shale gas reservoir

Abstract

The invention discloses a method for evaluating compressibility of a shale gas reservoir. The method sequentially comprises the following steps of (1) calculating a shale brittleness index Brit, (2), calculating a shale fracture toughness index Kn, (3), calculating a natural weak plane opening facility index Pn, (4), calculating a natural weak plane penetrated index Cn, (5), introducing a complex seam net probability index Fcf and a transforming volume probability index Fsrv, and determining a reservoir compressibility index FI, (6), according to the size of the reservoir compressibility index FI, evaluating the compressibility of a block shale reservoir. According to the method, various compressibility influence factors are considered, and particularly on the basis of a seam net forming mechanism, the influence of the natural weak plane is fully considered; the shortcomings of an existing evaluation method are overcome, and logging data are utilized for calculating brittleness and breaking toughness of the shale gas reservoir; and the dependency on experimental data is reduced. The method is used for evaluating the reservoir quality of a fractured well, has feasibility and accuracy and provides a new decision making method for facture well selecting and layer selecting of the shale gas reservoir.

Description

technical field [0001] The invention belongs to the field of oil and gas field development, and in particular relates to a multi-factor comprehensive evaluation method for the compressibility of shale gas reservoirs. Background technique [0002] Chong et al. defined fracability as the property that shale reservoirs can be effectively fractured to obtain production stimulation during hydraulic fracturing (Chong K, GrieserWV, Passman A.A completions guide book to shale-play stimulation in the last two decades [C] / / Proceedings of Canadian Unconventional Resources and International Petroleum Conference, 19-21 October, SPE 133874). However, this definition is vague and does not give an accurate explanation of "effective fracturing". Due to the low porosity and ultra-low permeability-tight characteristics of shale reservoirs, the porosity is generally 4% to 6%, and the permeability of unfractured shale matrix is ​​generally 10%. -4 ~10 -9 μm 2 , and the natural weak planes in...

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Problems solved by technology

The experimental evaluation method is to conduct a series of indoor experiments on shale cores, carefully observe and record the experimental phenomena and results, and compare the obtained series of experimental parameters with North American shale parameters, so as to evaluate the compressibility of shale in the target area , this type of method has a certain accuracy, but the operation is complicated, time-consuming and labor-intensive, and is not suitable for promotion in the field; the coefficient evaluation method can be subdivided into the brittleness coefficient method and the compressibility coefficient method, among which the brittleness coefficient method is the most widely used , compared with the experimental evaluation method, the coefficient evaluation method has the advantages of being intuitive, effective, simple to operate, and strong on-site application. However, the existing compressibility coefficient evaluation method has the disadvantage of considering a single factor or simple multi-factor superposition, and cannot fully and scientifically reflect Compressibility of Shale Reservoirs

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