Method for calculating bound water saturation of low-permeability tight sandstone

Abstract

The invention discloses a natural gas reservoir physical property analysis technology and relates to a method for calculating the irreducible water saturation of the low-permeability tight sandstonewhich comprises the following steps: screening a rock sample of the low-permeability tight sandstone, and acquiring characteristic parameters of a pore structure of the rock sample by adopting a physical experiment method; establishing a three-dimensional pore physical model by adopting a digital core technology according to the pore structure parameters; according to the actual given simulation temperature and pressure of the gas reservoir, determining water-phase and gas-phase high-pressure physical property parameters; and completely saturating the three-dimensional pore physical model withwater, setting a displacement pressure difference, simulating a gas-driven water process, and calculating the water saturation in the model after displacement is stabilized. The irreducible water saturation of the low-permeability tight sandstone gas reservoir under different temperatures and pressures can be effectively predicted, the test and analysis period can be greatly shortened, the defects and shortcomings of an existing experimental analysis method are overcome, a large amount of test and assay expenses are saved, and a foundation is laid for comprehensive evaluation, seepage law research, reserve calculation and the like of the tight sandstone gas reservoir.

Description

technical field [0001] The invention relates to a technique for analyzing physical properties of natural gas reservoirs, in particular to a calculation method for irreducible water saturation of low-permeability tight sandstone. Background technique [0002] Low-permeability tight sandstone is an important natural gas reservoir, containing abundant natural gas resources, and is one of the key fields of exploration and development at home and abroad. In order to efficiently develop natural gas that occurs in the pore space of low-permeability tight reservoirs, it is first necessary to have an accurate understanding of physical parameters such as fluid characteristics saturated with reservoir rocks, which is the basis and key to reservoir evaluation and natural gas development. [0003] At present, nuclear magnetic resonance method, mercury injection method and relative permeability curve method are mainly used to determine the irreducible water saturation of reservoir rocks t...

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Problems solved by technology

[0008] The purpose of the present invention is to overcome the defects of long time-consuming, large error and high cost in analyzing the irreducible water saturation of low-permeability tight sandstone in the existing core experiment method and on-site sealed coring, which cannot fully meet the requirements of this type of gas reservoir fluid. To solve the technical problem of parameter evaluation requirements, provide a calculation method for irreducible water saturation of low-permeability tight sandstone gas reservoirs, which can effectively predict the irreducible water saturation of low-permeability tight sandstone gas reservoirs under different temperature and pressure. The prediction results are accurate and reliable, and can greatly Shorten the test and analysis cycle, overcome the defects and deficiencies of existing experimental analysis methods, save a lot of test and laboratory costs, and lay a foundation for comprehensive evaluation of low-permeability tight sandstone gas reservoirs, seepage law research, reserve calculation, etc.

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