US 12,449,563 B1
Stress sensitivity analysis method for fractured gas reservoir
Nutao Wang, Chengdu (CN); Yue Cao, Chengdu (CN); Chengyang Zhang, Chengdu (CN); and Hang Li, Chengdu (CN)
Assigned to SouthWest Petroleum University, Chengdu (CN)
Filed by SouthWest Petroleum University, Chengdu (CN)
Filed on Feb. 28, 2025, as Appl. No. 19/066,208.
Claims priority of application No. 202410433702.2 (CN), filed on Apr. 11, 2024.
Int. Cl. G01V 99/00 (2024.01); E21B 49/00 (2006.01)
CPC G01V 99/00 (2013.01) [E21B 49/006 (2013.01)] 3 Claims
OG exemplary drawing
 
1. A stress sensitivity analysis method for a fractured gas reservoir, comprising the following steps:
S1, calculating a material balance quasi-time tca, comprising:
setting a single well controlled reserve G, and calculating the material balance quasi-time for each production data point:

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wherein G is the single well controlled reserve in 100 million cubic meters (m3); cti is an initial comprehensive compression coefficient; q is a daily production rate of a single well in cubic meters per second (m3/s); pp is a pressure of a normalized formation in megapascals (MPa); and ppi is an initial pressure of the normalized formation in MPa; wherein:

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wherein p is a pressure of the fractured gas reservoir in MPa; Z is a gas deviation factor, dimensionless; i is an initial state; Gp is a cumulative gas production of natural gas in 100 million cubic meters; and G is the single well controlled reserve in 100 million cubic meters;
S2, calculating a normalized production:

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wherein Δpp is a change in the pressure of the normalized formation; ppwf is a normalized bottom hole flowing pressure in MPa;
S3, calculating the single well controlled reserve G comprising:
drawing a relationship curve of

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and determining the single well controlled reserve G according to a line slope m, wherein G is expressed as:

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S4, analyzing and judging a stress sensitivity comprising:
setting a solution stress sensitivity coefficient α, an initial objective function Jgi, and calculating an objective function Jg by a following formula:

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wherein ki is an initial permeability in square micrometers (μm2); h is an effective thickness of the fractured gas reservoir; μ is a gas viscosity in millipascal·second (mPa·s); Bg is a gas volume coefficient, dimensionless; A is a single well control area in square meters (m2); CA is a shape factor; γ=0.57721 is an Euler-Mascheroni constant; rw is a well radius in meters (m); and establishing an optimized objective function M according to an inversion of Ig represented as

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so that:

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wherein n is a number of production data points;
repeating S1-S3, and performing an objective optimization in a G iteration until a convergence satisfies an allowable error of G;
finally, calculating a reservoir damage

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by the solution stress sensitivity coefficient α of the objective function M of a nonlinear solution method, wherein when α is decreased, Jg approaches the initial objective function Jgi; and calculating an average of Jg as:

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wherein when Jgave approaches Jg; the stress sensitivity is weaken, otherwise the stress sensitivity is strengthen.