China University of Petroleum

Yunkai Ji

Yongge Liu

Jian Hou

Nu Lu

Yajie Bai

Ermeng Zhao

Kang Zhou

Bei Wei

Qingjun Du

Yueliang Liu

Wenbin Wang

Wenbin Liu

Huiyu Wang

The application relates to the technical field of oil and gas field development, and discloses a correction method and system for a permeability model considering gas hydrate distribution, and a method and system for determining the permeability of the hydrate-bearing porous medium. The correction method includes: calculating a water mass and a hydrate saturation of each subregion of a porous medium in a dissociation process of a gas hydrate; calculating an average permeability of the porous medium in the dissociation process of the gas hydrate according to the hydrate saturation and a permeability model, wherein a value of a permeability characteristic parameter in the permeability model is an initial value of the permeability characteristic parameter; and determining the initial value of the permeability characteristic parameter as an optimal value of the permeability characteristic parameter under a condition that an difference between the average permeability of the porous medium and an actually measured permeability in the dissociation process of the gas hydrate is less than or equal to a preset value. In the application, through the corrected permeability model, the permeability characteristics of the porous medium considering the heterogeneous distribution of the hydrate can be accurately measured.

Method for correcting permeability model of porous medium in dissociation process of gas hydrate, and method and system for determining permeability of hydrate-bearing porous medium

A method for improving the gas recovery of a natural gas hydrate reservoir by using artificial impermeable layers is described. Artificial impermeable layers are formed by injecting cement slurry into the permeable overburden and underburden layers. When depressurization exploitation is performed, a large amount of seawater can be effectively blocked from entering a hydrate layer, and a production pressure difference between the hydrate layer and the production well is effectively increased, so that a hydrate decomposition rate and the gas recovery are improved.

Method for enhancing gas recovery of natural gas hydrate reservoir

A daily gas production rate of a methane hydrate deposit is calculated based on inflow performance relationship formulas. Step 1 determines the production stage, including the gas production rate trend of a production test and selecting an inflow performance relationship formula corresponding to the stage. Step 2 calculates basic coefficient terms related to energy conversion in the inflow performance relationship formula. Step 3 obtains other coefficient terms related to production in the inflow performance relationship formula. Step 4 predicts the gas production rate under other production pressure differences. Staged inflow performance relationship formulas characterize the complex methane hydrate deposit production performance. Gas production rate and deposit pressure under a large pressure differences are predicted through simple production tests under a small pressure difference, providing a basis for production design of the hydrate deposit and preventing accidents that may be caused by direct production under a large pressure difference.

Method for calculating daily gas production rate of methane hydrate deposit based on inflow performance relationship formulas

The disclosure discloses a method for obtaining formation parameters of a gas hydrate reservoir through well testing interpretation, which comprises: (1) establishing a physical model for well testing interpretation of the gas hydrate reservoir according to multiphase flow, hydrate dissociation, secondary hydrate formation and heat transfer exhibited in the well testing process of the gas hydrate reservoir; (2) establishing a mathematical model for well testing interpretation of the gas hydrate reservoir; (3) conducting spatial discretization and temporal discretization on the mathematical model, and adopting a finite volume method to obtain a numerical solution of bottom-hole pressure; (4) calculating a bottom-hole pressure variation curve and a production rate variation curve in the well testing process of the hydrate reservoir, and drawing theoretical curves of bottom-hole pressure difference and pressure difference derivative; and (5) matching a measured pressure curve with the theoretical curve to obtain the relevant formation parameters.

Method for obtaining formation parameters of gas hydrate reservoir through well testing interpretation

The example of implementation of the invention provides a method used for exploiting a natural gas hydrate reservoir and belongs to the field of natural gas hydrate reservoir exploitation. The method mainly comprises a heat-injecting vertical well and a production horizontal well. The production horizontal well is opened in a segmental manner. In combination with natural gas hydrate heat exploitation, heat flow injected into the vertical well is enabled to heat different positions of the natural gas hydrate reservoir to increase a recovery ratio of the natural gas hydrate reservoir. The method specifically comprises the steps of injecting a heat flow into the natural gas hydrate reservoir by utilizing the vertical well to promote decomposition of the hydrate; firstly opening a horizontal branch of the horizontal well fully and keeping depressurization exploitation. When gas production amount is reduced to a certain degree, dividing a segmentation number based on permeability of the natural gas hydrate reservoir and performing segmental exploitation on the horizontal branch from a toe end to a heel end to realize heat exploitation of the heterogeneous natural gas hydrate reservoir. The method makes full use of a horizontal well structure, reduces exploitation cost and provides effective measures for efficient exploitation of the heterogeneous natural gas hydrate reservoirs.

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Qingdao, China

Yunkai Ji