Method for measuring gas and water production dynamic relative permeability curve in undersaturation coal reservoir development

Abstract

The invention discloses a method for measuring a gas and water production dynamic relative permeability curve in undersaturation coal reservoir development. The method comprises the steps that gas well accumulation production Q is obtained; a production phase of a production well is judged; reservoir pressure p and reservoir water saturation Sw are obtained; the reservoir pressure p is introduced into an improved absolute permeability model, and the absolute permeability K is obtained; irreducible water saturation Swr is predicted by measuring the porosity phi; the reservoir water saturation Sw and the irreducible water saturation Swr are introduced into a relative permeability model, and the relative permeability kr is obtained; the relative permeability and the absolute permeability are coupled on the condition of the identical the reservoir pressure p and the identical reservoir water saturation Sw, and the effective permeability ke at the moment is obtained. The method solves the problem of measuring the undersaturation coal reservoir gas and water relative permeability curve, the positive and negative effects and the slippage effect in the developing process are taken into consideration, the changes of a two-phase common flow area relative permeability curve can be represented, the changes of a single-phase water stage relative permeability curve can be better represented, the influence of water invasion is taken into consideration, and the actual production of undersaturation coal gas reservoirs are better met; a nuclear magnetic resonance method is used, convenience, fastness and non-destruction are achieved, precision is higher, and practicability is higher.

Description

technical field [0001] The invention relates to a measurement method for the development of coal bed gas reservoirs, in particular to a method for measuring dynamic phase permeability curves of gas-water production in the development of undersaturated coal reservoirs. Background technique [0002] In recent years, China's coalbed methane industry has developed rapidly, and two major coalbed methane commercial areas, Qinshui Basin and Ordos Basin, have been established successively. Technological progress has also brought some new production problems. Among them, the undersaturated characteristics of coalbed methane reservoirs and the difficulty in reducing the reservoir pressure caused by the external water supply of coalbeds are severe challenges in the process of coalbed methane development. [0003] The coal reservoir fracture system is mainly composed of matrix and cleats. In the original state, coalbed methane is adsorbed on the inner surface of the matrix, and the clea...

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Problems solved by technology

However, this method is based on the development mechanism of saturated coalbed methane reservoirs, and only considers the change of the relative permeability curve in the gas-water two-phase flow stage, and lacks the characterization of the single-phase water stage, that is to say, this method is suitable for saturated coalbed methane reservoirs , it is not appropriate to apply it directly to undersaturated coalbed methane reservoirs with water invasion, and it cannot fully reflect the actual development of undersaturated coalbed methane reservoirs that have undergone a long drainage and pressure reduction process, and has certain limitations

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